Manufacturing method of functional nonwoven fabric

Abstract

To provide a manufacturing method of a functional nonwoven fabric in which a functional agent applied to the nonwoven fabric is hardly dissolved or detached.SOLUTION: A fiber web is formed by accumulating core-sheath type conjugate fibers. A core component of the core-sheath type conjugate fiber includes a copolymer of ethylene glycol and terephthalic acid. A sheath component includes a copolymer of ethylene glycol, adipic acid, terephthalic acid, isophthalic acid, and diethylene glycol. A wet web is formed by applying aqueous liquid containing a functional agent to the fiber web. By subjecting the wet web to needle punch, the core-sheath type conjugate fibers are three-dimensionally entangled with each other so as to obtain an entangled web. Heat is applied to the entangled web to soften or melt the sheath component. Thereby, the core-sheath type conjugate fibers are fused to each other, so that a functional nonwoven fabric in which the functional agent is fixed to the surfaces of the core-sheath type conjugate fibers can be obtained.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a functional nonwoven fabric having a specific function, and more particularly to a method for producing a functional nonwoven fabric having excellent water absorbency. [Background technology]

[0002] Conventionally, functional nonwoven fabrics that have water absorption and evaporation functions due to the application of a hydrophilic agent to the surface of the constituent fibers of the nonwoven fabric have been known (Patent Document 1). Such functional nonwoven fabrics are used in cooling equipment installed in supermarkets, convenience stores, etc., as water absorption and evaporation plates that absorb, retain, and evaporate drain water generated from the cooling equipment.

[0003] The present applicant has proposed a method for producing a needle-punched nonwoven fabric that can be thermoformed into a predetermined shape under a relatively wide range of heating and pressure conditions (Patent Document 2). This method comprises a first step of forming a fiber web by accumulating core-sheath composite fibers whose core component is a copolymer of ethylene glycol and terephthalic acid and whose sheath component is a copolymer of ethylene glycol, adipic acid, terephthalic acid, isophthalic acid, and / or diethylene glycol, and a second step of needle-punching the fiber web to three-dimensionally entangle the core-sheath composite fibers. The needle-punched nonwoven fabric obtained by this method has the advantage that, because the constituent fibers are core-sheath composite fibers with a specific sheath component, the sheath component softens or melts under a relatively wide range of heating and pressure conditions, making it easy to thermoform.

[0004] [Patent Document 1] Patent Publication No. 2017-156004 [Patent Document 2] International Publication No. 2018 / 190342 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0005] The applicant of the present invention discovered, while conducting research into the needle-punched nonwoven fabric described in Patent Document 2, that the sheath component of core-sheath composite fibers is prone to fixing functional agents such as hydrophilic agents. That is, the present invention is an improved invention of the invention described in Patent Document 2, and an object of the present invention is to provide a method for producing a functional nonwoven fabric in which the functional agent applied to the nonwoven fabric is less likely to dissolve or fall off. [Means for solving the problem]

[0006] The present invention relates to a method for producing a functional nonwoven fabric, comprising: a first step of forming a fiber web by accumulating sheath-core composite fibers, the core component of which is a copolymer of ethylene glycol and terephthalic acid, and the sheath component of which is a copolymer of ethylene glycol, adipic acid, terephthalic acid, isophthalic acid, and / or diethylene glycol; a second step of applying an aqueous liquid containing a functional agent to the fiber web to form a wet web; a third step of needle-punching the wet web to three-dimensionally entangle the sheath-core composite fibers to form an entangled web; and a fourth step of applying heat to the entangled web to soften or melt the sheath component, thereby fusing the sheath-core composite fibers together and fixing the functional agent to the surfaces of the sheath-core composite fibers.

