JP2010077544A - Polyphenylene sulfide fiber for papermaking and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a polyphenylene sulfide fiber for papermaking, which has a low heat shrinkage percentage and excellent water dispersibility in an amorphous polyphenylene sulfide fiber. <P>SOLUTION: The method for producing a polyphenylene sulfide fiber for papermaking includes heat-treating an amorphous polyphenylene sulfide fiber, obtained without drawing and heat fixing treatment of melt spun fiber, in a temperature range of 80-95°C. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polyphenylene sulfide fiber for papermaking and a method for producing the same.

  Nonwoven fabrics using polyphenylene sulfide (hereinafter referred to as PPS) fibers having excellent heat resistance and chemical resistance are used in various applications. In particular, for wet nonwoven fabrics, techniques using unstretched PPS fibers (amorphous PPS fibers) as a binder are disclosed (Patent Documents 1 and 2).

However, the amorphous PPS fiber has a high thermal shrinkage rate at high temperatures and is inferior in dimensional stability, and shrinks when drying in the paper making process. There was a problem that a good wet nonwoven fabric could not be obtained.
Japanese Patent Application Laid-Open No. 07-189169 JP 09-67786 A JP 2007-39840 A

  An object of the present invention is to provide a papermaking PPS fiber having a low thermal shrinkage and good water dispersibility in an amorphous PPS fiber, and a method for producing the same.

  The present invention relates to a method for producing PPS fibers for papermaking, characterized by heat-treating amorphous PPS fibers obtained without melt stretching and heat setting after melt spinning in a temperature range of 80 ° C to 95 ° C, And a PPS fiber obtained by the production method, wherein the heat of crystallization is 10 J / g or more, and the dry heat shrinkage at 150 ° C. × 30 minutes is 35% or less. is there.

  INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a papermaking PPS fiber having a low thermal shrinkage and good water dispersibility and a method for producing the same in an amorphous PPS fiber.

  The method for producing PPS fibers for papermaking according to the present invention is characterized in that amorphous PPS fibers obtained without subjecting melt-spun fibers to stretching or heat setting are heat-treated at a temperature range of 80 ° C to 95 ° C. To do. Amorphous PPS fibers soften easily when heated and can be used as a binder for wet nonwoven fabrics.

  Here, PPS is a polymer containing phenylene sulfide units such as p-phenylene sulfide units and m-phenylene sulfide units as repeating units. PPS may be a homopolymer of any of these units, or may be a copolymer having both units. Moreover, the copolymer with another aromatic sulfide may be sufficient.

  Moreover, as a weight average molecular weight of PPS, 40,000-60,000 are preferable. By setting it to 40,000 or more, good mechanical properties as PPS fibers can be obtained. In addition, when the viscosity is 60,000 or less, the viscosity of the melt spinning solution is suppressed, and a special high pressure resistant spinning equipment is not required.

  A melt-spun fiber, which is obtained without stretching and heat-setting, is an amorphous PPS fiber obtained by melt-spinning a PPS polymer through a die with an extruder-type spinning machine or the like. It refers to PPS fiber that is not stretched and is not subjected to heat setting treatment at a temperature equal to or higher than the crystallization temperature. It is a feature of the production method of the present invention that the amorphous PPS fiber thus obtained is heat-treated at a temperature range of 80 ° C. to 95 ° C. below the crystallization temperature. PPS fibers can be obtained. The heat setting treatment refers to a treatment from an amorphous state to a crystallized state by heat treatment at a crystallization temperature or higher. Further, the term “without substantially stretching” does not include stretching naturally occurring in the process of yarn production. However, from the viewpoint of suppressing dry heat shrinkage, the spontaneous stretching in the yarn forming process is preferably 1.2 times or less.

