JP2591685B2 - Bulky pulp sheet - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a bulky pulp sheet having excellent hydrophilicity and liquid absorbability.

<Prior Art> A method of forming a sheet using cellulose pulp by a cyclic forming method is described on page 27 of the textbook of nonwoven fabric technology seminar (Kagaku Brain, Osaka, 62.2.17). However, the essential disadvantage is that the cellulose pulp must be laminated with the binder, so that the pulp fibers are wetted by the binder, and the bent pulp fibers are completely two-dimensionally laminated. On the other hand, pulp fibers have a short fiber length and therefore have a small amount of entanglement between fibers, so a large amount of binder is required, 10 to 40% of the sheet weight, so that the sheet becomes hard and the properties of the binder become strong. There is a problem with its hygiene.

Anyway, the bulkiness of the sheet is limited, 2.5 g / c
A sheet having an apparent density of 0.04 g / cm ³ or less measured under an m ² load was not obtained. In addition, from the viewpoint of productivity, the layers must be gently laminated so as not to lose bulkiness, and there is a disadvantage that an improvement in production speed cannot be expected.

<Problems to be Solved by the Invention> The present invention further improves the bulkiness which is limited in the conventional pulp dry sheet molding method, and by mixing the binder fiber, even if a small amount or no organic binder is used, An object of the present invention is to provide a sheet having bulkiness and strength, and to provide a sheet having high flexibility, high water absorption, and a strong sheet when absorbing water, and a method for producing the sheet.

<Means for Solving the Problems> That is, the present invention relates to a cellulose pulp of 40 to 90% by weight and a polyester composite fiber 5 to 60 having a crimped form of three-dimensional crimp.
5 to 50% by weight of the heat-fusible binder fiber,
The apparent density obtained from the thickness under a load of 2.5 g / cm ² is 0.04 g / cm ²
The bulky pulp sheet described below, wherein the polyester conjugate fiber is a fiber in which polyesters (A) and (B) satisfying the following i) to iii) are conjugated in an eccentric core-sheath type or a side-by-side type, and A bulky pulp sheet characterized by being a composite fiber that exhibits a three-dimensional crimp of 30 or more pieces per 25 mm by a dry heat treatment at 180 ° C.

i) Polyester (A) is an ethylene terephthalate polyester having an intrinsic viscosity of 0.45 to 0.66 copolymerized with 1 to 6 mol% of isophthalic acid having a metal sulfonate group. ii) Polyester (B) is polyethylene having an intrinsic viscosity of 0.60 to 0.70. Terephthalate iii) The difference in melt viscosity during spinning of polyesters (A) and (B) is (A)-(B) = 100-1500 poise.

The cellulose pulp used in the present invention is preferably a non-bleached or bleached pulp from softwood or hardwood, a fibrous material such as waste paper, or a powdery material obtained by pulverizing fibers. Their fiber length is as short as 10 mm or less and can be uniformly dispersed in air. The compounding ratio is 40 to 90%, preferably 50 to 80%. 40
If it is less than 90%, the pulp component is small, and the liquid absorption rate is poor, which is not preferable. If it exceeds 90%, a bulky pulp sheet cannot be obtained. Other cellulosic pulp such as Kozo, Mitsumata, hemp, bast fiber such as ramie, cotton linter, bamboo,
Plant fibers such as straw can be used as well.

