JPS6352145B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a highly tear-strength nonwoven fabric made of polyester and polyolefin, and a method for producing the same. More specifically, the present invention relates to a polyester nonwoven fabric using a composite yarn made of polyolefin and polyester, and a method for producing the same. Conventionally, nonwoven fabrics made of polyester long fibers are
A web made by simply opening long fibers cannot be fixed in shape as a nonwoven fabric because there is no adhesion between the fibers, so the adhesion between the fibers must be achieved by some method. The simplest method is the no-binder method, in which a long fiber web made of a single polymer is manufactured using an air sucker or tow opening method, and then the shape is fixed by heat-pressing using an embossing roll with uneven surfaces. It is being This method is applied to various materials such as polyamide (e.g. nylon 6), polyolefin (e.g. polypropylene), and some of these have already been commercialized, but in the case of polyester, especially polyethylene terephthalate, other polyamides (especially nylon 6) are used. ) has the disadvantage of a higher melting point and difficulty in thermocompression bonding. In addition, methods have been proposed in which a composite or mixed fiber is spun using a combination of high melting point and low melting point polymers during web formation. In this case, the strength of the nonwoven fabric is maintained by the filament strength of the high melting point component, and the shape fixation of the nonwoven fabric is maintained by the adhesiveness of the low melting point component. As a method of combining high-melting point polymers and low-melting point polymers, for example, there is a method of producing a mixed web of filaments consisting of each polymer alone by extruding them from separate discharge holes and bonding them under heat (Japanese Patent Publication No. 50-6583). In this method, the high-melting point polymer and the low-melting point polymer form independent filaments, which has the advantage that the structure of the spinneret for production is simple and easy to maintain. (There is also a method of blending the fibers after an air sucker), so the spinning conditions must be adjusted to match the high melting point component, which results in spinning with the low melting point polymer set higher than the optimum spinning conditions. In other words, filaments made of low melting point polymers are prone to single filament breakage and discoloration due to polymer deterioration. In addition, since low melting point polymers are used as adhesives, if they are used in large amounts, the mechanical properties such as tensile strength of the nonwoven fabric will deteriorate, and if they are used in small amounts, it will be difficult to prevent the formation of fuzz on the surface of the nonwoven fabric. It has drawbacks such as difficulty in selecting a polymer that can be spun simultaneously with the polymer and in selecting the mixing ratio. As a method of more effectively utilizing a low melting point polymer as an adhesive component, a nonwoven fabric made of composite fibers made of a high melting point polymer and a low melting point polymer is known. The cross-sectional shape of the composite fiber is a sheath-core type (Tokuko Sho
45-2345), a laminated type (Japanese Patent Publication No. 42-21318), etc. In these, a low melting point polymer that constitutes a part of the surface of the composite fiber plays a role as an adhesive between filaments. Of course, it is also possible to blend these composite systems with high melting point polymers, and this is effective in increasing the strength of the nonwoven fabric. However, in these composite spinning methods, 2
Since different types of polymers are distributed and joined within the spinneret, the shape of the spinneret is inevitably complicated, which has disadvantages such as the height of the spinneret and the complicated shape that requires time and effort to maintain. In the case of composite spinning, two extruders are always required, resulting in high production equipment costs, and the resulting nonwoven fabrics are expensive. In view of the current situation, the present inventors have completed the present invention as a result of intensive research to obtain a polyester nonwoven fabric with excellent tear strength without using a composite sheath-core type spinner as described above. It came to this. The gist of the invention is as follows. That is, the first aspect of the present invention is a nonwoven fabric made of a filament made of a blend of 97 to 80% by weight of polyester and 3 to 20% by weight of polyolefin having a melting point lower than that of the polyester by 30°C or more. In the cross section, the central part is mainly polyester, and the outer periphery is mainly polyolefin.There is no clear boundary surface at the interface, and the bond between the filaments is only by thermal fusion between the polyolefins at the outer periphery of the filaments. A polyester nonwoven fabric characterized by being immobilized. The second aspect of the present invention is a melt flow rate (ASTM-D-1238: 230℃, 2.16
