DE69017762T2 - Recoverable voluminous nonwoven, method of manufacture and method of restoring the original shape. - Google Patents

Description

The present invention relates to a bulk-recoverable nonwoven fabric, a method for producing the same and a method for restoring the volume thereof, and particularly relates to a bulk-recoverable nonwoven fabric which can be preferably used as a padding, a base material for a corset cup, a base material for a shoulder pad, a filter and the like, a method for producing the same and a method for restoring the volume thereof.

A bulky nonwoven fabric containing a large amount of air is generally used as a padding for sportswear and the like, a filter and the like. Since the bulky nonwoven fabric contains a large amount of air, carrying or storing the bulky nonwoven fabric is like carrying or storing air. This is therefore a cost disadvantage because a large amount of space is required when carrying (transporting) a large amount of the bulky nonwoven fabric or storing it in a warehouse. It also has a disadvantage that it is inconvenient to handle the bulky nonwoven fabric in the manufacture of sportswear and the like because the nonwoven fabric is bulky and soft.

In order to eliminate the above-mentioned deficiencies, a method for restoring the volume A method of restoring a bulky nonwoven fabric (nonwoven fabric) is proposed, in which the bulky nonwoven fabric is wrapped in a film, air is removed from the bulky nonwoven fabric to reduce the volume of the bulky nonwoven fabric so that the nonwoven fabric can be easily transported or stored, and the volume of the nonwoven fabric is restored by blowing hot air into the nonwoven fabric when the nonwoven fabric is used.

However, there are some disadvantages in the above-mentioned method that the nonwoven fabric with reduced volume is difficult to restore to its original shape because the arrangement of fibers of the bulky nonwoven fabric is affected and wrinkles or deformations are caused when air is removed from the bulky nonwoven fabric. The method is also extremely poor in terms of labor because two processes are required for removing air from the nonwoven fabric and for restoring the volume of the nonwoven fabric by applying hot air. The above-mentioned method has not yet been improved in terms of its operability because the nonwoven fabric should be used in a bulky state when a sporting goods and the like are practically manufactured.

Another method in which latently curled fibers are compressed and fixed to each other with a powder resin having a low melting point when a non-woven fabric (nonwoven fabric) is produced and the powder resin having a low melting point is melted to restore the volume of the non-woven fabric by heating the non-woven fabric to a temperature of about 150ºC and the non- It is already known in the art that the woven fabric is subsequently cooled to solidify the molten powder resin to form a non-woven fabric (nonwoven fabric) having a new shape when the non-woven fabric is used in practice (see, for example, US-A-4 857 065).

However, when a wadding (padding) is produced by the above-mentioned method, the non-woven fabric (non-woven fabric) is compressed in a compressed state or in a deformed state at the time it is subjected to a post-treatment of the wadding because the powder resin melts when the wadding (padding) is heated. In addition, the non-woven fabric produced by the above-mentioned method has a disadvantage that it has a poor durability when the non-woven fabric is subjected to dry cleaning because the powder resin has a poor durability against a solvent and a poor heat resistance and the bonding of the fibers produced by the powder resin is destroyed. Since the fibers of the non-woven fabric (non-woven fabric) are fixed to each other only by the powder resin, the non-woven fabric has a poor dimensional stability when the powder resin is reheated to melt. It is therefore not preferable to use the non-woven fabric as padding. Furthermore, since the volume of the non-woven fabric is recovered by heating it to a temperature of about 150ºC, the influence of heat on the fibers of the non-woven fabric cannot be neglected.

The aim of the present invention is to provide a bulk-recoverable non-woven fabric which has excellent durability after recovery of the volume of the non-woven fabric, excellent dimensional stability and processability when a sporting article (sports clothing) and the like is manufactured therefrom and which reduces the costs during storage, as well as a method for producing the same and a method for restoring its volume.

The invention relates to a bulk-recoverable nonwoven fabric comprising a nonwoven fabric in which the fibers constituting it are bonded together by means of an adhesive to bond the fibers, characterized in that the nonwoven fabric is compressed and the compressed state is maintained by a temporary adhesive having a melting temperature at least 10°C lower than the melting temperatures of the fibers constituting it and the adhesive for bonding the fibers after being heated to a temperature of at most 100°C, the amount of the temporary adhesive being 5 to 40% by weight of the nonwoven fabric.

The present invention thus relates

a process for producing a bulk-recoverable nonwoven fabric comprising mixing the constituent fibers with thermally fusible fibers to form a web, bonding the web with an adhesive to bond the fibers together to form a nonwoven fabric, compressing and heating the nonwoven fabric to melt the thermally fusible fibers, characterized in that a compressed state of the nonwoven fabric is maintained by the thermally fusible fibers having a melting temperature of is at least 10ºC lower than the melting temperatures of the fibres that make it up and of the adhesive used to bond the fibres, and

a method for producing a bulk-recoverable nonwoven fabric comprising bonding a web with an adhesive to bond fibers together to form a nonwoven fabric, adding a powder resin having a low melting point to the nonwoven fabric, and pressing the nonwoven fabric, characterized in that the nonwoven fabric is heated to melt the powder resin having a low melting point and is fixed in a compressed state.

