JPS6327445B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to heat-adhesive fibers, and particularly to heat-adhesive fibers for polyethylene terephthalate (abbreviated as PET) fibers. Its purpose is to provide excellent thermal adhesion and
When used mixed with PET fibers or used alone to produce fiber aggregates such as dry and wet nonwoven fabrics, it has stable processability and the resulting fiber aggregates have excellent properties such as high heat resistance. The present invention provides a heat-adhesive composite spun fiber that provides quality and versatility. In recent years, polyester fibers such as PET have played an increasingly important role in the textile field, especially in the nonwoven fabric field. Along with this, the bonding method for fiber aggregates such as non-woven fabrics has been changed to thermal bonding from the viewpoint of production efficiency and energy saving, and the form of the adhesive component is fibrous, that is, there is a strong demand for thermal bonding fibers for polyester. ing. Conventionally, a common method for bonding polyester fibers such as PET is to use a polyester polymer similar to PET in chemical structure, solubility parameters, etc. as an adhesive. All of them are in the form of solvents or powders, and many copolymerized polyesters have been proposed as the polymer. However, the use of such copolymerized polyesters as adhesive fibers is difficult because these polymers generally have high adhesiveness, easy solubility, and meltability, but they also have low melting points, low secondary transition points, and amorphous properties. ,
For this reason, stable processability cannot be obtained in ordinary fiberizing processes such as spinning, drawing, crimp, etc., and also in nonwoven fabricizing processes. In other words, in the spinning and drawing process, the spun yarns easily stick or fuse, making it impossible to obtain satisfactory fibers. Even if it were to be made into fibers, albeit imperfectly,
In the subsequent crimping and cutting process as well as in the nonwoven process, problems such as sticking between single yarns and poor carding occur. Furthermore, the heat resistance of the obtained fiber aggregate is determined by the melting point of the copolyester, and therefore is not good. At the same time, its solvent resistance, chemical resistance, and weather resistance are also poor. On the other hand, it is possible to consider measures such as lowering the degree of modification of the copolymerized polyester, but this will definitely reduce the adhesiveness and will not provide any solution. On the other hand, Japanese Patent Application Laid-open No. 142866/1986 specifies PET fibers with low density and low degree of orientation.
Since PET fiber exhibits fusion properties at temperatures several to several tens of degrees Celsius lower than its melting point, it is commonly used to
A method for bonding fibers to nonwoven fabrics, etc., has been proposed. In this method, even if there is a slight difference in physical properties between the bonding fiber and the fiber to be bonded, the same PET is used, so the nonwoven fabric, etc. after bonding is formed only from PET, so it has very excellent physical properties. Since it is fibrous and can be thermally bonded, it can be said that the bonding operation is relatively easy and has some merits. However, the PET fiber that can be adhered by this method has low crystallinity and low degree of orientation, and is generally an undrawn spun yarn of PET or a cold drawn yarn thereof. Therefore, the thermal shrinkage of the fibers is large, on the order of several tens of percent, and in the thermal bonding process, the biggest obstacle when adhering nonwoven fabrics is change in the shape of the nonwoven fabric due to thermal shrinkage, and special consideration is required to prevent this. Therefore, as an adhesion method, a heat-pressing type such as a calendar roller method or an emboss roller method must be used. Therefore, the nonwoven fabrics that can be obtained are limited to those with a small bulk and a hard texture that lacks flexibility.
There was a problem in that the benefits of using heat-adhesive fibers were halved. The inventors of the present invention have made extensive studies in view of the drawbacks of these conventional adhesive fibers, and as a result have been able to provide an ideal thermally adhesive fiber that is extremely effective for specific applications in the form of a composite fiber. . That is, the composition of the heat-adhesive composite spun fiber of the present invention is a fiber-forming polybutylene terephthalate-based polymer A in which 80% or more of the repeating units are butylene terephthalate, and polyethylene that exhibits heat-fusibility at a temperature below the melting point of the polymer. Polymer A, which is composite-spun with terephthalate-based polymer B, such that polymer B occupies at least a portion of the outer surface of the composite spun fiber, and at a spinning speed of less than 1100 m/min.
is substantially in an oriented crystallized state, polymer B is substantially in an unoriented amorphous state, and the composite ratio of polymer A and polymer B is A/B = 20/80 to 80/20.
