JPS6260492B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates generally to nonwoven fabrics, including wood pulp fibers and thermoplastic polymer microfibers, which can be manufactured inexpensively and in a number of different combinations of properties for different applications. Regarding nonwoven fabrics. It is the object of the present invention to obtain an improved non-woven fabric that can be produced quickly and inexpensively in a single manufacturing step without the use of adhesives or the need for embossing or other treatments after the formation of the non-woven fabric. It is a purpose. It is also an object of the present invention to obtain an improved nonwoven fabric in which wood pulp fibers and polymeric fibers are co-ordinated and the final product has the desired combination of properties. It is also a related purpose to manufacture It is an object of one aspect of the present invention to obtain an improved nonwoven fabric with a unique combination of tensile strength, absorbency, and hand, having high absorbency while having wet strength comparable to dry strength. It is one of the objectives of one embodiment of the present invention to obtain a nonwoven fabric that exhibits high properties. It is also an object of the present invention to provide an improved nonwoven fabric that is highly elastic, ie, has the ability to recover from deformation, has a low bulk density, and can be manufactured at relatively low cost. It is also an object of the present invention for specific applications to provide improved nonwoven fabrics that have high absorbency for both oil and water. It is also an object of the present invention to obtain an improved nonwoven fabric in which there is little or no mutual bonding of the wood pulp fibers even after drying after wetting, and the original properties of the nonwoven fabric are well retained. In this connection, it is also a related object of the present invention to obtain a nonwoven fabric whose original physical structure remains almost unchanged even after drying after wetting. It is also an object of the present invention to obtain a process for producing a nonwoven fabric having a relatively large bulk per unit weight. Another object of the present invention is to provide a process for producing a nonwoven fabric using only air without wetting the components of the nonwoven fabric. Although the invention will now be described with reference to specific embodiments, it should be understood that the invention is not limited to these embodiments. On the other hand, all alternatives, modifications, and equivalents that can be included within the scope and spirit of the invention as defined in the claims are to be included in the present invention. Now, to explain according to the drawings, first of all, in FIG.
technique). This method is
Industrial and Engineering Chemistry
Published in Vol.48, No.8, pp1342-1346, USA
It is the same as described in a paper entitled "Superfine Thermoplastic Fibers" which describes research at the Naval Research Laboratory. Additionally, Naval Research
See also Report 111437 (issued April 15, 1954) and US Pat. No. 3,676,242 (issued July 11, 1972). The basis of this molding method is to extrude a molten polymer raw material into a thin stream through a die head 11, and stretch the polymer stream by a contracting flow of high-speed, high-temperature gas (usually air) sent from nozzles 12 and 13. It is then blown off into discontinuous microfibers of minute diameter. It is desirable that the die head is provided with at least one row of a plurality of closely spaced extrusion holes. Microfibers formed in this manner generally have an average diameter of no more than 10 microns, and rarely exceed 10 microns in diameter. The average diameter of the microfibers is usually about 1 micron or greater, preferably in the range of 2 to 6 microns, with an average diameter of about 5 microns. It should be noted here that although most of the microfibers are discontinuous, they have a fiber length longer than what is generally called staple fiber. The primary air stream 10 is combined with a secondary air stream containing defibrated wood pulp fibers to combine two different fiber raw materials in a single step. The length of a typical defibrated wood pulp fiber is approx.
0.5 to 10 mm, and the ratio of length to maximum width is approximately 10/
1 to 400/1. Its typical cross section is irregular with a width of 30 microns and a thickness of 5 microns. Secondary air flow 14 shown in this schematic layout
is made by a pulp sheet defibration apparatus of the type described and claimed in Assignee's US Pat. No. 3,793,678, "Pulp Picking Apparatus with Improved Fiber Forming Duct." This equipment is used for pulp and
It consists of a conventional picker roll 20 with picker teeth for defibrating the sheet 21 into individual fibers, and the pulp sheet 21 is fed radially onto the picker roll 20 by a feed roll 22. As the picker roll teeth break up the pulp sheet 21 into individual fibers, the separated fibers are conveyed downwardly through the forming nozzle or duct 23 and into the primary air stream. The housing 24 covers the picker roll 20 and provides a passage 25 between the housing 24 and the picker roll 20. From the duct 26, a sufficient amount of process air is supplied through the passage 25 to the picker roll at a speed close to the circumferential speed of the picker teeth to serve as a transport medium for the fibers passing through the forming duct 23. The air can be delivered by conventional means, such as a blower. To avoid agglomeration of the fibers, the individual fibers should be allowed to travel through the duct 23 at approximately the same speed as they leave the picker teeth after being defibrated from the pulp sheet 21. That is, the fiber should vary both in velocity and in its direction at the point of leaving the picker tooth. In particular, it is desirable that the speed of the fibers defibrated from the pulp sheet 21 in the duct 23 does not change by more than about 20%. This is a significant difference compared to other defibrating devices where the flow separation does not allow the fibers to move in an orderly manner from the picker, resulting in a fiber speed change of more than 100% during the journey. In order to maintain the desired fiber speed, the duct 23 is positioned such that its longitudinal axis is substantially parallel to the plane tangent to the picker roll 20 and the fibers are not affected by the picker teeth. Since the duct 23 is in this direction, due to the collision of the fibers on the duct wall,
Fiber velocity remains unchanged. Thus, if the pulp sheet 21 is fed radially toward the picker in a plane substantially parallel to the primary air flow, the surface in contact with the picker roll 20 at the contact point of the pulp sheet is 1 Next, it will be perpendicular to the airflow. Therefore, in the case of the embodiment shown in FIG. 1, the contact point between the sheet and the picker is also the point at which the defibrated fibers are released from the influence of the picker teeth, so the vertical axis of the duct 23 is the primary axis. perpendicular to the airflow 10. However, if the speed of the fibers is restricted due to the influence of the picker teeth after being separated from the pulp sheet 21, the axis of the duct 23 is adjusted appropriately so that it is in the direction of the fiber speed at the point where the fibers are no longer restricted. As shown in FIG. 1, the width of the duct is approximately equal to the height of the picker teeth of roll 20, and the passage between the picker teeth and picker roll housing 24 is very narrow. Because the width of the duct is like this,
The velocity of the process air supplied through duct 26 remains substantially constant both when moving with the picker and through duct 23. Moreover, since the velocity of the processing air is close to that of the picker teeth, and this velocity is essentially the same as the velocity of the defibrated fibers,
Processing air does not cause fiber velocity changes in the duct 23. Given that the width of the duct is approximately the same as the height of the picker teeth, for example less than about 1.5 times the height of the teeth, the air velocity in the duct 23 of the illustrated device will be at least 70% of the circumferential velocity of the picker teeth. Become. The length and width of the duct (width along the picker roll axis) are also important for optimizing wave formation. Preferably, the length of the duct should be as short as the overall equipment design allows. In the case of the device shown in FIG. 1, the minimum duct length is limited by the radius of the picker roll. In order to maintain a constant width of the web formed, the width of the duct should preferably be less than or equal to the width of the pulp sheet fed to the picker rolls. Returning again to the device shown in FIG. 1, it is desirable that the picker teeth used be relatively tall, for example 1/4 inch or larger. This height allows the use of wide ducts, so that the fibers are not interfered with by the walls. As shown in FIG. 1, primary airflow 10 and secondary airflow 14 preferably move at right angles to each other at their confluence. Other convergence angles can be used if necessary. The velocity of the secondary air stream 14 is significantly lower than the primary air stream 10 so that the composite stream 15 created by the merging flows continuously in the same direction as the primary air stream 10.
