JP2001029386A - Production of paper diaper and paper diaper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the production of a paper diaper having good stretchability and restorability in combination by subjecting elastic yarn to a stretch restoration processing to impart stretch of specific times of the elastic yarns, then causing the shrinkage restoration thereof and supplying such elastic yarn to a paper diaper production stage. SOLUTION: At the time of paper diaper production, the elastic yarn is subjected to the stretch restoration processing to previously impart the stretch of >=4 times to the elastic yarn then to cause the shrinkage restoration of the elastic yarn, following which this elastic yarn is supplied to the paper diaper production stage. At the time of supply of the elastic yarn to the paper diaper production stage, the elastic yarn is so treated that the expansion and contraction characteristics of the elastic yarn satisfy the inequality Pa/Pb<6 just before the elastic yarn is supplied to the paper diaper production stage. In the inequality, Pa is the stretching force (g) when the elastic yarn is stretched three times and Pb is the tension force (g) when the elastic yarn is stretch 4 times and is thereafter restored to 1.5 times. The elongation is preferably confined to <=80% of the breaking elongation of the elastic yarn and the shrinkage restoration to <=3 times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a disposable diaper.

[0002] More specifically, the present invention relates to a method for producing a disposable diaper having good stretchability and recoverability.

[0003]

2. Description of the Related Art Conventionally, disposable diapers have improved fit with the body such as around the abdomen, around the abdomen and around the waist.
For the purpose of preventing leakage of urine and the like, a nonwoven fabric into which an elastic thread is inserted has been used.

[0004] Such stretchable nonwoven fabrics have been manufactured by stretching a plurality of elastic yarns into a predetermined draft and laminating them with a plurality of nonwoven fabric sheets while maintaining that state.

[0005]

However, in recent years,
Functionality and aesthetics required for disposable diapers will be at a higher level, for example, the level of fit when worn is required to be comparable to that of women's underwear, better stretchability,
What is resilient is demanded.

[0006] Also, health problems such as after tightening to the skin due to the tightening of the gathering portion have been highlighted. For this reason, attempts have been made to improve the elastic yarn used, but no paper diaper having sufficiently satisfactory characteristics has been obtained.

The present invention is easy to stretch and has good tension force (unload power) at low elongation and high elongation (hereinafter, "tension force (unload power)" is referred to as "tension force") and elongation force (load). Power) [hereinafter, "stretching force (load power)" is referred to as "stretching force"], and an object of the present invention is to provide a method for manufacturing a disposable diaper that maintains an appropriate power and has excellent recoverability. .

[0008]

The method for manufacturing a disposable diaper according to the present invention has the following means for solving the above problems.

That is, the elastic yarn is subjected to elongation recovery of at least four times in advance, and then contraction recovery is performed.
A method for manufacturing a disposable diaper, comprising supplying the elastic yarn to a disposable diaper manufacturing process.

Also, a method for producing a disposable diaper, characterized in that when the elastic yarn is supplied to the disposable diaper manufacturing process, the following formula is satisfied immediately before the elastic yarn is supplied to the disposable diaper producing process.

Pa / Pb <6 Here, Pa: elongation force (g) when the elastic yarn is stretched three times Pb: elongate the elastic yarn at an elongation rate of four times, and then 1.5
Tensile force (g) when the elastic yarn is recovered to twice the elastic yarn. After the elastic yarn is subjected to elongation recovery of at least four times in advance and then contraction and recovery, the elastic yarn is removed. A disposable diaper manufactured by a disposable diaper manufacturing method, which is supplied to a disposable diaper manufacturing process.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing a disposable diaper of the present invention comprises:
The elastic yarn is stretched four times or more in advance and then subjected to an elongation recovery process for contraction and recovery, and then the elastic yarn is supplied to a paper diaper manufacturing process.

That is, in the present invention, after the elastic yarn is spun and before the production of the disposable diaper, the elastic yarn is subjected to elongation in advance, and then the elongation recovery treatment is performed.