extruding a mixed polymer consisting of 3 to 20% by weight of a polyolefin having a weight of 5 to 20 (as measured in kg) at a temperature 30°C or more higher than the melting point of the polyester;
The method for producing a polyester nonwoven fabric is characterized by taking it off at a speed of 3 km/min or more, opening it and making it into a web, and then thermocompression bonding at a temperature 20°C lower than the melting point of polyolefin. Hereinafter, the configuration, embodiments, and effects of the present invention will be explained in more detail. In the present invention, polyester with a high melting point and polyolefin, which is incompatible with polyester and has a low melting point, are mixed and spun, and the filaments are bonded together using the heat fusion properties of the polyolefin, thereby fixing the shape of the nonwoven fabric. By spinning the above-mentioned polyester and polyolefin under specific conditions in a combination of specific conditions, a filament having a new filament cross-sectional structure resembling a sheath-core structure in which the high melting point polyester is the core and the polyolefin is the sheath is produced. A nonwoven fabric consisting of The polyester used in the present invention may be polyethylene terephthalate, isophthalate, adipate, a copolymer of polyethylene terephthalate with isophthalic acid, adipic acid, or fumaric acid, or a blend thereof, or polybutylene terephthalate or a copolymer thereof. It's okay. In order to take advantage of the excellent heat resistance of a non-woven fabric, it is preferable that the melting point is 200°C or higher, but even if it is below 200°C, the melting point difference with polyolefin is 30°C or more, and applications that do not require heat resistance as a non-woven fabric. There is nothing wrong with using it for. The polyolefin used in the present invention is preferably polypropylene, polyethylene, etc., and isotactic polypropylene is particularly preferred. The polypropylene used here has a melt flow rate of
ASTM-D-1238: Preferably, the measured value at 230°C and 2.16 kg is in the range of 5 to 20. If the melt flow rate is less than 5, the mixing ratio of polyolefin is
If it exceeds 10% by weight, the spinnability during spinning will be extremely reduced and yarn breakage will occur frequently, which is undesirable.If the melt flow rate exceeds 20, the spinnability will not change, but the polyester and polyolefin will not phase separate. , which is not preferable because it approaches a homogeneous mixed state. The mixing ratio of polyolefin is preferably 3 to 20% by weight, particularly preferably 7 to 12% by weight from the viewpoint of spinning stability. The mixing ratio of polyolefin is determined by the stability of the blend spinning and the heat fusion properties after forming into a web, and if the mixing ratio of polyolefin is less than 3% by weight, an adhesive effect is observed during thermocompression bonding after forming into a web. do not have. In other words, the temperature of the partial press roll required to suppress fluff is not much different from that for 100% polyester. If the mixing ratio of polyolefin exceeds 20% by weight, the spinnability of the blended polymer will be extremely poor, making it difficult to spin at the high speed necessary to produce the strength necessary for a nonwoven fabric, and causing single filament breakage during spinning, which is undesirable. do not have. Naturally, even in this case, it is possible to form a web by spinning at a lower spinning speed, but this is not preferable because the polyester has not been sufficiently stretched and oriented and will shrink excessively during thermocompression bonding. Unlike conventional 100% polyester nonwoven fabrics, the present invention blends and spins polyolefin, which is not compatible with polyester and has a low melting point, and the filament obtained after spinning has polyester as a core and polyolefin as a sheath. It is characterized by its resemblance to a sheath-core structure. A combination of polymers that are compatible with polyester, for example, a combination of polyethylene terephthalate as a high melting point polymer and polyethylene terephthalate/isophthalate polymer copolymerized with 20 mol% isophthalic acid as a low melting point polymer, the melting point difference is 30°C or more. Even if
