JP2004263307A - Dry pulp nonwoven fabric having integrated layer structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dry nonwoven fabric having good water absorption and high wet strength without falling off fibers. <P>SOLUTION: The dry nonwoven fabric having an integrated layer structure comprises a surface layer part of both surfaces containing heat bonding synthetic fibers which are mutually heat bonded and have >5 to ≤12 g/m<SP>2</SP>weight and an inner layer part containing the heat bonding synthetic fibers to pulp fibers in (20/80) to (60/40) wt.% ratio in which the mutual synthetic fibers and/or synthetic fibers and pulp fibers are heat bonded and having 8-240 g/m<SP>2</SP>weight. The space between the right side and back side and inner layer part are integrated by heat bonding of the mutual synthetic fibers and the longitudinal and transverse strength ratio is 0.8-1.2 in dry and wet states. The strength ratio in the dry and wet states is 0.6-1.1 and the absorption of water is 8-20 g/g. The total weight is 20-250 g/m<SP>2</SP>. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００３４】
【発明の効果】
本発明は、熱接着性合成繊維を含む表裏層の目付を適正化し、また、内層の熱接着性合成繊維の量を増やすことによって、繊維の脱落を抑え、吸水性を損なうことなく、不織布の強度を、湿潤時の使用や繰り返し使用に耐えられるほどに上げることが可能になった。また、水や油のふき取り性もよく、層間剥離もなく、ふき取りの用途に非常に適している不織布を得ることができた。また、本発明の不織布は十分なヒートシール性を有する。また、生理用品、おむつなどの衛生材料や、メディカルの用途においても同様に好適である。
また、本発明の不織布はケミカルバインダー樹脂による残留モノマーの心配がなく、衛生的である。
さらに、不織布の製造工程において排水が出ず、排気にもケミカルバインダーのモノマーがなく、環境負荷が小さい。[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a dry pulp nonwoven fabric which is strong even when wet. More specifically, objective wipers for wet floors, kitchens, automobiles, etc., kitchen sheets for cooking utensil cleaning, food wiping, drip absorption, etc., and personal wipers for faces, hands, body, etc. The present invention relates to a non-woven fabric suitable for such purposes. Furthermore, the present invention, even when used in dry form, in these applications, since there are many cases where moisture is present, similar effects can be expected, and sanitary products, sanitary materials for diapers, The present invention also relates to a suitable nonwoven fabric for medical applications.
[0002]
[Prior art]
Conventionally known dry pulp nonwoven fabrics are based on a pulp fiber layer that is made by spraying or applying a chemical binder resin such as polyacrylate or polyvinyl acetate to the surface layer, or impregnating the entire fiber. Forming an inter-junction.
In such a nonwoven fabric, when the binder amount is increased, the resin forms a film and becomes hard, or causes a decrease in the water absorption capacity. A decrease in strength when wet is inevitable.
[0003]
In addition, a method of applying a powdery binder resin is also conceivable. In this case, it is difficult to form a film, but the number of adhesion points between the pulp fiber and the binder is reduced, and the number of detached fibers tends to increase. Therefore, it is difficult to produce a dry pulp nonwoven fabric which is excellent in wet strength while ensuring a texture that is not too hard, an appropriate water absorption, a small amount of fiber falling off, and a strength sufficient for practical use.
[0004]
A dry pulp non-woven fabric used as an absorbent insert material for sanitary products or used for cleaning at home or industry, the basis weight of a layer consisting only of the bonding fibers on the surface is 1 to 5 g / m ² , and the bonding of the inner layer portion A dry pulp nonwoven fabric having a fiber content of 2 to 10% by weight has been proposed (see Patent Document 1).
[0005]
Regarding the strength of this non-woven fabric, although it is sufficient for sanitary products such as absorbent insert materials for sanitary products, the strength of this non-woven fabric is completely mentioned as to whether it is strong even when wet, which is a major point of the present invention. It has not been. The nonwoven fabric of the technical content falling within the scope of this published patent has a small amount of binding fibers in the inner layer portion of 2 to 10% by weight, and it is hard to say that it is strong even when wet, and causes a remarkable decrease in strength when wet. And completely different from the intention of the present invention.
[0006]
[Patent Document 1]
JP 2000-504792 A
Further, an air-laid nonwoven fabric having a specific tear strength, which is formed by thermally bonding the intersections of binder fibers, has been proposed (Patent Document 2). However, mention is made of wet strength and water absorption when combined with pulp. There is no description suggesting the technology as a layered structure of the present invention.
