JP2006137085A - Tissue paper for thermal stencil paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide tissue paper for thermal stencil paper which has a sufficient strength in lamination with a thermoplastic resin film, excels in image clearness, causes few voids and is constituted of 100% polyester fibers. <P>SOLUTION: The tissue paper for the thermal stencil paper is constituted of polyester fibers A having a single fiber size of 0.01-0.6 dtex and an index of double refraction of 0.01-0.05 and polyester binder fibers B having a single fiber size of 0.2-2.0 dtex. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thin paper for a heat-sensitive stencil sheet which is perforated and made by heat from a xenon flash lamp or a thermal head.

  Conventionally, various proposals have been made as a thin paper for heat-sensitive stencil paper used for heat-sensitive stencil paper, and a thin paper for heat-sensitive stencil paper (for example, patent) consisting of a natural non-wood fiber alone such as Kozo, Mitsu or Manila hemp. Document 1), thin paper for heat-sensitive stencil paper (for example, Patent Document 2) in which natural fibers are mixed with synthetic fibers or recycled fibers are known.

  Thin paper for heat-sensitive stencil paper consisting of natural non-wood fibers alone has poor texture due to uneven fiber cross-section and fiber length during paper making, and binding fibers, which impedes ink permeability during heat-sensitive stencil printing. , There is a defect that white spots occur in solid printing. In addition, due to lack of wet dimensional stability, when printing is performed using a heat-sensitive stencil sheet obtained by laminating with a thermoplastic resin film, when water-containing ink is used, the dimensions change due to moisture contained in the ink. In addition, there is a drawback in that an image such as a printed character is distorted.

  In order to eliminate these drawbacks, a thin paper for heat-sensitive stencil paper in which natural fibers are mixed with synthetic fibers or recycled fibers has been proposed. By blending synthetic fibers or recycled fibers, white spots and wet dimensional stability are improved. However, as the amount of synthetic fibers or recycled fibers increases, the stiffness and strength of the heat-sensitive stencil thin paper decreases and large numbers of sheets are printed. In such a case, there is a problem in printing resistance such as a distortion in a printed image or tearing of a base paper during printing. For this measure, proposals have been made to impregnate resin into thin paper for heat-sensitive stencil paper mixed with natural fiber or recycled fiber (for example, Patent Documents 3 and 4), but depending on the resin to be impregnated, the fiber entanglement point There are drawbacks such as insufficient adhesion and obstruction of ink passage by forming a resin film. Furthermore, recently, market needs have become more sophisticated and clearer printability has been demanded. For this reason, in order to increase the resolution of thermal stencil printing, the thermal element density of the thermal head tends to increase from 300 to 400 dpi to 600 dpi. For this reason, a heat sensitive stencil sheet paper composed of 100% synthetic fiber has been proposed from a heat sensitive stencil sheet thin paper blended with natural fibers that are highly likely to block perforations through which ink passes.

  However, although the thin paper for heat-sensitive stencil paper composed of 100% synthetic fiber has excellent image clarity, the rigidity and strength of the thin paper is reduced, so the base paper is easily torn during lamination with a film or stencil printing, There is a problem that conveyance failure is likely to occur.

Patent Document 5 contains 5 to 70% of polyester fiber and / or acrylic fiber of 0.1 denier or less, and 10 to 30% of polyester fiber of 0.5 denier and 20 to 70% of polyester binder fiber are mixed. It is a thin paper for heat-sensitive stencil paper consisting of 100% synthetic fiber weighing 9 to 11 g / m ² . However, polyester fibers generally used for heat-sensitive stencil sheet paper have been heat-treated after being stretched at a high magnification, and when trying to bond them only with polyester binder fibers, the dryer temperature of the paper machine is increased. Therefore, there is a problem that it is easy to stick to the dryer.

Patent Document 6 discloses that 40 to 60% by weight of a polyester fiber having a single yarn fineness exceeding 0.1 denier and less than 0.3 denier, and a polyester fiber 30 having a single yarn fineness of 0.3 denier or more and less than 0.5 denier. It is a thin paper for heat-sensitive stencil paper comprising 100% polyester fiber having a basis weight of 7 to 10 g / m ² mixed with 5 to 15% by weight of polyester binder fiber having a fine yarn fineness of 1 to 2 denier. However, the thin paper has a problem in that the mixing ratio of the binder fiber (heat melting temperature is 110 ° C.) is too small to obtain sufficient strength, and the paper is cut during processing.