In the case of blend spinning, the rate of the transesterification reaction is fast, and because of their compatibility, they are dispersed and mixed too uniformly, so no adhesive effect can be found by mixing a low melting point polymer. This can also be seen from the fact that the melting point peaks obtained by DSC are unified. The present invention is characterized by the mixed state of polyester and polyolefin, which is not compatible with polyester and is not a homogeneously mixed and dispersed polyester/polyolefin blend as has been known so far. It is neither a uniformly mixed and dispersed system nor a sheath-core structure in which a core is made of polyester and a sheath is made of polyolefin. The filament of the present invention is characterized by a cross-sectional structure in which the central part of the filament is mainly composed of polyester and the outer peripheral part is mainly composed of polyolefin, and the filament has no clear boundary surface. FIG. 1 shows a typical cross-sectional structure of the filament of the present invention. As shown in FIG. 1, the central part of the filament is mainly made of polyester, and the outer peripheral part is made of polyolefin, and there is no clear boundary between them. Further, the outer peripheral portion has a sea-island structure in which polyolefin is a sea and polyester is an island, and the polyester is dispersed in a striped manner in the longitudinal direction of the filament. When this filament structure is made into a nonwoven fabric, the adhesion between the fibers necessary for fixing the shape is due to the thermal fusion of the polyolefin present on the outer periphery or surface of the fibers, so that the mechanical properties of the nonwoven fabric, especially the tensile strength, are improved. It is maintained by the polyester present in the center and the polyolefin containing polyester in the stripes present at the outer periphery, and the tear strength is maintained by heat fusion between the fibers of the polyolefin, and when compared with a nonwoven fabric made of 100% polyester,
Particularly high tear strength. On the other hand, compared to conventional nonwoven fabrics made of filaments with a polyester core and a polyolefin sheath, the texture is completely different, especially due to the effect of the streaky polyester on the outer periphery. That is, the slimy feeling characteristic of polyolefin is eliminated, and the bonded portions between filaments are separated into smaller pieces by streak-like non-bonded points, resulting in a flexible nonwoven fabric. The nonwoven fabric obtained by the present invention is uniformly mixed (in terms of weight) from a macroscopic perspective, and can be composed of filaments with relatively uniform denier and yarn properties, but as usual in blend spinning, the composition changes over time. However, in the case of spunbond nonwoven fabrics, for example, the denier of the resulting filaments varies, and even if the filaments have different diameters, a high-strength nonwoven fabric can be obtained without any problem. Filament denier from 0.5 denier to 15
Since it can be freely changed to denier or higher, it has many uses as a filter as a non-woven fabric.
In addition, by changing the blend ratio and single fiber denier, the size of the filter cavity can be changed freely, making it easy to manufacture various grades. Of course, the basis weight can be set arbitrarily, but it is also possible to laminate webs of different compositions or laminate with films. In the method for producing a polyester nonwoven fabric of the present invention, the spunbond production apparatus may be an apparatus having one extruder (for example, the apparatus described in Japanese Patent Publication No. 37-4993). It is easy to maintain because it does not require a complex spin head with two extruders like the polyester/polyolefin sheath-core type composite fiber manufacturing equipment, and it can also handle extruded waste and leftover edges cut to a certain width. The waste can be recycled in a granulator and used in blends up to a certain limit without changing quality, so there is no loss and there are great benefits. The weight ratio (%) of polyester and polyolefin is 97-80:3-20
It is necessary to be within the range of . The above weight ratio is mainly due to spinnability, and if it is blended in excess of 20% by weight, single filament breakage occurs frequently and high-speed indexing is difficult, making it impossible to obtain a high-strength nonwoven fabric.
The polyolefin used in the present invention needs to have a melting point 30°C or more lower than that of polyester. This temperature difference in melting point is necessary in order to fix the shape of the web, and because only the polyolefin contributes to the adhesive action between the filaments during heat-sealing, and does not cause the adhesive action between the polyester filaments. Considering the heat resistance after forming into a nonwoven fabric, a combination of polyethylene terephthalate and polypropylene is most preferable. The melt spinning temperature is usually set at a temperature 20°C or more higher than the melting point, but in the case of blend spinning of polyester and polyolefin, it is necessary to spin at a temperature slightly higher than when spinning polyester alone, that is, at least 30°C higher than the melting point of polyester. Below this value, stable spinning index cannot be obtained. Melt flow rate (ASTM-D-
1238 (measured value at 230° C. and 2.16 kg) is preferably 5 or more, but in the case of polyolefins with a melt flow rate of less than 5, 15 to 20% by weight is not preferable because spinning stability is poor. Melt flow rate is 5~