The present invention also relates to a method for restoring the volume of the regrowing nonwoven fabric, which comprises heating the regrowing nonwoven fabric to a temperature of at least the melting temperature of the temporary adhesive, but below the temperatures at which both the fibers constituting it and the adhesive for bonding the fibers melt, in order to restore the volume of the regrowing nonwoven fabric.

The regrowing non-woven fabric according to the invention (nonwoven fabric) comprises

A) a non-woven fabric (nonwoven fabric) whose constituent fibres are bonded together by means of an adhesive (adhesive) to bond the fibres together, and

B) a temporary adhesive (glue) having a melting temperature lower than that of the fibers that make it up and the adhesive (glue) for bonding the fibers, and

fixing the non-woven fabric in a compressed state by the temporary adhesive (adhesive).

The constituent fibers used in the present invention are not particularly limited. However, it is preferred that the constituent fibers recover the volume of a nonwoven fabric to a large extent when the temporary adhesive is melted to release the nonwoven fabric from the compressed state.

Representative examples of the constituent fibers that can regain the volume of the nonwoven fabric are, for example, crimped fibers such as high crimped fibers and the like. Among the crimped fibers, latently crimped fibers are preferred because the latently crimped fibers have a strong crimp when heated.

The curled fibers are elastic when the temporary adhesive (glue) that has temporarily bonded the constituent fibers is melted, so that the bonding strength of the temporary adhesive decreases because the deformed curled fibers return to their original state. The elasticity serves as a force for restoring the volume of the nonwoven fabric. Therefore, it is preferable that curled fibers having a high percentage of curl, a high percentage of residual curl and a high percentage of curl modulus are used.

The curled fibers having a high percentage of curl, a high percentage of residual (remaining) curl and a high percentage of curl modulus are here curled fibers having a curl percentage of 12 to 70%, a residual (remaining) curl percentage of 7 to 70% and a curl modulus percentage of 30 to 100%. The values of curl percentage, residual (remaining) curl percentage and curl modulus percentage here are understood to mean the values when the curl is visible. In the case where curl is not visible, the values are given when curl is visible.

Examples of the above-mentioned crimped fibers are a hollow fiber, a thick fiber having a fineness of at least 6 denier, a fiber having a large curl radius, a fiber having a three-dimensional spiral structure when heated or moistened, which is generally called a highly crimped fiber, and the like. A fiber having a crimp of about 4 to about 30 crimps per length of 25 mm produced by mechanical crimping can also be used other than the above-mentioned crimped fibers.

The percentage of curl, the percentage of residual (permanent) curl and the percentage of curl modulus are defined below.

A length (a) is measured when an initial tension of 2 mgf per 1 denier is applied to a sample. A length (b) is measured when a tension of 500 mgf per 1 denier is applied to a sample. After the tension of 500 mgf is removed and the sample is left to itself for 1 min, a length (c) is measured when an initial tension of 2 mgf per 1 denier has been applied to the sample.

The percentage of curl (%) and the percentage of remaining curl (%) are calculated from the following equations. The test was performed 20 times and the average value of the percentage of curl and the percentage of remaining curl was calculated. [Percentage of curl (%)] [Percentage of remaining curl (%)]

The percentage of curl modulus (%) is calculated from the following equation: [Percentage of curl modulus (%)]

As stated above, in addition to a porous fiber, a fiber having a high fineness and a fiber having a large curl radius, a fiber having a high percentage of curl, a high percentage of residual curl and a high percentage of curl modulus can be preferably used because the fiber has an excellent recovery of its volume.

The term "highly crimped fibre" as used here refers primarily to a fibre with a high Percentage of curl, with a high percentage of residual curl and with a high percentage of curl modulus and to a fiber with a three-dimensional spiral structure in the present application. Any fibers with apparent curl and fibers with latent curl can be used in the invention.

Examples of the fiber having a three-dimensional spiral structure when the fiber is heated to shrink it by dry heat or wet heat include, for example, a conjugated fiber having apparent curls, a conjugated fiber having latent curls, a fiber consisting of a component having a curl when subjected to a specific heat treatment, and the like.

Examples of the conjugated fiber are a side-by-side type conjugated fiber, a core-sheath type conjugated fiber, an eccentric conjugated fiber consisting of two components of a polyester having a low melting point and a polyester having a high melting point, and the like.

A fiber consisting of a component that exhibits a curl when subjected to a specific heat treatment is understood here to mean a fiber that is subjected to a heat treatment by scraping the fiber with a heated blade while tensioning the fiber or by scraping the heated fiber with a blade so that the arrangement of the molecules of the fiber is deformed by the contact of the fiber with the blade.

The fiber is shrunk to create a three-dimensional spiral structure by exposure to Heat in a state of dry heat or moist heat.

The curl may be visible or latent when a recoverable nonwoven fabric is made from it. A fiber having latent curl is very desirable from the viewpoint of volume recovery because the fiber exhibits curl when it is heated to restore volume. In general, the thickness of the nonwoven fabric in the depth direction becomes larger as the number of curls increases. On the other hand, the area of the nonwoven fabric in the width direction becomes smaller because shrinkage occurs in the width direction. Therefore, when the nonwoven fabric is required to be dimensionally stable in particular, it is desirable that the curl be visible at the time when the nonwoven fabric is made.

When a conjugated fiber that latently exhibits curls, or a fiber consisting of a component that exhibits curls when subjected to a specific heat treatment is used as a fiber with curls made visible, the curls can be made visible by heating the fiber to a temperature that produces curls after a resurfaceable nonwoven fabric (nonwoven fabric) has been produced.

