JP4856435B2 - Thermal adhesive composite fiber and method for producing the same - Google Patents

Description

  The present invention relates to a heat-adhesive conjugate fiber having high adhesive strength after heat-bonding and extremely low heat shrinkage during heat-bonding, and a method for producing the same.

Thermal adhesive composite fibers represented by the core-sheath type thermal adhesive composite fiber with the thermal adhesive resin component as the sheath and the fiber-forming resin component as the core are used for the fiber web by the card method, airlaid method, wet papermaking method, etc. After forming, the heat-adhesive resin component is melted with a hot air dryer or hot roll to form an interfiber bond, so there is no need to use an adhesive with an organic solvent as a solvent, and there is little discharge of harmful substances to the environment. In addition, the advantages of improving the production speed and the associated cost reduction are great, and it has been widely used mainly for fiber structures such as hard cotton and bed mats and nonwoven fabrics.
Among these, with the aim of further improving the strength of the nonwoven fabric and improving the nonwoven fabric production speed, studies have been made on improving the low-temperature adhesiveness or adhesive strength of the heat-adhesive conjugate fiber.

  In Patent Document 1, a ternary copolymer composed of propylene-ethylene-butene-1 is used as a sheath component, crystalline polypropylene is used as a core component, and these are composites of sheath component / core component = 20/80 to 60/40. It is disclosed that a heat-bondable conjugate fiber having a higher adhesive strength than conventional ones can be obtained by drawing a composite undrawn yarn obtained by spinning at a ratio of less than 3.0. However, such a fiber has a low draw ratio so that a uniform tension is not applied between the single yarns, the variation in neck deformation is large, and fineness unevenness is generated. was there.

  In Patent Document 2, the orientation index of the heat-adhesive resin component is set to 25% or less and the orientation index of the fiber-forming resin component is set to 40% or more by a high speed spinning method. A heat-fusible conjugate fiber that is fused and has a low heat shrinkage rate is disclosed. However, in the high speed spinning method, the current short fiber manufacturing process has a low yield in terms of both process stability and cost performance, and there are still many difficult issues for commercial production.

  Furthermore, neither patent document 1 nor patent document 2 discloses an example in which the core component is polyethylene terephthalate (hereinafter referred to as PET). By using PET as the core component, the melting point of the core component can be sufficiently higher than that of the sheath component compared to the case where the core component is polypropylene (hereinafter referred to as PP), so that the thermal bond strength can be further improved. In addition, it has a high rigidity in terms of bulkiness and has the potential to obtain a bulkier nonwoven fabric. However, even if low-magnification drawing or just undrawn yarn as in Patent Document 1 is applied, the orientation of the core component The heat shrinkage was large due to insufficient crystallinity. Furthermore, when high-speed spinning as in Patent Document 2 is applied, the temperature of the sheath component must be increased in accordance with the melting temperature of the core component, and the yarn is severely broken due to deterioration of the sheath polymer and large spinning draft. There was an easy problem.

JP-A-6-108310 JP 2004-218183 A

  The present invention has been made against the background of the above-mentioned prior art, and its purpose is to produce polyethylene terephthalate as a fiber-forming resin component, and to produce a bulky nonwoven fabric or fiber structure having high adhesive strength and low heat shrinkage. It is in providing a heat-adhesive conjugate fiber.

  As a result of intensive studies to solve the above problems, the present inventors have used a crystalline thermoplastic resin having a melting point 20 ° C. or more lower than that of PET as the thermoadhesive resin component, and spinning at 1800 m / min or less. By subjecting the undrawn yarn taken up at a speed to a constant length heat treatment at a magnification of 0.5 to 1.2 at a temperature higher than both the glass transition point of the thermal adhesive resin component and the glass transition point of the fiber-forming resin component, The inventors have invented a heat-adhesive conjugate fiber comprising PET having a high adhesive strength and a sufficiently low heat shrinkage ratio as a fiber-forming resin component.