[0007] In the present invention, a fiber web is first obtained whose constituent fibers are specific sheath-core composite fibers. Here, the specific sheath-core composite fibers have a core component made of a copolymer of ethylene glycol and terephthalic acid, and a sheath component made of a copolymer of ethylene glycol, adipic acid, terephthalic acid, isophthalic acid, and / or diethylene glycol. The copolymer constituting the core component is a polyester obtained by dehydration condensation of ethylene glycol as the diol component and terephthalic acid as the dicarboxylic acid component. Note that a small amount of other dicarboxylic acid components, such as isophthalic acid, may be mixed as the dicarboxylic acid component. The melting point of the copolymer constituting the core component is approximately 260°C, and the glass transition point is approximately 70 to 80°C. The copolymer constituting the sheath component is a copolymer polyester obtained by dehydration condensation of ethylene glycol and, optionally, diethylene glycol as the diol component, and adipic acid, terephthalic acid, and, optionally, isophthalic acid as the dicarboxylic acid component. Note that at least one of diethylene glycol and isophthalic acid must be used, and preferably both are used. Diethylene glycol and / or isophthalic acid are mixed to facilitate the fixation of the functional agent to the sheath component. When diethylene glycol is mixed into the diol component, the molar ratio of ethylene glycol to diethylene glycol is generally about 10:0.05-0.5. The mixing ratio of the dicarboxylic acid components, adipic acid and terephthalic acid, is arbitrary, but is generally about 1:1-10 (molar ratio) of adipic acid to terephthalic acid. When isophthalic acid is mixed into the dicarboxylic acid component, the molar ratio is generally about 0.04-0.6:1:1-10 (molar ratio). The melting point and glass transition point of the copolymer constituting the sheath component are arbitrary, but considering the fusion properties between the sheath components, the fixation properties of the functional agent, and the moldability by heating and pressure, a melting point of about 200°C and a glass transition point of about 40-50°C are suitable.

[0008] The weight ratio of the core component to the sheath component is approximately core component:sheath component = 1 to 8:1 (weight ratio). If the weight ratio of the core component is too low, the shape retention and mechanical strength of the resulting functional nonwoven fabric tend to decrease. If the weight ratio of the core component is too high, the sheath component softens or melts, making it difficult to fix the functional agent to the fiber surface. Furthermore, the fusion strength between the fibers decreases, making the surface of the resulting functional nonwoven fabric more likely to become fuzzed. The core component and sheath component may be arranged concentrically or eccentrically. However, if they are arranged eccentrically, they are more likely to shrink when heated, so a concentric arrangement is preferred.

[0009] Sheath-core conjugate fibers can be obtained by a known method in which a high-melting-point polyester as the core component and a low-melting-point copolymerized polyester as the sheath component are fed into a spinning device having conjugate spinning holes and melt-spinned. The sheath-core conjugate fibers may be either sheath-core conjugate continuous fibers or sheath-core conjugate staple fibers, but the use of sheath-core conjugate continuous fibers allows for the production of functional nonwoven fabrics with higher rigidity. To obtain a fiber web using sheath-core conjugate continuous fibers, the so-called spunbonding method is generally used. That is, the sheath-core conjugate continuous fibers obtained by melt spinning can be immediately accumulated into a sheet to obtain a fiber web. To obtain a fiber web using sheath-core conjugate staple fibers, the sheath-core conjugate staple fibers can be passed through a carding machine to open the fibers and accumulated into a sheet. The weight of the fiber web is 80 to 2000 g / m. 2 If the weight of the fiber web is too low, the thickness will be thin and the amount of functional agent adhered will tend to decrease, while if the weight of the fiber web is too high, the handling properties will tend to be reduced, such as needle punching becoming difficult.

[0010] Next, an aqueous liquid containing a functional agent is applied to the fibrous web to obtain a wet web. The fibrous web may be in a state where core-sheath composite fibers are accumulated, or may be pre-needle-punched to pre-entangle the core-sheath composite fibers for improved handleability, or may be pre-fused by applying a small amount of heat. The amount of aqueous liquid applied is approximately 25 to 95% by weight of the fibrous web. Methods for applying the aqueous liquid include spraying, coating methods such as roll coating and knife coating, and dipping. Various known functional agents, such as hydrophilic agents, antibacterial agents, antifungal agents, heat storage materials, and electromagnetic wave shielding materials, may be used alone or in combination. Particulate hydrophilic polyester resins are preferably used as hydrophilic agents. Particles of zinc pyrithione compounds are preferably used as antibacterial and antifungal agents. Depending on the type of functional agent, the aqueous liquid may be obtained by dissolving the functional agent in water. The concentration of the functional agent in the aqueous liquid is about 0.3 to 5% by weight.

