KR100376374B1 - Change of processing heat of nonwoven fabric - Google Patents

Abstract

Thermally bonded thermoplastic and partially thermoplastic nonwovens are thermally processed under low pull rate tension and result in significant improvements in the elasticity of nonwovens' consistency, softness and high commercial value. The resulting skin provides use for all nonwoven applications where softness, consistency and elasticity are useful. The method develops elasticity in one direction only, but both embodiments provide the ability to create longitudinal or transverse elasticity of the roll's preceding material. In addition, any preceding landings containing more than 70% heat-bonded thermoplastic fibers can be used in practice.

Description

Change of processing heat of nonwoven fabric

The present invention relates to thermoplastic fibers, or thermoplastic fibers and non-thermoplastic fibers, which are machine-modified under certain process conditions to produce a finished skin that is softer, less stiff, ductile, and exhibits a remarkable degree of elasticity, which is important and commercially valuable. A thermal adhesive nonwoven fabric containing a mixture. In one embodiment, the present invention relates to a laminate of a nonwoven fabric and a nonwoven fabric. In yet another embodiment, the present invention relates to a method and apparatus for thermally modifying a thermally bonded nonwoven fabric containing a thermoplastic fiber or a mixture of thermoplastic and non-thermoplastic fibers with a machine.

Nonwovens have created a huge industry in response to the demand for cheap materials to replace woven fabrics for use in many fields of disposable products. These include hygiene products such as diapers, sanitary napkins, masks and surgical gowns for adults and infants. Disposable hygienic protective articles including personal work items such as hoods, surgical packaging, coverall hoods and masks, and underwear.

Although cheap, nonwovens have some negative aspects. It is neither as strong nor durable as conventional woven fabrics. Less or less elasticity, consistency or elegance tends to be stiffer and less flexible than woven fabrics.

Today's most popular nonwovens are made from the fibers of thermoplastic fibers. These skins can be made from machine produced fibers or fibers extracted directly from the molten thermopolymer. The fibrous skin produced in this way has a very low strength before the fibers constituting the skin are bonded together with heat despite the method of forming the skin. Adhesion is done with a press roll of heat embossing or other thermal means that bond the fibers to their intersection to provide the required strength.

The main defects of nonwovens are elasticity or elongation, toughness, softness, and lack of consistency. Toughness is an important factor in the durability and practicality of disposable products. This is important from the point of view of practicality, even if these products are written and discarded for a short time. Softness is also important for any number of uses where disposable diaper face materials, disposable medical and industrial garments, disposable sheets and pillowcases and nonwovens come into contact with the skin.

For any fabric, whether it is a woven or nonwoven fabric, the ability to spread and restore the material is a desirable property because it improves toughness, consistency, and suitability of the resulting product. This property is generally called elasticity. In practical use the material requires only 30-50% recoverable spread to contribute to the disposable garment. As an example, a disposable twenty-four inch waist should only spread 50% to fit a 36 inch hip.

Some attempts to provide spread, elasticity, and increased toughness and consistency have had to incorporate elastomers into the nonwovens. This is achieved using films, bands or strings of natural or synthetic rubber. Disposable products of nonwovens using elastomers are very expensive and therefore exist only in limited use in the industry.

One method used to provide spreading or consistency was to crepe the fabric using various means of longitudinal mechanical compression. This provides some elongation in the direction of creping but no change in tensile strength or toughness. A serious drawback is that the creped material has very poor protective properties after stretching. Crepe also reduces the softness of the material.

Hassenmuller and others, U. S. Patent No. 5,244, 482 (1993), disclose a method in which a very high pull frame is used to coalesce the preceding landings, resulting in a reduction in the mean pore diameter and narrowing the pore diameter distribution. Very high pull rates require a change in the organization of the nonwoven fabric, creating a major change in pore diameter. Elasticity is created, but the resulting fabric is stiff and has a low modulus of elasticity. In addition, the patent places significant limitations on the degree of crystallinity, thermoplastic fiber content, fiber diameter, random fiber deposition, isotropic tension properties, and the physical properties of the preceding landings such as low tension elongation to breakage.