  More specifically, the above-mentioned problem is a composite fiber composed of a fiber-forming resin component and a heat-adhesive resin component, the fiber-forming resin component is made of polyethylene terephthalate (PET), and the heat-adhesive resin component is a fiber forming component. Thermally adhesive property, characterized by comprising a crystalline thermoplastic resin having a melting point 20 ° C. or more lower than that of the conductive resin component, having a breaking elongation of 130 to 600% and a 120 ° C. dry heat shrinkage of −10 to 5% The composite fiber and the undrawn yarn taken at a spinning speed of 1800 m / min or less are 0.5 to 1.1 at a temperature higher than both the glass transition point of the heat-adhesive resin component and the glass transition point of the fiber-forming resin component. This can be solved by the invention according to the method for producing a heat-adhesive conjugate fiber, characterized in that the heat treatment is performed at a constant length.

  Since the heat-adhesive conjugate fiber of the present invention uses PET as a fiber-forming resin component, it has bulkiness and high nonwoven fabric strength compared to the conventionally proposed high-adhesion and low heat-shrinkable heat-adhesive conjugate fibers. In order to further increase the adhesive strength, it is possible to set the thermal bonding temperature high, so that it is possible to produce a thermal bonding nonwoven fabric and a fiber structure at a high speed. Furthermore, since a process such as high-speed spinning is not required, the energy cost is low, and the loss of duffing switching and the number of yarn breaks are small, and the benefits of improving yield are great.

Hereinafter, embodiments of the present invention will be described in detail.
First, the present invention is a composite fiber composed of a fiber-forming resin component and a heat-adhesive resin component, the fiber-forming resin component is PET, and a crystalline thermoplastic resin having a melting point 20 ° C. lower than PET is heat-adhesive. It is a heat-adhesive conjugate fiber used as a resin component. Here, if the difference in melting point between PET and the heat-adhesive resin component is less than 20 ° C., the fiber-forming resin component is also dissolved in the step of melting and adhering the heat-adhesive resin component, and a high-strength nonwoven fabric or fiber structure is obtained. This is not preferable because it cannot be performed. This composite fiber is obtained by using a known composite fiber melting method or a die, obtaining an undrawn yarn at a spinning speed of 1800 m / min or less, and further comprising a PET glass transition point (hereinafter referred to as Tg) and a thermoadhesive resin component. It can be obtained by heat treatment under a constant length at a temperature higher than both of Tg of the thermoplastic crystalline resin, preferably higher by 10 ° C. or higher. In many cases, it becomes Tg (about 70 ° C.) of PET. Therefore, constant length heat treatment is performed at a temperature of 75 ° C., preferably 80 ° C. or more. If the temperature of the constant-length heat treatment is lower than this range, the shrinkage rate at the time of thermal bonding of the composite fiber increases, which is not preferable.

  The constant length heat treatment here is performed in a state in which an undrawn yarn obtained by melt spinning is drafted 0.5 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 the heat treatment. However, if the undrawn yarn has thermal stretchability due to the nature of the resin, the yarn is slackened between the rollers of the drawing machine. In order to prevent this, 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. Also, in the case of heat shrinkage derived from the properties of the resin and from the spinning and drawing conditions, it is the direction that increases the orientation of the fiber, so the undrawn yarn is being drawn during drawing instead of applying a draft larger than 1.0 times. The draft (overfeed) may be less than 1.0 times that does not cause looseness. The lower limit of the draft that does not sag is about 0.5 times. Below this, most polymer systems are not sufficiently contracted and tend to sag.

  Constant-length heat treatment may be performed on a heater plate, hot air spray, in high-temperature air, steam spray, or in a liquid heat medium such as a silicone oil bath. It is preferable to carry out in warm water that does not require washing.