[0011] The wet web obtained by applying the aqueous liquid is needle-punched. Needle-punching is performed by a well-known method, by penetrating needles into the wet web. This results in three-dimensional entanglement of the core-sheath composite fibers with each other, resulting in an entangled web. At this time, since the wet web contains water, the core-sheath composite fibers in the wet web are less likely to be cut by the needles. The punch density is 10 to 200 fibers / cm. 2 That's about it.

[0012] The resulting entangled web is heated to soften or melt the sheath component of the sheath-core composite fibers. The water in the aqueous liquid evaporates when heat is applied, followed by softening or melting of the sheath component of the sheath-core composite fibers. In this case, evaporation of the water in the aqueous liquid and softening or melting of the sheath component occur in one step. Alternatively, the resulting entangled web may be introduced into a dryer, where the water is evaporated, and then heated to apply heat. In this case, evaporation of the water in the aqueous liquid and softening or melting of the sheath component occur in two steps. The heating temperature is approximately 100°C to 220°C. After cooling, the sheath-core composite fibers fuse together with each other via the sheath component. Simultaneously with this fusion, the functional agent present in the entangled web adheres to the surface of the sheath-core composite fibers. The sheath component of the sheath-core composite fibers of the present invention can particularly firmly adhere functional agent particles. Pressure may also be applied in conjunction with heating to increase the fiber density of the resulting functional nonwoven fabric. When a hydrophilic agent is used as a functional agent, the water absorption rate is improved by increasing the fiber density. For example, when heating and pressing are performed using a heated embossing roll or a pair of heated flat rolls, the linear pressure may be about 10 to 150 kg / cm.

[0013] When applying heat and pressure, it is also possible to thermoform the web into any desired shape, such as a two-dimensional or three-dimensional shape. Alternatively, after applying heat to the entangled web to fix the functional agent to the surface of the core-sheath type composite fiber, the web may be thermoformed into any desired shape, such as a two-dimensional shape like a flat plate or a three-dimensional shape like a dish or bowl. Specifically, a press mold is used to thermoform the web into a two-dimensional or three-dimensional solid shape. In this case, it is preferable to preheat the web and then apply pressure with the press mold. Of course, the press mold may be heated in advance, and heating and pressure may be applied simultaneously. When thermoforming the web, the heating temperature is about 100°C to 220°C, and the pressure conditions are a surface pressure of 10 to 500 kg / cm during pressing. 2 During the thermoforming, the sheath component softens or melts again, but the subsequent cooling causes the core-sheath type composite fibers to fuse together, and the functional agent adheres to the surface of the core-sheath type composite fibers.

[0014] The functional nonwoven fabric obtained by the method of the present invention can be suitably used for various applications depending on the functional agent fixed to the surface of the core-sheath composite fiber. For example, when a hydrophilic agent is used as the functional agent, it can be suitably used as a water-absorbing and transpiration board or a transpiration board for a humidifier. Furthermore, when an antibacterial agent or antifungal agent is used as the functional agent, it can be used as a carpet base fabric or a base fabric for shoes or bags. When a heat storage material is used as the functional agent, it can be used as a snow melting material or heat retaining material. Furthermore, when a conductive material is used as the functional material, it can be used as a sheet heater or an electromagnetic wave shielding material. When a heat-shielding material is used as the functional material, it can be used as a lightweight resin cover with heat-shielding properties. When an insulating material is used as the functional material, it can be used as an insulating sheet, such as a cover or packaging material for transporting pre-cooled items such as pre-cooled fruits and vegetables at room temperature for long periods of time. [Effects of the Invention]

[0015] The functional nonwoven fabric obtained by the method of the present invention uses a specific polyester copolymer as the sheath component of the core-sheath composite fiber, which has the effect of enabling functional agents to be firmly fixed to the surface of the core-sheath composite fiber. Furthermore, when the wet web is needle-punched, the presence of water makes the core-sheath composite fiber less susceptible to cutting by needles, resulting in a functional nonwoven fabric with high mechanical strength. [Example]

