JP2622744B2 - Water-retaining nonwoven - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a nonwoven fabric using a polyolefin-based conjugate fiber, and more particularly, to a nonwoven fabric obtained by heat-treating the conjugate fiber and having fused contacts. And a nonwoven fabric which has excellent hydrophilicity and water retention and can be used in fields such as battery separators and wiping cloths.

[Conventional technology]

Nonwoven fabrics are known in which polyolefin-based composite fibers such as polypropylene / polyethylene and polyester / polyethylene are heat-treated and the low-melting-point components are fused to fix the contact points of the fibers. Such nonwoven fabrics are excellent in mechanical properties and chemical resistance, but are inherently hydrophobic and therefore unsuitable for applications requiring hydrophilicity such as battery separators and wiping cloths. . For the purpose of imparting hydrophilicity to polyolefin-based nonwoven fabrics, there is a method of applying a surfactant to the raw fibers or nonwoven fabric, but the surfactants run away during use, making it difficult to maintain stable hydrophilicity for a long time It is. Further, a method of mixing polyvinyl alcohol in polyolefin or imparting hydrophilicity by graft-polymerizing polyamide is also known.However, it has been put into practical use because of insufficient fiber properties or economical reasons. Absent.

[Problems to be solved by the invention]

An object of the present invention is to provide durable water retention easily and inexpensively without impairing the mechanical characteristics and chemical resistance, which are the essential characteristics of a nonwoven fabric composed of polyolefin-based composite fibers.

[Means for solving the problem]

The present inventor has conducted intensive studies to solve the above problems,
The present inventors have found that the intended purpose can be achieved by kneading a specific surfactant into the first component of the conjugate fiber, thereby completing the present invention. Further, the liquid retaining property can be further improved by kneading polyvinyl alcohol or polyamide into the first component, and by kneading the porous fine particles impregnated with the surfactant of the second component of the conjugate fiber. They have discovered that excellent water retention can be maintained for a long time, and have completed the second and third inventions of the present application.

The polyolefin-based composite fiber used in the present invention comprises crystalline polypropylene or thermoplastic polyester (hereinafter, both may be collectively referred to as a second component) and polyethylene (hereinafter, may be referred to as a first component). A fiber which is composite-spun in a sheath-core type or in a parallel type so that one component forms at least a part of the fiber surface over the length direction of the fiber. The composite ratio of both components is 70 / 30-30 / 70
The range of (volume ratio) is preferable. When the first component is less than 30/70, the adhesive strength between the fibers of the nonwoven fabric obtained by heat treatment becomes insufficient, and when the first component exceeds 70/30, the strength of the fiber itself becomes insufficient. In either case, the strength of the nonwoven fabric is undesirably reduced.

The specific surfactant used in the present invention is a monoglyceride of a fatty acid having 12 or more carbon atoms, and specific examples thereof include lauric acid monoglyceride, stearic acid monoglyceride, and oleic acid monoglyceride. These surfactants may be used alone or in a combination of two or more. First of composite fibers
The amount of the surfactant kneaded into the components is 3 to
10% (weight). If the kneading amount is less than 3%, the degree of improvement in the water retention of the obtained nonwoven fabric is low, and if it exceeds 10%, the spinnability of the conjugate fiber decreases, and both are not preferred.

The polyvinyl alcohol used in the present invention has a melt flow rate (JIS K 7210, according to condition 4 in Table 1) of 10
g / 10min or more and a saponification degree of 30 to 70% can be exemplified.

Nylon 6, nylon 6
6, a polyamide for ordinary fibers such as nylon 12, and the like. The amount of the polyvinyl alcohol or polyamide kneaded into the first component is 3 to 15% (weight). If the kneading amount exceeds 15%, phase separation occurs with the first component, and the spinnable yarn decreases, or the strength of the fusion point due to the first component in the nonwoven fabric decreases, which is not preferable.

Examples of the porous fine particles contained in the second component in the present invention include zeolite and silica gel having an average particle diameter of 5 μm or less and a particle diameter of 10 μm or more containing 5% or less. The conductive fine particles are used after being impregnated with the surfactant. The amount of the porous fine powder contained in the second component is 1 to 10% (weight), and if it exceeds 10%, the spinnability decreases, which is not preferable.

〔Example〕

The present invention will be described more specifically with reference to Examples and Comparative Examples. The definitions of terms used in each example and methods for measuring physical properties are as follows.