  The spinning speed needs to be 1800 m / min or less, preferably 1500 m / min or less, and more preferably 1300 m / min or less. If it exceeds 1800 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 form of the heat-adhesive composite fiber of the present invention is a composite fiber in which a fiber-forming resin component and a heat-adhesive resin component are bonded in a so-called side-by-side manner, but the fiber-forming resin component is a core component heat-adhesive. It may be a core-sheath type composite fiber having a resin component as a sheath component. However, a core-sheath type composite in which the fiber-forming resin component is the core component and the heat-adhesive resin component is the sheath component in that the heat-adhesive resin component can be arranged in any direction perpendicular to the fiber axis direction. It is preferably a fiber. Examples of the core-sheath type composite fiber include concentric core-sheath type composite fiber and eccentric core-sheath type composite fiber.

  For the thermoadhesive resin component (sheath component), it is necessary to select a crystalline thermoplastic resin. In the case of an amorphous thermoplastic resin, the molecular chains that are oriented during spinning are greatly shrunk as they become non-oriented simultaneously with melting. Preferable examples of the crystalline thermoplastic resin include polyolefin resins and crystalline copolyesters.

  Examples of the polyolefin resin include polyolefins such as polypropylene, high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, or crystalline propylene copolymer composed of propylene and other α-olefins, or Α-olefins such as ethylene, propylene, butene-1, or pentene-1, and unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, citraconic acid, or hymic acid, or these And modified polyolefins made of a copolymer with at least one comonomer such as an unsaturated compound having a polar group such as an acid anhydride or an acid anhydride.

  Examples of crystalline copolyesters include, as an acid component, the main dicarboxylic acid component is terephthalic acid or an ester-forming derivative thereof, and the main diol component is ethylene glycol, diethylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol. Or alkylene terephthalate obtained from a combination of 1 to 3 of these derivatives to aromatic dicarboxylic acids such as isophthalic acid, naphthalene-2,6-dicarboxylic acid, 5-sulfoisophthalic acid salt, adipic acid, sebacic acid Aliphatic dicarboxylic acid such as cyclohexamethylene dicarboxylic acid, alicyclic dicarboxylic acid such as cyclohexamethylene dicarboxylic acid, ε-hydroxycarboxylic acid, ω-hydroxycarboxylic acid and the like, polyethylene glycol, polytetramethylene glycol And alicyclic diols such as cyclohexamethylene dimethanol and the like, which are copolymerized so as to exhibit the target melting point.

  When the fiber-forming resin component is PET, the heat-adhesive resin component in the present invention may be in the form of a polymer blend of two or more crystalline thermoplastic resins whose melting point is 20 ° C. or lower than PET, A crystalline thermoplastic resin having a melting point difference of less than 20 ° C. with respect to an amorphous thermoplastic resin or PET may be contained within a range that does not significantly impair adhesion and low heat shrinkability.

  The elongation at break of the heat-adhesive conjugate fiber needs to be in the range of 130 to 600%, and preferably in the range of 170 to 450%. If the elongation at break is less than 130%, the orientation of the thermal adhesive component is high, so that the adhesiveness is inferior and the strength of the nonwoven fabric is reduced. On the other hand, if it exceeds 600%, the fiber strength becomes substantially too small to increase the strength of the heat-bonded nonwoven fabric.

  The heat-adhesive conjugate fiber of the present invention is characterized by a 120 ° C. dry heat shrinkage of −10 to 5%. 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 5%, the fiber density increases in the direction in which the adhesive strength decreases, and the texture becomes hard. On the other hand, when the shrinkage rate falls below -10% and becomes self-extending, 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 constant length heat treatment of about 0.5 to 1.2 times as a drawing draft as described above. Further, when the draft is less than 1.0 times, so-called overfeed rate is increased or the temperature of the relaxation heat treatment is increased, the self-extension rate tends to increase. If it exists, it will be finished bulky, and if it is a fiber structure, there exists an advantage which can provide the characteristic finished to low density. The preferable range of the 120 ° C. dry heat shrinkage is −8 to −0.2%, more preferably −6 to −1%.