(weight ratio) of undrawn composite spun fibers,
It is characterized by having a cutting elongation of 250% or less and a dry heat shrinkage rate of 8% or less at 150°C to 210°C. The fiber-forming polybutylene terephthalate polymer A used in the present invention, terephthalic acid or its derivative as the main acid component, and butylene glycol as the main glycol component, and 80 mol% of the repeating units are butylene terephthalate. say. A particularly preferred polyester is polybutylene terephthalate (hereinafter abbreviated as PBT) consisting only of butylene terephthalate.
It is. The reason for using this method is that PBT has a very fast orientation crystallization speed compared to PET, and it can be substantially oriented and crystallized just by winding it at a normal spinning speed of about 1000 m/min without hot stretching. be. Substantially oriented means that the birefringence Δn≧100×10 ⁻³ is measured using a sodium lamp (wavelength 589 mμ) equipped with a Beretsk compensator on a polarizing microscope. Substantially crystallized means that the temperature is 0°C to 10°C at a rate of 10°C/min in nitrogen using a differential scanning calorimeter (DSC).
It has already crystallized to such an extent that no exothermic peak due to crystallization appears when the temperature is raised to 300°C. Such a PBT undrawn spun yarn has a small dry heat shrinkage rate of 5% or less up to its melting point, and also has a breaking elongation of 250% or less, which is small compared to a spun yarn at a normal spinning speed. Therefore, when bonding is performed using the heat-adhesive fibers of the present invention, good form stability is achieved in fiber aggregates such as nonwoven fabrics. However, in fiber-forming PBT polymer A, butylene terephthalate is a repeating unit of 80
If it is less than mol%, the degree of modification of this polymer is too large and the normal spinning speed (spinning speed of 2000 m/min or less) is required.
In this case, the oriented crystallization rate decreases, and substantial oriented crystallization does not occur in the state of undrawn spun yarn, making it impossible to obtain fibers with a desired low shrinkage rate and cutting elongation of 250% or less.
Therefore, 80 mol% or more of the repeating units in the fiber-forming PBT polymer A must be butylene terephthalate. On the other hand, polyethylene terephthalate-based polymer B is most preferably polyethylene terephthalate consisting essentially of ethylene terephthalate units, but terephthalic acid and ethylene glycol are copolymerized with about 3 mol% or less of diethylene glycol or a small amount of other ethylene glycol derivatives. things are also used. And "substantially no oriented crystallization" means that the birefringence Δn≦50×10 ^-3 or less and an exothermic peak due to crystallization appears when the temperature is increased at a rate of 10°C/min in nitrogen using DSC. means. Only under the above conditions does PET fiber reach a temperature above its melting point.
PET exhibits the unique property of exhibiting mutual fusion and thermal adhesion even at temperatures 10°C to 80°C lower. On the contrary, ordinary crystallization with advanced orientation
PET drawn yarn or PET undrawn spun yarn spun at a spinning speed of 3,000 to 4,000 m/min or higher no longer exhibits fusion properties at temperatures below the melting point, and is no longer intended by the present invention. Next, in the cross-sectional structure of the conjugate fiber of the present invention, since the PET polymer B must come into contact with other fibers as an adhesive component, it must occupy at least a portion of the outer surface of the conjugate fiber. A more preferable composite fiber cross section is a core-sheath structure in which PET-based polymer B, which is an adhesive component, surrounds a fiber-forming PBT-based polymer in a sheath shape. In addition, PET-based polymer B and PBT-based polymer A are used to control adhesion.