It is important that the temperature range of the heat treatment is 80 ° C. to 95 ° C. below the crystallization temperature of the PPS fiber. By performing heat treatment in this temperature range, the amorphous PPS fiber can be appropriately thermally contracted in advance without being crystallized. Since the PPS fibers obtained by this heat treatment are not crystallized, they tend to soften when the temperature is raised. For example, the fibers are softened in the paper-making drying process and fused between the fibers constituting the wet nonwoven fabric. As usual, it can be used as a binder. In addition, since it is appropriately heat-shrinked in advance, shrinkage in a papermaking drying process or the like can be suppressed, and wrinkles, blisters, and the like can be reduced.
In addition, when making paper, it is necessary to disperse the fibers in water, and evenly dispersed paper can be obtained. However, the PPS fiber of the present invention can be heated between 95 ° C. Since the fusion has not progressed, the water dispersibility of the fibers is improved, and a paper with good texture can be obtained. Therefore, the PPS fibers of the present invention are particularly suitable for papermaking.

  As a means for heat treatment, any means such as contact with a hot roller or the like, heating with a band drier or dryer with hot air or steam, infrared irradiation, hot water bath, etc. may be used. Further, the state of the yarn to be heat-treated may be a continuous yarn state such as a tow, or may be applied in a cut fiber state that has been cut in advance. As a processing process, you may carry out by the continuous process like the above-mentioned hot roller and a band dryer, and may carry out by the batch type which throws a fixed quantity into a dryer etc. It is more preferable to carry out by a continuous process from the standpoint of production efficiency.

  It is important that the heat treatment of the present invention is performed without substantially applying tension to the PPS fiber. When heat treatment is applied with tension, the heat shrinkage during the heat treatment is not sufficient, and the heat shrinkage when the temperature becomes high due to drying or the like in the paper making process is increased, so that wrinkles, blisters and the like are generated. When applying heat with a band dryer or dryer, it means that the tension is not applied, and it means that it is placed on a net or bat without tension, and the fiber passes through a hot roller or hot water bath. In this case, the adjustment is made so that the fibers do not sag and do not pass through the process.

  The heat treatment time is determined by the ability of the heat treatment apparatus and the efficiency of heat conduction to the fiber, but there is no problem as long as the physical properties of the present invention are not impaired. In order to sufficiently exhibit the effect of suppressing crystallization, it is preferable to make the temperature as short as possible at high temperatures. However, if the time is too short, the effect of reducing shrinkage due to heat treatment does not appear, so that the preferable heat treatment time is 0.01 sec or more and 2 hours or less.

  As described above, a PPS fiber for papermaking having a heat of crystallization of 10 J / g or more and a dry heat shrinkage of 140 ° C. × 30 minutes of 35% or less can be obtained.

  The amount of crystallization heat is 10 J / g or more, further 15 J / g or more, and more preferably 20 J / g or more. If the amount of heat of crystallization is less than 10 J / g, there are too few non-crystallized parts, the softening is insufficient in the drying process and the like, and it is difficult to fuse, and the function as a papermaking binder is not sufficient.

  Here, about 2 mg of PPS fiber sample was precisely weighed, and the heat of crystallization was measured with a differential scanning calorimeter (manufactured by Shimadzu Corporation, DSC-60), heated at a heating rate of 10 ° C./min under nitrogen. The calorific value of the main exothermic peak was measured.

  The dry heat shrinkage is preferably 35% or less, more preferably 20% or less, and further preferably 15% or less. When it is larger than 35%, the dry heat shrinkage rate is too large, and the shrinkage when the temperature rises in the drying process becomes too large, and wrinkles and blisters are generated to obtain a good wet nonwoven fabric. I can't. The lower limit of the dry heat shrinkage rate is not particularly limited, and the lower the better. Therefore, it is good that it is 0 to 35%.

  The dry heat shrinkage was measured according to JIS L 1013: 1999 8.18.2 skein shrinkage (Method A).