In the present invention, there is a problem that unless the elastic yarn is stretched in advance and then contracted and recovered, it is difficult to impart to the disposable diaper the property of being easily stretched and easily contracted (restored).

As the elastic yarn in the present invention, a polyurethane elastic yarn, a polyether / ester elastic yarn or the like is preferably used.

The polyurethane-based elastic yarn is a long-chain diol such as copolyester diol as a soft segment and diphenylmethane-diol as a hard segment.
Diisocyanates such as 4,4 diisocyanate and a polyester type having a bifunctional hydrogen compound as a main component as a chain extender or polytetramethylene ether glycol as a soft segment, diphenylmethane-4,4 diisocyanate as a hard segment, chain extension The agent is a polyether type having a low molecular weight bifunctional hydrogen compound as a main component.

The polyether / ester type elastic yarn is a yarn mainly composed of polytetramethylene ether glycol as a soft segment and polybutyl terephthalate as a hard segment.

The elastic yarn can be obtained by spinning a polymer. Such polymers have two types of segments: (a) a soft segment which is a long chain polyether, polyester segment, and (b) a relatively segment derived from the reaction of an isocyanate with a diamine or diol chain extender. And hard segments that are short chain segments. Usually, polyurethane-based elastomers can be produced by chain-extending a prepolymer product obtained by capping a hydroxyl-terminated soft segment precursor with an organic diisocyanate with a diamine or diol.

Typical polyether soft segments include tetramethylene glycol, 3-methyl-1,
Examples include those derived from 5-pentanediol, tetrahydrofuran, 3-methyltetrahydrofuran, and the like, and copolymers thereof.

From the viewpoint of obtaining a disposable diaper that is easier to stretch, has better tension and stretching force at low elongation and high elongation, retains appropriate power, and has more excellent recovery, It is preferable to use a copolyether polyol obtained by ring-opening copolymerization of tetrahydrofuran as a polyol component.

In particular, the higher the degree of polymerization of the copolyether polyol is, the more preferable the effect of the elongation recovery treatment and the stability of the effect are.

Typical polyester soft segments include (a) ethylene glycol, tetramethylene glycol, 2,2-dimethyl-1,3-propanediol and (b) dibasic acids such as adipic acid and succinic acid. And the like.

The soft segments are formed from typical polyethers and polyesters or from polycarbonate diols such as poly- (pentane-1,5-carbonate) diol and poly- (hexane-1,6-carbonate) diol. It may be a copolymer such as a modified polyetherester.

In the present invention, bis- (p-isocyanatophenyl) -methane (MDI), tolylene diisocyanate (TDI), bis- (4-isocyanatocyclohexyl) -methane (PICM), and hexane are used as organic diisocyanates. Methylene diisocyanate, 3,
For example, 3,5-trimethyl-5-methylenecyclohexyl diisocyanate can be used. Among them, MDI is particularly preferred.

Various diamines, for example, ethylenediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, etc., are suitable as chain extenders for forming polyurethaneurea. Chain terminators can be included in the reaction mixture to help control the final molecular weight of the polyurethaneurea. Usually, a monofunctional compound having active hydrogen such as diethylamine can be used as the chain terminator.

The chain extender is not limited to the above-mentioned amine, but may be a diol. For example, ethylene glycol, 1,3-propanediol, 4-butanediol, neopentyl glycol,
1,2-propylene glycol, 1,4-cyclohexanedimethanol, 1,4-cyclohexanediol,
1,4-bis (β-hydroxyethoxy) benzene, bis (β-hydroxyethyl) terephthalate, paraxylylene diol, and the like can be used. The diol chain extender may be only one kind of diol, or may be composed of plural kinds of diols.

Further, it may be used in combination with a compound containing one hydroxyl group which reacts with an isocyanate group. in this case,
As a method for obtaining such a polymer, various methods such as a melt polymerization method and a solution polymerization method can be adopted. For the formulation of the polymerization, for example, a method of synthesizing a polymer by simultaneously reacting a polyol, a diisocyanate, and a chain extender comprising a diol can be employed.

