JPS6254894B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing flat and bonded fabrics of expanded vinyl plastisol on a multifilament core.

The production of vinyl-coated synthetic yarns in which the vinyl coating or encapsulation contains an unactivated blowing agent is known. Generally, synthetic yarns are continuous filament or multifilament yarns ranging from about 150 to about 2200 denier, and the yarns themselves are generally made of nylon, rayon, glass or polyester. The synthetic core yarn is completely encapsulated by extrusion into a cured vinyl plastisol, and the cross-section of the coated yarn is such that, if the core yarn is multifilament, the vinyl compound is only slightly interspersed between the individual filaments. It is shown that. Such a structure provides good adhesion to the core yarn. However, most of the vinyl resin surrounds and encapsulates the core yarn. Typically, the vinyl content of the final yarn ranges from 50 to 90% by weight.

An important use of such yarns is the production of fabrics (woven or non-woven). The main feature of the fabric manufacturing process is that it must be possible to produce threads in cured form without activating the blowing agent therein. Although it is possible to make fabric from yarn after activation of the blowing agent,
The process is uneconomical and the resulting fabric is less expensive than if the manufacturing process included curing the yarn to make the fabric without activating the blowing agent prior to making the fabric, and then activating the blowing agent. Inferior.

For many applications, it is also important to provide a relatively dense fabric with a minimum of material.
In this regard, the closeness of the fabric generally depends on the yarn diameter and the yarn components per inch in both the warp and weft directions. Therefore, it is quite difficult to reduce costs by dense fabrication.

Richmond U.S. Patent No.
No. 3,100,926 describes a fabric in which the threads are made by extrusion from a mixture of a thermoplastic resin and a blowing agent. The extruded yarn is then formed into a fabric-like material, which is in turn heat treated to decompose the blowing agent and generate gases that expand the thermoplastic yarn and permanently bond the thermosoftened yarn at the junction point. It has the dual function of joining. Richmond shows both non-woven fabrics and numerous woven fabrics. In general, extrusion coatings provide little flattening, while fabrics are made with very few, if any, open areas. Thus, such fabrics, when used in curtains or area dividers, serve to completely block areas from view. Clearly, it is the thread thickness in the plane of the fabric, rather than in the lateral direction, that is important in determining the "opacity" or "shade-factor" of the fabric. If thin threads are used to create the desired opacity, a greater number of strokes must be used. Conversely, if thicker threads are used, a larger amount of encapsulating material is required, increasing material costs.

Another difficulty with the method disclosed by Richmond is that the extrusion temperature must be controlled within a fairly narrow range. This is because an inappropriate temperature increase during extrusion can result in activation of all or part of the blowing agent. Even more importantly, the extrusion method described above eliminates the practical difficulties of final length yarn ends, yarn cutting, and handling of keeping the ends separate as the yarn exits a single die. Therefore, more than a small number of threads, such as two or three threads, cannot be processed simultaneously by a single extruder. Clearly, therefore, there are inherent problems with the extrusion method for making the fabrics described above, both with respect to process control and the substantially cylindrical shape of the threads in foamed form, that a more efficient and economical method would be desirable. It is desired that methods and products be developed.

It is therefore an object of the present invention to provide a method for producing multifilament core yarns encapsulated in a latently expandable plastisol.

Another object of the present invention is to provide a method for producing partially cured or fully cured latent expandable plastisol-encapsulated multifilament core yarns.

Another object of the present invention is to provide a method for manufacturing a fabric with controlled open area functionality.

Yet another object of the present invention is to provide a method of manufacturing a highly dense fabric using a minimum of material.

A related object of the present invention is to provide a method of manufacturing a fabric whose individual threads are significantly flattened during fabrication.

Yet another object of the present invention is to provide a method for manufacturing a fabric having junctions between the yarns where the yarns are joined together at their junctions and substantial flattening of the yarns occurs.

Yet another object of the present invention is to provide a method of manufacturing a fabric which is optionally flattened on one or both sides thereof.

Another object of the invention is to provide a method for producing partially cured or fully cured yarns consisting of a multifilament core encapsulated in a plastisol containing an unactivated blowing agent.

Yet another object of the invention is low cost. It is an object of the present invention to provide a method for manufacturing a fabric that is easy to manufacture and can be used as a screen that controls permeability to vision and permeability to air passage.