Japanese Patent Publication No.41-7623 Japanese Patent Publication No. 55-47997 JP 61-254396 A JP-A-1-271293 Japanese Patent No. 2726105 JP 2000-141936 A

  An object of the present invention is to provide a thin paper for heat-sensitive stencil paper having 100% polyester fiber which has sufficient strength at the time of lamination with a thermoplastic resin film, is excellent in image sharpness and has few white spots.

  As a result of repeated studies to achieve the above object, the present inventor used a fine fiber polyester fiber produced so that the orientation does not become high as a constituent fiber, and when this is combined with a binder fiber having a specific fineness, It has been found that a thin paper for heat-sensitive stencil paper having sufficient strength, excellent image sharpness, little whiteout, and balanced performance can be obtained.

  That is, according to the present invention, polyester fiber A having a single fiber fineness of 0.01 to 0.6 dtex (hereinafter abbreviated as dtex) and a birefringence (hereinafter abbreviated as Δn) of 0.01 to 0.05. And a thin paper for heat-sensitive stencil paper comprising a polyester-based binder fiber B having a single fiber fineness of 0.2 to 2.0 dtex.

  According to the present invention, the dispersibility of polyester fibers in water is excellent and the strength of the resulting thin paper is sufficient, so that no paper breakage occurs when laminating with a film, and image sharpness during thermal stencil printing is improved. It is possible to provide thin paper with excellent whiteness.

  In the present invention, it is important that the thin sheet for heat-sensitive stencil sheet is composed of polyester fiber A and polyester-based binder fiber B that satisfy specific requirements described below. Thereby, it is possible to provide a thin paper having sufficient strength at the time of laminating, excellent image sharpness, and few white spots.

  The single fiber fineness of the polyester fiber A needs to be 0.01 to 0.6 dtex, preferably 0.05 to 0.4 dtex, more preferably 0.1 to 0.3 dtex. When the single fiber fineness is larger than 0.6 dtex, the strength of the thin paper is lowered, the image sharpness is lowered, and the white spots become conspicuous. On the other hand, if the single fiber fineness is less than 0.01, the number of fibers is increased as compared with the one with a large fineness in making thin paper with the same basis weight, and therefore, entanglement of fibers during dispersion in water is likely to occur. White spots are also likely to occur.

In the present invention, it is important that the Δn of the polyester fiber A is 0.01 to 0.05, preferably 0.01 to 0.04. By suppressing the above Δn of such fine fibers, the present inventor can achieve not only the binder fibers described later but also the fine fibers with a binder function, and achieve high strength of the thin paper by their synergistic effect. I found. Therefore, when Δn is higher than 0.05, the binder function is lowered and the strength of the thin paper is lowered. On the other hand, when Δn is smaller than 0.01, the strength of the fiber is lowered, and the strength of the thin paper is also lowered.
In addition, since the polyester fiber used for the conventional thin paper is manufactured through normal spinning, drawing, and heat treatment processes, those having Δn of 0.10 or more are very common.

  Examples of the polyester constituting the polyester fiber of the present invention include polyethylene terephthalate (hereinafter abbreviated as PET) polyester, polytrimethylene terephthalate polyester, polybutylene terephthalate polyester, polyethylene naphthalate polyester, and the like. From the viewpoint of the strength of the thin paper, a polyester-based polyester and further a PET-based polyester copolymerized with 2 to 6 mol% of 5-sodium sulfoisophthalic acid (hereinafter abbreviated as SIP) are particularly preferable. This is because the dispersibility in water during papermaking of the polyester fiber copolymerized with SIP is more excellent. When the copolymerization ratio of SIP is less than 2 mol%, the dispersibility in water tends to be poor. On the other hand, when it exceeds 6 mol%, the melt viscosity at the time of spinning tends to be high and spinning tends to be difficult.

  The intrinsic viscosity of the PET polyester fiber A copolymerized with the above SIP is preferably 0.30 to 0.45, more preferably 0.33 to 0.40. When the intrinsic viscosity is lower than 0.30, the strength is lowered, and when it exceeds 0.45, the melt viscosity becomes high and spinning becomes difficult, and it becomes difficult to produce a fiber having a small fineness.