According to the invention, an adhesive (glue) for bonding the fibers is used to bond the structural fibers together. The adhesive for bonding the fibers is divided into a thermosetting resin binder and a thermally bonding fiber.

The thermosetting resin binder and the thermally bonding fiber act as an agent to maintain the original shape of the non-woven fabric when the non-woven fabric is reheated to restore the volume of the non-woven fabric. An agent which is not affected by heating to melt the temporary adhesive and reheating to restore the volume of the non-woven fabric is used as the adhesive for bonding the fibers.

Examples of the thermosetting resin binder are a self-crosslinking acrylic acid ester emulsion, a latex such as an ethylene/vinyl acetate copolymer latex, a polyvinyl acetate latex, a polyvinyl chloride latex, a synthetic rubber latex, a polyurethane latex or a polyester latex to which a crosslinking agent has been added, and the like.

Among them, an acrylic ester emulsion can be used particularly preferably. The reason why the acrylic ester emulsion can be used preferably is that the softness of a film (sheet) of an adhesive (glue) made from the acrylic ester emulsion can be adjusted widely and easily. In addition, the acrylic ester emulsion has excellent adhesion properties and water resistance to polyester fibers often used as one of the constituent fibers of the nonwoven fabric. In addition to the thermosetting resin binder, a resin binder having a melting temperature higher by at least 10°C than that of the temporary adhesive (glue) can also be used because the resin binder is little affected by heating and reheating.

Examples of the thermally bonded fiber are a completely fusible fiber consisting of a resin, for example, a non-stretched polyester, a low melting point polyester or a low melting point polyamide, a conjugated fiber in which one component is the above-mentioned resin, and the like. It is desirable that the melting temperature of the thermally bonding fiber is higher than that of the temporary adhesive (adhesive) by at least 10°C, preferably by at least 20°C. The melting temperature of the thermally bonding fiber is preferably 100 to 230°C.

Particularly, when the constitutive fiber (fiber constituting the fabric) is made of the conjugated fiber, the component of the conjugated fiber having a low melting point can be used as an adhesive for bonding the fibers. In this case, it is not necessary to use the thermosetting resin binder and the thermally bonding fiber. However, the melting temperature of the component having a low melting point should be higher than that of the temporary adhesive.

The term "melting temperature" as used herein means a temperature at which a solid melts and at which the solid phase and the liquid phase are in equilibrium with each other, which is generally referred to as melting point, when the solid is subjected to dry heating, or a temperature at which a non-crystalline material softens in the presence of water and at which the solid phase and the liquid phase of the non-crystalline material, which is the liquid phase, are in equilibrium with each other in the presence of water, when the non-crystalline material is subjected to wet (moist) heating.

According to the invention, the temporary adhesive (adhesive) mentioned below should satisfy the above-mentioned relationships, when the temporary adhesive is subjected to dry heating or moist (wet) heating.

An example in which the melting temperature in dry heating is different from the melting temperature in wet heating is explained below. The example is a case in which the temporary adhesive is, for example, polyvinyl alcohol. The polyvinyl alcohol has a melting temperature of about 120 to about 150ºC in dry heating. In contrast, the polyvinyl alcohol gives an adhesive strength when heated with steam having a temperature of about 100ºC because the polyvinyl alcohol swells and softens and then melts.

Therefore, when the polyvinyl alcohol is subjected to moist (wet) heating, the temperature can be set to about 100ºC.

Therefore, the melting temperature of the temporary adhesive sometimes depends on the conditions under which the temporary adhesive is subjected to dry heating or moist (wet) heating.

The temporary adhesive used in the present invention serves as an agent for temporarily reducing the volume of the non-woven fabric, that is, for forming a non-woven fabric having a high density so that the non-woven fabric can be easily handled first, and as an agent for reducing its adhesive strength to recover the volume of the non-woven fabric together with the elasticity of the curled fibers when the volume of the non-woven fabric is finally recovered. Therefore, a temporary adhesive having a melting temperature at which the fibers constituting the non-woven fabric and the adhesive for the fibers are not affected. An essential condition is that the melting temperature of the temporary adhesive is at least 10ºC lower than the melting temperatures of the fibers constituting the nonwoven fabric and the adhesive for the fibers. It is particularly preferred that the melting temperature of the temporary adhesive is at least 20ºC lower than the melting temperatures of the same.

Under the above conditions, it is preferable that the melting temperature of the temporary adhesive is 100°C or less. The reason why a temperature of 100°C or less is preferable is that the fibers constituting the nonwoven fabric are little affected and the volume of the nonwoven fabric can be easily recovered by means of a conventional heating system when the nonwoven fabric is sewn.

Examples of the forms of the temporary adhesive are a fibrous adhesive, a powder adhesive, and the like.

Representative examples of the fibrous temporary adhesive are thermally fusible fibers and the like. Examples of the form of the fiber are a conjugated fiber and a monocomponent fiber. When the conjugated fiber is used in the present invention, the treatment can be easily carried out because only the component having a low melting point of the conjugated fiber melts and the conjugated fiber does not excessively melt or adhere to the fiber constituting the nonwoven fabric, so that the hand feeling of the nonwoven fabric is not impaired.