The eccentric core-sheath type or side-by-side type polyester composite fiber (hereinafter simply referred to as polyester composite fiber) whose crimp form is a three-dimensional crimp used in the present invention is basically two kinds of polymers having different shrinkage rates. For example, as the polymer component (A) on the high shrinkage side, isophthalic acid having a main repeating unit of ethylene terephthalate and having a metal sulfonate group as a copolymer component is preferably 1 to 6; Mole% and isophthalic acid
Modified polyesters having a range of 〜80 mol% can be used. Even if isophthalic acid is not copolymerized, the polymerization reaction of the polyester proceeds appropriately to produce a polyester composite fiber having a latent crimping ability within the scope of the present invention, but in order to further increase the bulkiness of the sheet. Is preferably copolymerized with isophthalic acid. Further, isophthalic acid having a metal sulfonate group to be copolymerized is used to keep the melt viscosity at an appropriate level and to make latent crimp development capability manifest within the scope of the present invention. Examples of the isophthalic acid having a metal sulfonate group include 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, and 5-lithium sulfoisophthalic acid.
An ester-forming compound having a metal sulfonate group such as an ester-forming derivative is added in a range of 1 to 6 mol% when polyethylene terephthalate is polymerized, and the above-mentioned isophthalic acid is added and copolymerized as necessary. (A) is obtained. In addition, a polyethylene terephthalate polymer in which isophthalic acid having a metal sulfonate group is copolymerized in a high ratio in advance has been prepared, and a polyethylene terephthalate polymer in which isophthalic acid has been copolymerized in a high ratio has been prepared as necessary. Every
They can also be obtained by a master batch method or the like in which these are mixed with polyethylene terephthalate so that the copolymerization ratios thereof are in the range of 1 to 6 mol% and 0 to 80 mol%, respectively. If the copolymerization ratio of isophthalic acid having a metal sulfonate group is less than 1 mol%, the expression of shrinkage stress during heat treatment is weak, and the crimp development is inferior. If it exceeds 6 mol%, the melt viscosity of the polymer becomes so high that it is difficult to stably obtain a polymer having an appropriate degree of polymerization in the condensation reaction, and the crystallinity at the time of spinning becomes high, so that it tends to change with time. In this case, the drawability is lowered, and a composite fiber having a sufficient latent crimpability cannot be obtained. Preferably 1 to 5 mol%,
More preferably, it is 2 to 4 mol%. Further, a copolymer component other than the above may be introduced into the polymer (A) as long as the copolymer does not significantly impair shrinkability. The intrinsic viscosity of the polymer (A) is preferably from 0.45 to 0.66.

As the polymer component (B) on the low shrinkage side, for example, a polyester substantially composed of polyethylene terephthalate is used. Of course, the polymer (B) may be copolymerized as long as the crimping effect of the polymer (A) is not significantly reduced. Further, the intrinsic viscosity of the polymer (B) is 0.60 to
A degree of polymerization of 0.70 is preferred.

If necessary, for example, an inorganic substance such as titanium oxide, zirconium oxide, silicon oxide, alumina, other ceramics or a flame retardant, an antibacterial agent, a deodorant, a fragrance, and a hydrophilic agent such as sodium dodecylbenzenesulfonate may be mixed. You may. Further, other polymers may be added to the polymers (A) and (B) as long as the crimpability of the fiber is not significantly impaired.

The spinnerets used are round, triangular, +, ∞, T
Although a composite die having a hole shape such as a die is conceivable, it is needless to say that the present invention is not limited to these, and the composite form is not particularly limited. Is preferable in that it is excellent.

The polyester composite fiber used in the present invention is the above (A),
The two types of polymer components (B) are mixed at a temperature in the range of 270 to 290 ° C. using the above-mentioned base, and the composite ratio (A) :( B) = 40 to 60:60 to 4
In the range of 0, it is particularly preferable to use an eccentric core-sheath type or a side-by-side type, preferably a side-by-side type composite fiber as described above. The melt viscosities of the two types of polymer components at the time of spinning are always (A)> (B), and the difference in viscosity during the melt is 10%.
The range of 0 to 1500 poise, preferably 300 to 1000 poise is preferable for obtaining a conjugate spun fiber having excellent latent crimpability. As the composite ratio deviates from 50:50, a kneeing phenomenon is more likely to occur in the die discharge portion. Therefore, the range of (A) :( B) = 45 to 55:55 to 45 is most preferable.