  The fiber cross section is preferably a core-sheath cross section or an eccentric core-sheath cross section. In the side-by-side type, the effect aimed by the present invention can be somewhat reduced in the direction in which the shrinkage is large in the web state due to the development of three-dimensional crimp and the adhesive strength is also reduced. Further, it may be a solid fiber or a hollow fiber, and is not limited to a round cross section, but is an elliptical cross section, a multileaf cross section such as a 3-8 leaf cross section, or a polygon such as a 3-8 octagon. An irregular cross section such as a cross section may be used.

  The fineness may be selected according to the purpose and is not particularly limited, but is generally used in a range of about 0.01 to 500 dtex. This fineness range can be achieved by setting the diameter of the die through which the resin is discharged during spinning to a predetermined range.

  The composite ratio of the fiber-forming resin component and the heat-adhesive resin component is not particularly limited, but is selected according to the requirements for the strength, bulk, and heat shrinkage of the target nonwoven fabric or fiber structure. The ratio of the fiber-forming resin component / the heat-adhesive resin component is preferably about 10/90 to 90/10 by weight.

  In particular, in order to increase the adhesive strength, the heat adhesive resin component of the sheath component preferably has a melt flow rate (hereinafter referred to as MFR) in the range of 1 to 15 g / 10 min. MFR has a side surface indicating the fluidity of the polymer at the time of heat melting (the larger the fluidity, the better the fluidity) and a side surface indicating the molecular weight of the polymer (the higher the molecular weight, the smaller the molecular weight). It has been said that unless the value is larger than a certain value, the fluidity of the sheath component at the thermal bonding temperature is insufficient and a strong thermal bonding point is not formed. In many cases, those having an MFR of 20 g / 10 min or more (190 ° C., under 21.18 N, in the case of polypropylene under 230 ° C., 21.18 N) are used, but according to the composite fiber of the present invention, MFR Is less than 20 g / 10 min, the fluidity at the bonding temperature is good and the molecular weight can be increased, so that the strength of the resin itself can be increased, so that a strong thermal bonding point can be formed. The effect is the same even if the MFR is 20 g / 10 min or more, but it is preferable that the MFR is 15 g / 10 min or less to make the best use of the characteristics of the present invention. However, if MFR is smaller than 1, it is not preferable because it is inferior in sufficient spinnability in melt spinning, and spinning breakage is likely to occur. Therefore, a preferable MFR range is 1 to 15 g / 10 min, and a more preferable range is 2 to 12 g / 10 min. A person skilled in the art can select an appropriate resin for each component that meets the above range by measuring the MFR of each resin component before the composite fiber is manufactured.

  The form of the fiber can take any form such as multifilament, monofilament, staple fiber, chop, and tow depending on the purpose of use. When the heat-adhesive conjugate fiber of the present invention is used as a staple fiber that requires a carding process, the number of crimps may be within an appropriate range in order to impart good card-passability to the conjugate fiber. desirable.

  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) Melt flow rate (MFR)
Polypropylene resin was measured according to JIS-K7210 condition 14 (230 ° C., 21.18 N), and other resins were measured according to JIS-K7210 condition 4 (190 ° C., 21.18 N). The melt flow rate is a value measured using a pellet before melt spinning as a sample.

(3) 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.

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

(5) 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.

(6) Number of crimps and crimp rate Measured by the method described in JIS L 1015: 2005 8.12.1 to 8.12.2.

(7) 120 degreeC dry heat shrinkage rate It implemented at 120 degreeC in JISL 1015: 2005 8.15 b).