[0008]
[Patent Document 2]
JP 2000-345454 A
[Problems to be solved by the invention]
The present invention has been made to overcome such a problem, and an object of the present invention is to provide a dry nonwoven fabric which has no fibers falling off, has good water absorption, and is strong, particularly, has sufficient wet strength. Is to do.
[0010]
[Means for solving the problem]
The present invention includes a heat-bondable synthetic fiber, a surface layer portion on both sides, wherein the synthetic fibers are heat-bonded to each other and the basis weight is more than 5 g / m ² and 12 g / m ² or less; Are mixed at a ratio of 20/80 to 60/40% by weight, and the synthetic fibers and / or the synthetic fibers and the pulp fibers are heat-bonded, and the basis weight is 8 to 240 g / m ² . It is composed of a certain inner layer portion, and the entire surface between the front and back surfaces and the inner layer portion is also integrated by the thermal bonding between the synthetic fibers. 0.8 to 1.2, the ratio of strength between dry and wet is 0.6 to 1.1, water absorbency is 8 to 20 g / g, and total weight is 20 to 250 g. / M ² , wherein the layered structure is integrated The present invention relates to a dry pulp nonwoven fabric (hereinafter, also simply referred to as “dry nonwoven fabric”).
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
The nonwoven fabric of the present invention has a three-layer structure including an inner layer made of a heat-adhesive synthetic fiber and a pulp fiber and a surface layer containing the heat-adhesive synthetic fiber sandwiching the inner layer, and is integrated by heat bonding.
In the present invention, the thermoadhesive synthetic fibers which are the main component forming the surface layer or mixed with the pulp may be any as long as they are melted by heat and bonded to each other. The pulp is fixed in a network structure by bonding, and fibers using a polymer having high affinity for pulp fibers are particularly preferable. Examples include polyolefins, polyolefins grafted with unsaturated carboxylic acids, polyesters, polyvinyl alcohol, and the like.
[0012]
Among them, the core-sheath type or eccentric side-by-side type conjugate fiber is suitable as the polyolefin-based heat-adhesive synthetic fiber. Examples of the polyolefin 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 portion, a polymer having a higher melting point than the sheath and not changing at the temperature of the heat bonding treatment is preferable. Such combinations include, for example, polyethylene / polypropylene, polyethylene / polyester, polypropylene / polyester, and the like. These polymers may be modified as long as the functions and effects of the present invention are not impaired. Further, fibril-like fibers may be used. For example, SWP of Mitsui Chemicals, Inc. and the like can be mentioned.
[0013]
When the heat-bondable synthetic fiber is thin, the number of constituent fibers increases, so that the number of dropped fibers decreases and the texture becomes soft. When the thickness is large, the space between the fibers becomes large, so that a bulky nonwoven fabric is obtained, and a scraping effect can be expected. Therefore, the thickness of the fiber may be selected according to the application, but the fineness is preferably 0.5 dt to 50 dt, and more preferably 0.8 dt to 30 dt. If it exceeds 50 dt, the pulp may not be prevented from falling off, which is not preferable. On the other hand, if it is less than 0.5 dt, the productivity of the nonwoven fabric is lacking, so that it is not practical.
[0014]
Further, the length of the heat-adhesive synthetic fiber is preferably 1 to 15 mm. If the fibers are short, the mixing properties with the pulp are improved, and a more uniform non-woven fabric is easily formed. However, if it is less than 1 mm, it becomes powdery and a network structure due to inter-fiber bonding is difficult to form, and not only can the pulp not fall off, but also the non-woven fabric cannot be suppressed. Strength is low, and practicability is lacking. On the other hand, when the length is longer than 15 mm, the strength of the nonwoven fabric is increased, but the fibers are apt to be entangled in the pneumatic transport of the fibers during the production of the nonwoven fabric. Particularly preferred is 3 to 10 mm.
[0015]
On the surface layer, in addition to the above-mentioned heat-adhesive synthetic fibers, recycled fibers such as rayon, semi-synthetic fibers such as acetate, synthetic fibers such as polyester, polypropylene, polyamide, and vinylon, and natural fibers such as pulp, cotton, and hemp Etc. may be included. In this case, the proportion of the heat-adhesive synthetic fiber in the surface layer is preferably 70 to 100% by weight, more preferably 85 to 100% by weight. If the content is less than 70% by weight, the other fibers are likely to fall off, the effect of suppressing the pulp from falling off in the inner layer portion is reduced, and the wet strength is also reduced, causing a practical problem. .