  The blending ratio of the polyester fiber A is preferably 30 to 90% by weight, more preferably 40 to 80% by weight. When the blending ratio is less than 30% by weight, the blending ratio of the binder fiber B is increased, the dryer adhesion becomes strong and white spots are easily noticeable, and when the blending ratio exceeds 90% by weight, the blending ratio of the binder fiber B is decreased. The strength of the steel tends to be low.

  The polyester fiber A of the present invention can be produced by the following method. That is, the melt-spun unstretched yarns are aligned to form a tow, and the first stage stretching is performed at a temperature higher than the glass transition point (hereinafter abbreviated as Tg), followed by the second stage stretching at a temperature lower than Tg. In order to improve the dispersibility in water, the film is treated with an emulsion containing a polyether / polyester copolymer as a main component and then cut into a predetermined length with a drum cutter. As a result, a finer fineness and a low birefringence can be achieved simultaneously. In this case, for example, in the case of polyethylene terephthalate, it is desirable that the second-stage stretching is performed at a ratio of 2.0 times or less, preferably 1.5 times or less from the viewpoint of keeping the birefringence low. On the other hand, as a method for producing a polyester fiber having a fine fineness used for thin paper, generally, a method for producing a fine fineness fiber directly by spinning, or an undrawn yarn having a high fineness by spinning is used. There is a method of spinning and drawing this into a fine fiber, but in these methods, the orientation is so advanced that Δn exceeds 0.06.

  On the other hand, in the present invention, the single fiber fineness of the polyester-based binder fiber B needs to be 0.2 to 2 dtex, preferably 0.3 to 1.8 dtex. When the single fiber fineness is larger than 2 dtex, white spots are likely to occur. On the other hand, if the single fiber fineness is less than 0.2, the surface area of the binder component becomes too large, and dryer adhesion during papermaking tends to occur.

  As the binder fiber B, a core-sheath type composite fiber is preferably used. In this case, as the core component, a polyester in which 85 mol% or more of the main repeating unit is composed of ethylene terephthalate can be preferably used. When the ethylene terephthalate unit is less than 85 mol%, the thermal characteristics such as the melting point are deteriorated, which is not preferable. The polyester may contain known additives such as matting agents, pigments, fluorescent whitening agents, and ultraviolet absorbers. On the other hand, as the binder component of the sheath, a PET-based amorphous copolymer polyester can be preferably used. The copolymer polyester is composed of acid components such as terephthalic acid, isophthalic acid, 5-sodium sulfoisophthalic acid, adipic acid, and sebacic acid, and ethylene glycol, 1,3-propanediol, 1,4-butanediol, diethylene glycol, and the like. A copolymerized polyester obtained from terephthalic acid, isophthalic acid, ethylene glycol and diethylene glycol is particularly preferred from the viewpoint of cost.

  The binder fiber B can be produced by a known method. In order to improve the dispersibility in water, the binder fiber B is stretched, treated with an emulsion containing a polyether / polyester copolymer as a main component, and then stretched to a predetermined length with a drum cutter. It is desirable to cut it quickly.

  Furthermore, the blending ratio of the binder fiber B is preferably 10 to 70% by weight, more preferably 20 to 50% by weight. When the blending ratio is less than 10% by weight, the strength of the thin paper tends to be low. When the blending ratio is more than 70% by weight, dryer adhesion at the time of papermaking and white spots at the time of thermal stencil printing are likely to occur.

  In the present invention, the fiber length of the polyester fiber A and the binder fiber B is 2 to 15 mm, preferably 3 to 10 mm. When the fiber length is shorter than 2 mm, stable fiber cutting with a drum cutter becomes difficult, and the strength of the thin paper tends to be low. On the other hand, when the fiber length is longer than 15 mm, it is difficult to disperse the fibers in the paper during paper making, and a thin paper with large formation spots is obtained.

  Papermaking of the thin paper of the present invention is carried out by a known method. That is, the above polyester fiber is put into a pulper, stirred and dispersed, supplied to a paper net to form a wet paper, and wound into a roll after a drying process. The netting network is generally a circular network, a short network, or a slanted short network, but it may be a long network. The drying method may be a method of drying with a plurality of rotating heating rollers, but a method of drying with a Yankee dryer is preferred.

