JP2010174400A - Method for producing polyphenylene sulfide fiber for papermaking - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce a PPS fiber for papermaking which has small heat-shrinkage and good separation property in water in production of undrawn PPS fiber for papermaking. <P>SOLUTION: An undrawn polyphenylene sulfide staple fiber for papermaking is produced by producing an undrawn polyphenylene sulfide fiber by melt-spinning at a spinning velocity of 500-3,000 m/min, passing the undrawn fiber through a hot water bath at 70°C or more without drawing the fiber to effect heat-treatment for 0.5-10 sec, passing the heaet treated fiber through a dry-heat zone at 70-90°C in relaxed state to perform relaxation heat-treatment for 5-60 min, and cutting the resultant fiber to a predetermined length to obtain the staple fibers. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing polyphenylene sulfide fibers for papermaking having heat resistance and chemical resistance.

  Fibers made of polyphenylene sulfide (hereinafter abbreviated as PPS) are derived from the characteristics of PPS materials and are excellent in heat resistance, chemical resistance, flame retardancy, etc. It has been used for applications such as various filters, electrical insulating materials, paper-making canvases, and battery separators. Examples of PPS fiber products used in these applications include wet nonwoven fabrics made of PPS fibers.

  This wet nonwoven fabric is mainly composed of stretched PPS short fibers and unstretched PPS fibers (amorphous PPS fibers) as binder fibers for stretching thermocompression bonding.

  Examples of improvements relating to the PPS wet nonwoven fabric include the following.

  Japanese Patent Application Laid-Open No. 2007-39840 (Patent Document 1) proposes to use a polyphenylene sulfone stretched fiber and an unstretched PPS fiber refined by draw stretching in order to obtain a good PPS wet nonwoven fabric. . However, the draw-stretched unstretched fiber used in this method has a large thermal shrinkage at high temperatures and is inferior in dimensional stability, so it shrinks in the paper making process, causing wrinkles, blisters and dry unevenness in the wet nonwoven fabric. Therefore, there is a problem that it is difficult to obtain a good wet nonwoven fabric.

  JP-A-2004-285536 (Patent Document 2) proposes that the stretched PPS fiber is subjected to relaxation heat treatment at 130 to 160 ° C. to reduce the shrinkage in order to obtain a good PPS wet nonwoven fabric. Yes. In this method, a normal unstretched PPS fiber (dry heat shrinkage 40%) spun at a take-up speed of 800 m / min is used as the binder fiber. When the shrinkage ratio between the PPS stretched fiber and the unstretched PPS fiber is compared, the shrinkage ratio of the unstretched PPS fiber is much larger. It is difficult to sufficiently eliminate wrinkles, blisters and uneven drying.

JP 2007-39840 A JP 2004-285536 A

  The present invention solves the above-mentioned problems in the prior art, and in the production of unstretched PPS fibers for papermaking, the main object is to produce PPS fibers for papermaking that have a low heat shrinkage and good moisture fiber properties. To do.

  The method for producing a polyphenylene sulfide fiber for papermaking according to the present invention is such that a polyphenylene sulfide unstretched fiber produced by melt spinning is passed through a water bath at a temperature of 70 ° C. or higher without being stretched and subjected to a heat treatment for 0.5 to 10 seconds. After that, a relaxation heat treatment is performed for 5 to 60 minutes by passing through a dry heat region at a temperature of 70 to 90 ° C. in a relaxed state.

  According to the method of the present invention, an unstretched PPS fiber suitable for papermaking can be produced because it has a low thermal shrinkage ratio and good moisture fiber property.

  In the method for producing PPS fibers for papermaking according to the present invention, the unstretched PPS fibers produced by melt spinning are passed through a hot water bath at a temperature of 70 ° C. or higher without being stretched and subjected to a heat treatment for 0.5 seconds or longer. The heat treatment is carried out for 5 to 60 minutes by passing through a dry heat region at a temperature of 70 to 90 ° C. in a relaxed state.