The very high pull rate, known from US Pat. No. 5,244,482 to provide high lateral strengthening of the fiber, ends with a landing with a total change in his tissue. These changes have been demonstrated to increase the packing density, which reduces the average pore diameter, resulting in a significant improvement in the filtration effect.

U. S. Patent No. 5,244, 482 does not expect the use of very low pull rates and in fact places a lower limit on preferred pull rates of 5 to 10 times higher than the present invention.

U.S. Patent 5,244,482 is similar to U.S. Patent 5,053,066 and also alters the structure for filtration applications in relation to post-treatment treatment by the application of a very high pull rate to the preceding thermoplastics.

US Pat. No. 4,048,364 (1977) to Harding and others discloses the use of high pull rates to increase the tensile strength of the reburn of meltblown polypropylene fibers in which the pretreated state should have little or no fiber crystallization or heat resistance. Is starting. It is not stated whether elasticity is developed.

US Patents 5,441,550 and 5,443,606 for Hassen Muller and elsewhere describe the same method as US Pat. No. 5,224,482 but use different prior landings.

The use of high pull rate pull is well known and practiced in the film industry for arranging films for increased strength and toughness. A typical stretch roll arrangement is shown in US Pat. No. 4,408,974 (1983) to Commerio.

Another well-known example of high pull rate attraction is the pulling of thermoplastic textile fibers from the melt through a die using a continuous Godet roll, where each successive set of pull rolls is constantly rotating at high speed. There is this.

Now, to outline the present invention, the inventive land is produced by stretching the nonwoven fabric under very low pull rates and carefully controlled heat treatment conditions. This has the unexpected result of creating a significant improvement of high elasticity, softness and consistency in the preceding landings. This is accomplished without a significant change in the mean pore diameter or pore diameter distribution, which reduces the softness and consistency.

Surprisingly, these results do not help with the characteristics of the prior art, as is the case with the prior art. An assertive criterion is that the preceding skin is heat bonded and contains at least 70% thermoplastic fibers and the remaining fibers are non-thermoplastic. The method targets heat-bonding nonwovens that have resulted in melt blow, spun adhesion, and baffles, as well as laminations containing two or more of the aforementioned nonwovens and the aforementioned nonwovens and thermoplastic films.

The method of the present invention involves a thermally adhesive nonwoven fabric that contains at least 70% of thermoplastic fibers in a carefully controlled low pull rate elongation, while the skin is only at a temperature of 70 ° F. above its firing point. Low pull rate stretching may be performed in the longitudinal or transverse direction using any of the preceding landings indicated above. The resulting landing exhibits a surprisingly high and commercially valuable degree of elasticity. The resulting skin is softer, less deprived and shows improved toughness than the preceding skin. Elasticity appears in the direction perpendicular to the direction of stretching. Higher levels of elasticity are developed in both longitudinal and transverse cases using anisotropic preceding landings and pull rates below 9.5 in / in / min. Both of these properties make the present invention more prominent than US Pat. No. 5,244,482.

Accordingly, the present invention has several objects and advantages in addition to the objects and advantages of the method and the land described in the patent.

(A) Providing a method of producing a soft, matchable elastic nonwoven material that can serve many purposes for the use of nonwovens in disposable clothing and other products in which the material is in contact with the user's skin.

(B) providing a way to produce a soft, matchable elastic nonwoven material at a high speed to produce an economically viable, commercially viable, post-production method;

(C) To provide a very flexible way in the selection of preceding landings.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

As described above, the present invention provides a significant and commercially valuable degree of elasticity in which the transverse or longitudinal direction becomes apparent, which increases in softness and consistency, depending on the direction of the attracting pull. It is related to post-processing.