The weight of the thin paper is 4 to 15 g / m ² , preferably 5 to 10 g / m ² . When the weighing amount exceeds 15 g / m ² , the ink permeability at the time of thermal stencil printing decreases, and the image density and sharpness decrease. When it is less than 4 g / m ^2, the strength at the time of laminating with a thermoplastic film is insufficient, and stable lamination becomes difficult.

An adhesive can be used for laminating the thin paper and the thermoplastic film as long as the ink-passability of the obtained heat-sensitive stencil sheet is not hindered. As the adhesive, known emulsion latex type adhesives, solvent type adhesives (acrylic type, polyester type, vinyl acetate type, rubber type, etc.), reaction curing type adhesives, and the like can be used. A heat-sensitive stencil sheet can be obtained by applying these adhesives in a dry coating amount to 0.5 to 2.5 g / m ² thin paper or a thermoplastic film and then laminating.

Hereinafter, the present invention will be described more specifically with reference to examples. In addition, each item in an Example was measured with the following method.
(1) Intrinsic viscosity Measured at 35 ° C. using orthochlorophenol as a solvent.
(2) Glass transition point (Tg)
A thermal analyst 2200 manufactured by TA Instrument Japan Co., Ltd. was used, and the temperature was measured at a temperature rising rate of 20 ° C./min.
(3) Birefringence (Δn)
Using a commercially available polarizing microscope, a sodium lamp was used as the light source, and the retardation was calculated from the Berek compensator method with the sample immersed in α-bromonaphthalene.
(4) Paper strength (tensile strength)
It was measured by the method shown in JIS P 8113, and 2N / 15 mm or more was regarded as acceptable.
(5) Weighing It measured by the method shown by JISP8124.
(6) Dryer adhesiveness Using a square sheet machine manufactured by Kumagai Riki Kogyo Co., Ltd., each polyester fiber raw material is thoroughly stirred and mixed in water to disperse, and is formed on a wire of about 25 cm x about 25 cm. Pick up wet paper with filter paper. Next, the wet paper adhering to the filter paper is dried at room temperature, and then the polyester fiber paper is in contact with the drum surface using a high-temperature rotary dryer manufactured by Kumagai Riki Kogyo Co., Ltd. whose drum surface temperature is adjusted to 140 ° C. In this way, the bonding process is performed. The ease of peeling when the polyester fiber paper subjected to the adhesion treatment was peeled off from the drum was used as a substitute characteristic of the dryer tackiness, and the determination was performed as follows.
○ Easy to peel off.
△ Slightly difficult to remove, but no paper break occurs.
× It is very difficult to peel off and paper breaks occur.
(7) Image sharpness and white spots Polyester fiber paper and a biaxially stretched polyester film having a thickness of 2 μm are bonded to each other with a solvent-soluble copolymerized polyester-based adhesive 1.2 g (dry) / m ² for heat-sensitive stencil printing A base paper was used. The resulting heat-sensitive stencil sheet is overlaid with a manuscript and punched and printed using a commercially available 400 dpi heat-sensitive plate and printing machine. The ink density uniformity and white spots were visually evaluated.
(A) Sharpness The connection of dots of characters and the fatness were visually evaluated according to the following criteria.
◎ Very good ○ Good △ Slightly poor character dot connection, poor weight × character dot connection poorly, thick and difficult to read.
(B) White spot The visual judgment was made based on the following criteria including the uniformity of the solid portion.
○ Good without white spots.
△ There are some white spots.
× White spots are conspicuous and bad.

[Example 1]
(1) Production of polyester fiber A PET pellets having an intrinsic viscosity of 0.47 and Tg of 77 ° C. are dried at 170 ° C., melted at 290 ° C., and discharged at a polymer temperature of 285 ° C. through a die having 1192 holes. After cooling, it was taken up at a speed of 500 m / min to obtain an undrawn yarn having an intrinsic viscosity of 0.45 and a single fiber fineness of 3.4 dtex. The obtained undrawn yarns are aligned to form a toe of about 2 million dtex, and the first stage drawing is performed 14.7 times in warm water at 90 ° C., and then 1.1 times in warm water at 70 ° C. After performing the second stage stretching (total stretching ratio: 16.2 times), it was treated with an emulsion containing a polyether / polyester copolymer as a main component, and squeezed so that the water content was about 20%. The tow was cut to a length of 3 mm with a drum cutter to obtain a stretched polyester fiber A having a fineness of 0.21 dtex and Δn of 0.019.