  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 a copolymer having both units. Further, it may be a copolymer with another aromatic sulfide.

  The PPS used for melt spinning preferably has a melt flow rate value of 50 to 250, more preferably 70 to 170. When the melt flow rate value is less than 50, the viscosity of the PPS molten resin becomes high at the time of melt spinning, and the spinning equipment must be made to have a special high pressure resistance specification. That is, by setting the melt flow rate value to 50 or more, the solution viscosity at the time of melt spinning is suppressed, and a special high pressure resistant spinning equipment is not required. On the other hand, if the melt flow rate value exceeds 250, the melt viscosity of PPS is low during melt spinning, yarn breaks occur frequently during spinning, and the spinning process tends to be extremely poor. Moreover, setting the melt flow rate value to 250 or less is effective for obtaining good mechanical properties as PPS fibers.

  In the method of the present invention, first, PPS is melt-spun at a normal spinning speed to obtain an undrawn PPS fiber. This melt spinning can be carried out by melting PPS particles and pellets in an ordinary melt spinning machine such as an extruder type melt spinning machine, melt spinning through a die, cooling and solidifying, and drawing at 500 to 3000 m / min. Good. Undrawn fibers are fibers that have not been substantially drawn after spinning and are also referred to as amorphous PPS fibers. When the spinning speed is too high, the orientation stretching of the polymer is promoted in the spinning process, so the spinning speed is preferably 3000 m / min or less. On the other hand, if the spinning speed is too low, it is difficult to spin since the orientation of the polymer is difficult to proceed and the single yarns are likely to come into contact with each other during spinning to cause spun fusion.

  The unstretched PPS fibers thus obtained are taken up and once stored in a can, and then passed through a hot water bath having a temperature of 70 ° C. or higher without stretching, and subjected to heat treatment. The passing time in the warm water bath is 0.5 seconds or more, preferably 0.5 to 10 seconds. Next, relaxation heat treatment is performed by passing through a dry heat region at a temperature of 70 to 90 ° C. in a relaxed state. The time for passing through the dry heat zone is 5 to 60 minutes. By performing the heat treatment in this manner, a PPS fiber suitable as a papermaking binder fiber can be obtained.

  As the hot water bath having a temperature of 70 ° C. or higher, a hot water bath in which water or an aqueous solution containing a small amount of an additive is heated to a predetermined temperature of 70 ° C. or higher may be used. The temperature range of this hot water bath is 70 ° C. or higher, preferably 80 to 90 ° C. If it is less than 70 ° C., it is difficult to reduce the shrinkage ratio of the unstretched fibers after the heat treatment, and wrinkles, blisters, drying unevenness and the like are likely to occur in the wet nonwoven fabric in the paper making process. On the other hand, when the temperature exceeds 90 ° C., the glass transition point of the PPS fiber is exceeded, so that the fibers are likely to be fused with each other, and the fiber dispersibility in the paper making process is likely to deteriorate.

  In order to pass through the hot water bath without stretching, it is only necessary to control the yarn running speed either before the hot water bath or after the hot water bath. For example, a method may be employed in which the yarn traveling speed is not controlled by the roller before the warm water bath, and the yarn traveling speed is controlled to a predetermined value by the roller after the warm water bath.

  What is necessary is just to use a tunnel type conveyor movement type high temperature dryer as a dry-heat area of temperature 70-90 degreeC. The temperature in this dry heat region is 70 to 90 ° C, preferably 80 to 90 ° C. If it is less than 70 ° C., it is difficult to reduce the shrinkage ratio of the unstretched fibers after the heat treatment, and wrinkles, blisters, drying unevenness and the like are likely to occur in the wet nonwoven fabric in the paper making process. On the other hand, when the temperature exceeds 90 ° C., the glass transition point of the PPS fiber is exceeded, so that the fibers are fused with each other, the fiber dispersibility in the paper making process is poor, and the fiber is easily distributed unevenly.