An embodiment implementing a preferred method that will develop longitudinal elasticity is schematically illustrated in FIG. 1. A series of rotating rolls 3 each having a rubber or other surface coating 16 which provides a large coefficient of friction, which is unleashed from the master roll 1 and is released in the master roll 1, and is contained within the thermally controlled environment or oven 17. ) Through (15) and wound on the next winder roll (9). Each continuous roll of the series of rolls 5 to 13 has a higher rotational speed than the roll immediately preceding it. The absolute speed of each roll depends on the number of rolls and the tangential distance between the rolls and the nominal pull rate for the entire roll is 9 5 in / in / min or less. Its speed and differential speed are controlled by suitable gear units or individual variable speed motors. The tangential distance between each roll in a continuous state is determined so that the total pull rate or nougat pull rate for the successive rolls does not exceed 9.5 in / in / min despite the number of rolls. The pull rate is the formula, pull rate = (ΔL / L) X1 / t, where ΔL is the increase in length between rolls, L is the tangential length between rolls, and t is the time at which one point on the landing passes from one roll to the next. It is calculated using. The thermal environment or oven 17 is maintained below 70 ° F., which is the firing point of the preceding landings described below. The elongation of the landing 2 under certain method conditions causes the landing to decrease in width by increasing the length of the landing. An increase in base weight is noted compared to a prior landing. The resulting landing exhibits transverse elasticity.

Alternative embodiments

An alternative embodiment of carrying out the preferred method of developing longitudinal elasticity is schematically illustrated in FIG. 2. In the foregoing description, the landing is pulled in the longitudinal direction to develop the transverse elasticity, but in this embodiment the landing will spread laterally to develop the longitudinal elasticity.

The apparatus implementing the preferential method of transverse pulling consists of an oven or other thermally controlled environment and is initially a set of two opposing consecutive slots 33a, 33b running parallel to the longitudinal direction of the apparatus. Is inside. At the design point in the oven where the landing reaches its plastic point, the path of each slot begins to diverge transversely outward from the centerline of the device so that each slot has a specially designed arch curve until the distance between slots is equal to the desired spread. To follow. This is typically up to 40% pull. At this point each slot is bent back in a direction parallel to the longitudinal direction. The path of each slot is bent back out of the next oven and returned semi-longitudinally to the entrance of the device joining the beginning of the slot. Each slot houses endless chains 40a and 40b which in turn drive a number of commercially available fabric clamps 41. The chain is driven by a single variable speed motor via a reduction gear.

The shape of the curve 35 of the slot is of great importance and is designed such that the longitudinal velocity vector element increases at an appropriate rate to achieve the desired transverse pull rate. Similarly, the longitudinal velocity vector element should be reduced to achieve the desired longitudinal relaxation. If the arch curve and its velocity vector component are not correctly designed and the landing cannot be longitudinally relaxed, the attraction effect will be biaxial instead of shortening and less or less elastic. The pull rate is the formula, pull rate = (ΔL / L) X1 / t, where ΔL is the increase in the width of the landing between the grip clamps, L is the increase in the width of the landing after passing through the tensioning device, and t is the amount of It is calculated using the time drawn.

Using the apparatus described above, the preceding landing 27 is released from the master landing roll 25 and enters a lateral tension in the thermally controlled environment or oven 37. The landing is aligned between two longitudinal slots 33a, 33b that define the path of the longitudinal edge of the landing. In entering the transverse tension, the landings are gripped on parallel sides, respectively, by opposing sets of commercially obtainable fiber clamps 41 arched by clamp setting cams 34a, 34b. When the chain moves forward, the next set of opposite clamps is actuated by the clamp setting cams. This sequence is repeated as the chain and the landing move forward to the landing heating environment. Initially the slots run parallel to the longitudinal direction to provide time to reach the plastic point where the landing is ready to be attracted. When the landing reaches a temperature of 70 ° F., which is preferably a plastic point, the slots begin to diverge outward in the longitudinal direction so that each slot follows a specially designed curve until the distance between the slots is equal to the desired spreading. . The landings held by the fiber clamps successively following each opposing longitudinal edge thus develop at a desired pull rate of less than 9.5 inches per inch per minute to develop elasticity, bootiness and consistency. After the tensioning step is completed, the landing is cooled by leaving the oven or by atmospheric or forced cooling air. The temperature of the landing is reduced to 50 ° F. below the plastic point, and then released by the fiber clamp 41 release cams 36a, 36b and the landing is wound on the winder roll 28. The speed of the winder roll is controlled by a tension monitoring device such as the dancer roll 45 to prevent the spread of the landing before the winding is wound.

vernacular

The following definitions are in accord with recognized industrial and technical definitions and are for better understanding of the description of the preferred embodiments and methods, the experiments below, and the like.