(2) Manufacture of binder fiber B PET pellet with intrinsic viscosity of 0.63 is the core component, terephthalic acid is 60 mol%, isophthalic acid is 40 mol%, ethylene glycol is 96 mol%, diethylene glycol is 4 mol% Copolymerized amorphous copolyester having an intrinsic viscosity of 0.55 and Tg of 65 ° C. was used as a sheath component, and a composite spinneret having 1032 pores was used, and a weight ratio of 50 (core component) / 50 ( The composite ratio of the sheath component) was discharged at a spinning temperature of 275 ° C., and after cooling, it was taken up at a speed of 1200 m / min to obtain an undrawn yarn of a core-sheath type composite fiber having a single fiber fineness of 4.5 dtex. In addition, the emulsion was given so that the adhesion amount of the polyether / polyester copolymer would be 0.15% by weight before the take-up. The obtained unstretched lines are aligned to form a tow of about 450,000 dtex, stretched 3 times in hot water at 85 ° C., treated with an emulsion mainly composed of a polyether / polyester copolymer, and moisture content After being squeezed so as to be about 15%, it was cut into a length of 5 mm with a drum cutter to obtain a binder fiber B having a fineness of 1.5 dtex.

Using the obtained polyester fiber A and binder fiber B, a thin paper having a weight ratio of 8.0 g / m ² with a blending ratio of A / B of 40/60 based on weight according to a dryer adhesive evaluation method. Obtained. The results are shown in Table 1.

[Examples 2-3]
Thin paper was obtained in the same manner as in Example 1 except that the blending ratio of A / B was changed to 35/65 and 85/15, respectively, based on weight. The respective results are shown in Table 1 as Examples 2 and 3.

[Examples 4 to 5, Comparative Example 1]
In the production method of the polyester fiber A of Example 1, the polyester fiber A was prepared in the same manner as in Example 1 except that the first draw ratio was changed so that the fineness was 0.35 dtex, 0.55 dtex, and 0.65 dtex, respectively. Further, a thin paper was produced. The results are shown in Table 1 as Examples 4 and 5 and Comparative Example 1.

[Examples 6 to 7, Comparative Example 2]
In the production of the polyester fiber A of Example 1, the total draw ratio remains the same 16.2 times as in Example 1, and the second stage draw ratio is changed to 1.2 times, 1.3 times, and 1.4 times. Thus, polyester fibers A having Δn of 0.033, 0.045, and 0.060 were obtained, and thin paper was produced. The results are shown in Table 1 as Examples 6 and 7 and Comparative Example 2, respectively.

[Example 8]
A PET-based polyester pellet having an inherent viscosity of 0.37 and a Tg of 76 ° C. copolymerized with 4.5 mol% of SIP is dried at 150 ° C., melted at 300 ° C., and passed through a die having 1192 pores. The polymer was discharged at a polymer temperature of 0 ° C., and after cooling, it was taken up at a speed of 500 m / min to obtain an undrawn yarn having an intrinsic viscosity of 0.36 and a single fiber fineness of 3.1 dtex. The obtained undrawn yarns are drawn together to form a tow of about 1.5 million dtex, and the first stage drawing is performed 8.8 times in warm water at 85 ° C., followed by 1.7 times in warm water at 70 ° C. The second-stage stretching was performed, and the mixture was treated with an emulsion containing a polyether / polyester copolymer as a main component, and squeezed so that the water content was about 30%. The tow was cut to a length of 3 mm with a drum cutter to obtain a stretched polyester fiber having a fineness of 0.23 dtex and Δn of 0.033.
In Example 1, a thin paper was obtained in the same manner as Example 1 except that the polyester fiber A was changed to the polyester fiber. The results are shown in Table 1.

