JPH09296347A - Nonwoven fabric and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a nonwoven fabric having no problem of occurrence of an eluted substance and a smell, excellent in uniformity and strength and elongation characteristics. SOLUTION: This nonwoven fabric comprises a polyolefin having <1wt.% of a weight fraction of a low-molecular weight substance having <=2,000 molecular weight in a weight molecular-weight distribution curve, <1wt.% of a weight fraction of a high-molecular weight substance having >=1,000,000mol.wt., and 50,000-200,000 weight-average molecular weight as a raw material. The nonwoven fabric is produced by using the raw material by a spun-bond method or a melt flow method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-woven fabric having good uniformity, less generation of effluents and odors in a solvent, and excellent strength / elongation property, and a method for producing the non-woven fabric. The present invention relates to a non-woven fabric suitable for medical fluids, hygiene materials, wipers, battery separators, packaging materials, and the like, and a manufacturing method thereof.

[0002]

2. Description of the Related Art A spunbond method, a melt blow method, a flash spinning method and the like can be used to obtain long fiber nonwoven fabrics, and it is possible to produce long fiber nonwoven fabrics having various fiber diameters.
By the way, in the production of long-fiber nonwoven fabrics, in order to obtain finer fibers or to improve productivity, studies have been made to reduce the melt viscosity of a polymer as a raw material of fibers. However, when the method of reducing the polymer viscosity by heating is adopted, there is a problem that the spinning tension in the spinning wire is lowered, so that the CV% of the fiber diameter is increased and the yarn breakage is increased.

When the polymer molecular weight is lowered in order to reduce the viscosity of the polymer, the fibers contain a large amount of molecules having a considerably low molecular weight, and when the obtained nonwoven fabric product is dipped in a liquid such as a solvent or water. It is often seen that a significant amount of eluate is found in the non-woven fabric and odor is generated from the nonwoven fabric. Such non-woven fabrics have problems in safety or filtrate quality, which limits their use.

On the other hand, for example, Japanese Patent Application Laid-Open No. 1-156561 discloses an invention for obtaining a nonwoven fabric for a filter by using a raw material polymer having a small amount of a high molecular weight component and a narrow molecular weight distribution. Even with a raw material polymer called a rheology (CR) resin, there are problems that the CV% of the fiber diameter becomes large, the problem of yarn breakage becomes serious, and the strength and elongation characteristics deteriorate.

[0005]

SUMMARY OF THE INVENTION In consideration of the above circumstances, the present invention provides a non-woven fabric which is uniform and has good strength and elongation characteristics without the problem of elution and odor generation, and the non-woven fabric is produced with high productivity. The provision of a method of doing this is listed as an issue.

[0006]

As a raw material, the nonwoven fabric of the present invention has a molecular weight in a weight molecular weight distribution curve of 2000.
When a polyolefin having a low molecular weight of less than 1%, a high molecular weight of less than 1% and a weight average molecular weight of 50,000 to 200,000 is used. It has the gist.

The non-woven fabric of the present invention has a weight fraction of less than 1% in the polyolefin after being made into a non-woven fabric, the low molecular weight substance having a molecular weight of 2000 or less in the weight molecular weight distribution curve,
A high molecular weight substance having a molecular weight of 1,000,000 or more has a weight fraction of less than 1% and a weight average molecular weight of 50,000 to 200,000.
Most preferred for solving the problem. Further, the raw material polyolefin is a polyolefin polymerized using a metallocene catalyst, and the weight molecular weight distribution curve of the raw material polyolefin has one or more peaks in the range of molecular weight 10,000 to less than 70,000, and 70,000. A polyolefin having one or more peaks in the range of molecular weight of 10,000 to less than 70,000 in the weight molecular weight distribution curve, and a molecular weight of 7 A mixture of polyolefins having one or more peaks in the range of 10,000 to 1,000,000 is a preferred embodiment of the present invention.

Further, the nonwoven fabric of the present invention is 20% at 60 ° C.
The evaporation residue in the solvent after immersing the nonwoven fabric in ethanol aqueous solution, 95 ° C. water and 95 ° C. 4% acetic acid aqueous solution respectively and leaching for 30 minutes is 2 ppm or less in weight ratio with respect to the weight of the polymer. It is preferable that it is possible to secure the safety in conformity with the standards of the Food Sanitation Law, and to suppress the generation of odor with a small amount of eluate. A CV% of the fiber diameter of 50% or less is also a recommended requirement in that a non-woven fabric having uniformity can be obtained. Where C
V% is a value obtained by dividing the standard deviation of the fiber diameter by the arithmetic mean value of the fiber diameter.