They may be laminated side by side or in a multi-layered manner. Naturally, when PET-based polymer B no longer forms the outer surface of the fiber, thermal adhesion is no longer exhibited. The reason why the composite ratio of PBT polymer A and PET polymer B is A/B = 20/80 to 80/20 (weight ratio) is that the PET polymer, which is an adhesive component,
If the amount is less than % by weight, the adhesiveness, especially the adhesiveness with other PET fibers, will decrease and become impractical. On the other hand, 20% fiber-forming PBT polymer
If the weight is below the weight, even if this polymer component has low elongation and low shrinkage, its properties will not be fully expressed as a composite spun fiber, and when thermal bonding treatment is performed using this polymer component, the adhesive fiber will not be as strong as the adhesive fiber. Special measures are required to prevent the nonwoven fabric from changing its shape due to heat shrinkage, and the advantages of fibrous adhesive fibers are lost. From this point of view, the preferred range of composite ratio is A/B=20/
80~80/20 and preferably A/B=50/50~
It is 30/70. Next, an important point of the present invention is that the elongation at break of the heat-adhesive fiber of the present invention is 250% or less. When trying to make a non-woven fabric using the fibers of the present invention, this may occur at a low blending rate, but if the blending rate is high or the fibers of the present invention are 100%, if the elongation is over 250%, neps and needles may occur during carding. Troubles such as fibers sinking into the fabric occur frequently, making operational implementation impossible. It is preferably 200% or less. Further, it is necessary that the heat-adhesive fiber of the present invention has a dry heat shrinkage rate of 8% or less at 150°C to 220°C. The reason for this is that the PET polymer, which is the adhesive component of the heat-adhesive fiber of the present invention, exhibits its unique heat-bonding properties at a temperature of 150°C to 160°C or higher, so the heat-adhesive treatment is usually carried out at a temperature of 150°C or higher. carried out and also fiber-forming
Since the PBT polymer melting start temperature is 220 to 230°C, the process is carried out at a temperature of 220°C or lower, and therefore the dry heat shrinkage rate is at a level that does not pose a particular problem when bonding nonwoven fabrics in this temperature range, that is, 8% or less. The heat shrinkage rate must be the same. This is preferably less than 5% and more preferably less than 3%. Next, we will describe the method for producing the thermoadhesive composite spinning of the present invention, in which one component is PBT-based polymer A and the other component is PET using a conventionally known composite spinning device.
By using an arbitrary composite spinning nozzle as the system polymer B, a product having an arbitrary composite cross-sectional structure can be easily produced. The fibers can be produced by simply winding the fibers at a spinning speed of less than 1100 m/min, and there is no need for spinning at higher speeds or drawing with wet heat or dry heat. In fact, it is not preferable to carry out these operations because it promotes oriented crystallization of the PET-based polymer B, which is an adhesive component, and reduces the thermal fusion properties. Since no stretching step is required in this way, there is an advantage that the fiber cost can be reduced. The heat-adhesive composite spun fiber of the present invention obtained by the above method can be used in any form such as a filament, a staple, or a short cut, and can be used as a wet/dry nonwoven fabric or for other purposes. In particular, the heat-adhesive composite spun fiber of the present invention has very small thermal shrinkage at the heat-bonding temperature, so if 100% of it is used, it is blended with PET fiber in the amount necessary for bonding.