(8) Shrinkage ratio of web area Hot air dryer (Satake Chemical Machinery Co., Ltd.) maintained a circular non-heat treated web having a basis weight of 25 g / m 2 and a 30 cm diameter made of 100% heat-adhesive conjugate fiber formed by airlaid method at a predetermined temperature. Heat treatment is carried out by leaving in a hot air circulating constant temperature dryer (41-S4) manufactured by Co., Ltd. for 2 minutes, and the area shrinkage is determined from the sheet area A0 before shrinkage and the area A1 after shrinkage by the following formula.
Area shrinkage (%) = [(A0−A1) / A0] × 100

(9) Nonwoven fabric strong (adhesive strength)
A test piece having a width of 5 cm and a length of 20 cm was cut from the web after the heat treatment and measured at a gripping interval of 10 cm and an elongation rate of 20 cm / min. The adhesive strength was a value obtained by dividing the tensile breaking force by the weight of the test piece.

[Example 1]
Polyethylene terephthalate (PET) with IV = 0.64 dl / g, Tg = 70 ° C., Tm = 256 ° C. for the core component (fiber-forming resin component), MFR = 8 g / 10 min for the sheath component (thermal adhesive resin component), Using isotactic polypropylene (PP) with Tm = 165 ° C. (Tg is less than 0 ° C.) and melting to 290 ° C. and 260 ° C., respectively, using a known core-sheath composite fiber die, core: sheath = A composite fiber was formed so as to have a weight ratio of 50:50 and spun at a discharge rate of 1.0 g / min / hole and a spinning speed of 900 m / min to obtain an undrawn yarn. This was subjected to a constant length heat treatment 1.0 times in warm water at 90 ° C., which is 20 ° C. higher than the glass transition point of the core component, to an aqueous solution of an oil agent consisting of lauryl phosphate potassium salt / polyoxyethylene modified silicon = 80/20. After immersing the yarn, a mechanical crimp of 11 pieces / 25 mm was applied using a stuffing box, dried at 90 ° C., and then cut into a fiber length of 5.0 mm. The single yarn fineness measured with the tow before cutting was 11.0 dtex, strength 1.3 cN / dtex, elongation 170%, 120 ° C. dry heat shrinkage −1.9%.
This was an airlaid web, and the heat shrinkage of the web area at 180 ° C. was 0%, and the nonwoven fabric strength was 9.5 kg / g.

[Comparative Example 1]
A fiber was obtained in the same manner as in Example 1 except that constant length heat treatment of undrawn yarn in warm water was not performed. The single yarn fineness measured with the tow before cutting was 11.1 dtex, strength 1.2 cN / dtex, elongation 261%, 120 ° C. dry heat shrinkage 25.3%.
This was an airlaid web, and the area shrinkage of the web when thermally bonded at 180 ° C. was 25%, and the nonwoven fabric strength was 8.3 kg / g.

[Comparative Example 2]
A fiber was obtained in the same manner as in Example 1 except that the discharge rate was 2.2 g / min / hole and the undrawn yarn was drawn 2.2 times in warm water. The single yarn fineness measured with the tow before cutting was 11.0 dtex, strength 2.5 cN / dtex, elongation 73%, 120 ° C. dry heat shrinkage 8.2%.
This was an airlaid web, and the area shrinkage of the web bonded by heat at 180 ° C. was 6.5%, and the nonwoven fabric strength was 1.3 kg / g.

[Comparative Example 3]
A fiber was obtained in the same manner as in Example 1 except that the discharge amount was 1.5 g / min / hole and the undrawn yarn was drawn 1.5 times in warm water. The single yarn fineness measured with the tow before cutting was 10.8 dtex, strength 1.8 cN / dtex, elongation 122%, 120 ° C. dry heat shrinkage 18.9%.
This was made into an airlaid web, and the shrinkage ratio of the web area thermally bonded at 180 ° C. was 14%, and the nonwoven fabric strength was 5.1 kg / g.