Next, in order to give the sheet bulkiness, flexibility, stretchability, and elongation recovery, it is important to heat-treat the polyester composite fiber to express three-dimensional crimps, particularly spiral crimps. Furthermore, it is important that the number of spiral crimps and the shape (curvature) of the crimps at that time are sharp. Specifically, the number of crimps is 30 pieces / 25 mm or more by dry heat treatment at 80 to 180 ° C. It is preferred to express shrinkage. 30 crimps
If the thickness is less than 25 mm, the bulkiness, flexibility, and stretchability are significantly reduced, resulting in a sheet having a high bulk density. In addition, the shrinkage rate during heat treatment has an important relationship with the feeling, bulkiness and stretchability of the sheet, and the preset temperature and final drying heat treatment temperature, which are general processing conditions, should be selected to satisfy 80 to 180 ° C. Is good.

Such a polyester composite fiber having latent crimpability and heat shrinkability is characterized by a difference in melt viscosity between the polymer (A) on the high shrink side and the polymer (B) on the low shrink side, and the polymer (A) , The composite ratio of (A) and (B), and the stretching conditions and the tension heat treatment conditions in the stretching step after spinning. The stretching condition is to maximize the potential crimpability by stretching the fiber at 60-75% of the maximum stretching ratio after spinning. In this state, the tension heat treatment should be performed at 130-180 ° C. Thereby, high crystallinity can be maintained and a high latent crimping force is cultivated.

Further, the polyester conjugate fiber may be an un-crimped fiber for dry molding. However, in order to further improve the crimpability and dispersibility, the undispersed fiber is dispersed by a push-in type crimping machine which is a general method. Mechanical crimping that does not cause crimping, number of crimps 3 to 20
Raw cotton with 25 mm / 25 mm may be used. 20 crimps / 25
If it exceeds mm, it is not preferable because dispersion is not sufficiently performed by a mixer or a disperser. The fineness of polyester composite fiber is 0.5
1515 denier is good, and more preferably 2 to 6 denier. If it is less than 0.5 denier, the spiral crimping performance is good, but the crimping power is weak and bulkiness cannot be easily obtained. On the other hand, a region exceeding 15 deniers is unpreferable because it becomes a rough sheet and lacks flexibility, and furthermore, the strength of the sheet is weakened. Fiber length is 3-30mm, fiber length is 3m
If it is less than m, the fiber is too short, and the entanglement of the fibers is not preferable. On the other hand, if it exceeds 30 mm, the entanglement of the fibers at the time of dispersion becomes too strong to form pills and it is not possible to obtain a uniformly dispersed floc. The compounding ratio of the polyester composite fiber is required to be 5 to 60%, preferably 15 to 60%. If it is less than 5%, the effect of expressing bulkiness in the sheet is small, which is not preferable. On the other hand, if it exceeds 60%, it is not preferable because of problems such as poor water absorption rate and lack of economy.

The heat-fusible binder fiber used in the present invention is, for example, polyethylene, polyolefin-based fiber such as polypropylene, modified polyester or polyamide having a low melting point or low softening point by copolymerization, polyamide, ethylene-vinyl alcohol copolymer, ethylene -A synthetic fiber or a sheath component composed of a single component selected from a polyvinyl alcohol-based copolymer such as a vinyl acetate-vinyl alcohol copolymer, and a sheath component composed of a component selected from the above-described polymer, and a core component in which an unmodified polyester is used; Core-in-sheath composite fibers made of a polymer such as a polypropylene-based or polyamide-based polymer can be used.

Further, the fineness of the heat-fusible binder fiber is preferably 1 to 6 denier, and if it is 1 denier or less, the dispersibility becomes poor, which is not preferable. If it exceeds 6 denier, the binder effect is reduced and the feeling of the sheet is deteriorated. Is not preferred. It is preferable to use an uncrimped crimp to obtain dispersibility, but by giving a crimp of 20/25 mm or less in a range not impairing the dispersibility to improve bulkiness during heat treatment. Is also good. With crimps exceeding 20/25 mm, tangling of the yarn during dispersion is likely to occur. The fiber length should be 2 to 60 mm, 2 m
If it is less than m, it is difficult to obtain the binder effect, and if it exceeds 60 mm, it becomes a pill and dispersion becomes worse.