PET nonwoven fabric undergoes almost no morphological change during any thermal bonding process. Therefore, even when thermal bonding is performed using a calendar roller, the linear pressure can be reduced, and a bulky and flexible nonwoven fabric can be obtained. Furthermore, it is preferable to use an embossing type roller to thermally bond the dots, for example, in the form of dots, which provides flexibility and bulk as well as high strength. The dry nonwoven fabric obtained in this way has excellent fiber properties, heat resistance, solvent resistance, and chemical resistance because all adhesive points are made of PET, so it can be used in a wide range of fields. It is extremely effective as a facing for disposable diapers and other hygiene products, agricultural nonwoven fabrics such as vinyl house lining curtains, and nonwoven fabrics for various other industrial uses. Conventionally, it has not been possible to obtain bulky and flexible nonwoven fabrics made of PET fibers, but the fibers of the present invention have made it possible to do so, and the present invention is significant in that it has expanded the applications of PET nonwoven fabrics all at once. In addition, wet paper made using the thermoadhesive composite spun fiber of the present invention as an adhesive component or 100% can be made into PET paper in which all adhesive points are formed from PET by performing an appropriate thermal adhesive treatment using a calendar roller or the like. This paper is particularly suitable for electrical insulating paper because it has excellent heat resistance, solvent resistance, chemical resistance, and good electrical insulation properties. Next, the present invention will be explained with reference to Examples, but the present invention is not limited thereto. In the examples, [η] is the intrinsic viscosity (d/g) of polyester measured at 30°C in a mixed solvent of equal amounts of phenol and tetrachloroethane. Example 1 As fiber-forming PBT polymer A [η]=
1.10 PBT as PET polymer B [η]=
Using 0.70 PET, core-sheath type composite spinning was performed using Polymer A as the core and Polymer B as the sheath or adhesive component. The composite ratio of both core and sheath components is
PBT30wt%, sheath PET70wt%, and the spinning speed is
The speed was 1000 m/min, and the number of nozzle holes was 100. The obtained fiber had a single yarn denier of 300 dr/100 fil, a strength of 2.2 g/dr, an elongation of 190%, and a dry heat shrinkage rate of 1.3% in a free shrink state at 180°C. The PBT core of this composite fiber has a birefringence index: Δn=110×
10 ^-3 , and the birefringence of PET in the sheath: Δn=8×
It was 10 ^-3 . Also, for this fiber, the heating rate is 10
When DSC measurements were performed from 0℃ to 300℃ at a rate of ℃/min, an exothermic peak due to crystallization of PET was found at 132℃.
℃, but no exothermic peak associated with PBT crystals was observed, indicating that PET is essentially in an amorphous state.
PBT is substantially in a crystalline state. This heat-adhesive composite spun fiber of the present invention was bundled, mechanically crimped, and cut into a length of 51 mm to obtain a staple fiber. Next, this composite fiber of the present invention (hereinafter abbreviated as PET (PBT)) and a 3dr x 51mm
PET staple fibers (hereinafter abbreviated as PET-ST) are mixed in the proportions shown in Table 1,
A web with a basis weight of 40 g/m ² was created through a random webber. At this time, carding was in good condition. Subsequently, adhesion was performed using a dot-shaped embossed calender roller at a roller surface temperature of 180° C., a roller linear pressure of 25 kg/cm, and a processing speed of 10 m/min. At this time, as a control, a staple fiber (hereinafter abbreviated as PET (O)) obtained by cutting a 3 dr PET single spun raw yarn spun at a spinning speed of 1000 m/min into a length of 51 mm was used. This PET (O) has a strength of 1.42g/dr,
The elongation was 312% and the dry heat shrinkage rate in the free shrinkage state at 180°C was 66.3%. Table 1 shows the performance and appearance of these nonwoven fabrics. The measured values are width 25mm, sample length 10cm, tensile speed 300%/
It is expressed as the average value measured in the vertical and horizontal directions under conditions of 30 minutes.

[Table] As can be seen from Table 1, the heat-adhesive composite spun fibers of the present invention have low shrinkage and good adhesion during heat-bonding, so when treated with an embossing type calendar, they have high strength, flexibility, and shape. A nonwoven fabric with extremely good stability was obtained. On the other hand, the control PET(O) 100% had a high elongation and was not sufficiently crimp, so it could not be made into a nonwoven fabric at all. On the other hand, even when mixed with PET-ST, the elongation of PET(O) is 250%.