[0016] Example 1 A copolymer of ethylene glycol and terephthalic acid (melting point 260°C) was prepared as the core component. A copolymer of ethylene glycol, diethylene glycol, adipic acid, terephthalic acid, and isophthalic acid (melting point 200°C) was prepared as the sheath component. The diol components were 99 mol% ethylene glycol and 1 mol% diethylene glycol, and the dicarboxylic acid components were 19 mol% adipic acid, 78 mol% terephthalic acid, and 3 mol% isophthalic acid. Both the core component and the sheath component were fed into a spinning device with a multi-component spinning hole and melt-spun to obtain a core-sheath composite continuous fiber. The weight ratio of the core component to the sheath component was core component:sheath component = 8:2. This fiber was introduced into an air sucker installed below the spinning device, pulled and thinned at high speed, then opened using a known fiber-opening device, and collected and accumulated on a moving screen conveyor, resulting in a fiber weighing approximately 230 g / m. 2 A fiber web of

[0017] An aqueous solution containing 1.1% by weight of a hydrophilic polyester resin (Nicepol PR-99S manufactured by Nicca Chemical Co., Ltd.) and 0.35% by weight of an antibacterial agent (zinc pyrithione particles) was sprayed onto this fiber web until the weight reached 440 g / m 2 A wet web of 1000 g was obtained.

[0018] The obtained wet web was transferred to a needle punching device and punched at a punch density of 90 needles / cm. 2 The web was needle-punched with a needle depth of 12 mm, and then the water was evaporated in a dryer at 100°C to obtain an entangled web. The obtained entangled web was cut into a size of 1000 mm x 1200 mm, and two 1000 mm x 1200 mm entangled webs were stacked together and passed through a flat-plate heat press heated to a surface temperature of 205°C, where it was subjected to a heat molding treatment under conditions of a clearance of 2 mm and a treatment time of 60 seconds, to obtain a flat-plate functional nonwoven fabric. The weight of this functional nonwoven fabric was approximately 460 g / m 2 The thickness was about 1.7 mm and the water absorption rate was high.

Claims

1. a first step of forming a fiber web by collecting core-sheath type composite fibers, the core component of which is a copolymer of ethylene glycol and terephthalic acid, and the sheath component of which is a copolymer of ethylene glycol, adipic acid, terephthalic acid, and isophthalic acid and / or diethylene glycol; a second step of applying an aqueous liquid containing a functional agent to the fiber web to form a wet web; a third step of needle-punching the wet web to three-dimensionally entangle the core-sheath type composite fibers to form an entangled web; a fourth step of applying heat to the entangled web to soften or melt the sheath component, thereby fusing the core-sheath type composite fibers together and fixing the functional agent to the surface of the core-sheath type composite fibers; A method for producing a functional nonwoven fabric, comprising:

2. 2. The method for producing a functional nonwoven fabric according to claim 1, wherein the core-sheath type composite fiber is a core-sheath type composite continuous fiber or a core-sheath type composite short fiber.

3. 2. The method for producing a functional nonwoven fabric according to claim 1, wherein in the fourth step, pressure is applied to the entangled web together with heat.

4. 2. The method for producing a functional nonwoven fabric according to claim 1, wherein the functional agent is a hydrophilic agent, an antibacterial agent and / or an antifungal agent.

5. 5. The method for producing a functional nonwoven fabric according to claim 4, wherein the hydrophilic agent is a hydrophilic polyester resin.

6. 2. The method for producing a functional nonwoven fabric according to claim 1, wherein a step of evaporating water from the aqueous liquid is inserted between the third step and the fourth step.

7. 2. The method for producing a functional nonwoven fabric according to claim 1, wherein in the fourth step, water in the aqueous liquid is evaporated.

8. 2. The method for producing a functional nonwoven fabric according to claim 1, wherein the fourth step is performed during thermoforming or a thermoforming step is added after the fourth step.