In the present invention, benzotriazole-based ultraviolet absorbers, hindered amine-based weathering agents, hindered phenol-based antioxidants, various pigments such as titanium oxide and iron oxide, sulfuric acid, etc. Barium, zinc oxide,
Functional additives containing cesium oxide, silver ions and the like may be contained.

In the present invention, an elastic yarn can be produced by dissolving a polymer in a solvent to form a polymer solution and spinning the polymer solution.

As a solvent suitable for the polymer solution, N, N-
Dimethylacetamide (DMAc), dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone, and the like can be used. DMAc is a preferred solvent from the viewpoint of solubility in the polymer and the like.

From the viewpoint of spinnability, the concentration of the polymer solution is 30.
%, Preferably from 35% to 38% (based on the total weight of the solution).

The polyurethane elastic yarn using a diol as a chain extender is preferably spun by a melt spinning method, a dry spinning method, a wet spinning method or the like, and a polyurethane elastic yarn using an amine as a chain extender is usually used. It is preferably dry-spun. In the present invention, the spinning method is not particularly limited, but dry spinning using a solvent is desirable.

In the present invention, the elastic yarn may be either a multifilament or a monofilament, and the total fineness is preferably in the range of 420 to 2240 denier.

Further, when the spun elastic yarn is wound around a tube or the like, it is preferable that a silicone oil such as polydimethylsiloxane, a mineral oil or the like is applied.
Since a hot-melt adhesive or the like is used in the manufacturing process of disposable diapers, the amount of the oil agent is preferably in the range of 0 to 2% by weight from the viewpoint of not impairing the adhesiveness of the hot-melt adhesive.

The elastic yarn wound around a tube or the like can be used as a wound body (package) in a disposable diaper process.
The winding amount of the elastic yarn is preferably 1.5 kg or more from the viewpoint of reducing the frequency of replacing the wound body in the disposable diaper process.

In the present invention, the elastic yarn is usually unwound from the wound body by a rolling method (positive feeding, rolling take-off) or a warping method (over end), and can be supplied to a paper diaper manufacturing process.

Before the elastic yarn is supplied to the disposable diaper manufacturing process, the elastic yarn is stretched four times or more, and then contracted and recovered, thereby modifying the elasticity of the elastic yarn. is there.

The elongation is preferably not more than 80% of the breaking elongation of the elastic yarn used. If the elongation exceeds 80% of the elongation at break, the yarn may break due to breakage of the elastic yarn or an excessive load applied to a guide, etc. Failure tends to occur.

In the present invention, as a means for imparting elongation to the elastic yarn, a method of drafting between two pairs of nip rollers can be specifically adopted, and any method capable of drafting can be employed. Method may be used.

In the present invention, it is preferable that the contraction recovery rate of the elastic yarn to be used is in the range of 3 times or less.

The contraction recovery rate in the present invention refers to an elongation rate when the elastic yarn is brought into a state of an elongation rate lower than a given elongation rate.

In the present invention, the elongation recovery treatment can be performed in the step of winding the elastic yarn.

For example, the first step of the elastic yarn spinning winding process
Between the feed roll and the second feed roll, the elastic yarn is stretched by drafting at least four times, and then stretched between the second feed roll and the drive roll so that the elongation is three times or less. A shrinkage recovery process can be performed and wound up on a paper tube.

Further, the elongation recovery processing can be performed in the step of rewinding the elastic yarn.

For example, a nip roller is provided between the feed roller and the take-up roller in the elastic yarn rewinding process, and the elastic yarn is stretched between the feed roller and the nip roller. Shrinkage recovery is performed between the take-up rollers, and the roll can be wound up again.

Further, the elongation recovery processing can be performed in the process of producing a processed yarn, for example, using a covering machine.

When a covering machine is used, in the draft zone, the elastic yarn is drafted to give elongation, and then contraction and recovery are performed to perform elongation recovery processing.