Further objects and advantages of the invention will become apparent from the following description.

Hereinafter, a method for manufacturing the yarn of the present invention and a method for manufacturing a fabric (woven fabric or nonwoven fabric) using the yarn will be explained.

Method of Manufacturing Yarn According to the invention, multifilament yarn is encapsulated and impregnated with plastisol; passed through a die to control the thickness of the coating, so that the yarn coating is substantially circular in cross-section. It is then partially or completely cured at a temperature low enough so that the blowing agent is not activated. During the encapsulation and impregnation, the filaments of the multifilament yarn are preferably kept with little or no twisting.

The plastisol is generally a plasticizer containing 50-60% polyvinyl chloride resin and 50-40% of one or more plasticizers, fillers, pigments, stabilizers, inhibitors and other customary additives. It is a vinyl compound. Furthermore, a blowing agent is mixed into the plastisol. The blowing agent is selected to have an activation temperature substantially higher than the curing temperature of the plastisol. The amount of blowing agent present depends on the degree of expansion desired. A typical amount of blowing agent may be such that a 0.028 inch diameter cured thread will expand to about 0.054 inch diameter. Typically, the vinyl plastisol coating comprises 50-90% of the total amount of yarn obtained.

The yarn is multifilament, and organic filament yarns of materials such as rayon, nylon or polyester, or inorganic filament yarns of materials such as glass can be used. Among these, those made of polyester are preferred. Additionally, the filament yarn may generally range from about 70 to about 2200 denier.

As used herein, the term "multifilament core yarn" refers to a combination of multiple filaments forming a single multifilament yarn, and the term "filaments of a multifilament core yarn" refers to the individual filaments that make up the multifilament core yarn.

In the above method, the plastisol coated and impregnated thread is pulled through a circular die and a second b.
It is formed into the shape shown in the figure and then fully or partially cured at a temperature lower than the activation temperature of the blowing agent.

As used herein, the term "curing" refers to at least one stress, such as that experienced during subsequent processing such as forming into a fabric under tensile stress, stretching, calendering, foaming, and the like. Means hardening to a well-resistant state. Full cure produces maximum tensile strength. Partial curing of the yarn following each coating step provides faster processing than when the yarn is fully cured at this stage. Where the yarn is partially cured after coating, final curing takes place during subsequent foaming.

The temperature and duration of heating to produce partial cure will vary depending on the plastisol and its thickness. In many cases, air at 193℃ (380〓)
The preferred conditions are to expose for 6 seconds. However, suitable conditions in each case can be easily determined by a person skilled in the art.

The above sequence of steps, namely coating, die sizing and curing, is preferably repeated once;
It may be repeated more than once if desired. The purpose, of course, is to increase the final diameter of the cured thread. Conveniently, a yarn consisting of a single coating on a 12 mil diameter core is 20 mils in diameter, with each successive coating increasing in diameter by 8 mils. Obviously, after each successive coating, the die through which the thread is drawn must be larger in size than the die used for the previous coating. Also, each newly applied coating must be cured to the desired degree after being pulled through a sizing die, and the curing must occur at a temperature below the temperature at which the blowing agent is activated.

As noted above, the curing may be either partial (sufficient to eliminate tack and provide sufficient mechanical strength to withstand subsequent processing) or complete.

Importantly, the method of the present invention can process large numbers of yarns or ends, such as 80 or more, simultaneously.
Simultaneous processing of a large number of yarns results in a substantial reduction in costs. This is because a single furnace is sufficient for almost any number of yarns. The operating temperature of the curing oven is limited by the need to be below the activation temperature of the blowing agent. The length of the furnace over which the yarn is moved horizontally is limited by the increasing slack of the yarn, which is supported only at the ends. Passing the yarn through the oven quickly to partially cure it is of interest in increasing the production rate.

Method of manufacturing a fabric (non-woven or woven fabric) The yarn of the desired diameter and substantially circular cross-section produced as described above is a non-woven fabric (the fabric is generally designated by the numeral 12) as shown in FIG. can be formed into After formation into nonwoven fabric 12, the fabric is heated to a temperature sufficient to activate the blowing agent and bond the yarns at the junctions (flattening occurs at such junctions). If the thread is an organic material, some flattening will occur during the heating process due to the tensile stress caused by shrinkage of the thread. While it's soft,
The fabric may be further calendered so that the junctions formed by intersecting yarns such as 13 and 14 are further flattened. Also, in the calendering process, the threads are well flattened between the joint points so that they have a cross-section as shown in Figure 2c. In FIG. 2c, the yarn 16 consists of a multifilament core yarn 12 contained in and impregnated with plastisol 9.