20, particularly preferably in the range of 5 to 10, the filament of the present invention has a structure similar to a sheath-core composite fiber. Although it is better to change the spinneret used for spinning slightly depending on the denier of the filament, it is usually preferable to use a diameter in the range of 0.25 to 0.50 mm for stable spinning. The polymer discharged from the spinning hole is indexed and thinned by an air sucker or rotating roll, but at this time, high-speed indexing is required. In the case of ordinary polyethylene terephthalate, the index is set at 5 Km/min to suppress heat shrinkage during heat fusion, but in the case of blend spinning,
When spun at high speeds of 3 Km/min or higher, a structure resembling a sheath-core structure is obtained. This is completely different from the conventionally known uniformly dispersed fibers. 4.5Km/mi in terms of fiber heat shrinkability
It is particularly preferable to perform spinning with an index of n or more to obtain a high-strength nonwoven fabric, but during spinning it is preferable to use cold air to prevent filaments from fusing. 3Km/mi
In the case of low spinning speed below n, the conventional polyester or polyolefin becomes a filament in which it is uniformly dispersed, and the desired highly tear-strength nonwoven fabric consisting of phase-separated filaments cannot be obtained. It is surprising and unexpected that the features of the present invention have made it possible to create a nonwoven fabric made of filaments with a completely new structure. That is, polyester and polyolefin, which are not essentially compatible,
They are uniformly mixed in a molten state, subjected to shear in a spinneret nozzle, thinned by a large pulling force, cooled and solidified to obtain a filament with a special structure suitable for the nonwoven fabric of the present invention. After spinning, the fibers are indexed and thinned using an air satcher or a rotating roll (if indexed using a rotating roll, the fibers are further spread using an air saturker), and then made into a web on a collector. The web is thermocompressed using a known calendar roll or embossing roll, but at this time it is necessary to thermocompress at a temperature that is 20° C. lower than the melting point of the polyolefin. This is necessary to prevent fuzzing (suppressing fuzzing) as a nonwoven fabric. It is preferable to insert a static mixer into at least a portion of the polymer passage within the spinning machine, as this is effective in uniformly mixing the polyolefin and polyester within the filament. That is, in the present invention, polyester and polypropylene are once uniformly mixed and then spun using their phase separation properties, and as the mixing progresses, the dispersed streaks become thinner. Although the effects of the present invention can be sufficiently achieved by mixing only a chip blend using an ordinary extruder, it is preferable to use a static mixer in order to control the degree of mixing. A feature of the present invention is that only when indexed at high speed during spinning, a phase-separated structure similar to a filament having a polyester core and a polyolefin sheath is exhibited. This is due to the inner layer of fibers that occurs during high-speed indexing.
This shows that the difference in shear rate and cooling rate of the outer layer contributes to the viscosity and phase separation of polyester and polyolefin, and this new filament structure has a component ratio of 97 to 80% by weight of polyester and 3% by weight of polyolefin. ~20% by weight, and use a polyolefin with a melt flow rate of 5 to 20. This is achieved by extruding at a temperature 30° C. or more higher than the melting point of polyester and drawing at a speed of 3 Km/min or more. This will be explained in more detail in Examples below. Example 1 Using polyethylene terephthalate (intrinsic viscosity 1.0) as the polyester and polypropylene K1008 manufactured by Chitsuso Corporation (melt flow rate 10) as the polyolefin, they were chipped at a weight ratio of 95/5, melted in a single screw extruder, and then manufactured by Kenix Co., Ltd. The spinning temperature is 290℃ from the spindle of 0.30φ x 48 holes through a conduit with static mixer 5 emerents inserted.
It was discharged at a rate of 1 g/min per hole. At this time, an air suture car was installed at a position 130 cm below the spindle.
The filament was indexed and thinned at a pressure of 5.0 Kg/cm ² G, and a 42 cm wide web with a basis weight of 50 g/m ² was collected.
At this time, the filament was a single yarn of 1.9 denier, and the spinning speed was equivalent to 4.7 Km/min. The web was heat-pressed at 180°C using an embossing roll with a textured pattern. The tensile strength of the obtained nonwoven fabric was measured using the JIS-L-1068 strip method, and the result was 13.2 kg in the vertical direction and 6.9 kg in the horizontal direction at a width of 3 cm, and the tear strength by the benzylum method was 1.2 kg. Example 2 In the same manner as in Example 1, polyethylene terephthalate (PET) with an intrinsic viscosity of 0.64 and Chitsuso's polypropylene (PP) S5056 (melt flow rate 5) were used for spinning and thermocompression bonding, with the weight mixing ratio of polypropylene being changed. The results are shown in Table 1.