In other words, using a measuring instrument with a frame circumference of 1.125 m, the sample was rewound at a speed of 120 times / min, a small skein of 20 turns was made, and a load of 0.088 cN / dtex was applied to measure the skein length. It was. Next, remove the load, hang it in a dryer at 140 ° C. for 30 minutes in a way that does not prevent shrinkage, leave it for 30 minutes, leave it to room temperature, apply a load of 0.088 cN / dtex again, and measure the length. The dry heat shrinkage rate (%) was obtained by the following formula, and the average value of 5 times was calculated.
Sd = [(L−L1) / L] × 100
Where, Sd: dry heat shrinkage (%)
L: Length before drying (mm)
L1: Length after drying (mm)
The diameter of the PPS fiber of the present invention is preferably 30 μm or less for the purpose of improving the dispersibility of the fiber in the papermaking stock solution and obtaining a paper with good texture. More preferably, it is 25 μm or less, and most preferably 20 μm or less. In addition, the lower limit of the fiber diameter obtained by a normal direct spinning method is about 5 μm.

  Moreover, the presence or absence of crimp of PPS fiber is not limited. Moreover, you may mix the fiber which has a crimp, and the fiber which does not have. This is because the presence or absence of crimp has advantages in each of those having and not having. PPS fibers having crimps are suitable for obtaining a wet nonwoven fabric having improved strength due to improved entanglement between fibers. On the other hand, PPS fibers that do not have crimps are suitable for obtaining a uniform wet nonwoven fabric with little unevenness. Therefore, it is sufficient to determine whether or not to crimp the PPS fiber according to the application. When crimping is applied, it can be applied using a generally used push-in crimper or the like. The number of crimps is preferably 4 or more / 25 mm or more and 18 or 25 or less for the purpose of improving the strength of the paper and suppressing entanglement between fibers in the papermaking stock solution. The crimping may be performed before the heat treatment at 80 to 95 ° C. or after the heat treatment.

  The fiber length is preferably 1 to 15 mm. More preferably, it is 1-7 mm. By setting it as 1 mm or more, the entanglement force of fibers increases and the intensity | strength of a wet nonwoven fabric can be made high. Moreover, by setting it as 15 mm or less, it is possible to prevent unevenness of fabric weight and the like from occurring due to entanglement of fibers with each other.

  Furthermore, an oil agent or the like may be added to improve process passability or to improve water dispersibility for papermaking.

[Measurement and evaluation method]
(1) Amount of heat of crystallization About 2 mg of PPS fiber sample is precisely weighed and heated by a differential scanning calorimeter (manufactured by Shimadzu Corporation, DSC-60) at a temperature rising rate of 10 ° C./min. This was done by measuring the peak exotherm.

(2) Dry heat shrinkage rate Measured according to JIS L 1013: 1999 8.18.2 skein shrinkage rate (Method A).
Using a measuring machine having a frame circumference of 1.125 m, the sample was rewound at a speed of 120 times / min, a small skein with 20 turns was made, and a load of 0.088 cN / dtex was applied to measure the skein length. Next, remove the load, hang it in a dryer at 140 ° C. for 30 minutes in a way that does not prevent shrinkage, leave it for 30 minutes, leave it to room temperature, apply a load of 0.088 cN / dtex again, and measure the length. The dry heat shrinkage rate (%) was obtained by the following formula, and the average value of 5 times was calculated.
Sd = [(L−L1) / L] × 100
Where, Sd: dry heat shrinkage (%)
L: Length before drying (mm)
L1: Length after drying (mm).

(3) Water dispersibility About 1 g of PPS fiber sample is put into about 1 liter of water, put into a mixer ("Oster Blender OB-1" manufactured by Oster), stirred at 13600 rpm, and visually checked for fiber bundles. Confirmed with.
○: After stirring for 15 seconds, the fiber bundle was almost gone.
X: After stirring for 15 seconds, the fiber bundle remained.