Representative examples of the conjugated fiber are, for example, a conjugated fiber consisting of Low melting point polyester/high melting point polyester, low melting point polyamide/high melting point polyester, and the like. Examples of the shape of the conjugated fiber include a side-by-side type fiber, a core-sheath type fiber, an island-in-the-sea type fiber, and the like. Since the melting temperature of the low melting point component of the conjugated fiber is generally about 80 to about 100°C, heating and reheating for recovering the volume of the nonwoven fabric can be carried out at a low temperature. Thereby, some advantages can be achieved, that is, the energy can be reduced and the working efficiency is improved, and the fiber constituting the nonwoven fabric is not deteriorated.

It is not preferable that the ratio between the thermally fusible fiber and the other constituent fiber is too high because the nonwoven fabric is hardened and the constituent fiber is bonded in a deformed state when the nonwoven fabric is subjected to dry cleaning after the volume of the nonwoven fabric is recovered. On the other hand, if the ratio of the thermally fusible fiber is too low, the adhesive strength (bonding strength) of the temporary adhesive becomes insufficient and the dispersion of the thermally fusible fiber becomes uneven. Therefore, it is desirable that the content of the thermally fusible fiber in the fibers of the nonwoven fabric is 5 to 40% by weight, preferably 10 to 30% by weight.

Representative examples of the temporary adhesive having a powder form are a powdered resin with a low melting point and a water-soluble powdered resin.

Examples of the powdery resin having a low melting point are a resin powder having a melting temperature of at most 100°C, preferably about 80 to 100°C, for example, made of polyamide, polyethylene or an ethylene/vinyl acetate copolymer and the like.

Examples of the water-soluble resin powder are a water-soluble resin powder having a melting temperature of about 80 to 110°C in a wet heating state, such as polyvinyl alcohol and the like.

As stated above, the thickness of the nonwoven fabric whose constituent fibers are bonded together with the adhesive for bonding the fibers can be reduced to about 1/5 to about 1/30 of the original thickness of the nonwoven fabric because the compressed state of the nonwoven fabric is maintained by the temporary adhesive when the nonwoven fabric is cooled in a compressed state after the nonwoven fabric is heated and compressed at a temperature of 100°C or less.

The volume of the nonwoven fabric can be recovered to 5 to 30 times the volume of the compressed nonwoven fabric by applying heat at the same temperature as above after the nonwoven fabric has been transported or carried, stored, sewn and the like.

The term "thickness" used here means a thickness when a load of 0.01 g per 100 mm² sample is applied to a sample measuring 250 mm x 250 mm.

A method for producing a repulpable nonwoven fabric according to the present invention is explained below.

The process for producing a resurfacable nonwoven fabric differs depending on whether a thermosetting resin binder or a thermally bonding fiber is used as an adhesive to bond the fibers, or whether a thermally fusible fiber or a powdered resin with a low melting point is used as a temporary adhesive.

When a thermally bonding fiber is used as an adhesive for bonding the fibers and a thermally fusible fiber is used as a temporary adhesive, a sheet (nonwoven fabric) is produced by carding or the like after mixing the constituent fibers, the thermally bonding fiber and the thermally fusible fiber. A resurfaceable nonwoven fabric (nonwoven fabric) is formed by heating the sheet and melting the thermally bonding fiber so that the constituent fibers of the sheet are bonded together.

When a thermally bonding fiber is used as an adhesive for bonding the fibers and a resin powder having a low melting point is used as a temporary adhesive, a sheet (nonwoven fabric) is prepared by carding or the like after mixing the constituent fibers and the thermally bonding fiber. A resurfaceable nonwoven fabric (nonwoven fabric) is formed by heating the sheet and melting the thermally bonding fiber so that the constituent fibers of the sheet are bonded together, and adding the resin powder having a low melting point to the sheet.

When a thermosetting resin binder is used as an adhesive for bonding the fibers and a thermally fusible fiber is used as a temporary adhesive, a sheet is prepared by carding or the like after mixing the constituent fibers and the thermally fusible fiber. A resurfaceable nonwoven fabric is prepared by bonding the thermosetting resin binder to the sheet to bond the constituent fibers of the sheet together.

When a thermosetting resin binder is used as an adhesive for bonding the fibers and a resin powder with a low melting point is used as a temporary adhesive, a web is prepared by carding the constituent fibers or the like. A resurfacable nonwoven fabric is prepared by bonding a thermosetting resin binder to the web and adding the resin powder with a low melting point.

In the above-mentioned methods, it is preferable to blend a highly crimped fiber into the constituent fibers. In this case, the content of the highly crimped fiber in the constituent fibers can be appropriately adjusted according to the purpose or type of use of the resurfacing nonwoven fabric.

As stated above, when a resin powder having a low melting point is used as a temporary adhesive, it is difficult to produce a web by carding after mixing the building fibers and the resin powder having a low melting point. For example, when a resin powder having a low melting point is added to a web and the web is bonded with a thermosetting resin binder to form a non-woven fabric, In the case of nonwoven fabrics, it sometimes happens that the temporary adhesive does not act as a sufficient adhesive because the binder is wrapped and bound by the resin powder having a low melting point. Therefore, the resin powder is added to a nonwoven fabric after the nonwoven fabric is manufactured according to the present invention.