These fibers forming the surface layer are thermally bonded, and the pulp is fixed in a network structure by the inter-fiber bonding. The basis weight must be more than 5 g / m ² and not more than 12 g / m ² . If it is 5 g / m ² or less, the amount of synthetic fibers having water resistance and the number of bonding points between the fibers are small, so that not only a sufficient wet strength that can withstand wiping can not be secured, but also the number of dropped fibers tends to increase. Unlike applications where emphasis is placed on absorbency, such as sanitary materials, when used for wiping, fibers tend to fall off, and such nonwoven fabrics are not practical for applications such as wipers and kitchen sheets. On the other hand, when it exceeds 12 g / m ² , the water-resistant heat-bonding layer becomes too thick, the moisture absorption into the inner layer becomes insufficient, and the texture becomes hard, which also lacks practicality. As the basis weight increases, the strength increases but the water absorption decreases. However, within the scope of the present invention, it is possible to obtain a nonwoven fabric which has sufficient water absorption, has strength even when wet, has no fibers falling off, and has a soft texture.
In addition, since the amount of the synthetic fibers is large, the oil absorption is good, and the affinity with the oil is good, so that there is an advantage that dirt is easily removed.
[0016]
In the inner layer portion, the heat-adhesive synthetic fiber and the pulp fiber are integrated by heat bonding. The same or different heat-bondable synthetic fibers may be used for the surface layer. As the pulp fiber, a ground pulp having a length of 0.2 mm to 5 mm is preferable.
As for the mixing ratio of the heat-adhesive synthetic fiber and the pulp fiber in the inner layer portion, if the ratio of the heat-adhesive synthetic fiber is less than 20% by weight based on the total of the adhesive synthetic fiber and the pulp fiber, the falling-off fiber increases and the strength increases. In particular, the strength when wet is reduced. Such a product, such as a sanitary product, can be used for applications that do not have strength but emphasize water absorbency and softness, but does not endure the use of the nonwoven fabric for wiping, which is the object of the present invention. . On the other hand, if it exceeds 60% by weight, the amount of pulp fibers contributing to the absorbency decreases, and not only the water wiping property and the absorbency are lacking, but also the hand becomes hard and lacks practicality.
[0017]
As the ratio of the heat-adhesive synthetic fiber increases, the strength increases, but the water absorption decreases.
Thus, it has been difficult to achieve both sufficient strength, particularly strength when wet, and water absorption.
These balances are very important for wipers and kitchen sheets. Only when the ratio is within the range of the present invention, a nonwoven fabric having sufficient water absorption and sufficient strength even when wet can be obtained. In addition, the amount of the dropped fibers is small, and such a nonwoven fabric has sufficient strength to be washed, squeezed and dried even if it is soiled, and can be used repeatedly several times. Further, since the ratio of the thermosynthetic fibers is large, the bulk is small and the thickness can be reduced, so that the handleability is excellent and the space is saved.
[0018]
In the inner layer, the heat-bondable synthetic fibers and the heat-bondable synthetic fiber and the pulp fiber are heat-bonded. The weight of the inner layer is preferably from 8 to 240 g / m ² . If it is less than 8 g / m ² , the amount of pulp is too small and water absorption is insufficient, while if it is more than 240 g / m ² , the whole becomes plate-like and not suitable for this use.
In addition, the entire nonwoven fabric is also integrated between the front and back surfaces and the inner layer by heat bonding between the heat-bondable synthetic fibers. Furthermore, it has sufficient heat sealing properties.
[0019]
Such a nonwoven fabric may be produced by any method as long as it is a dry nonwoven fabric, but a nonwoven fabric by an airlaid method is preferable. The nonwoven fabric manufactured by the airlaid method is preferable because the fibers forming the nonwoven fabric are randomly and three-dimensionally oriented in the longitudinal direction, the width direction, and the thickness direction of the nonwoven fabric.
[0020]
Here, the nonwoven fabric by the airlaid method can be obtained as follows.