The present invention relates to a method for producing a specific stretch and a specific elasticity between the spinning of the elastic yarn and the insertion of the elastic yarn into the disposable diaper manufacturing machine, in particular, after the spinning and before laminating the elastic yarn between the nonwoven sheets. By performing the shrinkage recovery in this order, it is possible to give the elastic yarn easy-to-extend performance without impairing the contraction (restoring) force of the elastic yarn.

In the present invention, the elastic yarn just before it is supplied to the disposable diaper manufacturing process is provided with a characteristic that is excellent in elongation recovery property with a small difference between the elongation force and the tension force.

When expressed quantitatively, the elasticity of the elastic yarn immediately before being supplied to the disposable diaper manufacturing machine satisfies the following expression.

That is, Pa / Pb <6, where Pa: elongation force (g) when elongating the elastic yarn three times Pb: elongating the elastic yarn at an elongation rate of four times, and then 1.5
Tensile force when recovered to double (g) The elasticity of the elastic yarn used in the present invention is Pa / Pb <6.
It is assumed that.

This indicates that the hysteresis of the elastic yarn is small and that the slope of the curve is flat. The minimum value of Pa / Pb is preferably as close to 1 as possible.

In general, the hysteresis of the elastic yarn tends to become smaller as the number of times of the elongation recovery process increases, for example, as the second cycle becomes longer than the first cycle, and the third cycle, and the slope of the curve becomes flatter. , P
Although a / Pb becomes a value close to 1, Pa / Pb shows a value close to 1 in the first measurement in the present invention.

That is, in the present invention, the elastic yarn is subjected to elongation recovery processing in advance, and is improved into a yarn having a small hysteresis and a flat curve, and then supplied to a paper diaper manufacturing process.

[0055]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples.

The evaluation method of the present invention will be described. [Elongation at break, elongation force, tension force] The elongation at break of the elastic yarn was determined using one elastic yarn having a sample length of 5 cm using a commercially available tensile tester.
Elongate at a constant speed of 50 cm / min and read the elongation at break. The elongation force and tension force are stretched once to 1 to 4 times, and the elongation force at 3 times elongation and 1 time at return. .
Five times the tension was read and averaged as N = 15. [Evaluation of disposable diapers] A disposable diaper wearing test was performed on 10 babies and infants.
The presence or absence of urine leakage was investigated. [Example 1] Polyurethane-based elastic yarn (trade name "Lycra" manufactured by Toray DuPont, type 127, dull yarn, 56
(0 denier) was wound up for the purpose of performing the elongation recovery treatment on the wound body (winding amount: 200 g).

A nip roller was provided between the feed roller and the take-up roller in the rewinding process, and the rotation speed of the roller was adjusted so that the elongation rate of the elastic yarn between the feed roller and the nip roller was quadrupled.

The rotation speed of the roller was adjusted between the nip roller and the winding roller such that the elongation of the elastic yarn became 1.1 times, and the yarn was wound on a paper tube at a winding speed of 50 m / min.

The elongation at break, elongation force, and
Table 1 shows the tension.

FIG. 1 shows an SS curve.

[0061]

[Table 1]

The elastic yarn wound around the paper tube was supplied to the paper diaper step by positive feeding to produce a paper diaper. The resulting disposable diaper is excellent in detachability, fits the movement of the body and expands and contracts.
It had an appropriate tension force, high urine leakage prevention properties, no uncomfortable feeling of pressure or stiffness, and excellent elasticity with less after tightening (red mark) on the skin. Comparative Example 1 A disposable diaper was manufactured under the same conditions as in Example 1 except that the rotation speed of the roller was adjusted so that the elongation rate of the elastic yarn was tripled between the feed roller and the nip roller.

The elongation at break, elongation force, and
Table 1 also shows the tension.

FIG. 1 also shows the SS curve.

The elastic yarn wound around the paper tube was supplied to the paper diaper step by positive feeding to produce a paper diaper. The obtained disposable diaper was inferior to the one of Example 1 in the elastic properties in which red marks were also confirmed. [Example 2] Polyurethane-based elastic yarn (trade name “Lycra” manufactured by DuPont, type 902C, clear yarn, 56)
(0 denier) was wound up for the purpose of performing the elongation recovery treatment on the wound body (winding amount: 200 g).