The amount of the adhesive added to the constituent fibers varies depending on the type of the adhesive. For example, when the adhesive for bonding the fibers is a thermosetting resin binder, the amount (solid content) of the thermosetting resin binder is usually set to a value of 3 to 50% by weight, preferably 5 to 30% by weight of the nonwoven fabric. If the amount of the thermosetting resin binder is less than the above range, there is a risk that the durability or strength of the nonwoven fabric becomes insufficient after the volume of the nonwoven fabric is restored. If the amount of the thermosetting resin binder is above the above range, there is a risk that it becomes difficult to produce a bulky nonwoven fabric, and there is a risk that only a nonwoven fabric with a low percentage of volume recovery is formed and that the hand feel of the nonwoven fabric becomes hard after the volume of the nonwoven fabric is recovered.

If the adhesive is a thermally bonding fiber, the amount of thermally bonding fiber used is different depending on the type of thermally bonding fiber.

If the thermally bonded fiber is a fully fusible fiber, the amount of fully fusible fiber is adjusted so that the completely fusible fiber is contained in a nonwoven fabric in a content of 30 to 55% by weight, preferably 35 to 50% by weight. If the amount of the completely fusible fiber is below the above range, there is a risk that the durability in dry cleaning and washing after the volume of the nonwoven fabric is restored will be deteriorated. If the amount of the completely fusible fiber is above the above range, there is a risk that the production of a bulky nonwoven fabric will be difficult.

When the thermally bonding fiber is a conjugated fiber, the amount of the conjugated fiber is adjusted so that the conjugated fiber is contained in a nonwoven fabric in a content of 30 to 95% by weight, preferably 40 to 90% by weight. When the amount is below the above range, there is a risk that the durability in dry cleaning and washing will be impaired after the volume of the nonwoven fabric is restored. When the amount of the conjugated fiber is above the above range, there is a risk that a sufficient amount of a temporary adhesive cannot be mixed into the nonwoven fabric and that the thickness of the nonwoven fabric becomes too thin after the nonwoven fabric is compressed.

In the above-mentioned temporary adhesive, if the amount of the temporary adhesive is too large, there is a risk that the temporary adhesive will interfere with the volume recovery of the nonwoven fabric, and if the amount of the temporary adhesive is too small, there is a risk that no sufficient effect can be achieved by adding the temporary adhesive. Therefore, when the temporary adhesive is a thermally fusible fiber, it is preferable that the amount of the thermally fusible fiber is 5 to 40% by weight, preferably 10 to 30% by weight, of the nonwoven fabric. When the above-mentioned temporary adhesive is a resin powder having a low melting point, it is preferable that the amount of the resin powder having a low melting point is 5 to 40% by weight, preferably 10 to 30% by weight, of the nonwoven fabric. Since the weight of the repulpable nonwoven fabric according to the present invention depends on the purpose of use of the repulpable nonwoven fabric and the like, the weight cannot be absolutely specified. For example, when the regenerative nonwoven fabric is used as padding for sportswear, it is preferable that the weight is about 30 to about 200 g/m². When the regenerative nonwoven fabric is used as a filter, it is preferable that the weight is about 50 to about 400 g/m².

The nonwoven fabric is heated to a temperature at least 10°C lower than the melting temperatures of the constituent fibers and the adhesive for bonding the fibers, and is compressed to produce a nonwoven fabric having a thickness of about 1/5 to about 1/30 of the original thickness of the nonwoven fabric. When the nonwoven fabric is heated, a portion of the thermally fusible fiber melts and the nonwoven fabric is fixed in the compressed state.

Examples of heating and pressing methods are the roll pressing method, the flat pressing method and the like. The roll pressing method is preferred from the standpoint of productivity because a non-woven fabric (nonwoven fabric) can be continuously heated and pressed together.

When the nonwoven fabric comes from a roll press machine, a flat press machine or a belt press machine for heating and pressing a nonwoven fabric, the nonwoven fabric is fixed in a compressed state because the temporary adhesive is cooled, thereby solidifying and being fixed at the same time. It is desirable that the nonwoven fabric be allowed to cool or forcibly cooled after heating while continuously keeping the nonwoven fabric in a compressed state to fix the nonwoven fabric more firmly in a compressed state. If the above heating and pressing process can be carried out while not lowering the temperature of the heated nonwoven fabric, a pressing step can be carried out after heating.

In each of the above heating and pressing methods, the nonwoven fabric (nonwoven fabric) may be pressed on the entire surface or at some points (locations) of the surface. It is preferable that the nonwoven fabric is pressed at some points of the surface because the nonwoven fabric is temporarily bonded at the points and as a result, the volume of the nonwoven fabric can be easily recovered by reheating the nonwoven fabric.

The regrowing non-woven fabric (nonwoven fabric) thus produced regains its volume when the non-woven fabric (nonwoven fabric) is subjected to a heat treatment at a temperature lower than the melting temperatures of the constituent fibers and the adhesive for bonding the fibers. Preferably the volume of the nonwoven fabric is recovered by supplying water vapor thereto because the volume can be easily recovered. The volume recovery percentage and the expansion ratio of the nonwoven fabric as defined below are at least 70% and at least 5 times, respectively. The rebound nonwoven fabric according to the present invention has various excellent physical properties such as durability to washing and dry cleaning before pressing the nonwoven fabric and after the volume recovery of the nonwoven fabric as compared with conventional nonwoven fabrics.