The blending ratio of the heat-fusible binder fiber must be 5 to 50% by weight, preferably 10 to 40% by weight. If the amount is less than 5% by weight, no effect is exhibited on sheet strength and elasticity recovery properties when mixed with polyester conjugate fiber and cellulose pulp and prevention of generation of fluff on the sheet surface.

Next, as the strength improving effect and the hardness imparting effect of the obtained sheet, a thermoplastic or thermosetting, water-soluble or other emulsion or aqueous solution can be used as an organic binder.

As the thermoplastic emulsion, polyethylene, polypropylene and other polyolefin-based, polyvinyl acetate-based,
Polyvinyl chloride is preferred, and other polyvinylidene chloride-based, polyamide-based, polyurethane-based, and polyester-based ones can also be used.

The thermosetting emulsion is preferably an acrylic, phenolic or epoxy type, but is preferably a resin formed by a reaction with formalin such as urea, ethylene urea, melamine, benzoguanamine, etc. Systems, novolak systems, furan systems, polyisocyanate systems, and their copolymers can also be used.

As a water-soluble resin for imparting hydrophilicity to the sheet, there is a starch-based resin as a natural product, and dextrin, acid-modified starch, oxidized starch and other starch derivatives are preferred as the modified starch.

As the cellulosic type, complex polysaccharides such as arabic gum, tragacanth gum, guar gum, and alginic acid are preferable, and other protein type casein, soy protein, albumin, glue, and gelatin can be used. On the other hand, polyvinyl alcohol and its copolymer are preferable as the synthetic product, and other isobutene-maleic anhydride copolymer, polyacrylamide, polyethylene oxide, polyvinylpyrrolidone, polyvinyl acetate copolymer, acrylic copolymer, and the like are used. be able to.

A method of applying such an organic binder to fibers is as follows.
For example, there are a method of spraying an organic binder uniformly in a spray state on fibers dispersed in the air before the laminating step, and a method of spraying or impregnating the fibers after laminating the fibers. The attached amount of the organic binder is preferably 5% by weight or less based on the sheet weight. The organic binder need not always be used in consideration of the feeling and bulkiness. If the binder is used in an amount exceeding 5%, not only the bulkiness cannot be obtained but also the properties of the binder become strong, which is not preferable.

In producing a bulky pulp sheet, the cellulose pulp is kept in a dry state, and the dispersibility of the pulp is increased as much as possible even if the pulp is made into a sheet with fibrous material or the pulp fiber is crashed into a powder state. For this purpose, it is put into a pulper or a mixer with blades which can be pulverized or disintegrated and dispersed at high speed in the air, and disintegrated and dispersed until it becomes a single fiber or individual particles. Separate by air cyclone or vibrating mesh to remove undispersed or impurities.

The obtained cellulose pulp has a moisture content of 0 to 10%.
A predetermined amount of the dried polyester composite fiber is charged and mixed. The input amount is 15 to 60% based on the sheet weight, and mixing and stirring are performed at 10,000 to 20,000 rpm as in the case of cellulose pulp. Or you may defibrate with blended cotton.

Further, the heat-fusible binder fiber specified in the present invention is added to the mixed fiber, and similarly mixed and stirred to obtain a mixed fiber floc. In order to prevent unfibrillated materials and lumps from being mixed in the mixed cotton-like material, a roller guard may be passed through to further improve the uniformity of the mixing property, or between a roller with a garment such as a card roller. Crushed sliver or mixed cotton. A predetermined amount is transported by air to the collecting box by a rotary pulp that discharges a certain amount of the mixed cotton.

Inside the box, there is an organic binder spray device,
It is preferable to provide a movable net for stacking sheets below and a certain amount of air vent.