(4) Papermaking test “Torucon (registered trademark)” manufactured by Toray Industries, Inc., product number S301 (PPS drawn yarn, heat-fixed, single fiber fineness 1 dtex, crimped 13 threads / 25 mm, cut length 6 mm) The PPS fibers obtained in the examples or comparative examples were mixed at a weight ratio of 15:85, an aqueous dispersion having a fiber concentration of about 1% by weight was prepared, and a handmade paper machine (Kumagaya Riki Kogyo K.K. A wet sheet nonwoven fabric with a basis weight of 100 g / m ² was obtained using a mold sheet machine with automatic couching) and subjected to a couching treatment. The non-woven fabric is put into a KRK rotary dryer (standard type) manufactured by Kumagaya Riki Kogyo Co., Ltd., and is processed at a temperature of 120 ° C. and a processing time of about 2.5 min / time. (Drying process passability) and paper strength (paper strength) after drying were confirmed. In the drying process passability, wrinkles at the time of drying were evaluated as ○ when there was little shrinkage wrinkle and continuous papermaking was possible, and when it was estimated that shrinkage wrinkles or peeling occurred and continuous papermaking was impossible. Also, the paper strength was evaluated as “○”, which was considered to be capable of continuous papermaking by fusing between fibers, and “×” was assumed to be a paper strength weakly cut and inferior continuous papermaking.

[Examples 1 to 4, Comparative Examples 1 to 5]
(Heat treatment)
50 g of “Torcon (registered trademark)” manufactured by Toray Industries, Inc., product number S111 (PPS undrawn yarn, no heat-fixing treatment, single fiber fineness 3 dtex, crimp number 6 crests / 25 mm) It is put into a hot air dryer (Yamato Kagaku Co., Ltd. blast constant temperature thermostatic machine DKN601) set in advance, and after heat treatment for a predetermined time and taken out, the length is 6 mm in order to evaluate water dispersibility and papermaking properties. Cut with a guillotine cutter. Dry heat shrinkage was used in the state of long fibers.

  In Comparative Example 1, S111 that was not subjected to heat treatment was used.

  In Comparative Example 5, a fixed amount of S111 was wound around a wooden frame of 30 cm square and fixed, and heat treatment was performed in a constant length state while suppressing thermal shrinkage.

(Evaluation results)
For fiber samples heat-treated as described above, cut fibers are used for crystallization heat, water dispersibility, papermaking properties (drying process passability, paper strength), long fibers are cut to a predetermined length, and dry heat shrinkage The rate was measured and the results are summarized in Table 1.

  At the heat treatment temperatures of Examples 1 to 5, it is possible to obtain PPS fibers for papermaking that have a large amount of crystallization heat, a small dry heat shrinkage, and a good water dispersibility. The wrinkle was improved, and the paper strength of the obtained wet nonwoven fabric was sufficiently strong. On the other hand, in Comparative Examples 1 to 6, Comparative Examples 1 and 2 had too large a dry heat shrinkage, and wrinkles were generated in the drying process. In Comparative Examples 3 to 5, fusion of fibers progressed and water dispersibility was poor. Furthermore, the amount of heat of crystallization is small, the adhesive strength between fibers is small, the paper strength of the obtained paper is weak, and continuous papermaking is considered impossible. In Comparative Example 6, the dry heat shrinkage ratio was large, and wrinkles were generated in the drying process.

  The PPS fiber for papermaking of the present invention can be used as a PPS fiber used for a wet nonwoven fabric, particularly as a binder for a wet nonwoven fabric.

Claims (4)

  A process for producing polyphenylene sulfide fibers for papermaking, characterized in that after melt spinning, amorphous polyphenylene sulfide fibers obtained without being subjected to stretching and heat setting treatment are heat-treated in a temperature range of 80 ° C to 95 ° C.   The method for producing polyphenylene sulfide fibers for papermaking according to claim 1, wherein the heat treatment is performed without applying tension.   A polyphenylene sulfide fiber obtained by the production method according to claim 1, wherein the heat of crystallization is 10 J / g or more and the dry heat shrinkage of 140 ° C. × 30 minutes is 35% or less. Polyphenylene sulfide fiber for papermaking.   The polyphenylene sulfide fiber for papermaking according to claim 3, wherein the fiber length is 1 to 15 mm.