JPH0325538B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention has high strength, is flexible, strong,
The present invention also relates to a nonwoven fabric that is extremely resistant to folding and wrinkles. In recent years, nonwoven fabrics have been used for sanitary materials such as paper diapers, surface materials such as wipers, tablecloths, covering materials for furniture, materials for general clothing, hats, coats, interlining for clothing, cushion materials for wall coverings, filters, etc. It is widely used in various other fields. Conventionally, nonwoven fabrics made of fiber aggregates made of synthetic fibers, semi-synthetic fibers, or natural fibers and bonded to each other using a binder have been widely used as such nonwoven fabrics. In some cases, the material is further processed by needling or embossing. Among the uses of nonwoven fabrics, especially in the fields of tablecloths, covering materials for furniture, interlining for clothing, materials for hats, etc., they undergo various operations such as cutting, sewing, washing, and wearing. from,
In addition to not changing the generally required dimensional stability, flexibility, stiffness, etc., it is very important that the material has high strength and is extremely resistant to folding and wrinkles. The degree of occurrence of creases varies depending on the material composition of the nonwoven fabric, the binder, the molding conditions, the method of applying the binder, etc.; for example, reducing the amount of binder or applying dot bonding in the thickness direction of the nonwoven fabric. It is known that the occurrence of creases can be improved to some extent by increasing the mobility of the fibers constituting the nonwoven fabric. However, a nonwoven fabric that simultaneously satisfies the two requirements of being extremely resistant to creases and having improved strength has not yet been obtained. If such a nonwoven fabric is attempted to be obtained using conventional techniques, a contradiction will arise in the processing to satisfy the above two demands. That is, it is effective to increase the amount of binder used to meet the demand for improved strength. However, as the amount of binder increases, the texture of the resulting nonwoven fabric becomes rougher and harder, and folds and wrinkles are more likely to occur.Furthermore, depending on the binder, a sticky feeling may occur, and in particular, the fibers constituting the nonwoven fabric are hydrophobic. In the case of synthetic fibers made of synthetic resins, such as polypropylene fibers and polyester fibers, although they have excellent physical properties as fibers, the bondability between the fibers and the binder is extremely poor, so they are used in large quantities in order to obtain the high strength of nonwoven fabrics. If such a binder is used, the excellent physical properties will be diminished, the texture will become rougher and harder, folds and wrinkles will easily occur, and the strength will still not be sufficient. The present inventors have discovered that hydrophobic synthetic resin fibers such as polypropylene fibers and polyester fibers are contained as all or part of the constituent fibers, effectively retaining the excellent physical properties unique to these fibers, and having high strength. As a result of intensive research with the aim of providing a nonwoven fabric that is highly flexible and extremely resistant to folding and wrinkles, we have developed a composite fiber made of hydrophobic synthetic resin, one of the composite components of which is a foam. A fiber aggregate containing composite fibers with a structure in which this composite component predominately forms the fiber surface as a hydrophobic synthetic resin composite fiber is united with a binder using the unevenness of the foam surface of the composite fiber. The present invention was completed based on the discovery that the object can be achieved by That is, the gist of the present invention is to provide a composite fiber consisting of two or more composite components that can be separated in the cross section of the fiber, in which the composite component that predominantly forms the fiber surface includes a large number of foam cells, and Composite fiber made of hydrophobic synthetic resin with a structure that has many irregularities formed by the rupture of foam cells on the fiber surface.
The nonwoven fabric is characterized in that fiber aggregates containing 20% by weight or more are integrated by a binder attached between the fibers. The present invention will be explained in detail below. The hydrophobic synthetic resin composite fibers (hereinafter sometimes referred to as foamed composite fibers) used in the present invention are hydrophobic synthetic resins such as polyethylene,
Composite fibers are not particularly limited as long as they are made of polypropylene, polyester, etc. and have a main shell composite component of the foam described later, but those made from polypropylene or polyester are preferable because they have a wide range of uses. The composite structure of a hydrophobic synthetic resin composite fiber is composed of two or more composite components that can be separated in the cross section of the fiber, and a specific composite component among them forms the dominant surface of the fiber. Here, "predominantly forming the fiber surface" means forming 50% or more of the fiber surface. Typical examples of such composite structures include the sheath-core type and the parallel type, but they are not necessarily limited to these types. It may also have a structure in which the outer skin composite component (sometimes referred to as a composite skin component) is divided into several parts. The most important feature of the hydrophobic synthetic resin composite fiber used in the present invention is that the main outer skin composite component is a foam that includes a large number of fine foam cells, and that the surface of the fiber formed by it is a foam. It has a large number of fine irregularities consisting of pores formed by rupture of foam cells. Foamed composite fibers having such a foam as the main skin composite component can be produced by various known methods. Composite fibers such as those shown in 1983-151048 are particularly useful in the present invention. The fineness of foamed composite fiber is
0.5 to 30 d/f (denier per filament) is suitable. The reason is that the fineness of the foamed composite fiber is