Clearly, using the method of the invention described above, the threads are flattened in the plane of the fabric, reducing the size of the voids. Accordingly, the desired light blocking factor may be achieved with less weight or fewer threads per inch than if the threads were circular in cross-section. The present invention exhibits similar advantages for extruded yarns with limited flattening.

When fabrics are made from yarns made according to the method of the invention, in order to soften the yarns and activate the blowing agent, they are treated in exactly the same way as in the case of non-woven fabrics as described with reference to FIG. The fabric can be heated either during tenter frame drafting or calendering. The tenter frame subjects the fabric to tensile stress in both the longitudinal and lateral directions, partially flattening the fabric during the process.

Surprisingly, it is found that the fabric is flattened to a greater extent by heating under tensile stress at the joint points. This is shown in FIG. code 21
The woven fabric is generally shown as having warp threads 22 and weft threads 23
Consisting of Planarization is maximum at the junction indicated at 24. Each warp thread is bonded to a respective weft thread during the heating process. The bond thus formed is permanent.

Furthermore, the proportion of open area to total area of the fabric can be easily established by tensile stress during drafting and by controlled calendering. In the flattening process, the open area between the threads is reduced, the degree of reduction being proportional to the twist of the thread filaments, the tensile stress applied to the threads, and the roll pressure used for calendering. These techniques allow the degree of fabric opening to be controlled. Such control is desirable for controlling the traversal of the fabric by light or by moving air.

An alternative method of foaming the blowing agent and flattening the fabric is illustrated in FIG. Fabric 25 is passed over roll 26 and heated sufficiently by infrared source 31 or hot air to cause foaming and softening of one side of the fabric. The fabric is then rolled onto roll 27 in such a direction that the softened side of the fabric is placed relative to roll 27.
carried over to flatten the outer surface of the fabric and join the threads at the junctions between the warp and weft threads. Foaming of the other side of the fabric is performed by heating with a heat source 32. If it is desired that both sides of the fabric be flattened, the fabric is also subjected to rolls 28 while still soft under tensile stress. If the fabric is a partially cured yarn, curing is completed during the foaming operation.

It is important that the temperature of the various rolls be kept below the temperature at which the softened fabric adheres to the roll surface. This temperature can be easily determined by those skilled in the art. These rolls are conveniently cooled internally if a cooling step proves necessary.

As mentioned above, the preferred filament is polyester. This fabric tends to shrink at foaming temperatures, which is the main reason for foaming, flattening and bonding operations under tensile stress. Although widening eliminates the tendency to shrink in both the warp and cross directions, in loosely woven fabrics the fabric selvage may be pulled loosely. Although this difficulty is eliminated by the method shown in FIG. 5, the fabric exhibits some tendency to shrink in the transverse direction when so treated. Transverse shrinkage can be minimized by keeping the fabric tight against the various rolls. Shrinkage is substantially eliminated by increasing the coefficient of friction between the fabric and the roll. This can be done by roughening the surface of the roll or by coating the roll with a layer 29 of high friction material such as silicone rubber.

Construction of Yarns and Fabrics Produced by the Process of the Invention It is known to make fabrics (woven or nonwoven) from somewhat similar yarns formed by extrusion. Such a fabric is shown in FIG. 1, where the fabric is designated generally by the reference numeral 1 and is woven with warp threads 2 and weft threads 3. The warp and weft threads are joined together at a joining point as indicated by 4. As can be seen from this figure, the open area consisting of the spaces between the threads (representative spaces are designated 5) is relatively small. If such a fabric is used as a windbreak or to provide shade or protection, the apertures 5 are preferably small compared to the total area. However, as mentioned above, manufacturing these types of fabrics with the prior art is expensive. The aforementioned Richmond U.S. Patent No.
When the yarns are coated by extrusion methods, such as in No. 3,100,926, flattening of the yarns is minimal and therefore production of relatively dense fabrics requires a large number of yarns per inch.