In the production method according to the present invention, as a raw material, a low molecular weight substance having a molecular weight of 2000 or less on a weight molecular weight distribution curve has a weight fraction of less than 1% and a molecular weight of 100.
Using a polyolefin having a high molecular weight of 10,000 or more and a weight fraction of less than 1% and a weight average molecular weight of 50,000 to 200,000,
It is characterized by being manufactured by a spun bond method or a melt blow method.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention discloses a polyolefin-based non-woven fabric and a method for producing the non-woven fabric. The greatest feature of the present invention is that the raw material of the non-woven fabric is polyolefin whose molecular weight in the weight-molecular weight distribution curve is 2000 or less. The weight fraction of a certain low molecular weight substance is less than 1%, the weight fraction of a high molecular weight substance having a molecular weight of 1,000,000 or more is less than 1%, and the weight average molecular weight is 50,000 to 200,000.

The weight average molecular weight of the raw material polyolefin is
If it is less than 50,000, thread breakage will occur more often, and conversely 20
When it exceeds 10,000, it is not preferable because the fibers are difficult to be thinned and the productivity is not improved. The weight average molecular weight and the weight molecular weight distribution curve / weight fraction in the present invention are determined by gel permeation chromatography (GPC: Wate).
What was measured using the rs150-C ALC / GPC) apparatus was adopted.

In the present invention, in the weight molecular weight distribution curve of the raw material polyolefin, the weight fraction of the low molecular weight substance having a weight molecular weight of 2000 or less must be less than 1%. This is because this low molecular weight substance is likely to be an eluate due to the solvent and may cause the odor of the nonwoven fabric. It is also necessary that the weight fraction of the high molecular weight substance having a weight molecular weight of 1,000,000 or more is less than 1%. This is because if the raw material contains a large amount of high-molecular-weight substances exceeding 1,000,000, the elongation of the fibers is hindered and the productivity cannot be increased.

In the present invention, the polyolefin after being made into a non-woven fabric, like the raw material polyolefin, has a weight fraction of less than 1% and a molecular weight of 1,000,000 or more in the low molecular weight product having a molecular weight of 2000 or less in the weight molecular weight distribution curve. It is preferable that the weight fraction of the high molecular weight product is less than 1% and the weight average molecular weight is 50,000 to 200,000. The small difference in the molecular weight characteristics between the raw material and that after being made into a non-woven fabric means that the polymer does not undergo thermal decomposition so much in the non-woven fabric manufacturing process, and in order to obtain a non-woven fabric with excellent safety. The above requirements are important. That is, the raw material polymer used in the present invention has good melt extensibility and can be spun at a relatively low temperature, so that thermal decomposition of the polymer during the spinning process could be suppressed.

The raw material polyolefin in the present invention is preferably a polymer polymerized by using a metallocene catalyst. When a metallocene catalyst is used, the molecular weight of the polymer can be controlled and the distribution can be sharpened, so that it is easy to suppress the amount of low molecular weight substances or high molecular weight substances in the raw material polyolefin to less than 1%. .

In the present invention, as the raw material polyolefin,
When a molecular weight distribution curve having one or more peaks in the molecular weight range of 10,000 to less than 70,000 and one or more peaks in the range of 70,000 to 1,000,000 is used, the strength and elongation are It has also been found that a non-woven fabric having excellent properties and a small amount of elution can be manufactured with extremely good productivity without causing yarn breakage. This is because the polyolefin having a peak in the molecular weight range of 10,000 to less than 70,000 serves to develop the melt extensibility required when the molten polymer is thinned to form fibers, and the peak is in the range of 70,000 to 1,000,000. It is considered that this is because the polyolefin contained does not deteriorate the productivity and improves the strength / elongation property of the nonwoven fabric.