A predetermined amount of defibrated heat-adhesive synthetic fibers were conveyed while being uniformly dispersed in an air stream, and the fibers blown out from a screen having pores provided in a discharge portion were installed at a lower portion. The fibers are deposited on the net while dropping it onto a metal or plastic net and suctioning air at the bottom of the net. Next, the mixture of the heat-adhesive synthetic fiber and the pulp fiber is similarly deposited on the above-mentioned deposition sheet. In addition, fibers based on thermo-adhesive synthetic fibers are deposited on these sheets.
Next, the whole is heat-treated to a temperature at which the heat-adhesive synthetic fiber sufficiently exhibits its adhesive effect, whereby the dry pulp nonwoven fabric of the present invention can be obtained. In order to sufficiently exhibit the adhesive effect, a heat treatment at a temperature higher by 15 to 40 ° C. than the melting point of the adhesive component of the heat-adhesive synthetic fiber is required.
[0021]
As described above, in the nonwoven fabric manufactured by the airlaid method, the fibers can be randomly and three-dimensionally oriented in the flow direction, the width direction, and the thickness direction of the nonwoven fabric. Since these are thermally bonded, delamination does not occur. In addition, the nonwoven fabric manufactured by the airlaid method has good uniformity, and thus has less variation in performance.
If necessary, a calendar process or an embossing process can be further performed.
[0022]
In the nonwoven fabric of the present invention, the ratio of strength between warp and weft must be 0.8 to 1.2, preferably 0.85 to 1.2, both when dry and when wet. If one of the strengths is low, practical problems are likely to occur.
Also, the ratio of strength between dry and wet should be 0.6-1.1, preferably 0.7-1.1. A non-woven fabric having a strength of less than 0.6 greatly reduces the strength when wet as compared with the time of drying, that is, becomes weaker when wet, which deviates from the intended purpose of the present invention and causes practical problems. Further, when wet, the strength increases due to the surface tension between the fibers due to the presence of moisture, and may exceed 1, which is also within the scope of the present invention, unless there is another means for bonding in the presence of some moisture. It does not usually exceed 1.1.
[0023]
Wipers, kitchen sheets, sanitary materials, and the like to which the nonwoven fabric of the present invention is applied need to have an appropriate water absorption, and the water absorption is 8 to 20 g / g, preferably 10 to 18 g / g. Must. If it is less than 8 g / g, the wiping property and the water retention property in practical use are lacking, and there is a problem in practical use. On the other hand, if it exceeds 20 g / g, the amount of water retained by the nonwoven fabric itself is too large, and there is a problem in handleability.
[0024]
The basis weight of the entire nonwoven fabric is preferably ²⁰ to 250 g / m ² , and an appropriate basis weight can be selected according to the application.
[0025]
The nonwoven fabric of the present invention may be integrated with other sheets as long as the intention of the present invention is not impaired. For example, if it is integrated with a breathable sheet, in making the nonwoven fabric of the present invention, the breathable sheet is placed on a wire mesh, and fibers are deposited thereon to easily form a composite sheet. be able to.
Examples of the sheet to be integrated include commonly known dry nonwoven fabric, wet nonwoven fabric, paper, spunbond, meltblown, plastic net, perforated film, split yarn cloth, coarse-knit knitted fabric, cold gauze, and the like. Preferably, the sheet is made of a heat-adhesive material, and the air permeability is preferably large.
[0026]
【Example】
The present invention will be described with reference to examples, but the present invention is not limited to these examples.
[0027]
Example 1
A core-sheath composite fiber (F6. 2.2 dt, 5 mm in length, manufactured by Teijin Fibers Co., Ltd.) having a core of polyethylene terephthalate and a sheath of polyethylene is used as the heat-adhesive fiber of the front and back layers, and the core is used as the inner layer. Is a composite fiber of polypropylene and a sheath of copolymerized polyethylene (Nisso Polypro Fiber Co., Ltd., Intac, 1.7 dt, length 5 mm) and pulp (NB416Kraft, manufactured by Weyerhaeuser) in a ratio of 30% by weight and 70% by weight, respectively. Using the mixture, the heating temperature was set to 145 ° C., and a nonwoven fabric was manufactured by an airlaid method.
The basis weight of the front and back layers was 6 g / m ² , and the basis weight of the inner layer was 33 g / m ² . The thickness was 0.54 mm.
Table 1 shows the physical properties such as the strength of warp and weft, the ratio thereof, the ratio between dry and wet states, and water absorption.
