JP4955278B2 - Polyester fiber for airlaid nonwoven fabric and method for producing the same - Google Patents

Description

  The present invention relates to a fiber for an air laid nonwoven fabric, and more particularly to a polyester fiber for an air laid nonwoven fabric that has an excellent amount of spinning from a screen.

  Air-laid non-woven fabrics have a uniform fiber orientation with no difference between the direction of travel and the width direction, compared to non-woven fabrics manufactured by the card method, which is widely used in the past, and are more bulky than non-woven fabrics made by papermaking. It is a field that has easy-to-use features and has recently increased production. In general, as shown in Patent Document 1, the airlaid nonwoven fabric fibers are imparted with a flat zigzag or spiral-shaped apparent crimp in order to impart bulkiness. However, if the number of crimps or the crimp rate is increased in order to improve bulkiness, the fiber opening property is reduced in the air opening process, and unopened bundles and web spots are more frequently generated. Often have poor appearance quality and poor nonwoven fabric strength. In particular, polyester fibers have higher fiber friction than polyolefin fibers as disclosed in Patent Document 1, and therefore it is difficult to increase the spinning amount. In order to increase the spinning amount, it was necessary to add a polydimethylsiloxane-based silicone leveling agent in an amount of 25% by weight or more in the oil component. Therefore, there was a tendency to be inferior in flameproofness due to the silicone-based smoothing agent.

In addition, the finer the fineness, the larger the surface area of the fibers, and the easier it is to aggregate as a fiber bundle, making it difficult to open. When a crimper of a general indentation crimping method is used, the number of crimps increases as the fineness becomes finer, so that the openability is further deteriorated. Polyester fibers, especially polyethylene terephthalate fibers, have higher rigidity than polyolefins, etc., so the degree of crimping tends to be large and the screen penetration tends to be poor. On the other hand, when the fiber length is long, The strength can be increased, but on the other hand, there is a drawback in that the passing ability of the screen is deteriorated and the production capacity is lowered. Patent Document 2 proposes a fiber having a good airlaid property by defining the ratio of the crimp height to the crimp cycle (H / L), that is, the so-called crimp inclination to be optimum for each fineness. . However, the number of crimps exemplified as an example is too small when the fineness is small, so the stuffing pressure of the push-in crimper has to be lowered, and the crimp does not crimp. It was easy to develop near crimped spots. In addition, when the fineness is large, the number of crimps is set too large. Therefore, if the stuffing pressure is increased, the back pressure is increased and the crimper is likely to rattle. Heating the tow with steam or the like before the crimper reduces the rigidity of the fiber and reduces rattling, but the crimpability increases and the H / L becomes too high, so the screen does not pass well. As a result, not only the spinning amount is reduced, but also a fuzzy fiber mass tends to be formed.
Therefore, conventionally, a polyester fiber for airlaid nonwoven fabric that is remarkably excellent in spinnability has not been proposed.

JP-A-11-81116 JP 2005-42289 A

  The present invention has been made against the background of the above-described prior art, and its purpose is for air-laid nonwoven fabrics that are extremely excellent in air laid properties, in particular, spinnability from screens, and that can produce air-laid nonwoven fabrics that are well-formed and bulky. It is to provide a polyester fiber.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have conducted constant length heat treatment of unstretched yarn of polyester fiber at a temperature higher than the glass transition point (Tg), or after stretching, By overfeeding in the temperature range, the inventors have reached the invention of a composite fiber for airlaid nonwoven fabric that has a low crimp rate and recovers its bulk performance after passing through a screen, despite a large number of crimps.