[Percentage of volume recovery (%)] =

[Thickness after reheating to recover volume]/[Thickness before heating and compression] x 100

[Expansion ratio (x-fold)] =

[Thickness after reheating to recover volume]/[Thickness after heating and compression]

When the recoverable nonwoven fabric is used for, for example, clothes and the like, it is preferable from the viewpoint of processability that the volume of the nonwoven fabric is recovered after sewing is completed. However, if the volume cannot be recovered after sewing because a heat treatment for recovering the volume damages the outer fabric or a lining of clothes, etc., the volume of the non-woven fabric can be recovered after the non-woven fabric has been transported, stored or cut.

As stated above, the nonwoven fabric offers some advantages in that the recyclable nonwoven fabric of the present invention can be reduced in volume before the nonwoven fabric is used, so that the nonwoven fabric can be conveniently handled when the nonwoven fabric is transported or stored, and the cost for transporting or storing the nonwoven fabric can be reduced.

The invention is described and explained in more detail in the following examples. It is to be understood that the present invention is not limited to the examples and that various changes and modifications can be made in accordance with the invention without thereby departing from the scope of the present invention.

example 1

Fibers consisting of 90 wt.% of a highly crimped polyester fiber (melting point 256ºC, fineness 3 denier, fiber length 51 mm) as a constituent fiber and 10 wt.% of a core-sheath type conjugated polyester fiber with a low melting point (core: polyester (melting point 256ºC), sheath: polyester with a low melting point (melting point 87ºC), fineness 3 denier, fiber length 51 mm) as a temporary adhesive were carded to form a web (nonwoven fabric) weighing 55 g/m². Thereafter, the web was impregnated with a self-crosslinking acrylic acid ester emulsion as a binder to to bond the constituent fibers of the sheet together, and a nonwoven fabric weighing 60 g/m² was obtained. Some points of the nonwoven fabric were pressed together by a heating roller at a temperature of 100ºC under a gauge pressure of 2 kg/cm². After 30 days, water vapor at a temperature of 100ºC was applied to the nonwoven fabric to recover the volume. At this time, the volume recovery percentage was 85% and the expansion ratio was 11 times.

The blending ratio between the core-sheath type conjugated polyester fiber having a low melting temperature and the highly crimped polyester fiber was changed to 3, 5, 15, 20, 30, 35, 40 or 45 wt% to prepare a sheet (nonwoven fabric) weighing 55 g/m². Each of the sheets was impregnated with a self-crosslinking acrylic acid ester emulsion to bond the constituent fibers of the sheet together, and nonwoven fabrics weighing 60 g/m² were obtained. Some points (sites) of each of the nonwoven fabrics (nonwoven fabrics) were compressed and heated in the same manner as in Example 1. After 30 days, water vapor having a temperature of 100°C was applied to each of the nonwoven fabrics (nonwoven fabrics), and the volume recovery percentage and the degree of expansion were determined as in Example 1. The results are shown in Table 1. As is clear from Table 1, when the content of the core-sheath type conjugated polyester fiber is 5 to 40 wt%, favorable physical properties can be imparted to the nonwoven fabric. Table 1 Test No. Content of core-sheath type conjugated polyester fiber with a low melting point (wt.%) Volume Recovery percentage (%) Expansion rate (x-fold)

After the nonwoven fabric containing 15% by weight of a core-sheath type conjugated polyester fiber as obtained in Example 1 was allowed to stand for 30 days, the volume of the nonwoven fabric was recovered with water vapor having a temperature of 100°C.

For comparison, a conventional non-woven fabric (nonwoven fabric) that had neither been compressed nor bonded was produced.

The above two nonwoven fabrics were tested for washing resistance and dry cleaning resistance. As a result, it was found that the washing resistance and dry cleaning resistance of each of the above two nonwoven fabrics were Class 3 and Class 5, respectively. No change was observed after pressing for bonding. The durability of the nonwoven fabric of the present invention was superior to that of the conventional nonwoven fabric.

The test methods for determining resistance to washing and resistance to dry cleaning were as follows.

Resistance to washing

A sample with a size of 250 mm x 250 mm was prepared from the obtained non-woven fabric. The sample was wrapped in a nylon taffeta and washed in a strong water stream by means of an automatic washing machine with reverse rotation for 90 minutes at a water temperature of 40 ± 3ºC, the amount of 0.2% aqueous synthetic detergent solution used which does not contain phosphorus compounds. was 32 l and clothes were introduced into the washing machine in such quantities that the weight ratio between the water in the sample and the clothes introduced was 50:1.

After that, the sample was washed with water, dehydrated and air dried, then the surface of the sample was observed. The evaluation was as follows:

Class 5: no change in appearance was observed;

Class 4: the non-woven fabric was slightly deformed;

Class 3: the non-woven fabric was moderately deformed and uneven;

Class 2: severe deformation of the non-woven fabric was observed and severe unevenness occurred;

Class 1: the non-woven fabric was clearly deformed and the non-woven fabric was partially destroyed.