Combining the two air streams is somewhat similar to an aspirator effect, with fibers in the secondary air stream 14 being sucked into the primary air stream as they pass through the outlet of the duct 23. In any case, the important thing is that the primary air flow and the secondary air flow merge in a turbulent state,
A speed difference was provided between the two air streams to ensure complete mixing of the pulp fibers in the secondary air stream and the melt-spun microfibers in the primary air stream. In general, increasing the velocity difference between the primary and secondary air streams will result in a more uniform mixing of the two feedstocks;
If the two flow velocities are slow and the speed difference is small, the components tend to be mixed. To maximize production speed, it is generally desirable to have the primary air flow at an initial sonic velocity (in nozzles 12 and 13) and the secondary air flow at or below the sonic speed.
Naturally, the primary air stream expands with decreasing velocity as soon as it leaves the nozzles 12,13. The flow rate of the primary air that entrains surrounding air while drawing the polymeric microfibers is always greater than the flow rate of the secondary air used to introduce the pulp fibers. The primary air jet increases in volumetric flow rate by more than five times while the maximum jet velocity decreases to 20% of its original value. However, the pulp fibers should be introduced at the beginning of the diffusion zone of this microfiber jet. This is because it exposes the mixture of both fibers to the strong micro-turbulence occurring in this part of the diffusion zone and mixes both fibers while the polymeric microfibers are still in their hot and soft nascent state. be. Behind the diffusion zone of the microfiber jet, the magnitude of the disturbance becomes larger compared to the fiber entanglement, and the energy in the disturbance also decreases continuously. This extremely strong small disturbance field causes the short pulp fibers to be mechanically incorporated into the microfiber matrix in the best possible manner. As the velocity of the high velocity air stream carrying the microfibers decreases, the fibers are released from the suction forces that originally created the microfibers from the polymeric melt. When the microfibers relax, they are able to follow small vortices well enough to disperse into the gaseous medium,
While floating, it entangles with relatively short wood pulp fibers, trapping and restraining them. The resulting product is a tightly bonded mixture of wood pulp fibers and polymeric microfibers, which are composited by physically capturing and mechanically entangling them while floating in space. It is desirable to begin this combination operation while the microfibers are still in their hot, soft, nascent state. The microfibers are drawn either before or after their entanglement with the wood pulp fibers. The amount of stretching is from about 3.8 microns (0.015 inch) fiber diameter (a typical extrusion hole diameter) to about 5 microns (0.0002 inch) or less. Most stretching occurs within about 3 inches of the die end face before the primary air velocity drops below about 250 feet per second. Since the wood pulp fibers are introduced into the microfiber stream approximately 1 inch from the die end face, drawing of the microfibers continues after merging with the wood pulp fibers. Because of their extremely small cross-sectional area, polymeric microfibers are at least as small as traditional textile fibers made from the same polymers.
It is 50 to 100 times more flexible, and is very flexible and malleable in its initial state of formation at high temperatures. Microfibers are significantly longer, thinner, limp, and more flexible than wood pulp fibers;
As soon as the two fiber streams meet, they twist and wrap around the relatively short, thick, and stiff wood pulp fibers. This entanglement creates a strong and connective fiber-to-fiber bond, interconnecting two different types of fibers, without any adhesive, molecular or hydrogen bonds. Within this matrix, the microfibers have great flexibility with many microfibers spaced apart by intertwining with relatively stiff pulp fibers. When various types of torsional force are applied to this matrix, the entangled pulp fibers can freely change their direction, but it is the microfibers that return the pulp fibers to their original position after the torsional force is removed. These are the elasticity and repulsive force of the net. The tightly bonded composite fiber structure is formed solely by the mechanical entanglement and mutual bonding of these two different fibers. The microfibers themselves and the anchoring structure to the wood pulp fibers provide a bending hinge between the fibers of the product structure. The fibers are not rigidly bonded to each other, and at their bond points the fibers can rotate, twist, and bend. With an appropriate microfiber content, this fibrous system can have a woven-like "hand" and drape, and can be made malleable while retaining some elasticity and resilience. This structure also exhibits deflection resiliency and wet strength comparable to dry strength, even when wet with water and the wood pulp fibers swell and soften. Even when the microfiber content is as low as 1% by weight, this wood pulp fiber containing structure results in a greatly improved absorbent nonwoven fabric. For example, such nonwoven fabrics have improved shape retention and lower lint counts compared to nonwoven fabrics made by conventional methods that also contain a high content of wood bulp fibers. This wood pulp fiber content structure and the other characteristics described above are achieved by air forming the nonwoven fabric without adhesives or any other processing or treatment. Nonwoven fabrics that use adhesives to incorporate wood pulp fibers are not flexible and have low absorption capacity and absorption rate, which is a significant difference compared to this improved nonwoven fabric. The spatial extent of the wood pulp fibers requires a relatively high level of microfiber content. Pulp fibers maintain their shape under the forces of microfiber flow and high temperatures without melting or undergoing any substantial structural changes, thereby physically interfering with polymer-to-polymer interactions. This suggests that the breaking length or tensile strength increases unexpectedly at very low levels of microfiber content;