  It is important that the temperature range of the relaxation heat treatment in the dry heat region is a temperature range slightly lower than the glass transition point (about 90 ° C.) of the PPS fiber, that is, a temperature range of 70 to 90 ° C., particularly 80 to 90 ° C. It is. By performing the relaxation heat treatment in this temperature range, the unstretched PPS fiber can be appropriately heat-shrinked in advance without crystallizing.

  Thus, the PPS undrawn fiber obtained by performing the heat treatment in the warm water bath and the relaxation heat treatment in the dry heat region is not easily crystallized, and thus is easily softened when the temperature is raised. It is possible to exert the function as a conventional binder fiber, which is softened by the process of fusing the fibers constituting the wet nonwoven fabric together.

  In addition, since the heat shrinkage rate is lowered in advance by moderate heat shrinkage, shrinkage in the papermaking drying process can be suppressed, and wrinkles, blisters, and the like can be reduced.

  Further, in order to obtain a paper with good texture, it is necessary to uniformly disperse the PPS short fibers in water at the time of papermaking, but the PPS unstretched short fibers according to the present invention are heat-treated to reduce the dry heat shrinkage rate. However, the conditions are adopted so that the fusion between the fibers does not proceed during the heat treatment. As a result, the PPS short fibers according to the method of the present invention have good water dispersibility and are particularly suitable for wet papermaking.

  Regarding the heat treatment time in the hot water bath and the heat treatment time in the dry heat region, an optimum value may be determined depending on the ability of the heat treatment apparatus and the efficiency of heat conduction to the fibers. In order to fully exhibit the crystallization inhibitory effect, it is preferable to shorten the time as the temperature increases. However, if the time is too short, the effect of reducing shrinkage does not appear. If the time is too long, fusion between fibers tends to occur, and dispersibility of short fibers tends to occur during papermaking. From this point, the treatment time in the hot water bath is 0.5 to 10 seconds, preferably 1 to 3 seconds. The relaxation heat treatment time in the dry heat region is 5 to 60 minutes, preferably 20 to 50 minutes.

  The PPS undrawn fiber obtained by heat treatment as described above has a single yarn fineness of 0.5 to 4 dtex, a crystallization heat amount by DSC measurement of 10 J / g or more, and 150 ° C. × 30 minutes. The dry heat shrinkage is preferably 35% or less. By having these characteristics, it becomes particularly suitable as a binder PPS fiber for papermaking.

  The single yarn fineness is 0.5 to 4 dtex, preferably 1 to 3 dtex. If the fineness is less than 0.5 dtex, yarn breakage occurs frequently during spinning, and the spinnability is remarkably deteriorated. On the other hand, if it exceeds 4 dtex, the thickness of the papermaking becomes large at the time of papermaking, and it is not suitable for papermaking applications requiring thin materials.

  The amount of crystallization heat is 10 J / g or more, further 15 J / g or more, more preferably 20 J / g or more. If the amount of heat of crystallization is less than 10 J / g, there are too few uncrystallized parts, and the softening in the drying process or the like becomes insufficient, and the fusing function as binder fibers for papermaking is not sufficient.

  The dry heat shrinkage is preferably 35% or less, more preferably 20% or less, and still more preferably 15% or less. When the dry heat shrinkage rate is larger than 35%, the shrinkage when the temperature rises in the drying process or the like becomes too large, causing wrinkles and swelling, and it is difficult to obtain a good wet nonwoven fabric. The smaller the dry heat shrinkage rate, the better. Therefore, 0 to 35% is preferable.

  Moreover, as a fiber length of a short fiber, 1-15 mm is preferable. More preferably, it is 1-7 mm. By setting it to 1 mm or more, the entanglement force between the fibers increases, and the strength of the wet nonwoven fabric can be increased. Moreover, by setting it as 15 mm or less, it can avoid that fibers entangle and become a lump of a lump, and can prevent a fabric weight unevenness etc. arising.

  As described above, according to the method of the present invention, it is possible to produce unstretched PPS fibers for papermaking with low heat shrinkage and good moisture fiber properties.