【table】

[Table] Example 3 Same as Example 2, polyethylene terephthalate and Chitsuso polypropylene (S5056) were used9
The mixture was kneaded and extruded using an extruder at a weight ratio of 0/10. As a comparative example, one was used which was produced by indexing at a low speed of 1000 m/min, continuously stretching to 2.9 times, and then opening with an air sucker.

[Table] Temperature Example 4 A similar experiment was conducted using polyethylene terephthalate (PET) with an intrinsic viscosity of 0.64, polypropylene (PP) manufactured by Chitsuso Corporation, and general grades K1014, K1008, and K1800 (melt flow rate 3.5 to 20). All weight ratios are PFT/PP (88/12). The experimental results are shown in Table 2. (Weight 50g/m ² )

[Table] Example 5 Using polyethylene terephthalate as the polyester and polypropylene S5056 made by Chitsuso as the polyolefin, and setting the weight mixing ratio of polypropylene to 10%, a nonwoven fabric according to the present invention and a nonwoven fabric with a sheath-core composite structure as a comparative example were prepared in Example 1. The physical properties of the obtained nonwoven fabric are shown in Table 3.

[Table] As is clear from Table 3, the physical properties of the mechanical strength of the nonwoven fabric are the same as those of conventional nonwoven fabrics obtained from sheath-core structural filaments, and the texture is less slimy and soft to the touch. ,
This shows very favorable results.

[Brief explanation of the drawing]

FIG. 1 is an enlarged view showing the cross-sectional structure of a filament constituting the nonwoven fabric of the present invention.

Claims (1)

[Scope of Claims] 1. A nonwoven fabric made of a filament made of a blend of 97 to 80% by weight of polyester and 3 to 20% by weight of polyolefin having a melting point lower than that of the polyester by 30°C or more, the cross-section of the filament being The central part of the filament is mainly polyester, and the outer peripheral part is mainly polyolefin, and there is no clear boundary surface at the interface, and the polyester is dispersed in the polyolefin in the filament length direction in the filament length direction, A polyester nonwoven fabric characterized in that the bond between the filaments is fixed only by heat fusion between polyolefins on the outer periphery of the filaments. 2 97 to 80% by weight of polyester and 3 to 20% by weight of polyolefin, which has a melting point 30°C or more lower than the polyester and has a melt flow rate (ASTM-D-1238: measured at 230°C and 2.16 kg) of 5 to 20. A mixed polymer is extruded at a temperature of 30°C or more higher than the melting point of polyester, taken off at a speed of 3 km/min or more, opened and made into a web, and then thermocompressed at a temperature of 20°C or more lower than the melting point of polyolefin. A method for producing a polyester nonwoven fabric characterized by: 3. The manufacturing method according to claim 2, characterized in that polypropylene is used as the polyolefin. 4. The manufacturing method according to claim 2, wherein the mixing ratio of polyolefin is 7 to 12% by weight. 5. The manufacturing method according to claim 2, wherein the take-up speed is 4.5 Km/min or more.