Thereafter, there is an unexpected change in the strength of the microfiber web, as evidenced by a drop below the straight line of strength versus microfiber content. To achieve a homogeneous texture, it is preferred that the wood pulp fibers be uniformly distributed throughout the microfiber matrix. Wood pulp fibers have been found to reduce the undesirable effects of "shot" or polymer agglomeration that are inherent in most microfiber spinning processes. With a web made of 100% microfiber,
These polymer aggregates easily fuse with each other and with nearby microfibers, making the web rough to the touch, stiff, and unsightly. Wood pulp fibers have the effect of eliminating the "shot" in both texture and appearance by interfering with the bonding of "shot" molecules with each other and with the microfibers. To form the mixed fibers in composite stream 15 into a composite fiber mat or web, a pair of vacuum rolls 30 and 31 having perforated surfaces are continuously rotated over a pair of stationary vacuum nozzles 32 and 33. Pass this stream 15 through the nip. When the composite stream 15 enters the nip between rolls 30 and 31, the mixed fibers pass through the two rolls 3
0 and 31 and is slightly compressed, while the entire conveyance is sucked into two vacuum nozzles 32 and 33. In this way, the more you can pull out of the nip of the vacuum roll, the more
A web 34 made of self-supporting composite fibers having sufficient shape retention is formed and sent to a winding roll 35. Web 34 wound on roll 35
is shown in Figure 2. The structure of the wood pulp fibers in the composite fiber matrix and the other characteristics described above are obtained without any processing or treatment of the air-infused web. If it is necessary to increase the strength of the composite web 34, it can be embossed using either ultrasound or high temperature to flatten the thermoplastic microfibers within the embossments into a film-like structure. This film-like structure, described in more detail below with respect to FIG. 11, serves to rigidly support the wood pulp fibers in position within the embossments.
In the process of FIG. 1, the composite web 34 passes through an ultrasonic embossing section consisting of an ultrasonic calendering head 40 which is vibrated against a patterned anvil roll 41. The embossing pattern as well as the embossing conditions (eg, pressure, speed, input power) can be appropriately selected to impart desired properties to the final product. After passing through the embossing nip, the web has an embossed area that is approximately 5% to 50% of the surface area of the nonwoven fabric, and a density of individual embossed areas that is approximately 5% to 50% of the surface area of the nonwoven fabric.
It is desirable that a discontinuous pattern of 7.7 to 15.5/cm ² (50-100/in ² ) is applied. The most appropriate embossing conditions for a given nonwoven fabric will vary depending on the individual constituent fibers. As a thermoplastic polymer for microfibers,
For nonwoven fabrics made from polypropylene, a Branson ultrasonic device (Model 460) with a continuous ultrasonic module was used with an input power of 700 watts and a 10"
50psi pressure on 0.5″ ultrasonic horn,
It has been found that by pressing against a patterned anvil roll 41, the strength of this nonwoven fabric can be substantially improved. Suitable patterns for anvil rolls are shown in FIGS. 3-5. A suitable speed for the web to pass through the embossing section is 25-150 ft/min. One of the main advantages of the present invention is that it takes advantage of all the advantages of the melt-spinning process, and at the same time, by combining the melt-spun-produced microfibers with varying amounts and types of wood pulp fibers, It becomes possible to impart various desired combinations of properties to the final product that cannot be achieved using the spinning process alone. As a result, using this manufacturing process,
It is possible to produce a variety of specially tailored nonwoven fabrics for various uses. For example, polymeric microfiber mats can be produced efficiently at high speeds by melt spinning, but these mats have limited liquid retention and absorbency;
It is generally not suitable for use as a wiping cloth. However, by using the manufacturing process of the present invention, microfibers made by melt spinning are combined with wood pulp fibers, and the liquid holding and absorbing properties of pine can be used as a wiping cloth. It can be improved to a level that is suitable even for Furthermore, since wood pulp fibers are often cheaper and more readily available than the polymeric materials from which microfibers are made, combining two different types of fibers reduces the cost of the resulting composite mat. become. Although the nonwoven fabrics of the present invention show that certain properties are due to pulp fibers, the nonwoven fabrics necessarily contain a significant amount of thermoplastic microfibers. As a result, it is possible to modify this nonwoven fabric by performing secondary heat treatments such as hot calendering, embossing, or spot bonding. An additional advantage of compounding two types of fiber materials by mixing and turbulence of two air streams is that a composite web is obtained in which both fiber materials are uniformly distributed throughout. . As mentioned above, this result is achieved by providing a substantial velocity difference between the two air streams; the larger the velocity difference, the more uniform the composite, and the smaller the velocity difference, the more the first feedstock will be mixed. There is a tendency for the second raw material to be concentrated throughout. If necessary, a product with uniform properties in all directions of the web plane may be used.