The mixed cotton-like material laminated to a predetermined rice basis weight or thickness is taken out of the net conveyor and placed in a radiant type air bath at 80 to 250 ° C and subjected to a drying heat treatment at a fiber temperature of substantially 80 to 180 ° C. By doing so, the bulky pulp sheet of the present invention can be obtained. The organic binder may be sprayed to give the obtained bulky pulp sheet a strong force, or to harden the surface and prevent the generation of fluff.

The characteristic of the bulky pulp sheet obtained in this way is that the apparent density when the thickness is measured with a load of 2.5 g / cm ² is 0.04
It is a very bulky sheet of less than g / cm ³ .

Regarding flexibility, eccentric core-sheath type or side-by-side type polyester composite fiber, which generates spiral crimp, despite the fact that cellulose pulp is as large as 40 to 90%, has a spring shape in the thickness direction of the sheet, that is, in the three-dimensional direction. That the polyester composite fiber and the heat-fusible binder fiber have a smaller elastic modulus than the cellulose pulp and have a softness that gives flexibility in the sheet structure. I think that the.

Furthermore, the high water absorption is attributed to the bulkiness of which the apparent density is 0.04 g / cm ³ or less. As for the stiffness when absorbing water, the cellulose pulp has an extremely low Young's modulus when wet, but because the polyester composite fiber and the heat-fusible binder fiber are hydrophobic, they are not affected by moisture and have a low Young's modulus. It is firm and firm to hold.

As described above, since the bulky sheet of the present invention has a high hydrophilicity and a high liquid absorption amount and liquid absorption rate, it is widely used in the field of disposable materials from the viewpoint of its feeling, for example,
Sanitary material sanitary napkin absorbents, paper diapers, and household and industrial wipers, cooking oil absorbents, drip absorbents for maintaining freshness, fresh vegetable moisture absorbents, interlining, slippers, shoes for clothing It is widely used for packaging materials, cushioning materials, agricultural sowing sheets and the like.

<Examples> Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto.

Examples 1-4 and Comparative Examples 1-2 Exposed softwood pulp sheet (Canadian freeness)
760ml) with 16,000rpm mixer
, PET with latent spiral crimping performance
Polyester composite fiber arranged in side-by-side type
(Soft N- made by Kuraray Co., Ltd.) 790 2.5 denier
Fiber length 5mm crimp number 16 / inch) and heat-fusible binder
-As a fiber, a modified polyester with a sheath of 110 ° C
The core is a normal polyester Sofi made by Kuraray Co., Ltd.
Nut N720 (2 denyl, 5 mm fiber length) and sheath polyes
Chi Co., Ltd., whose core is a composite fiber of polypropylene
Tsso's EA CHIP (3-denier fiber length 5mm)
These were mixed at the mixing ratio shown in Table 1 at 16000 rpm for 2 minutes.
The mixture was stirred for a while to obtain a uniform mixed floc.

While discharging a certain amount of these mixtures from between the card-type needle-shaped rolls, a certain amount is discharged by air, and the mixture is sent into a collecting box equipped with a Teflon mesh moving at a constant speed,
The layers were stacked while only air was exhausted from Teflon mesh. Some (Examples 2 to 4 and Comparative Examples 1 and 2) were sprayed in such a manner that a predetermined amount of an organic binder was sprayed thereon, and then sprayed.
Heating was performed simultaneously with drying at 0 ° C. for 2 minutes to obtain a bulky sheet as shown in Table 1.

The organic binder used was acrylic latex (Nicazole-A02 manufactured by Nippon-Carbide Co., Ltd.).