More specifically, the above-mentioned problem is a polyester fiber for air laid nonwoven fabric obtained by subjecting an undrawn yarn to a constant length heat treatment at a magnification of 0.60 to 1.2 at a temperature 10 ° C. or more higher than the glass transition point of the polyester. there, at least 80 mol% consists of polyester a repeat of alkylene terephthalate, fineness is not less 10 dtex or less, or a fiber length of more than 8 mm, elongation after the fixed-length heat treatment from 130 to 600%, the number of crimps 8.5 crest / 25 mm or more, crimp ratio / crimp number is 0.65 or less, crimp elastic modulus is 70% or more, and 180 ° C. dry heat shrinkage is −20 to 2%. The polyester fiber for air laid nonwoven fabric and the undrawn yarn taken at a spinning speed of 1500 m / min or less at a temperature higher by 10 ° C. or more than the glass transition point of the polyester at 0.60 This can be solved by the invention according to the method for producing polyester-based fibers for air-laid nonwoven fabric, characterized in that the heat treatment is performed at a constant ratio of 1.2.

  The present invention makes it possible to provide a fiber for an air laid nonwoven fabric having a high fineness or a long fiber length and having a high screenability, that is, a very high productivity and a soft and bulky texture. did. In addition, a conventional indentation type crimper can stably provide crimps, and therefore, crimps are uniform and a non-woven fabric with good texture can be produced.

Hereinafter, embodiments of the present invention will be described in detail.
First, when the embodiment is a single-component fiber, the synthetic polymer constituting the fiber is preferably a polyester having alkylene terephthalate as a main repeating component. Polyester having alkylene terephthalate as a main component is a polyester in which 80 mol% or more of the constituting repeating units are occupied by repeating alkylene terephthalate. Means alkylene terephthalate. Preferably, 90% by mole or more of the constituting repeating units are occupied by alkylene terephthalate. Moreover, it is preferable that 80 mol% or more is occupied by the repeating unit of ethylene terephthalate. Moreover, you may include what has 1 type, or 2 or more types of another dicarboxylic acid component, an oxycarboxylic acid component, and another diol component as a copolymerization unit as needed.

  In this case, examples of the dicarboxylic acid component suitable as the other copolymerization component include aromatic dicarboxylic acids such as diphenyldicarboxylic acid and naphthalenedicarboxylic acid or ester-forming derivatives thereof, dimethyl 5-sodium sulfoisophthalate, 5-sodium sulfo Examples thereof include metal sulfonate group-containing aromatic dicarboxylic acid derivatives such as bis (2-hydroxyethyl) isophthalate, aliphatic dicarboxylic acids such as oxalic acid, adipic acid, sebacic acid, and dodecanedioic acid, or ester-forming derivatives thereof. . Examples of the oxycarboxylic acid component include p-oxybenzoic acid, p-β-oxyethoxybenzoic acid, or ester-forming derivatives thereof.

  Examples of suitable diol components as the copolymerization component include ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, aliphatic diols such as neopentyl glycol, 1,4- Examples thereof include polyalkylene glycols such as bis (β-oxyethoxy) benzene, polyethylene glycol, polytrimethylene glycol, and polybutylene glycol.

  Among these, an appropriate alkylene terephthalate is selected according to the purpose to be used, and a single yarn fineness, crimping performance, and fiber length satisfying the requirements of the present invention are imparted. The fiber for air laid nonwoven fabric of the present invention, which is made of polyester having such an alkylene terephthalate as a main component, can be produced by the following method.