A nip roller was provided between the feed roller and the take-up roller in the rewinding step, and the rotation speed of the roller was adjusted so that the elongation rate of the elastic yarn between the feed roller and the nip roller became four times.

The rotation speed of the roller was adjusted between the nip roller and the winding roller such that the elongation of the elastic yarn became 1.1 times, and the yarn was wound on a paper tube at a winding speed of 50 m / min.

The elongation at break, elongation force,
Table 2 shows the tension.

FIG. 2 shows the SS curve.

[0070]

[Table 2]

The elastic yarn wound around the paper tube was supplied positively to the paper diaper step to produce a paper diaper. The resulting disposable diaper is excellent in detachability, fits the movement of the body and expands and contracts.
It had an appropriate tension force, high urine leakage prevention properties, no uncomfortable feeling of pressure or stiffness, and excellent elasticity with less after tightening (red mark) on the skin. Comparative Example 1 A disposable diaper was manufactured under the same conditions as in Example 2 except that the rotation speed of the roller was adjusted so that the elongation rate of the elastic yarn was tripled between the feed roller and the nip roller.

The breaking elongation, elongation force,
Table 2 also shows the tension.

FIG. 2 also shows the SS curve.

The elastic yarn wound around the paper tube was supplied to the disposable diaper step by positive feeding to produce a disposable diaper. The obtained disposable diaper was inferior to the one of Example 2 in inferior elastic properties in which a red mark was also confirmed.

[0075]

According to the present invention, it is easy to stretch, has a moderately high tension force at low elongation, has a moderate elongation force and tension force that is not too high even at high elongation, and has a stiffness even at high elongation. A disposable diaper with excellent restoring power, that is, it expands and contracts to fit the movement of the body, and has an appropriate tension force even when the fabric is stretched or contracted, and has high urine leakage prevention , And no uncomfortable feeling of pressure or tension,
It is possible to provide a disposable diaper having excellent elasticity with less (tightening) after tightening to the skin.

[Brief description of the drawings]

FIG. 1 is a graph showing S- of elastic yarns in Example 1 and Comparative Example 1.
It is a schematic diagram showing an S curve.

FIG. 2 shows S- of elastic yarns in Example 2 and Comparative Example 2.
It is a schematic diagram showing an S curve.

Claims (8)

[Claims] 1. A method for manufacturing a disposable diaper, comprising: applying an elongation of at least 4 times to an elastic yarn in advance, and then subjecting the elastic yarn to an elongation recovery process for contraction and recovery, and then supplying the elastic yarn to a paper diaper manufacturing process. . 2. The method for producing a disposable diaper according to claim 1, wherein the elongation rate is not more than 80% of the breaking elongation of the elastic yarn. 3. The method for producing a disposable diaper according to claim 1, wherein the shrinkage recovery rate is set to 3 times or less. 4. The disposable diaper according to claim 1, wherein the elongation recovery processing is performed in a stretch zone provided between the spinneret of the elastic yarn and the winding step. Production method. 5. The stretch recovery process according to claim 1, wherein the stretch recovery process is performed in a stretch zone provided between the feed roller and the take-up roller in the rewinding step of the elastic yarn. Manufacturing method of disposable diapers. 6. A method for producing a disposable diaper, characterized in that when the elastic yarn is supplied to the disposable diaper manufacturing process, the following formula is satisfied immediately before the elasticity of the elastic yarn is supplied to the disposable diaper producing process. Pa / Pb <6 Here, Pa: elongation force (g) when the elastic yarn is extended three times, Pb: elongate the elastic yarn at an elongation rate of 4 times, and then 1.5 times
Tension when recovered to double (g) 7. The method for producing a disposable diaper according to claim 1, wherein the elastic yarn is a polyurethane elastic yarn. 8. A disposable diaper manufactured by the method for producing a disposable diaper according to any one of claims 1 to 7.