This is because if it is smaller than 0.5d/f, special processing techniques are required to mold the nonwoven fabric, and the fiber material cost is also high. Furthermore, if the fineness of the foamed conjugate fibers is greater than 30 d/f, the texture of the resulting nonwoven fabric will be extremely rough and hard. The fiber aggregate serving as the nonwoven fabric of the present invention must contain the above-mentioned expanded conjugate fibers in an amount of 20% by weight or more; if the content is less than 20% by weight, the strength-improving effect of the obtained nonwoven fabric is insufficient. The fibers other than the foamed conjugate fibers constituting the fiber aggregate are not particularly limited, and various fibers may be used singly or in combination depending on the purpose, but synthetic resins that are the same as or closely related to the foamed conjugate fibers may be used. Preferably, the fiber consists of: Various types of binders are useful as the binder used in the present invention, such as polychloroprene rubber latex type, acrylic ester copolymer type, butadiene/acrylonitrile rubber latex type,
NBR-based, SBR-based latex, polyurethane-based,
Examples include polyvinyl alcohol-melamine formaldehyde intermediate condensation polymer resin systems, diglycidyl bisphenol A type emulsion-modified polyamine systems, and the like. In the nonwoven fabric of the present invention, the fiber aggregate is integrated by the binder attached between the fibers. It is desirable that the amount of the binder be as small as possible in order to prevent the occurrence of creases in the nonwoven fabric, and on the other hand, it is desirable that the amount of the binder be as large as possible in order to improve the strength of the nonwoven fabric (or prevent fluffing). The nonwoven fabric of the present invention does not require a large amount of binder to sufficiently improve the strength of the nonwoven fabric. Therefore, the amount of the binder capable of achieving both of the above two effects may be appropriately selected depending on the intended use of the nonwoven fabric, but in general, 5 to 70% by weight based on the weight of the fibers is appropriate. The nonwoven fabric of the present invention can be molded by a commonly used method such as a card method or a random wafer method. For example, in the case of the card method, it is implemented as follows. First, foam composite fibers alone or a fiber mixture containing a predetermined amount are carded to form a web. Next, a predetermined amount of a diluted binder solution is applied to this web by a roll contact method, a spray method, or an impregnation method. The binder may be applied primarily to the surface layer of the web, or may be applied uniformly in the thickness direction, or may be spot-adhered by a printed dot method. Next, this web is dried using a hot air circulation dryer, a suction drum dryer, etc. to obtain a nonwoven fabric. Furthermore, this nonwoven fabric may be subjected to special processing such as needling processing, compaction processing using a press, embossing processing, and the like. In addition, as another method for forming nonwoven fabrics, the web obtained by a carding machine or the like is subjected to consolidation treatment using a pressure roll or press machine or needle patching treatment, and if necessary, further consolidation treatment is performed to form a nonwoven fabric. After obtaining the material, a high-strength nonwoven fabric can be obtained by applying a binder. In the thus obtained nonwoven fabric of the present invention, since the foamed conjugate fibers are used as fibers constituting the nonwoven fabric, the unevenness due to the fine cleavage pores on the surface of the foamed conjugate fibers is reduced per weight of the binder. In addition to increasing the adhesion area, the binder enters the cleavage hole and forms a wedge-shaped structure.
Compared to conventional nonwoven fabrics, the binder acts more effectively and exhibits extremely strong adhesive force, resulting in improved strength of the nonwoven fabric even with a small amount of binder. In addition, in the nonwoven fabric of the present invention, the foamed composite fiber itself has 1
Not only is it flexible because it is a partially foamed material, but it also has a smooth feel and is highly flexible due to the adjusted amount of bonding agent, and is extremely resistant to creases. In addition to the above reasons, the reason for this softness may also be that there are a considerable number of fine cleavage pores that are not filled even with the binder, making it easy for the fibers to slide against each other. Further, since the nonwoven fabric of the present invention contains foamed conjugate fibers containing a large number of fine foamed cells, it has no transparency and has a unique pearl-like texture. Next, the present invention will be explained in more detail with reference to Examples. The evaluation items shown in each example were measured as follows. Nonwoven fabric strength: 2cm x 15 with the warp direction of the nonwoven as its length direction
cm or 5 cm x 15 cm sample piece, grasping interval 10
Measure the strength using a tensile tester at a tensile speed of 10 cm/min and take the average of the measured values of 5 samples. Measurements are made for each nonwoven fabric sample in two cases: before washing and after washing. Condition of creases and wrinkles: After washing a 20cm x 20cm nonwoven fabric sample in a household washing machine with only water and no detergent for 60 minutes, the top of the sample was fixed and hung to dry at room temperature for 24 hours.
After washing and drying the sample, we observed the degree of creases and divided them into 5 grades: "No", "Slightly present", "Slightly present", "Present", and "Very noticeable". The observation results of each sample were integrated and evaluated. Examples 1 to 4, Comparative Examples 1 to 4 In parallel type composite spinning of polypropylene, azodicarboxylic acid amide is contained as a blowing agent in only one side component, and the fiber is spun, and the parallel type of polypropylene has a foam as the main outer composite component. Foamed composite fiber (3d x 64mm, crimp count 12.4/inch, strength 3.7
g/d) was obtained. This main skin composite component formed 69% of the fiber surface, and many fine pores were present on the surface. This foamed composite fiber was passed through a carding machine to form a web, and then compacted with a pair of metal flat rolls to obtain a nonwoven fabric material with a basis weight of approximately 25 g/m ² . After using SBR latex as a binder and impregnating it into the above nonwoven fabric material, the liquid content was adjusted to various levels using a squeezing roll and immediately dried at 130℃ for 20 minutes in a hot air circulation dryer to reduce the amount of binder attached. Four different types of nonwoven fabrics of the present invention were obtained. As a comparative example, a polypropylene fiber (3D x 64 mm, number of crimp 12.2 threads/inch, tenacity 3.8
g/d), and in the same manner as above, a nonwoven fabric having a binder adhesion amount almost corresponding to each example was obtained. These nonwoven fabrics were tested for nonwoven fabric strength and crease generation, and the results shown in Table 1 were obtained.