Ground elasticity: A characteristic of a material's structure or structure that allows it to spread to 200% and recover at least 85% of its original dimensions within 5 minutes if its spread stress is removed.

Plastic Point: The plastic point was defined for the experiment as a temperature at which the sample nonwoven fabric was stretched at least 40% in 5 seconds when subjected to a stress equal to 10% of its normal tensile strength of breakage.

Pull rate: A physical deformation of the dimensions of an object under tension. Classically, the pulling rate is the rate at which an object is stretched in a single direction. This is typically measured in inches per inch of length of the object being pulled per minute. It may also be expressed as a percentage.

ASTM Test Method D-638 A2.13 describes the pull rate as the ratio of crosshead movement divided by the initial distance between the crossheads. The crosshead applied in this case is a jaws holding the material which is subject to force or stress. The pull rate for this calculated result is accurate unless there is a substantial change in cross-sectional area.

The distortion rate is As arithmetic equation.

Where L ₁ is the original gauge length, L ₂ is the stretched length and t is the time to stretch the material.

Experimental data

In order to evaluate the elasticity, softness and consistency of the lands after the processing heat treatment, a series of experiments were conducted on various lands. The lands were used without prior selection to refuse lands with physical properties of anisotropy as required by the prior art of US Pat. No. 5,244,482, room temperature elongation greater than 40%, or other specific physical organizational and chemical properties.

Trial runs included spunbond, meltblowing, lint-bonded, thermally bonded, and laminated landings. Fiber formats were polypropylene, polyester and nylon. Lamination of spunbond and polyurethane foam was also included. These materials were pulled in the longitudinal direction and were characterized by the development of transverse spreads.

The materials are converted to processing heat at temperatures in the range from 40 to 50 ° F above their individual firing points, using production line speeds in excess of 400 feet per minute to achieve excellent elastic, excellent production properties of softness, consistency and precision. Had.

All samples were tested for elasticity by measuring recovery of 10 cm samples after 15 cm or 50% elongation. Recovery was measured after 10 seconds and 5 minutes. All samples had at least 85% recovery after 10 seconds and at least 90% recovery after 5 minutes. The results are shown in Table 1.

Table 1

Softness is a very difficult property to measure. The spinning industry tests softness by weekly methods, usually using panelists. In this case, the samples of Table 1 were evaluated by five members using the standard blind sample test method. Samples of the preceding and treated landings were evaluated on a scale of 10 for smooth and 1 for robust 1-10. The sample was not confirmed except for the code number, and there was no confirmation whether the sample was a processed sample or a preceding sample. All samples had a significant improvement. These results are shown in Table 2.

TABLE 2

It was found that the reduction of the landing width after pulling during the trial run for the transverse elasticity was a good induction for the improvement of the optimum elasticity. It was found that the reduction in landing width should be between these data shown in Table 3.

TABLE 3

Prior art US Pat. No. 5,244,482 records extremely high filtration capacity due to a significant reduction in pore diameter and pore distribution. This phenomenon appears to be related to the very high pull rate shown in US Pat. No. 5,244,482 and subsequent severe plastic deformation and tissue degeneration. Filtration tests were performed on the samples of the preceding examples. The results of these tests indicate little or no improvement in filtration capacity. This further distinguishes the present invention from US Pat. No. 5,244,482.

Table 4

Alternative embodiment

Trial runs to develop longitudinal spread included spunbond, meltblowing, lint-free thermal bonding and stacking landings. Fiber formats included polypropylene, polyester and nylon. Lamination of spunbond and polyurethane foam was also included. These materials were pulled laterally and were characterized by the development of longitudinal spread.

The materials were heat treated at production line speeds of more than 250 feet per minute to change the softness, consistency and high elasticity of the excellent production properties.

All samples were tested for elasticity by measuring recovery of 10 cm samples after 15 cm or 50% elongation. Recovery was measured after 10 seconds and 5 minutes. All samples had at least 85% recovery after 10 seconds and at least 90% recovery after 5 minutes. The results are shown in Table 5.