The above-mentioned action is difficult to obtain with a polymer having a weight-molecular weight distribution curve having only one peak at a molecular weight of 2,000 to 1,000,000. A polymer obtained using a metallocene catalyst generally exhibits a sharp molecular weight distribution having one peak, but if the molecular weight range is made too narrow, the spinning tension becomes too small and thread breakage easily occurs. Further, in the case of a polymer having a small weight average molecular weight, which has only one peak on the relatively low molecular side, the resulting nonwoven fabric has a small tensile strength, and its use is significantly restricted.
On the other hand, a polymer with a large weight average molecular weight, which has only one peak on the high molecular side, has sufficient strength for the non-woven fabric and reduces problems with odors and eluates, but if the polymer viscosity is high, spinning / thinning Since the melt extensibility at that time is insufficient, it is difficult to expect improvement in productivity. Of course, even if there is only one peak, there is no problem in applying the present invention if the polymer viscosity is appropriate.

For the above reasons, the most preferable raw material in the present invention has one or more peaks in the molecular weight range of 10,000 to less than 70,000, and even in the range of 70,000 to 1,000,000.
It is a polyolefin showing a weight molecular weight distribution curve having three or more peaks. Then, in order to obtain such a polyolefin, a metallocene catalyst is used, and a polyolefin having one or more peaks in the range of the molecular weight of 10,000 to less than 70,000 and a molecular weight of 70,000 to 100 in a weight-molecular weight distribution curve.
It is the easiest to synthesize polyolefins having one or more peaks in the range of 100,000 and then mix the two. The mixing ratio is not particularly limited, but it is preferable from the viewpoint of productivity that the polyolefin having one or more peaks in the molecular weight range of 10,000 to less than 70,000 be 50% by weight or more, but if it is too large, the strength decreases. Therefore, it is recommended to select appropriately according to the application. The raw material polyolefin may be mixed with a twin-screw extruder or may be chip-blended with a single-screw extruder during spinning. of course,
It is also possible to blend two or more polyolefins. Moreover, the peroxide (peroxide) is 3 to 10%.
A method of mixing the masterbatch polymer containing the compound and decomposing the component on the high molecular weight side of the weight molecular weight is also preferable.

"Having one or more peaks" means having two or more inflection points. In FIG.
The polyolefin polymerized by the conventional Ziegler-Natta catalyst is shown in FIG.
The weight molecular weight distribution curve of the polyolefin obtained by synthesizing the polyolefin having a peak in the range of less than 70,000 and the polyolefin having the peak in the range of 70,000 to 1,000,000 in molecular weight is shown. In addition, this polyolefin is an image view of the one used in Example 2 described later. The inflection points are indicated by black dots a.

As the polyolefin used as a raw material in the nonwoven fabric of the present invention, general-purpose polypropylene and polyethylene, which have excellent chemical resistance and are inexpensive, and copolymers containing them are preferable, and polybutene, polymethylpentene, polybutylene, and the like are used. Copolymers containing can also be used.

Since the non-woven fabric of the present invention contains few low molecular weight substances having a molecular weight of 2000 or less, it is possible to easily pass the elution test of "Standards for packaging and containers" of the Food Sanitation Law. This elution test method is the evaporation when the solvent is evaporated after leaching for 30 minutes at 95 ° C (20% ethanol aqueous solution is 60 ° C) with three kinds of leaching solutions of 20% ethanol aqueous solution, water and 4% acetic acid solution. The residue is 30 ppm or less in weight ratio with respect to the weight of the polymer. Since the non-woven fabric of the present invention contains few low molecular weight substances having a molecular weight of 2000 or less, which is one of the causes of the eluate, and can meet more severe conditions, the evaporation residue was set to 2 ppm or less as a preferable criterion. A small amount of evaporation residue means that the non-woven fabric has little eluate when immersed in water or another solution, and the odor of the non-woven fabric is transferred to drinking water or alcoholic beverages, and impurities are eluted. It is particularly suitable as a filter for liquids such as drinking water and alcoholic beverages because it is not mixed in. When the non-woven fabric is used as a liquid filter, the amount of evaporation residue for each solution is preferably 1.5 ppm or less, more preferably 1.0 ppm or less.