By embossing or the like, the thickness of the web can be made without substantially changing it. There is a wide variety of thermoplastic polymers that can be used to produce melt-spun microfibers, and by appropriate selection of the polymers or combinations thereof,
Nonwoven fabrics with various physical properties can be made. Among the many useful thermoplastic polymers, thermoplastic elastomers based on polyolefins such as polypropylene and polyethylene, polyamides, polyesters such as polyethylene terephthalate, and polyurethanes are used in producing the nonwoven fabrics described herein. It is thought that it has a wide range of uses. Although Pitzcarole, as shown in the illustrated layout, is preferred for creating a secondary air stream containing wood pulp fibers, synthetic fibers such as staple nylon fibers and natural fibers such as cotton, flax, jute, and silk can be used. Other equipment can be used to create a secondary air stream that includes additional fibrous materials and/or specified materials. If necessary, add wood pulp fiber and another
Two additional materials can be conveyed in one secondary air stream. There are a number of controllable variables, both primary and secondary airflow, as well as web composition and basis weight, to impart a certain combination of properties to the resulting fibrous web. Process parameters that are sensitive to control in the primary air flow include air flow temperature (preferably in the 600-700° range), air flow velocity (preferably at sonic speed inside the die head), and polymer extrusion rate. (preferably around 0.25g/min per hole),
There are the temperature of the polymer and the mass flow ratio of air and polymer (preferably in the range of 10/1 to 100/1). The controllable variables in the secondary airflow are the air flow rate and circumferential speed of the Pitzka roll, the velocity of the airflow (in the subsonic range, preferably 50-250 ft/sec), and the fiber length (typical The length is around 3.0mm). The relationship between the primary air flow and the secondary air flow can also be controlled, and it is generally desirable that the velocity ratio between the primary air flow and the secondary air flow be in the range of 5/1 to 10/1. The relative proportions of raw materials introduced by the primary and secondary air streams can vary over a wide range, with polymeric microfibers typically ranging from 1% to 80% of the weight of the finished mat. Although the angle between the primary and secondary air flows at the meeting point can also be varied, it is generally desirable for the two flows to meet at right angles to each other. Similarly, the particular point at which the two streams meet can also vary with respect to the upstream melt spinning die and the downstream roll with a perforated surface. The production of nonwoven fabrics according to the invention is illustrated in the following examples. The results of measuring the physical properties of nonwoven fabrics made with various constituent components are also described. Measurements were made essentially according to the method described below. (a) Uncompressed thickness Using a thickness tester manufactured by Cwtom Scientific Instruments, for Example-X
Measurements were made with 0.5 oz/in ² of pressure applied to the nonwoven at 1 in ² foot, and 0.004 psi of pressure applied to the nonwoven at 7.07 in ² foot for the remaining examples. (b) Bulk density Bulk density (g/cm ³ ) was calculated using the measured uncompressed thickness and known sample basis weight (bulk density = basis weight/thickness). (c) Oil absorption After weighing a 4 square inch sample, it was immersed in mineral oil for 30 seconds at room temperature, then taken out, suspended with a glass rod for 45 seconds to drain the oil, and the sample was weighed again. . The weight increase is the weight of oil absorbed by the sample. Substitute this weight for the specific gravity of the oil (0.831g/
me) to determine the volume, which was then divided by the dry weight of the sample to determine the "oil absorbency." (d) Water absorption The test is the same as the oil absorption test except that water is used instead of oil. In order to uniformly wet the entire sample, in the absorption tests shown in Tables 1 and 2,
It was performed using a 0.5% aqueous solution of Aerosol OT surfactant. (e) Breaking length Tensile strength tests are performed on nonwoven fabric samples with a width of 1.0 inches and a length of 3 inches (longer samples can also be used, but the exposed length between the jaws of the testing machine is 3 inches). The tests were conducted using an Instron testing machine (Model No. A70). At temperature 70-77〓, relative humidity 40-50%, tensile speed 10in/mi
A load was applied to the sample at n, and the measured tensile strength was divided by the basis weight of the sample to determine the fracture length. To measure wet tear length, soak the sample in water for 30 seconds,
The sample was then placed on blotting paper to remove excess water and tested. When measuring redry tear length, samples were wetted as described above and tested after air drying. (f) Elongation In the tensile strength test described above, the increasing length of the sample is measured, and the elongation is the percentage increase in the length of the sample just before the sample breaks. (g) Lint Count Clamp a 6 inch square sample around the periphery of two parallel inner plates placed 4 inches apart from each other on a common vertical axis. One of the inner plates is then moved repeatedly, rotating 180 degrees with each stroke, relative to the other inner plate, bending, twisting, and crumpling the specimen. Diameter 47mm, hole size
0.45 micron Millipore filter (No.
HAWP-047-00) was placed under the sample so that its center was slightly outside the periphery of the two disks, and this disk repeating motion was continued 50 times. Next, the particles captured on the filter are observed through a microscope with 40x magnification using a TV camera and monitor. 9 different 1.64×2.43mm on filter
Count all particles larger than 13 microns within the visual range. Eight of these nine viewing zones are equally spaced around the circumference of the filter, and one at the center of the filter. The average number of the nine particles obtained was determined, and the obtained average number was recorded as the "lint number". (h) Specific volume “Initial specific volume” is the uncompressed thickness (cm,
It was determined by dividing the sample's basis weight (g/cm ² ) by the basis weight (g/cm ² ) of the sample. Next, a pressure of 0.49 psi was applied evenly over the surface of the sample, and after 1 minute, the compressed thickness was measured under this load using the thickness tester described above, and the obtained compressed thickness was divided by the basis weight. , the "specific volume under load" was determined. The load was then removed from the sample, and after 1 minute the recovered sample thickness was measured in the same manner as described above to determine the uncompressed thickness (applying 0.004psi of pressure and using a 7.07in ² foot). The "recovery specific volume" was calculated by dividing the obtained thickness after recovery by the basis weight. EXAMPLE A composite nonwoven fabric containing 53.5% bleached sulfite pulp fibers and 46.5% melt-spun polypropylene microfibers was made according to the general process shown in FIG. First, the final temperature is 600〓
Polypropylene (Exxon resin, CD-523)
Extrusion at a rate of 221bs/hr (equal to 0.42g/min per die orifice), temperature 700〓, flow rate
It was stretched in a primary air flow of 15001 bs/hr and the flow velocity was sonic. A secondary air flow containing floating pulp fluff is used to defibrate roll pulp (Rayfluff This secondary air stream was created by joining the primary air and polypropylene microfiber streams at right angles approximately 1 inch from the die tip. The velocity of the primary airflow at the confluence point was estimated to be 5-10 times the velocity of the secondary airflow. The composite web was then assembled between vacuum rolls covered with wire mesh with a 12.5 mil roll nip gap 22 inches from the tip of the extrusion die. The following are the properties of the composite nonwoven fabric that were measured. Basis weight 99g/ ^m 2Uncompressed thickness 1.55mm Bulk density 0.064g/cm ^3Oil absorption 18.8ml/g Longitudinal breaking length 196m Longitudinal elongation 20% Lateral breaking length 358m Elongation: 34% In addition, this web has the characteristics of being felt or cloth-like, compressible and cushion-like, flexible and not stiff. Possible uses for these properties include diapers, polishing cloths, small Band-Aids, makeup removal pads, hairdressing and beauty aid products. Furthermore, it has been found that this nonwoven fabric very effectively attaches and retains small particles such as dust, so it could be effectively used as a dust cover. Although most of the weight of this nonwoven fabric is made up of hydrophilic wood pulp fibers, it is difficult to get wet with water. This property is advantageous for application pads for cosmetics and other application products where it is desirable to isolate substances applied to the surface of the pad. Example A part of the composite nonwoven fabric of Example was pressed against an anvil roll with an embossed pattern shown in FIG. 5 and embossed by ultrasonic calendering. The measured characteristics are shown below. Basis weight 91g/ ^m2 Thickness 0.81mm Bulk density 0.112g/ ^cm3 Oil absorption 8.8ml/g Longitudinal breaking length 822m Longitudinal elongation 36% Lateral breaking length 444m Lateral elongation 26% Additionally, this nonwoven fabric, while still having a cloth-like feel, is stronger and stiffer than the non-embossed example nonwoven fabric. Embossing also results in less surface lint by more tightly bonding the individual pulp fiber sections in the embossed areas. Applications include disposable dish wipes, durable industrial or household wipes, napkins, and wet wipes impregnated with cleansers, astrins, and the like. Example 52% fibrous pulp (Rayflutt XQ) and 48% melt spun polypropylene fiber (Exxonresin,
A composite nonwoven fabric containing CD-523) was manufactured using the same manufacturing method as in Example, except that the distance from the web forming roll nip to the end of the extrusion die was 14 7/8 inches. The measured characteristics are shown below. Basis weight 92.3g/m ^2Thickness 0.74mm Bulk density 0.125g/cm ^3Oil absorption 9.7ml/g Longitudinal tear length 693m Longitudinal elongation 10% Lateral tear length 590m Lateral direction Elongation of 18% This nonwoven fabric has a
It is stiff, blind, and has poor adaptability, and its texture is stiffer than that of clothing.