[Examples 9 to 11]
Implementation was carried out except that PET copolymer pellets having a SIP copolymerization ratio of 2.3, 3.5, and 5.5 mol%, an intrinsic viscosity of 0.37, and a Tg of 74 to 77 ° C., respectively. In the same manner as in Example 8, polyester fibers were obtained and thin paper was produced. The respective results are shown in Table 1 as Examples 9, 10, and 11.

[Examples 12 to 13]
In both cases, polyesters were copolymerized in the same manner as in Example 8 except that PET was copolymerized with 4.5 mol% of SIP and Tg was 76 ° C., and PET-based polyester pellets having intrinsic viscosities of 0.33 and 0.42, respectively. Fiber was obtained and thin paper was produced. The respective results are shown in Table 1 as Examples 12 and 13.

[Example 14, comparative example 3]
In the production of the binder fiber B of Example 1, only the discharge amount was changed to obtain the binder fiber B having a single fiber fineness of 1.8 dtex and 2.3 dtex, and a thin paper was produced in the same manner as in Example 1. The results are shown in Table 1 as Example 14 and Comparative Example 3, respectively.

[Example 15]
PET pellets with an intrinsic viscosity of 0.63 are core components, terephthalic acid is copolymerized in a proportion of 60 mol%, isophthalic acid is 40 mol%, ethylene glycol is 96 mol%, and diethylene glycol is 4 mol%. Using a composite spinneret with 900 pores and an amorphous copolyester of 0.55 as a sheath component, discharge at a composite ratio of 50 (sheath component) / 50 (core component) at a spinning temperature of 275 ° C. Then, after cooling, it was taken up at a speed of 500 m / min to obtain an undrawn yarn of a core-sheath type composite fiber having a single fiber fineness of 6.5 dtex. In addition, an emulsion was applied so that the attached amount of the polyether / polyester copolymer was 0.20% by weight before the take-up. The obtained unstretched lines are aligned to form a tow of about 1 million dtex, followed by 10-fold first-stage stretching in 90 ° C warm water, followed by 1.8-fold second-stage in 63 ° C warm water. Stretching, treating with an emulsion containing a polyether / polyester copolymer as the main component, squeezing so that the moisture content is about 20%, and then cutting to a length of 5 mm with a drum cutter, the fineness is 0 A binder fiber of .36 dtex was obtained.
In Example 1, a thin paper was obtained in the same manner as in Example 1 except that the binder fiber B was changed to the binder fiber. The results are shown in Table 1.

[Comparative Example 4]
A binder fiber B having a fineness of 0.17 dtex was obtained in the same manner as in Example 15 except that the first stage draw ratio was changed to 17 times and the second stage draw ratio was changed to 2.2 times, and thin paper was produced. The results are shown in Table 1.

  According to the present invention, it is possible to provide a thin paper for heat-sensitive stencil paper comprising 100% polyester fiber having sufficient strength at the time of laminating with a thermoplastic resin film, excellent image sharpness, and few white spots. it can. For this reason, the above-mentioned thin paper for heat-sensitive stencil paper can sufficiently cope with the high resolution of heat-sensitive stencil printing which has been strongly demanded recently, and its industrial utility value is extremely high.

Claims (5)

  Heat sensitivity comprising polyester fiber A having a single fiber fineness of 0.01 to 0.6 dtex and birefringence of 0.01 to 0.05 and polyester binder fiber B having a single fiber fineness of 0.2 to 2.0 dtex. Thin paper for stencil paper.   The thin paper for heat-sensitive stencil paper according to claim 1, wherein the polyester fiber A comprises a polyethylene terephthalate polyester copolymerized with 2 to 6 mol% of 5-sodium sulfoisophthalic acid.   The thin paper for heat-sensitive stencil paper according to claim 2, wherein the polyester fiber A has an intrinsic viscosity of 0.30 to 0.45.   The binder fiber B is a polyester composite fiber having a polyethylene terephthalate polyester as a core component and an amorphous copolymer polyester composed of terephthalic acid, isophthalic acid, ethylene glycol and diethylene glycol as a sheath component. The thin paper for heat-sensitive stencil paper as described in any of the above. The thin paper for heat-sensitive stencil paper according to any one of claims 1 to 4, comprising 30 to 90% by weight of polyester fiber A and 10 to 70% by weight of binder fiber B, and having a basis weight of 4 to 15 g / m ^2. .