Resistance to dry cleaning

A sample of 250 mm x 250 mm in size was prepared from the obtained nonwoven fabric and wrapped in nylon taffeta. A commercially available Perchlene dry cleaner was used as a detergent. A loaded fabric was used so that the total amount of laundry was 500 g. A procedure comprising washing at a temperature of 25°C for 8 minutes, draining solvent for 1 minute, stripping solvent for 4 minutes, drying at 60°C for 5 minutes and deodorizing for 2 minutes was repeated 3 times. Thereafter, the surface of the sample was observed. The evaluation was the same as in the above-mentioned test to determine resistance to washing.

Example 2

A highly crimped polyester fiber (melting point 256ºC, fineness 3 denier, fiber length 51 mm) as a constituent fiber was carded to form a sheet (nonwoven fabric) having a weight of 55 g/m². The sheet was impregnated with a self-crosslinking acrylic acid ester emulsion as a binder to bond the constituent fibers of the sheet together. Thereafter, a polyvinyl alcohol resin powder was spread on the surface of the sheet in an amount of 10 g/m² to form a nonwoven fabric (nonwoven fabric) having a weight of 70 g/m². Some points (sites) of the nonwoven fabric (nonwoven fabric) were compressed by a heating roller having a temperature of 120ºC at a gauge pressure of 3 kg/cm². After 30 days, water vapor at a temperature of 100ºC was applied to the non-woven fabric to recover (restore) the volume. At this time, the volume recovery percentage was 80% and the expansion ratio was 7 times.

The resistance to washing and the resistance to dry cleaning of the non-woven fabric were Class 3 and Class 5, respectively. The non-woven fabric had excellent durability, which was the same as that of a non-woven fabric that had not been compressed or fixed.

Comparison example 1

Fibres consisting of 80% by weight of a highly crimped polyester fibre (melting point 256ºC, fineness 3 denier, Fiber length 51 mm) and 20 wt.% of a core-sheath type conjugated polyester fiber having a low melting point (core: polyester (melting point 256ºC), sheath: polyester having a low melting point (melting point 578ºC), fineness 4 denier, fiber length 51 mm) as a constituent fiber were carded to form a nonwoven fabric having a weight of 60 g/m². Some points (locations) of the nonwoven fabric were compressed by a heating roller having a temperature of 100ºC under a gauge pressure of 2 kg/cm². After 30 days, water vapor having a temperature of 100ºC was applied to the nonwoven fabric to recover the volume. At this time, the volume recovery percentage was 40% and the expansion ratio was 6.5 times.

The resistance to washing and the resistance to dry cleaning were Class 1 and Class 2, respectively. The non-woven fabric (nonwoven fabric) therefore had a problem with regard to durability.

Comparison example 2

A highly crimped polyester fiber (melting point 256ºC, fineness 3 denier, fiber length 51 mm) as a constituent fiber was carded to prepare a sheet (nonwoven fabric) weighing 49.5 g/m². A polyamide powder resin having a low melting point was applied to the sheet in an amount of 10.5 g per m² of sheet to prepare a nonwoven fabric (nonwoven fabric) weighing 60 g/m². Thereafter, some points (sites) of the nonwoven fabric (nonwoven fabric) were compressed by means of a heating roller at a temperature of 100ºC under a gauge pressure of 2 kg/cm². After 30 days, water vapor at a temperature of 100ºC was applied to the nonwoven fabric (nonwoven fabric), to restore (recover) the volume. At this time, the volume recovery percentage was 40% and the expansion ratio was 4.5 times.

When the dry cleaning resistance of the non-woven fabric was tested, it was class 2 to 3. The durability of the above non-woven fabric was inferior to that of the non-woven fabric using a resin binder.

Since the obtained nonwoven fabric had low dimensional stability, a test to determine the resistance to washing could not be carried out on the obtained nonwoven fabric.

Example 3

Fibers consisting of 60 wt.% of a highly crimped polyester fiber (melting point 256ºC, fineness 3 denier, fiber length 51 mm), 30 wt.% of a core-sheath type conjugated polyester fiber with a low melting point (core: polyester (melting point 256ºC), sheath: polyester with a low melting point (melting point 110ºC), fineness 4 denier, fiber length 51 mm) and 10 wt.% of a core-sheath type conjugated polyester fiber with a low melting point (core: polyester (melting point 256ºC), sheath: polyester with a low melting point (melting point 87ºC), fineness 3 denier, fiber length 51 mm) were carded to produce a web (a nonwoven fabric) weighing 60 g/m². Then, heat was applied to the web (nonwoven fabric) at a temperature of 150ºC so that the constituent fibers were bonded together and a nonwoven fabric (nonwoven fabric) was obtained.

Some points (sites) of the non-woven fabric were compressed by a heating roller at a temperature of 100ºC under a gauge pressure of 2 kg/cm2. After 30 days, water vapor at a temperature of 100ºC was applied to the non-woven fabric to recover the volume. At this time, the volume recovery percentage was 45% and the expansion ratio was 8 times.

The resistance to washing and the resistance to dry cleaning were Class 3 and Class 3, respectively. The nonwoven fabric (nonwoven fabric) had favorable durability, which was the same as that of the nonwoven fabric that had not been compressed to fix the constituent fibers.