As a result of the unevenness formed on the surface of the web by the surface of the wire roll for forming the web, the surface texture is slightly rough. Also, it is difficult to get wet. This nonwoven fabric could be used as a garment interfacing or as a limited use mat or table cloth. Example A part of the composite nonwoven fabric of Example was pressed against an anvil roll with an embossed pattern shown in FIG. 5 and embossed by ultrasonic calendering. The measured characteristics are shown below. Basis weight 92.5g/m ^2Thickness 0.71mm Bulk density 0.130g/cm ^3Oil absorption 7.2ml/g Longitudinal breaking length 694m Longitudinal elongation 22% Lateral breaking length 644m Lateral elongation 27% This nonwoven fabric has sufficient strength and durability for scrubbing and polishing applications, and is resistant to water. This nonwoven fabric can be used for limited use mats and tablecloths. Example 47% fiberized pulp (Rayflutt XQ) and 52.3%
This is a composite nonwoven fabric containing polypropylene (Exxon resin, CD-523) melt-spun fibers, made according to the general manufacturing method described above. The polyprene resin was modified during the extrusion process by adding 6.5% of the weight of the melt-spun fibers as a surfactant. This modified fiber is heated to a final temperature of 575〓,
It was extruded at a rate of 23 lbs/hr and stretched in a primary air flow at a temperature of 700 ㎓, a flow rate of 1500 lbs/hr, and a flow velocity of sonic. The input of pulp fibers and the compounding process are the same as in the example. The obtained nonwoven fabric is easily wetted by water. The measured characteristics are shown below. Basis weight 94.5g/m ^2Thickness 1.42mm Bulk density 0.066g/cm ^3Oil absorption 17.9ml/g Longitudinal breaking length 159m Longitudinal elongation 39% Lateral breaking length 168m Lateral elongation 63% This nonwoven fabric is very similar in quality to the nonwoven fabric of the example, except that it is easily wetted by water, so its potential uses are also similar. Example A part of the composite nonwoven fabric of Example was pressed against an anvil roll with an embossed pattern shown in FIG. 5, and embossed by ultra-long wave calendering. The measured characteristics are shown below. Basis weight 94g/m ^2Thickness 0.71mm Bulk density 0.132g/cm ^3Oil absorption 8.0ml/g Water absorption 6.2ml/g Longitudinal dry tear length 801m Elongation 39% Lateral dry tear Cross-section length 680 m 〃 〃 Elongation 45% Longitudinal wet tear length 754 m 〃 〃 Elongation 43% Transverse wet tear length 572 m 〃 Elongation 48% Longitudinal redrying tear length 778 m 〃 〃 Elongation 50 % Transverse re-drying tearing length 649 m 〃 Elongation 61% This non-woven fabric does not change its physical and mechanical properties in the wet state or after re-drying from the wet state; It can be used in both dry and wet conditions and has potential use as a limited use or durable wiping cloth. Example A composite nonwoven fabric containing 74% fiberized pulp (Rayfluff It was made using the same method as in the example except that the wire roll nip gap was 30 1/4 inch and the wire roll nip gap was 105 mil. The measured characteristics are shown below. Basis weight 181g/m ² Uncompressed thickness 4.06mm Bulk density 0.045g/cm ³ Oil absorption 26.8ml/g Longitudinal breaking length 59m 〃 Elongation 24% Lateral breaking length 139m 〃 Elongation 40% This nonwoven fabric is also soft and bulky. Compressible, like a cushion. It has characteristics such as somewhat resembling cotton wadding. Due to its high absorbency, it could be used in sanitary napkins, diapers, bandages, etc. Other uses include makeup removal pads, application pads, fillings, beauty pads (eg braziers), hairdressing and beauty aids, nursery products, and decorative uses. EXAMPLE A composite nonwoven fabric containing 50% hardwood pulp fibers and 50% melt-spun polypropylene microfibers was made according to the general process shown in FIG. Polypropylene resin (Exxon resin, CD—
523, containing 10% by weight of surfactant) at a final temperature of 635〓 and 0.33 per die orifice.
Extrude at a speed of 58 g/min, with a total polymer flow rate of 58 g/min.