Carding was poor because it was much larger and lacked crimping. In other words, there was a high incidence of sinking of the cotton in the clothing and occurrence of neps. Despite such poor process performance, we managed to obtain a nonwoven fabric. However, this nonwoven fabric shrinks significantly during the thermal bonding process, which means that the fibers are pulled apart in areas other than those bonded in dots with the embossing calendar, making the entire nonwoven fabric look like it is wavy and creating irregularities with poor flatness. There were many of them. In addition, the texture was hard, and the soft texture that was aimed for using an embossing calendar was not achieved at all, and the product had no commercial value. Comparative Example 1 Same polymer and same composite ratio as Example 1,
Core-sheath composite spinning was performed using PBT as the core and PET as the sheath. At this time, the spinning speed was 4000 m/min. The obtained fiber had a single yarn denier of 300 dr/100 fil, a strength of 3.3 g/d, an elongation of 97%, and a dry heat shrinkage rate of 1.9% in a free shrink state at 180°C. However, the birefringence of PET that forms the core of this fiber: Δn=62×
10 ^-3 and 0℃ to 300 at a heating rate of 10℃/min.
DSC measurements conducted up to ℃ showed no exothermic peak associated with crystallization of PET, and substantially oriented crystallization was observed. These fibers other than the present invention are bundled, mechanically crimped, and cut into staple fibers in the same manner as in the examples, and are made into regular PET staple fibers (PET-ST).
The fibers were mixed in arbitrary proportions and passed through a random web to form a web with a basis weight of 40 g/m ² . This was passed through a calender roller with a roller surface temperature of 150 to 210° C. at a roller linear pressure of 20 to 60 kg/cm and a processing speed of 10 m/min to perform thermal bonding. However, as expected, since the PET of the sheath component was substantially oriented and crystallized, no thermal bonding effect was exhibited, and no thermal bonding points were formed on the nonwoven fabric. Example 2 The fiber of the present invention obtained in Example 1 was cut into lengths of 5 mm to obtain short cuts of PET (PBT) (abbreviated as PET (PBT) SC in this example). PET short cut (0.7Dr x 5
mm) (abbreviated as PET-SC in this example) and basis weight
The paper is mixed to 50 g/m ² and then subjected to a linear pressure of 18 with a calender roller consisting of a heated matte roller and a non-heated roller.
Thermal bonding was carried out at Kg/cm and processing speed of 30 m/min. During this period, there were no problems with paper making or thermal bonding process. The obtained wet-laid nonwoven fabric, that is, PET paper, is shown in Table-2.
As shown in Figure 2, the fracture length was good.

[Table] Also, since all the adhesive points are made of PET, this paper has excellent heat resistance and good electrical insulation properties, making it suitable for coil insulating paper, power cable insulating paper, and capacitor insulating paper. Summer.

Claims (1)

[Scope of Claims] 1. A fiber-forming polybutylene terephthalate polymer (A) (abbreviated as Polymer A) in which 80 mol% or more of the repeating units are butylene terephthalate, and polyethylene that exhibits thermal fusibility at a temperature below the melting point of the polymer. Polymer A is obtained by composite spinning a terephthalate-based polymer (B) (abbreviated as Polymer B) at a spinning speed of less than 1100 m/min such that Polymer B occupies at least a portion of the outer surface of the composite spun fiber. Polymer B is substantially in an oriented crystallized state, Polymer B is substantially in an unoriented amorphous state, and the composite ratio of Polymer A and Polymer B is A/B = 20/80 to 80/20.
(weight ratio) of undrawn composite spun fibers,
A heat-adhesive composite spun fiber characterized by having a cutting elongation of 250% or less and a dry heat shrinkage rate of 8% or less at 150°C to 210°C. 2. The thermoadhesive composite spun fiber according to claim 1, wherein the composite spun fiber has a core-sheath type cross-sectional structure in which polymer A is a core and polymer B is a sheath.