  The method of the present invention will be described in detail below using examples. Each characteristic value used in the present invention is obtained by the following method.

[Melt flow rate value]
According to JIS K7210 (1999 revision), the melt flow rate value is measured at a temperature of 315.5 ° C. and a load of 5000 g.

[Amount of crystallization]
About 2 mg of a PPS fiber sample is precisely weighed and heated with a differential scanning calorimeter (manufactured by Shimadzu Corporation, DSC-60) at a heating rate of 10 ° C./min under nitrogen, and the calorific value of the observed main exothermic peak is measured. By doing so, the amount of crystallization heat is obtained.

[Dry heat shrinkage]
Measured according to JIS L 1015-7.15. The sample short fiber was affixed to a lubricant paper, the length (original length, Amm) was measured by applying an initial load equivalent to 300 mg per denier, and then heat-treated for 30 minutes at 150 ° C. dry heat. Is measured (process length, Bmm), and the dry heat shrinkage is obtained by the following equation.

Dry heat shrinkage rate (%) = [((A) − (B)) / (A)] × 100
[Water dispersibility]
About 1 g of PPS short fiber sample (fiber length: 6 mm) is put into about 1 liter of water, and then put into a mixer (Oster Blender OB-1 manufactured by oster) and stirred at 13600 rpm. The dispersion state of the fibers after stirring for 15 seconds is visually confirmed, and determined according to the following criteria.
Good: After stirring for 15 seconds, the fiber bundle was almost gone.
Poor: After stirring for 15 seconds, the fiber bundle remained.

(Examples 1-3)
A granular polyphenylene sulfide having a melt flow rate value of 165 was melted by a usual method, spun at a spinning speed of 1100 m / min, and taken off. The undrawn yarn is heat-treated without passing through a hot water bath at a predetermined temperature (passing time of the hot water bath for 1 second), and further passed through a dry heat zone at a predetermined temperature in a relaxed state (drying). The heat treatment was performed for 30 minutes) to produce unstretched PPS fiber having a single yarn fineness of 3.0 dtex (toe fineness of 59.0 ktex). In order not to cause stretching when passing through the hot water bath, the yarn running speed before the hot water bath was not controlled, and the yarn running on the roller after the hot water bath was controlled to 60 m / min. Moreover, in order to make the thread | yarn at the time of passing through a dry-heat area into a relaxation | loosening state, the thread | yarn of a relaxation | loosening state was mounted and passed on the conveyor which moves in the dry-heat area | region.

  About the obtained unstretched PPS fiber, the dry heat shrinkage, the heat of crystallization, and the adhesion state between the fibers were measured, and the results are shown in Table 1. Moreover, it cut | disconnected to length 6mm, was set as the short fiber, and water dispersibility was evaluated. The obtained unstretched PPS fiber had a low dry heat shrinkage, a large amount of heat of crystallization, and good water dispersibility, and was suitable for a papermaking binder fiber.

(Examples 4 to 5)
An unstretched PPS fiber having a single yarn fineness of 3.0 dtex was produced and evaluated in the same manner as in Example 2 except that the time for passing through the dry heat region was changed to 40 minutes or 50 minutes. The obtained unstretched PPS fiber had a low dry heat shrinkage ratio, a large amount of heat of crystallization and good water dispersibility, and was suitable for a papermaking binder fiber.

(Examples 6 to 7)
An unstretched PPS fiber having a single yarn fineness of 3.0 dtex was produced and evaluated in the same manner as in Example 2 except that the time for passing through the warm water bath was changed to 2 seconds or 3 seconds. The obtained unstretched PPS fiber had a low dry heat shrinkage, a large amount of heat of crystallization, and good water dispersibility, and was suitable for a papermaking binder fiber.

(Comparative Example 1)
An unstretched PPS fiber having a single yarn fineness of 3.0 dtex was produced and evaluated in the same manner as in Example 2 except that the temperature of the hot water bath was changed to 50 ° C and the temperature of the dry heat region was changed to 50 ° C. did.