[Example 2]
Polyethylene terephthalate (PET) with IV = 0.64 dl / g, Tg = 70 ° C., Tm = 256 ° C. for the core component (fiber-forming resin component), MFR = 20 g / 10 min for the sheath component (thermal adhesive resin component), After using high density polyethylene (HDPE) with Tm = 133 ° C. (Tg is less than 0 ° C.) and melting at 290 ° C. and 250 ° C., respectively, using a known core / sheath composite fiber die, core: sheath = 50 A composite fiber was formed so as to have a weight ratio of 50 and spun at a discharge rate of 0.73 g / min / hole and a spinning speed of 1150 m / min to obtain an undrawn yarn. This was subjected to a constant length heat treatment 1.0 times in warm water at 90 ° C., which is 20 ° C. higher than the glass transition point of the core component, to an aqueous solution of an oil agent consisting of lauryl phosphate potassium salt / polyoxyethylene modified silicon = 80/20. After dipping the yarn, 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 5.0 mm. The single yarn fineness measured with the tow before cutting was 6.5 dtex, strength 0.8 cN / dtex, elongation 445%, 120 ° C. dry heat shrinkage −1.6%.
This was an airlaid web, and the area shrinkage of the web bonded by heat bonding at 150 ° C. was 0%, and the nonwoven fabric strength was 7.9 kg / g.

[Example 3]
Polyethylene terephthalate (PET) with IV = 0.64 dl / g, Tg = 70 ° C., Tm = 256 ° C. for the core component (fiber-forming resin component), MFR = 8 g / 10 min for the sheath component (thermal adhesive resin component), 80% by weight of isotactic polypropylene (PP) with Tm = 165 ° C. (Tg is less than 0 degree), MFR = 8 g / 10 min, Tm = 98 ° C. (Tg is less than 0 degree) with maleic anhydride-methyl acrylate graft copolymer Known by using pellets blended with 20% by weight of polymerized polyethylene (m-PE; maleic anhydride = 2% by weight, methyl acrylate = 7% by weight) and melting at 290 ° C. and 250 ° C., respectively. A composite fiber was formed using a core-sheath composite fiber base of 5:50:50, and a discharge rate of 0.73 g / min / hole, spinning speed. It was spun at 1150m / min, to obtain an unstretched yarn. This was subjected to a constant length heat treatment 1.0 times in warm water at 90 ° C., which is 20 ° C. higher than the glass transition point of the core component, to an aqueous solution of an oil agent consisting of lauryl phosphate potassium salt / polyoxyethylene-modified silicon = 80/20. After dipping the yarn, 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 5.0 mm. The single yarn fineness measured with the tow before cutting was 11.1 dtex, strength 1.2 cN / dtex, elongation 150%, 120 ° C. dry heat shrinkage −4.0%.
This was an airlaid web, and the area shrinkage of the web bonded by heat at 180 ° C. was 0%, and the nonwoven fabric strength was 11.4 kg / g.

[Example 4]
Polyethylene terephthalate (PET) with IV = 0.64 dl / g, Tg = 70 ° C., Tm = 256 ° C. for the core component (fiber-forming resin component), MFR = 40 g / 10 min for the sheath component (thermal adhesive resin component), Using Tm = 152 ° C. and Tg = 43 ° C. crystalline copolyester (co-PET-1: isophthalic acid 20 mol% -tetramethylene glycol 50 mol% copolymer polyethylene terephthalate), the temperatures become 290 ° C. and 255 ° C., respectively. After melting as above, a composite fiber is formed using a known core-sheath composite fiber die so as to have a weight ratio of core: sheath = 50: 50, discharge amount 0.71 g / min / hole, spinning speed 1250 m. Spinning at / min, an undrawn yarn was obtained. This was subjected to a constant length heat treatment 1.0 times in warm water at 90 ° C., which is 20 ° C. higher than the glass transition point of the core component, to an aqueous solution of an oil agent consisting of lauryl phosphate potassium salt / polyoxyethylene modified silicon = 80/20. After the yarn was immersed, 11 crimps / 25 mm of mechanical crimps were applied using an indentation type crimper, dried at 90 ° C., and then cut into a fiber length of 5.0 mm. The single yarn fineness measured with the tow before cutting was 5.7 dtex, the strength was 1.0 cN / dtex, the elongation was 400%, and the 120 ° C. dry heat shrinkage was −3.5%.
This was an airlaid web, and the area shrinkage of the web bonded by heat at 180 ° C. was 0%, and the nonwoven fabric strength was 11.0 kg / g.