In FIG. 2a, an extrusion encapsulated multifilament yarn is indicated generally by the numeral 7. A yarn 7 consisting of a central multifilament core yarn 8 of a material such as rayon, nylon, glass or polyester is encapsulated in plastisol 9. As can be seen from this figure, the plastisol 9 encapsulates the core yarn 8 but does not impregnate the boundaries of the core. Only a relatively small amount of flattening is possible per encapsulation.

Referring now to Figures 2b and 2c, it can be seen how the present invention overcomes the problems of the prior art. In Figure 2b, a multifilament formed in accordance with the present invention is shown. Here, the yarn is designated generally by the reference numeral 11 and comprises a multifilament core yarn 12 and a plastisol coating 9. As can be seen from this figure, the coating 9 not only encapsulates the core 12 but also impregnates it. This impregnation significantly increases the final amount of yarn flattening.

Uses of the fabric produced by the method of the invention When the fabric is used to provide shadows, the opacity of the fabric is quite high. However, even when the fabric is used for shading purposes, it is generally desirable to have the cooling effect of a breeze available. For this purpose, open areas of the fabric must be provided. Such open areas are provided by the fabrics of the present invention, which can be used as sunshades, screens between opposing lanes of traffic and between adjacent tennis courts, as waterproof canvas on trucks, as furniture fabrics, and as lightweight fluorescent safety clothing. It was found to be suitable as When the above fabric is used for fencing,
The apertures may be as large as 2 inches by 2 inches. Thus, the open area is substantially from 0 to about 99
It may vary up to %.

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

EXAMPLE A 1000 denier continuous filament polyester yarn was double coated with a latent expandable vinyl coating to a 28 mil diameter. The yarn had an overlap of about 1 pound per 1,000 yarns and was generally circular in cross-section with a well-protected core yarn as the inner core.

The cured yarn could be woven into a 6-strokes-per-inch structure in both the weft and warp. The fabric was then passed through a tenter frame, keeping the fabric taut in both the weft and warp directions. Pass hot air through the fabric at approximately 191℃ (375〓),
This softened the vinyl and released the blowing agent. Under these conditions, the yarn expanded from 28 mils to approximately 54 mils. At the same time, tensile stress was applied to the fabric to flatten the warp and fill yarns at the points where they intersected and bonding occurred at each of these points. The result was a very stable fabric of expanded flat vinyl-covered yarn in the weft and warp directions. Flattening was due in part to stress on the threads at the intersections and was greatest at such intersections. The width of the thread was increased to approximately 65 mils while the thread was further reduced in thickness. As described above, by maintaining each filament of the multifilament substantially unkinked, yarn flattening during the foaming operation was maximized.

Furthermore, flattening could be achieved by calendering the fabric while it was still soft. Round 28 mil threads in the woven structure, 90 mil width while protecting the core yarn and retaining the 30% foam structure
It could be flattened into a mill. Planarization by the three roll method shown in FIG. 5 produced essentially the same fabrication.

The product had excellent resistance to outdoor weather and could be made in many colors. The product also has good abrasion resistance and its core yarn is protected from deterioration due to sunlight. The above products can be used as outdoor fencing around gardens, courtyards and miscellaneous enclosures, especially as fencing material to reduce glare between parallel opposing lanes on highways. The products can also be used as barrier fences on ski slopes, as home shade cloths and as protection against the wind. Depending on the open area, both adjusted visibility and airflow can be achieved.

The materials used are conventional and readily available. For example, a suitable blowing agent is azodicarbonamide, and this material
It decomposes at 200°C (392°C) and is sold under the trade name Azocel by Fairmount Chemical Co., Ltd., Newark, New Jersey.
Company, Inc (Fairmount Chemical
Company).

[Brief explanation of the drawing]

FIG. 1 shows a foamed fabric according to the prior art. FIG. 2 is a cross-sectional view of an extrusion-encapsulated multifilament yarn according to the prior art. 2nd b
The figure is a cross-sectional view of an encapsulated and impregnated multifilament yarn formed in accordance with the teachings of the present invention.
FIG. 2c is a cross-sectional view of the thread shown in FIG. 2b after flattening in accordance with the teachings of the present invention. FIG. 3 is a nonwoven fabric formed in accordance with the teachings of the present invention.
FIG. 4 shows a fabric that has been foamed and flattened in accordance with the teachings of the present invention. FIG. 5 shows an apparatus for foaming and flattening fabric according to the invention.