Stretching was carried out in a primary air stream at a temperature of 690°C flowing at twice the mass flow rate. A secondary air stream containing floating pulp fibers is created by defibrating a roll pipe (hardwood with an average fiber length of 1.5 mm) in a Pitzka device without using a stripping air stream, and is made from the tip of the extrusion die by approx. At 2 inches, the primary air and polypropylene microfiber flow merged at right angles. The composite web was then deposited on the surface of a wire mesh covered vacuum roll 5.5 inches from the tip of the extrusion die. The various properties measured are shown below. Basis weight 85g/m ² Thickness 1.57mm Bulk density 0.054g/cm ³ Moisture absorption 15.8ml/g Longitudinal dry tearing length 137m 〃 〃 Elongation 33% Horizontal dry tearing length 83m 〃 〃 Elongation 59% This web is easily wetted by water and has an extremely soft feel. The drapability is the same as the above-mentioned webs, but it has a softer surface texture. Example A composite nonwoven fabric containing 50% cedar pulp fibers and 50% melt-spun polypropylene microfibers was made using the same method as in the example. The secondary air flow containing pulp fibers has an average fiber length of 3.9mm.
It was made by defibrating roll pulp manufactured by Cedanier. The various properties measured are shown below. Basis weight 83g/m ² Thickness 1.77mm Bulk density 0.047g/cm ³ Moisture absorption 18.9ml/g Longitudinal dry tearing length 119m 〃 〃 Elongation 26% Horizontal dry tearing length 60m 〃 〃 Elongation 46% This web is easily wetted by water. The equipment used in each of the above examples for ultrasonic calendering was the aforementioned Branson equipment set at 50 psi on the horn and at a web passage speed of 211 ft/min. Figures 6 to 8 are scanning electron micrographs of nonwoven fabrics produced by the following method. This nonwoven fabric is made of 50.4% soft wood pulp fibers (Longlac-18, pine pulp with an average fiber length of 3.2 mm) and 49.6% melt-spun polypropylene fibers (Exxon resin, CD-18).
It is a composite nonwoven fabric containing 392). The nonwoven fabric directs a secondary air stream carrying suspended wood pulp fibers at right angles to the primary air stream containing hot air and melt-spun polypropylene fibers to join approximately 2 inches from the die end. It was made by
Melt-spun fibers are made from polypropylene resin at a final temperature.
The spun fibers were extruded at a rate of 0.31 g/min per die orifice at a temperature of 630°, and the extruded spun yarn was drawn in a primary air flow at a temperature of 690° flowing at a mass flow rate of 66.1 times the total polymer flow rate. The secondary air flow is
It was made by feeding a carded web of wood pulp fibers through a pair of feed rolls into a fiber gun consisting of a pair of nozzles located on opposite sides of the web. That is, the carded web is unraveled into individual fibers by a high-speed air jet coming out of a nozzle, the fibers are introduced into a high-speed air stream, and this fiber stream is guided through a duct to join the primary air stream of the melt-spun fibers and then passed through an extrusion die. from the end
The composite web was deposited on the surface of a vacuum roll covered with wire mesh 5.5 inches apart. Figure 6 (80x) shows the uniformity of the composite fiber structure, the randomness of the fiber directions, the overall entanglement of the pulp fibers and the melt-spun fibers, and the relative diameters of both fibers. Figure 7 (300x magnification) further shows the overall entanglement of the melt-spun microfibers of the pulp fibers, the relative dimensions of the fibers, and the large voids within the web. Figure 8 (1000x magnification) shows a section of pulp fibers supported by a large number of intertwined microfibers. The diameter variation of melt spun fibers is typically 3-5 microns. There is not much bonding between polypropylene fibers within the web, but as you can see from the photo, there is bonding between large diameter fibers and fibers of different sizes (in the case of this photo, the fibers are approximately 14 microns in diameter). (fiber-to-fiber bonds of approximately 5 microns). This type of bonding is rare in bulky, low density webs, and it is clear that the primary basis for the web's shape retention is the extensive physical entanglement of both the pulp fibers and the melt-spun microfibers. No bond between polypropylene fibers and cellulose pulp fibers was found. This lack of interfiber bonding gives low density webs excellent softness, flexibility, and drapability. Because the surface and internal structure is uniform,
Nonwovens exhibit properties of both synthetic resin microfibers and pulp fibers. For example, even in composite nonwoven fabrics that are mostly pulp fibers, the presence of low surface energy microfibers on the surface limits their wettability. Additionally, the distribution of thermoplastic fibers throughout the web allows the web structure to be thermally modified through processes such as calendering, spot bonding, and lamination to other thermoplastic webs or films. Summer. Figures 9-11 are scanning electron micrographs of nonwoven fabrics made by the same method as described above, with the following exceptions. In other words, this nonwoven fabric has 48.5% soft wood pulp fiber (Longlac-18, average fiber length
3.2mm corn pine pulp) and 51.5% melt-spun polypropylene fiber (Exxon resin, CD-
392), extrusion speed per die orifice is 0.28g/min, primary air of 700〓 and 665
It was made with a mass flow ratio of 85:1 for the polymer 〓, and was further pressed against an anvil roll with an embossed pattern shown in Figures 3 and 4 and subjected to ultrasonic calendering to create a high-density material. It has become. Figure 9 (600x) and Figure 10 (600x) again
In this case, the web exhibits a general intertwining of melt-spun microfibers and pulp fibers in dense but non-embossed areas. FIG. 11 (300x magnification) shows an embossed portion corresponding to the recess 43 in FIG. 4, formed by intensive calendering. The fiber structure of the thermoplastic fibers is lost in this embossed area, and the resulting film serves to hold the pulp fibers firmly in place. Nonwoven fabrics typically calendered in this manner have increased tensile strength and density, and have decreased liquid absorption but increased liquid conductivity. Due to the presence of hydrophobic and water-resistant fibers, composite nonwoven fabrics are stable in water and water solvents. Additionally, polyolefin fibers increase the absorbency of oils and solvents. The incorporation of pulp fibers within the matrix of melt-spun microfibers results in increased bulk and a hollow structure. Due to the overall intertwining of pulp fibers and microfibers, the overall composite structure has good shape retention and abrasion resistance, and if necessary, an adhesive can be applied to stabilize the web structure. Although easy to use, this composite nonwoven fabric does not require adhesives. EXAMPLE Microfibers were produced by extruding polypropylene resin (Hercules PC 973) at the speeds and temperatures indicated for each series. The velocity of the primary air is 830 in all cases.