[Comparative Example 4]
Polyethylene terephthalate (PET) with IV = 0.64 dl / g, Tg = 70 ° C., Tm = 256 ° C. for the core component (fiber-forming resin component), MFR = 40 g / 10 min for the sheath component (thermal adhesive resin component), Amorphous copolymerized polyester (co-PET-2: isophthalic acid 30 mol% -diethylene glycol 8 mol% copolymerized polyethylene terephthalate) having a Tg of 63 ° C. (no melting point) is used, so that the temperatures become 290 ° C. and 250 ° C., respectively. Then, a composite fiber is formed using a known core-sheath composite fiber die so as to have a weight ratio of core: sheath = 50: 50, discharge amount 0.71 g / min / hole, spinning speed 1250 m / Spinning was performed at min to obtain an undrawn yarn. This was subjected to a constant length heat treatment of 1.0 times in warm water at 65 ° C., and after the yarn was immersed in an aqueous solution of an oil agent composed of lauryl phosphate potassium salt / polyoxyethylene modified silicon = 80/20, an indentation type crimper was Using 9 pieces / 25 mm of mechanical crimps, dried at 55 ° C., and then cut to a fiber length of 5.0 mm. The single yarn fineness measured with the tow before cutting was 5.7 dtex, the strength was 1.5 cN / dtex, the elongation was 180%, and the dry heat shrinkage at 120 ° C. was 75%.
When this was made into an airlaid web and thermally bonded at 180 ° C., the shrinkage was large, and neither the web area shrinkage rate nor the nonwoven fabric strength could be measured.

  Since the heat-adhesive conjugate fiber of the present invention uses PET as a fiber-forming resin component, it has bulkiness and high nonwoven fabric strength compared to the conventionally proposed high-adhesion and low heat-shrinkable heat-adhesive conjugate fibers. In order to further increase the adhesive strength, it is possible to set the thermal bonding temperature high, so that it is possible to produce a thermal bonding nonwoven fabric and a fiber structure at a high speed. Further, since a process such as high-speed spinning is not required, the energy cost is low, and the loss of duffing switching and the yarn breakage are small, so that the yield is improved.

Claims (7)

  A composite fiber comprising a fiber-forming resin component and a heat-adhesive resin component, wherein the fiber-forming resin component is made of polyethylene terephthalate, and the heat-adhesive resin component has a melting point that is 20 ° C. lower than the fiber-forming resin component A heat-adhesive conjugate fiber comprising a heat-resistant thermoplastic resin, having a breaking elongation of 130 to 600% and a 120 ° C. dry heat shrinkage of −10 to 5%.   The heat-adhesive conjugate fiber according to claim 1, wherein the fiber-forming resin component is a core-sheath conjugate fiber in which the core component is a core component and the heat-adhesive resin component is a sheath component.   The heat-adhesive conjugate fiber according to claim 1, wherein the heat-adhesive resin component is a polyolefin resin.   The heat-adhesive conjugate fiber according to any one of claims 1 to 2, wherein the heat-adhesive resin component is a crystalline copolyester.   The heat-adhesive conjugate fiber according to any one of claims 1 to 4, wherein a melt flow rate (MFR) of the heat-adhesive resin component is 1 to 15 g / 10 min.   An undrawn yarn taken at a spinning speed of 1800 m / min or less is determined at a magnification of 0.5 to 1.2 under a temperature higher than both the glass transition point of the heat-adhesive resin component and the glass transition point of the fiber-forming resin component. 6. The method for producing a thermoadhesive conjugate fiber according to any one of claims 1 to 5, wherein a long heat treatment is performed.   The method for producing a thermoadhesive conjugate fiber according to claim 6, wherein the constant-length heat treatment is performed in warm water.