Claims (1)

Claims: 1. A multifilament core yarn is immersed in a plastic sol compound containing an effective amount of a blowing agent having an activation temperature higher than the curing temperature of the plastic sol compound to coat the filaments of the yarn with the plastic sol compound. impregnating and encapsulating substantially the entire circumference of the yarn; drawing the impregnated and encapsulated core yarn through a sizing die to bring the core yarn to a selected thickness; and at least fabric forming the yarn. curing the yarn at a temperature below the temperature at which the blowing agent is activated so as to withstand the stresses experienced during subsequent processing such as drawing out, calendering, and foaming; A method of manufacturing yarn for textiles or nonwovens in which the filaments of the yarn remain essentially untwisted during dipping, impregnation, encapsulation, pulling, sizing and curing. 2. The method of claim 1, wherein the sequence of encapsulation and impregnation, sizing, and curing is repeated at least once, and the pores of the sizing die are increased by a selected amount during each repetition of the sequence. 3. The manufacturing method according to claim 1 or 2, wherein the multifilament core yarn is made of polyester, rayon, glass, or nylon. 4. The manufacturing method according to claim 3, wherein the multifilament core yarn is made of polyester. 5. A method according to any one of claims 1 to 4, wherein the filament core yarn is made of nylon, rayon, or polyester in a shape ranging from about 70 to 2200 denier. 6. The manufacturing method according to any one of claims 1 to 5, in which a large number of yarns are manufactured at the same time. 7. Immersing a multifilament core yarn in a plastic sol compound containing an effective amount of a blowing agent having an activation temperature above the curing temperature of the plastic sol compound to impregnate the filaments of the yarn with the plastic sol compound and to encapsulating substantially the entire circumference; drawing the impregnated and encapsulated core yarn through a sizing die to bring the core yarn to a selected thickness; and curing the yarn at a temperature below the temperature at which the blowing agent is activated to an extent that it can withstand the stresses experienced during subsequent processing such as foaming, and dipping the filaments of the yarn; A fabric is obtained from the yarn obtained by a method that maintains it essentially twist-free during impregnation, encapsulation, drawing, sizing and curing, then activating the blowing agent and softening the fabric. creating a space between the yarns by heating the fabric to a temperature high enough to cause the yarns to simultaneously expand and flatten and bond the yarns together at their junctions. A method for manufacturing a fabric comprising: 8. The manufacturing method according to claim 7, wherein the yarns are combined as warp and weft yarns by a weaving method to obtain a woven fabric. 9. The method of claim 8, further comprising the step of heating the fabric in a tenter frame that applies tensile stress to the fabric in both warp and transverse directions. 10. Claims 7-9 further comprising the step of calendering the fabric while it is in a softened state, thereby further flattening the fabric and reducing its open area. A method for manufacturing the fabric according to any one of paragraphs. 11 The filament yarn is about 1000 denier, the resulting yarn after encapsulation and curing is about 0.028 inches in diameter, and the amount of blowing agent is such that, when activated, the blowing agent expands the yarn to a diameter of about 0.059 inches. 10. The fabric manufacturing method according to claim 9, wherein the amount is 12. The method of claim 11, wherein the tensile stress applied during drawing out is such that the yarn is flattened to a width of about 0.090 inches. 13 Passing the fabric over a first roll and heating one side of the fabric remote from the first roll to a temperature sufficient to complete curing of the partially cured yarn. foaming and softening the yarn and then passing the fabric through the second roll in a direction such that the one side of the fabric contacts the second roll (with the fabric being under tensile stress in the longitudinal direction); , thereby activating the blowing agent by the steps of flattening the one side of the fabric and joining the threads of the fabric at warp and weft junctions. Production method. 14 heating the other side of the fabric opposite the one side to a temperature sufficiently high to complete curing of the other side of the fabric in which the threads comprising the other side are partially cured; heating to foam and soften the threads on the other side, and then passing the fabric under tensile stress over a third roll in the warp direction so that the other side contacts the third roll while still soft. 14. A method of manufacturing a fabric according to claim 13, further comprising the steps of: , thereby flattening said other side. 15. A method of making a fabric according to claim 13 or claim 14, including the step of providing a high coefficient of friction surface for contact by the fabric to minimize or eliminate lateral shrinkage.