Table 5

Thus, the data indicate that the present invention and the nonwovens thus produced produce unique nonwovens with unique properties that improve their performance in all applications requiring high elasticity, improved softness and consistency. In addition, the advantage of the present invention to make the processing thermal landing change at a low pull rate,

It is possible to use materials that are brittle in contact in applications that contact the skin,

Allows the replacement of expensive, soft nonwovens, reducing costs for producers and consumers of disposable products,

Increasing the integrity and spread of disposable coatings will reduce the amount of material required per piece when using non-spread and non-integrated products,

Since the low pull rate system targets nonwoven fabrics that contain a large percentage of cellulose-based non-plastic fibers, disposable coatings have the added advantage of providing a soft, ventilated moisture to improve wearer comfort.

Although the foregoing descriptions include specific applications, they should be construed as merely illustrative of some embodiments of the present invention, not as limiting the scope of the present invention.

1 is a diagram illustrating the arrangement of a roll and thermal environment to provide longitudinal pull to a landing resulting in transverse elasticity.

FIG. 2 is a diagram illustrating the arrangement of components that provide lateral pull to a landing resulting in longitudinal elasticity.

Claims (17)

In the method for producing a nonwoven fabric having a transverse elastic properties, (a) the plasticizing point of an anisotropic preceding skin consisting of a mixture of thermally bonded plastic and non-plastic fibers, which are directly worn on the skin, up to 70% -100% of thermoplastic fibers and the rest containing non-thermoplastic fibers. Unwinding into the heated heating means at a temperature of 70 ° F., (b) narrowing the transverse dimension of the landing, lengthening of the length and improving the elasticity of the 80% recovery after 50% elongation in the same plane or perpendicular direction as the pulling force, and improved softness and improved Pulling a heating of 3.5 in / in / min-9.5 in / in / min within the landed heating means, characterized by an integrity, a 5% basis weight increase and a 20% maximum pore diameter reduction. Continuously pulling longitudinally by means of variable tension means sufficient to provide a nominal pull rate, the rate being calculated based on the gauge length between the individual components of the tension means; (c) winding the landing of cooling to the mandrel The method consists of. The method of claim 1, The tensioning means are a plurality of rotating pull rolls coated with high friction means and the speed of each continuous roll is increased to provide a total pull rate of 3.5 in / in / min-9.5 in / in / min between its speed and the roll. A method for producing a nonwoven fabric having transverse elastic properties, which is divided into layers. The method of claim 2, A method for producing a nonwoven fabric having transverse elastic properties, wherein the series of pull rolls is 4 or more and 20 or less. The method of claim 1, A method for producing a nonwoven fabric having transverse elastic properties in which tension means are located in a heating means. The method of claim 1, A method for producing a nonwoven fabric having transverse elastic properties in which a tension means is located outside the heating means. Heating of the heating is governed by a variable tension means sufficient to provide a pull rate of 3.5 in / in / min-9.5 in / in / min, the pull rate being calculated based on the gauge length between the individual components of the tension means. 80% recovery of the improved elasticity of the resilience, improved softness, and improved integration after the resulting landing has been stretched 50% in the direction of the plane and perpendicular to the same plane as the narrowness of its transverse dimension, the increase in its length and the pulling force. Subject to variable tension means sufficient to provide sex, The anisotropic preceding skin consists of a mixture of heat-bonded plastic and non-plastic fibers, which are worn directly on the skin, the mixture containing up to 70% to 100% of thermoplastic fibers and the rest containing non-thermoplastic fibers, and the preceding skin A nonwoven fabric produced using the method of claim 1 which is continuously drawn in the landed heating means by a plurality of tensioning means. The method of claim 6, The thermoplastic fiber is a nonwoven selected from the group comprising polyolefins, polyesters, polyamides and their respective copolymers. The method of claim 6, The non-thermoplastic fiber is a nonwoven fabric selected from the group consisting of natural cellulose fibers, regenerated cellulose, natural fibers, glass, inorganic fibers or metal fibers. The method of