  The pelletized polyester is dried by a conventional method, melt-spun in a known polyester fiber spinning equipment equipped with a screw extruder or the like, and an undrawn yarn taken up at a spinning speed of 1500 m / min or less is 10 from the glass transition point of the polyester. It is obtained by a production method in which constant-length heat treatment is performed at a magnification of 0.60 to 1.2 at a temperature higher than C.degree. The spinning speed needs to be 1500 m / min or less, preferably 1300 m / min or less, and more preferably 1200 m / min or less. If it exceeds 1500 m / min, the orientation of the undrawn yarn is increased, which hinders the high adhesiveness targeted by the present invention, and increases the number of yarn breaks, resulting in poor productivity. Moreover, even if the spinning speed is slower than this range, the productivity is naturally deteriorated. The constant length heat treatment here is performed in a state where an undrawn yarn obtained by melt spinning is subjected to a draft of 0.60 to 1.2 times. Substantially, it is performed at a magnification of 1.0 so that there is no deformation in the fiber axis direction before and after heat treatment. However, when thermal elongation occurs in the undrawn yarn due to the nature of the resin, the yarn is prevented from loosening between the rollers of the drawing machine. Therefore, a draft larger than 1.0 times may be applied. Giving a draft exceeding 1.2 times is not preferable because the undrawn yarn is drawn. In addition, in the case where strong heat shrinkage occurs due to the nature of the resin, the orientation of the fiber is also increased, so that the undrawn yarn does not loosen during drawing instead of applying a draft larger than 1.0 times. It may be a draft (overfeed) of less than 0 times. However, the lower limit of the draft is about 0.60 times, and if it is less than this, it becomes difficult to suppress the elongation of the polyester fiber to 600% or less. If the temperature of the constant-length heat treatment is not higher than the glass transition point of the polyester by 10 ° C. or more, the shrinkage rate at the time of heat bonding is undesirably increased. Constant-length heat treatment may be performed on a heater plate, in hot air spray, in high-temperature air, steam spray, or in a liquid heat medium such as a silicon oil bath. It is preferable to carry out in warm water where there is no need for water.

  Another method is to use a known polyester fiber melt spinning apparatus to stretch undrawn yarn taken at a spinning speed of 1500 m / min or less at a temperature lower than the glass transition point of polyester, and then polyester glass. There is a method of performing overfeed heat treatment at a temperature of 0.50 to 0.9 at a temperature 10 ° C. or more higher than the transition point. The stretching method and the overfeed heating method are the same as the above-mentioned constant length heat treatment method, but it is particularly preferable to carry out in warm water with good heating efficiency. The draw ratio is not particularly limited as long as it is 1.1 times or more, but is preferably about 60 to 80% of the breaking elongation of the undrawn yarn. Even with such a drawing method, a low modulus composite fiber can be obtained.

  The low crimping performance (that is, the crimp ratio / the number of crimps is small) with good openability can be produced by the production method of the present invention because the polyester fiber is not substantially stretched. Therefore, the crimping rate is low due to the fact that the rigidity is substantially low, the fiber is easily deformed by the crimper box, but is not easily fixed, and is not preheated before entering the crimper box. Is difficult to increase. Therefore, it is difficult to be entangled in the shape of a hairball, it is easy to be discharged from the screen, and it is difficult to be a defect on the web. Furthermore, since the polyester fibers produced under the spinning and drawing conditions as described above often exhibit self-stretchability, the air-laid nonwoven fabric is bulky and is finished into a soft nonwoven fabric with a good texture in combination with the low modulus of the fiber itself.

  In the present invention, the ratio of the crimp ratio (CD) to the number of crimps (CN) as defined in JIS L1015: 2005 8.12.1 to 8.12.2, CD / CN is 0.65 or less. And the crimp elastic modulus (described in JIS L1015: 2005 8.12.3. The residual crimp rate is divided by the crimp rate and expressed as a percentage) to be 70% or more. The number of crimps and the crimp rate are set low, and the crimp elastic modulus (CE) is set high. By setting the number of crimps and the crimp rate low, it becomes easier to pass through the screen, and when the crimp elastic modulus is made higher, the crimp is recovered after passing through the screen. It breaks agglomeration between fibers and becomes easier to open, further improving the spinnability. The range of the number of crimps (CN) is 8.5 peaks / 25 mm or more, preferably about 9-20 peaks / 25 mm, more preferably 9.5-13 peaks / 25 mm. If CN exceeds 20 ridges / 25 mm, the entanglement between the fibers may be too strong and pills are likely to occur. Conversely, if the CN is less than 8.5 ridges / 25 mm, the fiber will pass through the screen when the fiber length becomes long. It becomes difficult to form a lump of fibers on the bundle, and the spreadability and screenability are deteriorated. When the ratio of crimp (CD) to the number of crimps, CD / CN exceeds 0.65, the peak of crimp becomes sharp and the entanglement between fibers is intensified. Become. When the crimp elastic modulus is less than 70%, the bundled fibers are likely to remain after passing through the screen. In order to achieve such a range of CD / CN ratio and CE, for example, it is preferable to carry out crimping on the composite fiber without applying temperature. Furthermore, it is more preferable to crimp the composite fiber while cooling with cold air or the like.