Further, in the present invention, the nonwoven fabric preferably has a CV% of the fiber diameter of 50% or less, more preferably 30%.
% Or less, particularly preferably 20% or less. Generally, when the viscosity of the polymer is lowered, the tension of the spinning wire is lowered, so that the spinning becomes unstable and the CV% of the fiber diameter, which is the standard for the variation of the fiber diameter, becomes large. In particular, when a melt-blowing method is adopted as a spinning method, a polymer having a considerably low viscosity is used, so that the CV% of the fiber diameter is often 50 to 100%. However, when the raw material polyolefin specified in the present invention is used. The CV% is 50% or less. When the fiber diameter CV% is large, the uniformity of the nonwoven fabric is reduced, the physical properties vary greatly, and the frequency of yarn breakage is high, which causes a problem in lint-free property when used for wipers, filters, etc. Occurs. Therefore, in the present invention, the CV% of the preferable fiber diameter is
As a result, 50% or less was adopted.

The method for producing the nonwoven fabric of the present invention is carried out by using the raw material polyolefin specified in the present invention, that is, a low molecular weight substance having a molecular weight of 2000 or less in the weight molecular weight distribution curve, having a weight fraction of less than 1% and a molecular weight of 1,000,000. The above high molecular weight product has a weight fraction of less than 1% and a weight average molecular weight of 5
If a polyolefin of 10,000 to 200,000 is used, its production method is not particularly limited, but it is possible to adopt a spunbond method or a melt blow method which can obtain a non-woven fabric having good dimensional stability by self-bonding or entanglement treatment of fibers. Recommended.

[0023]

The following examples are for clarifying the present invention, and the present invention is not limited thereto. The physical properties in the examples were measured by the following methods.

(A) Fiber diameter CV% From a magnified photograph of 1000 times (scanning electron microscope), 20
CV% was obtained by reading the fiber diameter of 0 or more fibers and dividing the standard deviation by the arithmetic mean value and displaying the value in percentage.

(B) Tensile Strength Tensile strength in the longitudinal direction (machine line direction) was measured (machine direction) according to the general long fiber nonwoven fabric test method of JIS L1906-1994. The sample was cut into a rectangle of 2 × 10 cm and measured at a test length of 5 cm, a gripping width of 2 cm, and a crosshead speed of 100% / min.

(C) Evaporation residue amount (quantification of elution amount) It was measured according to the evaporation residue test method of the Ministry of Health and Welfare Notification No. 20 of February 16, 1982. Considering that the operating temperature may exceed 100 ° C, and that the ethanol solution has the highest amount of evaporation residue, the nonwoven fabric is immersed in a 20% ethanol solution and kept at 60 ° C for 30 minutes. The amount of evaporation residue was compared.

(D) Spinning condition and sheet pinhole Regarding the spinning condition, the yarn breakage condition in the vicinity of the spinning nozzle was visually observed by illuminating light from the rear. The sheet pinhole was observed from the back of the non-woven sheet by illuminating uniform light of a fluorescent lamp and observing the presence or absence of the pinhole.

Examples 1-3 Weight average molecular weight polymerized with metallocene catalyst 62,0
Polypropylene of 00 (Polymer A: 0.1% by weight of a low molecular weight substance having a molecular weight of 2000 or less, 0% by weight of a high molecular weight substance having a molecular weight of 1,000,000 or more) and a weight average polymerized using a metallocene catalyst. Polypropylene chips with a molecular weight of 107,000 (Polymer B: 0% by weight of low molecular weight substances with a molecular weight of 2000 or less and 0% by weight of high molecular weight substances with a molecular weight of 1,000,000 or more) were mixed at different weight ratios, and Kneading and extruding with a shaft extruder and spinning by melt blow method 3
A non-woven fabric having a basis weight of 0 g / m ² was produced. The polymer extrusion temperature is 250 ° C., 1.0 g / min per single hole is discharged, traction air temperature: 300 ° C., air supply pressure: 0.7
It was set to kg / cm. The conditions and results are shown in Table 1. Note that the significant figures in Table 1 are unified into two digits.

Comparative Examples 1-2 Polypropylene having a weight average molecular weight of 134,000 polymerized by a Ziegler-Natta catalyst (polymer C: molecular weight 20)
1.8% by weight of a low molecular weight substance of 00 or less, molecular weight 10
Melt-blowing method was carried out by using a high-molecular-weight material having a weight fraction of 0,000 or more (3.7% by weight) alone (Comparative Example 1) and an equivalent mixture of Polymer C and Polymer A used in Example 1 (Comparative Example 2). Was spun into a non-woven fabric. The extrusion conditions are as in Example 1.
The same as above.