[Table] From Table 1, when the amount of binder attached is almost the same, the strength of the nonwoven fabric of the present invention is significantly superior to that of the comparative example. The difference tends to be more pronounced as the amount of binder attached increases. Examples 5 to 8, Comparative Examples 5 to 7 Polyester sheath-core type foamed conjugate fibers (3d× 38mm, number of crimp 11.8 threads/inch, strength 3.4g/
d) was obtained. There were many fine pores in the main skin composite component. The above polyester foam composite fiber and regular type polyester fiber (3d x 38mm, number of crimp 12.4 crimp/inch, strength 3.9g/d)
The fiber mass obtained by mixing the fibers in various proportions is passed through a carding machine to form a web, which is then needle-punched once on each side, and then passed through a pair of metal flat rolls for consolidation. Approx.
A nonwoven material of 40 g/m ² was obtained. Next, each nonwoven fabric material is impregnated with an emulsion mainly composed of polyvinyl acetate as a binder, and dried in a hot air circulation dryer at 120°C for 30 minutes to reduce the amount of binder attached.
20% by weight of various nonwoven fabrics were obtained. These nonwoven fabrics were tested for nonwoven fabric strength and occurrence of creases, and the results shown in Table 2 were obtained.

[Table] Table 2 shows that when the proportion of foamed composite fibers is 20% by weight or more, creases do not occur and the strength of the nonwoven fabric becomes stable and high. Examples 9 to 12, Comparative Examples 8 to 10 Polypropylene sheath-core foamed composite fibers (6d
×64mm, number of crimp 11.2 threads/inch, strength 3.6g/d) and regular type polypropylene fiber (6d×
64 mm, crimp number 11.8 threads/inch, strength 4.5 g/d) in various proportions, the resulting fiber mass is passed through a carding machine to form a web, and then this web is needle-rolled twice on each side. After punching, it is passed through a pair of metal flat rolls and consolidated to a fabric weight of approximately 60.
A nonwoven material of g/m ² was obtained. NBR as binder
After impregnating the above-mentioned nonwoven fabric materials with the latex, the nonwoven fabrics were compacted using metal rolls and then dried at 130°C for 30 minutes using a hot air circulation dryer to form various nonwoven fabrics with a binder adhesion of about 18% by weight. Obtained. The results shown in Table 3 were obtained regarding the strength of the nonwoven fabric and the occurrence of creases.

[Table] Table 3 also shows that when the proportion of foamed composite fibers is 20% by weight or more, there is no or slight creases, and the nonwoven fabric has excellent strength. While the nonwoven fabrics had a smooth texture, the nonwoven fabrics of Comparative Examples 8 to 10 had a waxy texture.

Claims (1)

[Scope of Claims] 1. A composite fiber consisting of two or more composite components that can be separated in the fiber cross section, in which the composite component that predominantly forms the fiber surface contains a large number of foam cells, and the fiber surface contains a large number of foamed cells. A fiber aggregate containing 20% by weight or more of hydrophobic synthetic resin composite fibers having a structure with many irregularities formed by the rupture of foam cells is integrated by a binder attached between the fibers. Characteristic non-woven fabric. 2. The nonwoven fabric according to claim 1, wherein the hydrophobic synthetic resin composite fiber is a polypropylene composite fiber. 3. The nonwoven fabric according to claim 1, wherein the hydrophobic synthetic resin composite fiber is a polyester composite fiber. 4. The nonwoven fabric according to any one of claims 1 to 3, wherein the hydrophobic synthetic resin composite fiber has a single fiber fineness of 0.5 to 30 deniers.