  Further, an object of the present invention is a composite fiber composed of a fiber-forming resin component and a heat-adhesive resin component, and is a composite fiber for an airlaid nonwoven fabric having a fineness of 10 dtex or less or a fiber length of 8 mm or more. From these values, a fiber having a small fineness or a long fiber length is generally difficult to pass through a screen provided in an air laid nonwoven fabric manufacturing apparatus. The reason is that if the fineness is small, the aggregation between the fibers is strong and it is difficult to open the fibers, and if the fiber length is long, the fibers are not rounded to the size that passes through the holes of the screen. From this tendency, if the crimping performance is further strong, the fibers are entangled and become pilled, and the screen holes are easily blocked. Moreover, when the pill ball accidentally passes the screen, it becomes easy to produce a fuzz ball-like defect and a textured spot on the web, which causes a problem in quality of the nonwoven fabric. In view of this point, the present invention is a composite fiber for obtaining a non-woven fabric having a good texture and good quality even when the fiber has a low fineness or a long fiber length, which has been problematic in terms of quality, and has a fineness of 10 It is necessary that it is not more than decitex or the fiber length is not less than 8 mm. The fineness is preferably 1 to 9 dtex or the fiber length is 9 to 50 mm, more preferably the fineness is 5 to 9 dtex or the fiber length is 9.5 to 30 mm.

  The polyester fiber of the present invention has a feature that the 180 ° C. dry heat shrinkage is −20 to 2%. Since there is little shrinkage at the time of thermal bonding, there is little shift of the bonding point at the fiber intersection, and the bonding point becomes strong. Further, when the shrinkage rate is negative, that is, a so-called self-elongation state, the fiber density in the non-woven fabric is lowered before heat bonding, and a non-woven fabric that is soft and has a good texture can be obtained by being bulky. When the shrinkage rate exceeds -2%, the fiber density increases in the direction in which the adhesive strength decreases, and thus the texture becomes hard. On the other hand, when the shrinkage rate is less than −20% and self-elongates, the adhesion point is shifted during thermal bonding, and the nonwoven fabric strength is also lowered.

  In order to achieve both the above-mentioned high breaking elongation and a low dry heat shrinkage rate, it is achieved by performing a constant length heat treatment of 0.60 to 1.2 times as a drawing draft as described above. Further, when the draft is less than 1.0 times, the so-called overfeed rate is large, specifically, the magnification is set to 0.50 to 0.90 times, and the temperature of the heat treatment is increased, the self-stretching rate tends to increase, which is preferable. . When such a treatment is performed, there is an advantage that by imparting appropriate self-stretchability, a non-woven fabric can be given a bulky finish and a fiber structure can be given a low-density finish. The preferable range of the 180 ° C. dry heat shrinkage is −11 to 1.5%, more preferably −8 to 0%.

  The cross-sectional shape may be solid or hollow, and may be an irregular cross-section such as a triangle or a star or an irregular hollow. These hollow fibers and atypical fibers can be obtained by melt spinning using a known spinneret.

  Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. In addition, each item in an Example was measured with the following method.

(1) Intrinsic viscosity (IV)
A fixed amount of the polymer was weighed and dissolved in o-chlorophenol at a concentration of 0.012 g / ml, and then determined at 35 ° C. according to a conventional method.

(2) Melting point (Tm), glass transition point (Tg)
A thermal analyst 2200 manufactured by TA Instrument Japan Co., Ltd. was used, and the temperature was measured at a temperature rising rate of 20 ° C./min.

(3) Fineness Measured by the method described in JIS L 1015: 2005 8.5.1 Method A.

(4) Strength / Elongation Measured by the method described in JIS L 1015: 2005 8.7.1. Since the fiber of the present invention tends to vary in the strength and elongation due to the efficiency of the constant length heat treatment, it is necessary to increase the number of measurement points when measuring with a single yarn. Since the number of measurement points is preferably 50 or more, here, the number of measurement points is defined as 50, which is defined as the average value.