Spinnability: Not possible if one or more single yarn breaks occur per minute, and is indicated by x. One or more single yarn breaks occur once or less per minute for 10 minutes or more. Indicated as good, and a single thread breakage of not more than once in 10 minutes is indicated as good.

Fiber strength: In accordance with JIS L 1013 (Testing method for chemical fiber filament yarn), tensile strength measured at a gripping distance of 20 cm and a tensile speed of 20 cm / min is 2 g / d or more. , Those less than 2 g / d are not allowed and are indicated by x.

Water retention: A sample piece (10 cm × 10 cm) cut from a nonwoven fabric (having a basis weight of 60 g / m ² ) was used for dioctyl sulfosuccinate.
After immersion in 30 ml of washing water containing 0.2% and 0.1% of isopropyl alcohol for 10 minutes, the operation of suspending vertically and removing the liquid for 10 minutes is repeated 10 times. Thereafter, 500 ml of ion-exchanged water is sprayed in a suspended state, and air-dried at room temperature for 24 hours.
The air-dried sample whose weight (D) has been measured is immersed in a 30% KOH aqueous solution at room temperature for 60 minutes, then suspended vertically for 10 minutes to cut the liquid, and the weight (W) is measured. Calculated as% water retention = 100 × (WD) / D.

Durable water retention: A nonwoven fabric sample (10 cm × 10 cm) is washed in the same manner as in the water retention test, and then stored in 60 ml of ion-exchanged water at room temperature for one year. 30% KO after air drying this stored sample
Measure the water retention rate by immersion in H aqueous solution.

Examples 1 to 5 and Comparative Examples 1 to 7 A first extruder was supplied with a melt flow rate (g / 10 min, 190
C) 25 high density polyethylene and the type and amount of surfactant, polyamide or polyvinyl alcohol shown in Table 1 are supplied to the second extruder and the melt flow rate (g / 10min, 230 ° C) 35 Crystalline polypropylene is supplied, and the extrusion amount and extrusion temperature of both extruders are both 600 g / h.
r, under a condition of 250 ° C., a composite spinning is performed using a parallel type composite spinneret (100 holes) to obtain an undrawn yarn of 15 d / f, which is stretched by 3 times, and mechanically crimped (12 threads / 25mm) and cut length 5
It was cut into 1 mm to form a 5d / f staple. The staples were formed into a web with a roller card machine, and heat-treated at 140 ° C. for 3 minutes with a suction dryer to obtain a nonwoven fabric (with a basis weight of 60 g / m ² ) in which fiber contacts were fixed by fusion of high-density polyethylene. A test piece (10 cm × 10 cm) was cut from these nonwoven fabrics, and the physical properties were measured. The results are shown in Table 1.

Examples 6 and 7, Comparative Examples 8 and 9 A high-density polyethylene and monoglyceride stearate (3%) were supplied to a first extruder in the same manner as in Example 1,
The crystalline polypropylene used in Example 1 and the surfactant-containing zeolite shown in Table 2 were supplied to the second extruder, and the other procedure was the same as in Example 1 to obtain a nonwoven fabric.
The physical properties of these nonwoven fabrics are shown in Table 2.

[Effects] As is clear from the data shown in Tables 1 and 2, the nonwoven fabric of the present invention composed of a conjugate fiber containing a specific surfactant was not washed after washing 10 times with washing water. The water retention is also large, and in particular, when porous fine particles impregnated with a surfactant are contained, excellent water retention can be maintained for a long period of time. Such a nonwoven fabric excellent in water retention is suitably used as a battery separator or a wiping cloth. On the other hand, when the above-mentioned surfactant is not contained, or when it is attached to the fiber surface as a spinning oil, water retention is inferior.

Claims (2)

(57) [Claims] 1. A non-woven fabric in which contact points of a fiber obtained by heat-treating a polyolefin-based conjugate fiber are fused, wherein the first component of the conjugate fiber is a monoglyceride of a fatty acid having 12 or more carbon atoms in an amount of 3 to 10% ( (Weight) and 3-15% (weight) of polyvinyl alcohol or polyamide. 2. The water-retaining nonwoven fabric according to claim 1, wherein the second component of the conjugate fiber is impregnated with a monoglyceride of a fatty acid having 12 or more carbon atoms, and 1 to 10% by weight of porous particles.
Water-retaining nonwoven fabric contained.