[0030]

[Table 1]

As is clear from Table 1, the non-woven fabrics obtained in Examples 1 to 3 have a small average fiber diameter and excellent strength / elongation. It was possible to manufacture with good productivity without generating pinholes. It was also found that the amount of evaporation residue was extremely small. In particular, the non-woven fabrics obtained in Examples 2 and 3 in which the polymers A and B are blended can be stably produced without any yarn breakage, are excellent in strength and texture, and are uniform non-woven fabrics without defects such as pinholes. I was able to get it. The nonwoven fabric of Example 1 has a slightly low tensile strength, but this is because the average fiber diameter is extremely small, and there are few practical problems.

On the other hand, in Comparative Examples 1 and 2, when the discharge amount per single hole was about 0.3 g / min, it was possible to manufacture a nonwoven fabric having a small average fiber diameter of about 2 μm, but it is the same as the Example. At a large discharge rate of about 1.0 g / min, the occurrence of yarn breakage became remarkable, and the average fiber diameter also became considerably large. The obtained non-woven fabric had many defects such as pinholes, and the strength was low in consideration of the fact that the fiber diameter was large. Furthermore, the problem that the amount of eluate is large was also clarified.

[0033]

The long-fiber nonwoven fabric of the present invention is a long-fiber non-woven fabric having excellent uniformity and excellent strength and elongation characteristics with little odor and little amount of substances eluted in a solvent. Therefore, it is extremely suitable for liquid filters for soft drinks, wipers, battery separators, packaging materials, medical non-woven fabrics, sanitary materials, heat insulating materials and the like. Further, the production method of the present invention enables efficient production of a nonwoven fabric.

[Brief description of drawings]

FIG. 1 is a weight molecular weight distribution curve of general polypropylene.

FIG. 2 is a weight molecular weight distribution curve of the blended polypropylene used in the examples.

[Explanation of symbols]

 a Inflection point

Claims (8)

[Claims] 1. As a raw material, a weight fraction of a low molecular weight substance having a molecular weight of 2000 or less in a weight molecular weight distribution curve is less than 1%, and a weight fraction of a high molecular weight substance having a molecular weight of 1,000,000 or more is less than 1%, and A non-woven fabric using a polyolefin having a weight average molecular weight of 50,000 to 200,000. 2. The polyolefin after being made into a non-woven fabric,
The weight fraction of a low molecular weight substance having a molecular weight of 2000 or less in a weight molecular weight distribution curve is less than 1%, the weight fraction of a high molecular weight substance having a molecular weight of 1,000,000 or more is less than 1%, and the weight average molecular weight is 50,000 to 20. The non-woven fabric according to claim 1, which is 3. The nonwoven fabric according to claim 1, wherein the raw material polyolefin is a polyolefin polymerized by using a metallocene catalyst. 4. The weight-molecular weight distribution curve of the raw material polyolefin has one or more peaks in the molecular weight range of 10,000 to less than 70,000, and also has one or more peaks in the range of 70,000 to 1,000,000. The nonwoven fabric according to any one of claims 1 to 3, which is a product. 5. A polyolefin having a weight-molecular weight distribution curve having one or more peaks in the molecular weight range of 10,000 to less than 70,000 and a molecular weight of 70,000 to 100.
The nonwoven fabric according to claim 4, which is a mixture of polyolefins having one or more peaks in the range of 100,000. 6. A 20% aqueous ethanol solution at 60 ° C., 95
The non-woven fabric was dipped in water of 4 ° C and 4% acetic acid solution of 95 ° C for 30 minutes, and the evaporation residue in the solvent after leaching for 30 minutes was 2 ppm in weight ratio with respect to the weight of the polymer.
The nonwoven fabric according to any one of claims 1 to 5, which is as follows. 7. The CV% of the fiber diameter of the fibers in the nonwoven fabric is 50.
The nonwoven fabric according to any one of claims 1 to 6, which is at most%. 8. A method for producing the non-woven fabric according to claim 1, wherein the raw material has a weight fraction of less than 1% of a low molecular weight substance having a molecular weight of 2000 or less in a weight molecular weight distribution curve, A high molecular weight substance having a molecular weight of 1,000,000 or more has a weight fraction of less than 1% and a weight average molecular weight of 50,000 to 2
A method for producing a non-woven fabric, which is produced by a spun bond method or a melt blow method using 0,000 polyolefin.