Example 4

Fibers consisting of 90 wt.% of a core-sheath type conjugated fiber with a low melting point (core: polypropylene, sheath: polyethylene (melting point 130ºC), fineness 14 denier, fiber length 76 mm) as a building fiber and 10 wt.% of a core-sheath type conjugated polyester fiber with a low melting point (core: polyester (melting point 256ºC), sheath: low melting point polyester (melting point 87ºC), fineness 3 denier, fiber length 51 mm) as a temporary adhesive were carded to prepare a web (nonwoven fabric) weighing 300 g/m². Thereafter, heat was applied to the web at a temperature of 150ºC to bond the constituent fibers of the web together, and the thickness of the web was adjusted by means of a heating roller so that a nonwoven fabric (a nonwoven fabric) with a thickness of 20 mm was obtained.

Some points (sites) of the non-woven fabric were compressed by a heating roller at a temperature of 110ºC under a gauge pressure of 4 kg/cm2. After 3 days, water vapor at a temperature of 100ºC was applied to the non-woven fabric to recover the volume. At this time, the volume recovery percentage was 105% and the expansion ratio was 11 times.

The non-woven fabric was investigated for the initial pressure loss and the collection efficiency of dust as an air filter. At a wind speed of 2.5 m/s and a dust concentration of 22.3 mg/m³, the initial pressure loss and the collection efficiency were investigated. As a result, it was found that the initial pressure loss was 10 mm Aq and the average dust collection efficiency was 80% until the pressure loss reached 20 mm Aq. From the above results, it can be seen that the non-woven fabric satisfies the physical properties required for an air filter.

Example 5

Fibers consisting of 10 wt.% of a core-sheath type conjugated polyester fiber (core: polyester (melting point 256ºC), sheath: polyester with a low melting point (melting point 87ºC), fineness 3 denier, fiber length 51 mm) as a temporary adhesive and 90 wt.% of a core-sheath type conjugated polyester fiber with a low melting point (core: polyester (melting point 130ºC), sheath: polyester with a low melting point (melting point 125ºC), fineness 2 denier and fiber length 51 mm) as a building fiber were carded to prepare a web (nonwoven fabric) having a weight of 50 g/m². Thereafter, heat was applied at a Temperature of 150ºC was applied to the web to bond the constituent fibers of the web together, and some points (locations) of the web were compressed by a heating roller having a temperature of 100ºC at a gauge pressure of 2 kg/cm² to produce a nonwoven fabric.

After 3 days, water vapor at a temperature of 100ºC was applied to the non-woven fabric to restore (recover) the volume. At this time, the volume recovery percentage was 90% and the expansion ratio was 12 times.

The obtained repulpable nonwoven fabric and a conventional nonwoven fabric (weight 50 g/m², produced by applying heat at 150°C) consisting of a polyester fiber (melting point 256°C) in which the constituent fibers were not compressed to bond them together were examined for washing resistance and dry cleaning resistance. As a result, it was found that the washing resistance was of Class 4 and the dry cleaning resistance was of Class 4. No change caused by compression for bonding was observed in the nonwoven fabric of the present invention.

Claims (9)

1. Bulk-recoverable non-woven fabric comprising a non-woven fabric made of building fibers bonded together by means of an adhesive for bonding the fibers, characterized in that the non-woven fabric is compressed and that the compressed state is maintained after heating to a temperature of at most 100°C by means of a temporary adhesive having a melting temperature that is at least 10°C lower than the melting temperatures of the building fibers and the adhesive for bonding the fibers, the amount of the temporary adhesive being 5 to 40% by weight, based on the non-woven fabric. 2. A resurfacable nonwoven fabric according to claim 1, wherein the adhesive for bonding the fibers is a thermosetting resin binder. 3. The resurfacable nonwoven fabric according to claim 1, wherein the adhesive for bonding the fibers is a thermally bonding fiber. 4. The resurfacable nonwoven fabric (nonwoven fabric) according to claim 1, wherein the constituent fiber consists of a conjugated fiber and the adhesive for bonding the fibers is a component having a low melting point of said conjugated fiber. 5. A resurfacable nonwoven fabric according to claim 1, 2, 3 or 4, wherein the temporary adhesive is a thermally fusible fiber. 6. A resurfacable nonwoven fabric according to claim 1, 2, 3 or 4, wherein the temporary adhesive a powdered resin with a low melting point. 7. A method for producing a regrowing nonwoven fabric, in which a building fiber and a thermally fusible fiber are mixed together to form a web, the web is bonded with an adhesive for bonding the fibers to form a nonwoven fabric, the nonwoven fabric is pressed together and heated to melt the thermally fusible fiber, characterized in that a compressed state of the nonwoven fabric is maintained by the thermally fusible fiber having a melting temperature which is at least 10°C lower than the melting temperatures of the building fibers and the adhesive for bonding the fibers. 8. A process for producing a regrowing nonwoven fabric, in which a web is bonded with an adhesive for bonding the fibers to form a nonwoven fabric, a powdered resin is added to the nonwoven fabric, and the nonwoven fabric is compressed and heated to melt the powdered resin, characterized in that the compressed state of the nonwoven fabric is maintained by the powdered resin having a melting point which is at least 10°C lower than the melting temperature of the constituent fibers of the web and the adhesive for bonding the fibers. 9. A method for recovering the volume of a non-woven fabric (nonwoven fabric), characterized in that the recovering non-woven fabric (nonwoven fabric) according to claim 1 is heated to a temperature heated to a temperature at least equal to the melting temperature of the temporary adhesive, but below the temperatures at which both the build-up phase and the adhesive for bonding the fibres melt in order to restore the volume of the nonwoven fabric.