(5) Crimp number (CN), crimp rate (CD), crimp elastic modulus (CE)
It was measured by the method described in JIS L 1015: 2005 8.12.1 to 8.12.3.

(6) 180 degreeC dry heat shrinkage rate It implemented at 180 degreeC in JISL1015: 2005 8.15 b).

(7) Web Quality Using a Dan-Webforming forming drum unit (width: 600 mm width, forming drum screen hole shape: 2.4 mm × 20 mm rectangle, opening rate: 40%), drum rotation speed 200 rpm, needle An airlaid web having a basis weight of 30 g / m 2 made of 100% short fibers taken out by unpacking the package was collected under conditions of a roll rotation speed of 900 rpm and a web conveyance speed of 30 m / min.
The appearance of the air laid web in a 30 cm square is observed and evaluated according to the following criteria.
Level 1: A fiber lump with a diameter of 5 mm or more and spotted spots (shading) are not seen, and the texture is uniform.
Level 2: The number of fiber masses having a diameter of 5 mm or more is less than 5, and spotted spots (shading) can be visually confirmed.
Level 3: 5 or more fiber masses having a diameter of 5 mm or more are seen, spotted spots (shading) are conspicuous, and the texture is uneven.

(8) Maximum spinning amount In the above-mentioned “web quality” measuring method, the fiber supply amount to the drum is increased by 2 kg / hr, and the fiber is not discharged from the drum when operated in a steady state for 5 minutes. The fiber supply amount at a level before the occurrence of clogging is defined as the maximum spinning amount.

[Example 1]
Polyethylene terephthalate (PET) with IV = 0.64 dl / g, Tg = 70 ° C., Tm = 256 ° C. was melted at 290 ° C., and a discharge rate of 0.15 g / min / Spinning was performed at a hole and a spinning speed of 1150 m / min to obtain an undrawn yarn. This was subjected to heat treatment at a constant length of 1.0 times in warm water of 90 ° C., which is 20 ° C. higher than the glass transition point of PET, and the yarn was put into an aqueous solution of an oil agent composed of lauryl phosphate potassium salt / polyoxyethylene- modified silicone = 80/20. After dipping the strip, 11 crimps / 25 mm of mechanical crimps were applied using an indentation type crimper, dried at 135 ° C., and then cut into a fiber length of 10 mm. The single yarn fineness measured with the tow before cutting was 1.2 dtex, strength 1.5 cN / dtex, elongation 350%, CN = 10.8 peak / 25 mm, CD = 3.8%, CD / CN = 0.35. CE = 79%, 180 ° C. dry heat shrinkage was −0.2%. At this time, the airlaid web quality was level 1, and the maximum spinning amount was 120 kg / hr.

[Comparative Example 1]
Example 1 except that the discharge amount was 0.40 g / min / hole, the spinning speed was 1150 m / min, and the film was stretched 2.9 times in warm water at 70 ° C. and then stretched 1.15 times in warm water at 90 ° C. Same as above. Single yarn fineness was 1.2 dtex, strength 4.8 cN / dtex, elongation 47%, CN = 12.0 mountain / 25 mm, CD = 14.5%, CD / CN = 1.20, CE = 79%. It was. The 180 ° C. dry heat shrinkage rate was + 5.1%. The airlaid web quality at this time was level 1, but the maximum spinning amount was as low as 40 kg / hr.

[Example 2]
The same procedure as in Example 1 was performed except that the amount of discharge was 0.10 g / min / hole, the spinning speed was 1150 m / min, and the heat treatment was performed 0.7 times overfeed in warm water at 90 ° C. The single yarn fineness is 1.3 dtex, strength 1.2 cN / dtex, elongation 370%, CN = 9.7 mountain / 25 mm, CD = 3.3%, CD / CN = 0.34, CE = 85%. It was. The 180 ° C. dry heat shrinkage ratio was −10.1%. The airlaid web quality at this time was level 1, and the maximum spinning amount was 115 kg / hr.