  The obtained unstretched PPS fiber had a high dry heat shrinkage rate. Using this unstretched PPS fiber as a short fiber having a length of 6 mm and using it as a binder fiber, a wet nonwoven fabric was produced from the stretched PPS short fiber by a normal wet papermaking method. A good wet nonwoven fabric could not be obtained.

(Comparative Example 2)
An unstretched PPS fiber having a single yarn fineness of 3.0 dtex was produced and evaluated in the same manner as in Example 2 except that the temperature of the hot water bath was changed to 95 ° C and the temperature of the dry heat region was changed to 95 ° C. did.

  The obtained unstretched PPS fiber had poor water dispersibility, and a portion fused between the fibers was observed. Using this unstretched PPS fiber as a short fiber having a length of 6 mm and using it as a binder fiber, a wet nonwoven fabric was produced from the stretched PPS short fiber by a normal wet papermaking method. As a result, the unstretched PPS fiber was not split in the papermaking process. The unevenly distributed portion increased and a good wet nonwoven fabric could not be obtained.

(Comparative Example 3)
Unstretched PPS with a single yarn fineness of 3.0 dtex in the same manner as in Example 2 except that the time passing through the hot water bath was changed to 0.2 seconds and the time passing through the dry heat region was changed to 3 minutes. Fibers were manufactured and evaluated. The obtained unstretched PPS fiber had a high dry heat shrinkage rate. Using this unstretched PPS fiber as a short fiber having a length of 6 mm and using it as a binder fiber, a wet nonwoven fabric was produced from the stretched PPS short fiber by a normal wet papermaking method. As a result, wrinkles, swelling, uneven drying, etc. occurred in the papermaking process. A good wet nonwoven fabric could not be obtained.

(Comparative Example 4)
An unstretched PPS fiber having a single yarn fineness of 3.0 dtex was obtained in the same manner as in Example 2 except that the time passing through the warm water bath was changed to 15 seconds and the time passing through the dry heat region was changed to 70 minutes. Manufactured and evaluated.

The obtained unstretched PPS fiber had poor water dispersibility, and a portion fused between the fibers was observed. Using this unstretched PPS fiber as a short fiber having a length of 6 mm and using it as a binder fiber, a wet nonwoven fabric was produced from the stretched PPS short fiber by a normal wet papermaking method. As a result, the unstretched PPS fiber was not split in the papermaking process. The unevenly distributed portion increased and a good wet nonwoven fabric could not be obtained.
(Comparative Example 5)
The undrawn yarn at the stage of being spun and pulled in Examples 1 to 3 was evaluated in the same manner as in the Example. As a result, the dry heat shrinkage was as high as 40% and the crystallization heat amount was 25 J.

Claims (4)

  The polyphenylene sulfide unstretched fiber produced by melt spinning is passed through a hot water bath at a temperature of 70 ° C. or higher without being stretched and subjected to a heat treatment for 0.5 to 10 seconds, and then a dry heat region at a temperature of 70 to 90 ° C. A process for producing polyphenylene sulfide fibers for papermaking, characterized by performing a relaxation heat treatment for 5 to 60 minutes by passing the fibers in a relaxed state.   The method for producing polyphenylene sulfide fibers for papermaking according to claim 1, wherein the spinning speed at the time of melt spinning is 500 to 3000 m / min.   The polyphenylene sulfide undrawn fiber is an undrawn fiber obtained by melt spinning a granular polyphenylene sulfide having a melt flow rate value of 50 to 250, and the single yarn fineness of the polyphenylene sulfide fiber obtained by relaxation heat treatment is 0. The heat of crystallization according to DSC measurement is 10 J / g or more, and the dry heat shrinkage rate at 150 ° C. for 30 minutes is 35% or less. Or the manufacturing method of the polyphenylene sulfide fiber for papermaking of 2.   The method for producing polyphenylene sulfide fiber for papermaking according to claim 1, 2 or 3, wherein after the heat treatment for relaxation, the fiber length is cut to 1 to 15 mm to produce a polyphenylene sulfide short fiber.