Although the speed was subsonic in the range of 1390ft/sec, the air temperature was kept constant at 665〓. The secondary air stream containing suspended pulp fluff is generated in the Pickker apparatus at an initial velocity of 77
ft/sec. It was made by defibrating a roll pipe (Rayfloc XJ. Southern pine pulp with an average fiber length of about 3.0 mm) using an air flow of about 14,401 bs/hr. The composite web was assembled onto a perforated vacuum roll 7.5 inches from the extrusion die tip. The properties of the composite nonwoven fabrics measured for Series A to Series E are summarized in Table 1, along with the data for Rayfloc XJ 100% pulp air-forming wadding.

【table】

【table】

[Table] This data demonstrates the broad spectrum effects of microfibers in the range of 7-31% (even lower percentages) on tear length, water absorption, and specific volume recovery. For example, a fiber made of 100% wood pulp fibers has less than 50% recovery after applying a load of 0.49 psi, whereas a nonwoven fabric containing two types of fibers has a recovery of at least 60% or more. ,
Most samples show high recovery rates of 80% and above. The data also show that a microfiber content of 7% (even a low percentage) has a significant effect on the moisture absorption of the composite nonwoven. This is 100
% wood pulp fibers are very suitable for use in applications where liquid absorption capacity is required (such as diapers and feminine napkins). This is because if absorption capacity can be increased at a lower cost, it will be possible to provide products with excellent performance in a highly competitive market. When products require high shape retention,
It can be used with a microfiber content of 40%-60%. This is because within this range, even if the microfiber polymer is hydrophobic, it maintains a sufficiently high absorption value. As expected, the breaking length value increases easily by increasing the microfiber content. However, the microfiber content should be between 3% and 1%.
%, there is an unexpected and commercially important jump in fracture length. This means that webs containing up to 99% wood pulp fiber can be mechanically assembled, transported and processed without sophisticated processing technology. Similarly, it is possible to make absorbent cores for diapers with excellent shape retention without the use of adhesives or other special stabilizing techniques. Example XI Two samples containing 1.5% and 3% microfibers, respectively, were made in the same manner as the sample in Example X, using slightly lower extrusion speeds, die temperatures, and air temperatures. The properties measured for these two samples are shown below.

【table】

[Table] Figures 14 and 15 show graphs of some of the properties measured in the above Examples and XI. The horizontal axis in Figure 14 represents the microfiber content, and the horizontal axis in Figure 15 represents the wood pulp fiber content. Curve 100 in FIG. 12 represents the initial specific volume; curve 1
01 represents the specific volume under load, and the curve 102 represents the recovery specific volume. The recovery specific volume increased rapidly at low levels of microfiber content (this effect was not plotted in Figure 12, but was shown in the example).
XI data), even at very low levels of microfibers, at least 25
You can see that cc/g is always present. Figure 13 plots data for all five series of Example samples, plus two samples of Example XI. However, since the gaps in the plotted data are relatively close, only one curve is used to represent it. In the plotted data, the * mark indicates series A, the × mark indicates series B, the △ mark indicates series C, the □ mark indicates series D, and the 〓 mark indicates series E.
, △ indicates two samples of Example XI. 13th
As can be seen from the figure, the absorbency increases rapidly at the lowest microfiber content, around 1.5%, and the absorbency decreases from 100% to 100% wood pulp until the microfiber content reaches a minimum of about 50%. It can be seen that the level of non-woven fabric is maintained.
At microfiber contents of 30% and above, the absorbency is greater than or equal to 30 minus 0.25 times the weight percentage of microfibers. This curve represents the shape retention of the composite nonwoven fabric, and it is noteworthy that the shape retention of the 100% wood pulp nonwoven fabric, which has almost no shape retention and cannot even be measured using normal methods. It can be seen that the lint count is less than 600 minus 5.5 x (weight percent of microfibers). Figure 15 shows a plot of the tear length for the Example Series A samples. In the plotted data, the * mark indicates the tearing length in the longitudinal direction, and the × mark indicates the tearing length in the transverse direction.From these curves, it can be seen that the tearing length in both directions corresponds to an increase in the microfiber content. It can be seen that when the pulp content is 90% or more, the breaking length is always at least 5 m, which means that the free span when the nonwoven fabric breaks under its own weight is 5 m.
It means that. Reference Example: A composite nonwoven fabric containing 35.6% high crimp nylon sulphate (purity 2.5 denier, fiber length 1.375 inches) and 64.6% melt-spun polypropylene fiber, the secondary air flow carrying the suspended sulphur was The primary air stream containing hot air and melt-spun polypropylene fibers was oriented perpendicularly to meet approximately 2 inches from the end of the die. The melt-spun fiber is made of polypropylene resin at a final temperature of 630〓 and 0.25 g/min per die orifice.
The extruded spun yarn was drawn in a primary air flow at a temperature of 690°C flowing at a mass flow rate of 81 times the total polymer flow rate. The secondary air flow was created by feeding a carded web of nylon fiber through a pair of supply rolls into a fiber gun consisting of a nozzle located on opposite sides of the web. That is,
A high-velocity air jet from the nozzle unravels the carded web into individual fibers, which feed the fibers into a high-velocity air stream that is guided through a duct to join the primary air stream of the melt-spun fibers and pass through the end of the extrusion die. The composite web was deposited on the surface of a vacuum roll covered with wire mesh 5.5 inches from the surface. The following are the measured characteristics. Basis weight 56g/m ^{2Longitudinal} dry tearing length 518m Longitudinal dry elongation 77% Wet tearing length 573m Elongation 87% Longitudinal dry tearing length 330m Elongation 92% Wet breaking length: 323 m Elongation: 78% This web is characterized by a large degree of improvement in toughness, tensile strength, and elongation, and is superior to the pulps described in the examples above. This suggests that fabric may be used as a third component to impart these properties to microfiber composite nonwovens. In the case of either two-component or three-component nonwovens containing sulphate additives, their possible uses include garment interfacing, durable industrial or household wipes, wet wipes impregnated with cleaners, etc.