Examples 5 to 8 and Comparative Examples 3 to 5 Powdered pulp (crush pulp) dispersed as a cellulose pulp with a mixer at 16000 rpm, and a side-by-side type polyester composite fiber having the same spiral crimping performance as in Examples 1 to 4 ( Kuraray's Soft N-
790 2.5 denier fiber length 5 mm) and Kuraray's Soft N-720 2 denier fiber length 5 mm) as a heat-fusible binder fiber were mixed and stirred at 16,000 rpm for 2 minutes at the mixing ratio shown in Table 2 to obtain a uniform mixed cotton-like material. I got

Otherwise, bulky pulp sheets were obtained in the same manner as in Examples 1 to 4. For comparison, a sheet was formed in the same manner as in Examples 5 to 8 using only cellulose pulp, and a part (Examples 6, 8 and Comparative Example 4) was sprayed so that a predetermined amount of an organic binder was adhered thereto. Heat treatment was performed simultaneously with drying for minutes.
The results are shown in Table 2.

In addition, the measuring method of each characteristic value etc. in this invention is as follows.

(1) Intrinsic viscosity: measured at 30 ° C. in a mixed solution of equal weights of phenol and ethane tetrachloride.

(2) Fineness: Measured by the method of JISL-1015-7-5-1A.

(3) Number of crimps: Measured according to the method of JISL-1015-7-12-1.

(4) Free shrinkage: Treated in an atmosphere of 170 ° C for 30 minutes according to the method of JISL-1015-7-15, 300 per denier
Measured with a load of mg.

(5) Measurement of sheet properties Basis weight: JISP8124 Bulk density: Four sheets are stacked, a plastic plate is applied to 2.5 g / cm ² , the thickness is measured with a micrometer, and the average value per sheet Was determined from the thickness.

Strength and elongation: JISP8113 Liquid absorption: Water was used as the liquid substance.

The weight (W ₀ ) of a sample cut into a size of 10 cm × 10 cm is measured. Leave the sample in water for 15 minutes to confirm that the air in the sample has been replaced. The sample is lifted into the air, and the weight of the sample (W ₁ ) at the time when the droplet stops falling is measured.

It is a value obtained from the above.

(6) Hand: Judgment was made as follows.

◎ Feel like rabbit hair (softness with slimy feeling) ○ 〃 (soft feel) △ Feel like cloth (rough) × Feel like paper (crisp) (7) Drying When elastic recovery, cut the sheet as it is into a 10 cm square sheet and layer it to a thickness of about 10 cm, place a plastic on this surface and apply a total load of 500 g,
After resting for 60 minutes and removing the load, recovery to the original thickness was observed after 60 minutes.

◎… 80% or more recovery ○ …… 60-80% recovery △ …… 40-60% 40 ×… 20-40% 〜 ××… 20% or less〃 (8) Sufficient elastic recovery when wet Was observed in the same manner as in the case of dry elastic recovery.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shoji Okito 7471 Otoshima Tamashima, Kurashiki-shi, Okayama Examiner, Kuraray Co., Ltd. Examiner Masato Matsunawa 57-13661 (JP, B2)

Claims (1)

(57) [Claims] 1. 40 to 90% by weight of cellulose pulp and 5 to 60% by weight of a polyester composite fiber whose crimp form is a three-dimensional crimp.
2.5g / c containing 5-50% by weight of heat-fusible binder fiber
A bulky pulp sheet having an apparent density of 0.04 g / cm ² or less as determined from the thickness under a load of m ² , wherein the polyester composite fibers satisfy polyesters (A) and (B) satisfying the following i) to iii): ) Is a fiber composited in an eccentric core-sheath type or a side-by-side type, and 25 m by dry heat treatment at 80 to 180 ° C.
A bulky pulp sheet characterized by being a composite fiber exhibiting three or more three-dimensional crimps per m. i) Polyester (A) is an ethylene terephthalate polyester having an intrinsic viscosity of 0.45 to 0.66 copolymerized with 1 to 6 mol% of isophthalic acid having a metal sulfonate group. ii) Polyester (B) is polyethylene having an intrinsic viscosity of 0.60 to 0.70. Terephthalate iii) The difference in melt viscosity during spinning of polyesters (A) and (B) is as follows: (A)-(B) = 100-1500 poise