The strength and water absorption were measured by the following methods.
(1) Strong: According to JIS L-1913. However, the width of the test piece was 25 mm, and the grip interval was 100 mm.
(2) Water absorption: A test piece of 100 mm x 100 mm weighed in advance was immersed in water at 20 ° C for 1 minute, placed on a glass plate inclined at 45 ° for 1 minute, and then weighed again. Is measured, and the water absorption is calculated by the following equation.
{Circle around (1)} Water absorption per area (g / m ² ): The weight of the absorbed water is divided by the area of the test piece and expressed as g / m ² .
(2) Water absorption per own weight (g / g): The weight of the absorbed water is divided by the weight of the test piece and displayed as g / g.
[0028]
Example 2
Except that the ratio of the adhesive composite fiber to the pulp in the front and back layers was 90/10, the basis weight was 8 g / m ² , the ratio of the adhesive composite fiber to the inner layer and the pulp was 25/75, and the basis weight was 49 g / m ^2. In the same manner as in Example 1, a nonwoven fabric was manufactured by the airlaid method.
The thickness was 0.68 mm.
[0029]
Example 3
A nonwoven fabric was formed by the airlaid method in the same manner as in Example 1 except that the basis weight of the front and back layer portions was 10 g / m ² , the ratio of the adhesive conjugate fiber to the pulp of the inner layer portion was 40/60, and the basis weight was 100 g / m ^2. Manufactured.
[0030]
Comparative Example 1
A nonwoven fabric was formed by an airlaid method in the same manner as in Example 1 except that the basis weight of the front and back layer portions was 4 g / m ² , the ratio of the adhesive conjugate fiber to the pulp of the inner layer portion was 8/92, and the basis weight was 52 g / m ^2. Manufactured.
[0031]
Comparative Example 2
A nonwoven fabric was formed by an air laid method in the same manner as in Example 1 except that the basis weight of the front and back layers was 16 g / m ² , the ratio of the adhesive conjugate fiber to the pulp of the inner layer was 70/30, and the basis weight was 23 g / m ^2. Manufactured.
[0032]
Comparative Example 3
An air-laid nonwoven fabric made of only pulp having a basis weight of 58 g / m ² was prepared, and an emulsion of a polyacrylate resin was impregnated to a solid content of 8 g / m ² and then dried at a hot air temperature of 130 ° C. to obtain a resin type. Air-laid nonwoven fabric.
Table 1 shows the physical properties of the nonwoven fabrics obtained in the above Examples and Comparative Examples.
[0033]
[Table 1]

[0034]
【The invention's effect】
The present invention optimizes the basis weight of the front and back layers containing the heat-adhesive synthetic fibers, and also increases the amount of the heat-adhesive synthetic fibers in the inner layer to prevent the fibers from falling off, without impairing the water absorption, and for the nonwoven fabric. The strength can be increased to withstand wet use and repeated use. In addition, the nonwoven fabric was excellent in wiping properties of water and oil, was free from delamination, and was very suitable for wiping applications. Further, the nonwoven fabric of the present invention has a sufficient heat sealing property. Further, it is similarly suitable for sanitary products, sanitary materials such as diapers, and medical applications.
Further, the nonwoven fabric of the present invention is sanitary because there is no concern about residual monomers due to the chemical binder resin.
Furthermore, no wastewater is produced in the nonwoven fabric manufacturing process, and there is no chemical binder monomer in the exhaust air, and the environmental load is small.

Claims (1)

A heat-bondable synthetic fiber, wherein the heat-bondable synthetic fiber and the pulp fiber each comprise a heat-bondable synthetic fiber having a basis weight of more than 5 g / m ² and not more than 12 g / m ^2; An inner layer portion which is mixed at a ratio of 80 to 60/40% by weight and which is made by thermally bonding the synthetic fibers and / or the synthetic fibers and the pulp fibers, and having a basis weight of 8 to 240 g / m ² ; As a whole, between the front and back surfaces and the inner layer portion, the synthetic fibers are also integrated by thermal bonding, and the ratio of warp and weft is 0.8 to 1 in both dry and wet conditions. 0.2, the ratio of strength between dry and wet is 0.6 to 1.1, the absorbency of water is 8 to 20 g / g, and the total basis weight is 20 to 250 g / m ² . Dry pulp with integrated layered structure, characterized by the following: Non-woven fabric.