This will likely include the use of limited-use mats, tablecloths, and similar non-woven fabrics.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional and partially schematic side view showing a method and apparatus for producing a nonwoven fabric according to the present invention. FIG. 2 is a partial perspective view of the nonwoven fabric. FIG. 3 is a partial perspective view of an embossed nonwoven fabric. FIG. 4 is a partial cross-sectional view of the nonwoven fabric shown in FIG. 3 taken along line 4--4. FIG. 5 is a partial perspective view of a nonwoven fabric using different embossed patterns. Figures 6-8 are scanning electron micrographs taken at various magnifications of a typical example (composite nonwoven fabric consisting of 50% soft wood pulp fibers and 50% polypropylene microfibers). Figure 6 is 80x, Figure 7
The figure is 300x, and Figure 8 is 1000x. Figures 9-11 are scanning electron micrographs of a second exemplary embodiment (composite nonwoven fabric consisting of 48.5% soft wood fibers and 51.5% polypropylene microfibers). Figures 9 (600x) and 10 (600x) show the non-embossed part, and Figure 11 (300x) shows the embossed part. FIGS. 12 to 15 are graphical representations of data measured for some of the embodiments described in the present invention for easy understanding. 10...Primary air flow, 11...Nozzle head, 1
2, 13... Nozzle, 14... Secondary air flow, 15... Combined flow, 20... Picker roll, 21... Roll pulp, 22... Feed roll, 23... Duct, 24... Housing, 25... Passage, 26... Duct, 30,3
1... Vacuum roll, 32, 33... Vacuum nozzle, 34
...Composite web, 35... Winding roll, 40... Ultrasonic calendering head, 41... Anvil roll, 42... Ultrasonic device, 35'... Non-embossed portion, 43... Embossed portion, 44... Embossed portion.

Claims (1)

[Scope of Claims] 1. A base body formed from microfibers with an average diameter of 10 microns or less obtained by melt-spinning a thermoplastic polymer, and a matrix formed from microfibers having an average diameter of 10 microns or less, and the entire base body so as to be restrained within the base body. A nonwoven fabric comprising wood pulp fibers dispersed throughout the microfibers and connected to the microfibers by mechanically entangling them, the microfibers and the wood pulp in a defibrated state. and the fibers are mixed in air under turbulent conditions to form a composite fiber structure in which the wood pulp fibers engage at least a portion of the microfibers and the microfibers are spaced apart from each other. A nonwoven fabric characterized in that the microfibers and the wood pulp fibers are tightly bonded without any adhesion, molecular bonding, or hydrogen bonding. 2. Claim 1, wherein the microfibers and the wood pulp fibers are mixed in the air under a turbulent condition when the microfibers are in a soft initial state of production at a high temperature. Nonwoven fabric as described. 3. The nonwoven fabric according to claim 1, wherein the wood pulp fibers are uniformly distributed throughout the matrix of microfibers to form a homogeneous nonwoven fabric. 4 The length of the wood pulp fiber is within the range of about 0.5 to 10 mm, and the ratio of the length to the maximum width is about
The nonwoven fabric according to claim 1, which has a molecular weight within the range of 10/1 to 400/1. 5. The nonwoven fabric of claim 1, wherein the microfibers have an average diameter of about 1 micron or more. 6 The microfibers account for about 1% or more of the weight of the nonwoven fabric.
The nonwoven fabric according to claim 1, which accounts for 80%. 7. The nonwoven fabric according to claim 1, wherein the recovery specific volume of the nonwoven fabric is at least 75% of the initial specific volume. 8. The nonwoven fabric of claim 1, wherein the microfibers constitute about 25% or less of the weight of the nonwoven fabric. 9. The nonwoven fabric of claim 1, wherein the microfibers account for at least 5% of the weight of the nonwoven fabric, and the lint count is less than or equal to 600 minus 5.5 x (weight percentage of microfibers). 10. The nonwoven fabric of claim 1, wherein the wood pulp fibers account for at least 40% of the weight of the nonwoven fabric and have a recovery volume of at least 25%. 11. The nonwoven fabric of claim 1, wherein the microfibers account for at least about 30% of the weight of the nonwoven fabric, and the absorbency is greater than 30 minus 0.25 x (weight percentage of microfibers). 12. The nonwoven fabric of claim 1, wherein the wood pulp fibers account for at least about 90% of the weight of the nonwoven fabric and have a tear length of at least 5 meters. 13. the nonwoven fabric has an initial specific volume of at least 25, a recovery specific volume of at least 75% of the initial specific volume, and a lint number less than 600 minus 5.5 x (weight percentage of microfibers); Nonwoven fabric according to claim 1, having an absorbency greater than 30 minus 0.25 x (weight percentage of microfibers) and a tearing length of at least 5 m. 14. A method of manufacturing a nonwoven fabric having a unique combination of properties of tensile strength, absorbency, and hand, comprising: (b) creating a secondary air flow containing defibrated wood pulp fibers; (c) adding said secondary air flow to said primary air flow; merging under turbulent conditions to create a composite air stream containing an intimate mixture of said microfibers and said wood pulp fibers; (d) directing said composite air stream to a web-forming surface over which said microfibers are formed; A matrix of fibers is air-formed, at which time some of the microfibers are bonded to each other at regular intervals by at least defibrated wood pulp fibers, and The defibrated wood pulp fibers are dispersed throughout the microfiber matrix;
interconnected by mechanical intertwining with the microfibers and confined within the matrix, without any adhesion, molecular or hydrogen bonding;
A method consisting of forming a tightly bonded composite fiber structure only by mechanically intertwining both fibers. 15. The manufacturing method according to claim 14, wherein the microfibers are produced by drawing a polymer filament extruded from at least one row of straight extrusion holes. 16. The manufacturing method according to claim 14, wherein the primary air flow and the secondary air flow are combined when the microfibers are in a high temperature and soft initial state of production. 17. The manufacturing method according to claim 14, wherein the wood pulp fibers are uniformly distributed throughout the matrix of microfibers to form a homogeneous nonwoven fabric. 18 The length of the wood pulp fibers is approximately 0.5 to 10 mm.
range, and the ratio of the length to the maximum width is approximately 10/
Claim 14 in the range of 1 to 400/1
Manufacturing method described in section. 19. The method of claim 14, wherein the microfibers have an average diameter of about 1 micron or more. 20. Claim 1, wherein the microfibers account for about 1 to 80% of the weight of the fiber mixture.
The manufacturing method described in Section 4. 21. The method of claim 14, wherein the microfibers are less than about 25% by weight of the fiber mixture.