claim 6, A nonwoven fabric in which the preceding landing is laminated on a thermoplastic elastic film. The method of claim 6, The preceding skin is a non-woven fabric which is a thermally adhesive laminate containing two or more thermoplastic skins selected from the group consisting of non-woven fabrics of spunbond, non-woven fabrics of melt blown, fluff-bonded nonwovens, thermoplastic foams and thermoplastic films. An apparatus for manufacturing a nonwoven fabric having longitudinal elastic properties, (a) a variable tensioning means is located in the skinned heating means, each having two parallel, opposing, parallel paralleled pinned means for holding the preceding skin, each of which is attached to a link of the continuous chain, (b) the chain is in a slot such that each of the opposing successive shaping means is pulled through a semi-curve curve parallel to the landing path in the longitudinal direction and adjacent to the landing edge and parallel to the landing path. A device of construction, which deflects outward to a new distance to bend back and separate the opposing parallel slots, defining the width of the landing after the distance is drawn, 40% wider than the original width of the parallel slots before entering the tensioning means. . The method of claim 11, Designed with an arched curve, (a) 3.5 in / in / min-9.5 in / in / min, the transverse distortion calculated by the actual distance between the edges of the fin means and the longitudinal velocity of the landing of the heating of the point entering the tension means. ego, (b) the longitudinal velocity of the landing decreases at a rate proportional to the change in the transverse velocity such that the longitudinal distortion is less than 1.0 in / in / min, A device for producing a nonwoven fabric having longitudinal elastic properties. A method of manufacturing a nonwoven fabric having a transverse elastic property, (a) anisotropic mixing of thermobonding thermoplastic and non-thermoplastic fibers, wherein said blend contains 70% of thermoplastic fibers, thereby unwinding the prior landing into a heated heating means at a temperature of 70 ° F. above the plastic point of the preceding landing, (b) the longitudinal axis of the landing, which is located in said landing heating means, to provide a cumulative pull rate of 3.5 in / in / min-9.5 in / in / min, which is a distortion rate calculated based on the change in the landing width. To convey continuously in the longitudinal direction to the variable tension means, which pull the said landing in the transverse direction to (c) improves the landing hardness of 85% recovery after said landing is widened in its transverse dimension, shortened in its length and stretched 50% in the same plane or perpendicular direction as the pulling force, and improved softness Simultaneously reducing the longitudinal velocity of the landing at a rate proportional to the increase in the width of the landing to improve the 5% base weight increase and the 20% reduction in the maximum pore diameter. (d) winding the cooling of the mandrel to the mandrel, the speed of the mandrel being controlled by the tension measuring means disposed between the mandrel heating means and the mandrel, The method consists of. The landing of the heating is governed by a variable tension means sufficient to provide a pull rate of 3.5 in / in / min-9.5 in / in / min, the pull rate being calculated based on the gauge length between the individual components of the tension means. Improvement in the resilience of the landing elasticity of 80% or more after 50% elongation in the plane or at a right angle, such as the narrowing of its transverse dimension, the increase in its length and the pulling force, and the improved softness, Characterized by an improvement in improved integrity, The anisotropic preceding skin consists of a mixture of heat-bonded plastic and non-plastic fibers, which are worn directly on the skin, wherein the mixing contains up to 70% to 100% of thermoplastic fibers and the rest contain non-thermoplastic fibers, and the preceding skin has many A nonwoven fabric produced using the method of claim 11 which is continuously drawn in the landed heating means by means of tensioning means. The method of claim 14, The thermoplastic fiber is a nonwoven selected from the group comprising polyolefins, polyesters, polyamides and their respective copolymers. The method of claim 14, The non-thermoplastic fiber is a nonwoven fabric selected from the group consisting of natural cellulose fibers, regenerated cellulose, natural fibers, glass, inorganic fibers or metal fibers. The method of claim 14, The preceding stopper is a nonwoven fabric that is a thermally adhesive laminate containing at least two thermoplastic skins selected from the group consisting of nonwoven fabrics of spunbond, nonwoven fabrics of melt blow, nonwoven fabrics that are thermally bonded to cause fluff, thermoplastic foams and thermoplastic films.