[ Reference Example 3]
The amount of discharge was 0.25 g / min / hole, spinning speed was 1100 m / min, drawn 3.0 times in warm water at 63 ° C., and further subjected to 0.65 times overfeed constant length heat treatment in warm water at 90 ° C. Same as Example 1. The single yarn fineness was 1.2 dtex, strength 3.0 cN / dtex, elongation 130%, CN = 12.0 mountain / 25 mm, CD = 12.5%, CD / CN = 1.04, CE = 64%. It was. The 180 ° C. dry heat shrinkage percentage was −7.5%. The airlaid web quality at this time was level 1, and the maximum spinning amount was 130 kg / hr.

[Example 4]
After melting to 280 ° C. using 15 mol% copolymerized polyethylene terephthalate (PETI) of isophthalic acid with IV = 0.64 dl / g, Tg = 65 ° C. and Tm = 215 ° C., a known round hole cap is used. Then, spinning was performed at a discharge rate of 0.15 g / min / hole and a spinning speed of 1150 m / min to obtain an undrawn yarn. This was subjected to heat treatment at a constant length of 1.0 in warm water at 90 ° C., 25 ° C. higher than the glass transition point of PETI. After the strip was immersed, 11 crimps / 25 mm of mechanical crimps were applied using an indentation type crimper, dried at 110 ° C., and then cut into a fiber length of 10.0 mm. The single yarn fineness measured with the tow before cutting was 1.25 dtex, strength 1.2 cN / dtex, elongation 390%, CN = 11.0 peak / 25 mm, CD = 3.2%, CD / CN = 0.29. CE = 84%. The 180 ° C. dry heat shrinkage rate was + 1.1%. The airlaid web quality at this time was level 1, and the maximum spinning amount was 110 kg / hr.

[Comparative Example 2]
Example 4 is the same as in Example 4 except that the discharge amount was 0.40 g / min / hole, the spinning speed was 1150 m / min, and the film was stretched 2.9 times in warm water at 70 ° C. and then stretched 1.15 times in warm water at 90 ° C. Same as above. The single yarn fineness was 1.3 dtex, strength 4.2 cN / dtex, elongation 55%, CN = 10.8 crest / 25 mm, CD = 13.1%, CD / CN = 1.21, CE = 63%. It was. The 180 ° C. dry heat shrinkage rate was + 4.6%. The airlaid web quality at this time was level 1, but the maximum spinning amount was as low as 30 kg / hr.

  The present invention makes it possible to provide a fiber for an air laid nonwoven fabric having a high fineness or a long fiber length and having a high screenability, that is, a very high productivity and a soft and bulky texture. did. In addition, a conventional indentation type crimper can stably provide crimps, and therefore, crimps are uniform and a non-woven fabric with good texture can be produced.

Claims (3)

A polyester fiber for airlaid nonwoven fabric obtained by subjecting an undrawn yarn to a constant length heat treatment at a magnification of 0.60 to 1.2 at a temperature 10 ° C. or more higher than the glass transition point of the polyester, wherein 80 mol% or more is alkylene It is made of polyester which is a repetition of terephthalate, has a fineness of 10 dtex or less or a fiber length of 8 mm or more, an elongation of 130 to 600% after the constant length heat treatment , a number of crimps of 8.5 crests / 25 mm or more, A polyester fiber for an airlaid nonwoven fabric having a crimp ratio / crimp number of 0.65 or less, a crimp elastic modulus of 70% or more, and a 180 ° C. dry heat shrinkage of -20 to 2%.   2. The polyester fiber for air-laid nonwoven fabric according to claim 1, wherein the cross-sectional shape of the polyester fiber is a solid round cross section, a hollow round cross section, an irregular solid cross section, or an irregular hollow cross section.   The undrawn yarn taken at a spinning speed of 1500 m / min or less is subjected to a constant length heat treatment at a magnification of 0.60 to 1.2 at a temperature higher by 10 ° C. or more than the glass transition point of the polyester. The manufacturing method of the polyester fiber for air laid nonwoven fabric of 2 description.