Warm water soluble male fastener tape and method of making same

Abstract

A warm water-dissolvable male type hook-and-loop fastener having a base and a plurality of male hooking elements protruding from the surface of the base, both the base and the male hooking elements comprising a polyvinyl alcohol-based resin having a polymerization degree in the range of 300 to 700 and a saponification degree in the range of 80 to 99 mol%, and both the base and the male hooking elements being dissolved in warm water having a temperature of 45 to 90°C but not being dissolved in water having a temperature of less than 45°C.

Description

Technical Field

[0001] This invention relates to a male hook-and-loop fastener having a male hook-and-loop element on its surface and being soluble in warm water, and a method for manufacturing the same. More specifically, it relates to a warm water-soluble male hook-and-loop fastener that is insoluble in water at room temperature but rapidly dissolves in warm water at a temperature higher than room temperature, causing the hook-and-loop force to disappear and the shape and presence of the male hook-and-loop fastener to also disappear, and a method for manufacturing the same. Background Technology

[0002] One method for mounting objects onto the surface of an object has long been the following: A male hook-and-loop fastener with hook-and-loop hook elements (either hook-shaped or mushroom-shaped) is mounted on the surface of one of the objects, while a loop hook-and-loop fastener with loop hook elements is mounted on the surface of the other. The hook-and-loop hook elements of the two fasteners are then overlapped to hook the two hook elements together, thereby fixing the object to the surface of the object. Because it allows for repeated hooking and unhooking, and because it can be easily peeled off and repositioned in cases of incorrect installation, it has gained popularity as an mounting method.

[0003] In recent years, hook and loop fasteners have been used to secure sanitary products to underwear or to fasten disposable diapers around the waist. Now, sanitary products and disposable diapers with hook and loop fasteners are discarded as part of the garbage after use and are eventually incinerated.

[0004] If these sanitary products, disposable diapers, and other disposable products can be flushed down the toilet just like used toilet paper, then the labor and odor control measures for waste disposal in each household will become very simple. Therefore, there will be no need for the labor and fuel required for further waste recycling and incineration. Therefore, it is hoped that sanitary products, disposable diapers, etc., can be flushed down the toilet. Along with this, it is also hoped that the hook and loop fasteners that make up such sanitary products, disposable diapers, etc., can be water-soluble at room temperature that dissolves quickly in toilet water and loses their hook-and-loop force.

[0005] Generally speaking, hook and loop fasteners, as described above, comprise a combination of male hook and loop fasteners and loop fasteners. Regarding loop fasteners, the problem of room temperature water solubility can be easily solved by using fabric with room temperature water-soluble fibers present in a loop shape on the fabric surface. However, for the other type, male hook and loop fasteners, it is necessary to have hook-shaped hooking elements on the surface that can maintain a hook shape under tensile force. Several solutions have been proposed for room temperature water-soluble male hook and loop fasteners with such hook-shaped hooking elements.

[0006] For example, in Patent Document 1, a room-temperature water-soluble male hook and loop fastener suitable for use in disposable products that can be disposed of in toilets, etc., is described using a water-soluble resin obtained by graft polymerization of a copolymer of polyoxyethylene with vinyl alcohol and allyl alcohol.

[0007] However, as described in the patent document, hook and loop fasteners that are water-soluble in low-temperature conditions like tap water can easily dissolve during wear by coming into contact with bodily fluids at higher temperatures. Therefore, they would dissolve before being disposed of in the toilet, causing the hook and loop to disappear and rendering them unusable in practice. For this reason, sanitary products and disposable diapers using water-soluble hook and loop fasteners have not yet been industrialized.

[0008] Recently, research has been conducted on the following attempt as part of solving environmental problems: instead of incinerating used sanitary products, disposable diapers, and other disposable products as waste, they are recycled, mixed with warm water and crushed to separate them into various raw materials, which are then washed, sterilized, and the pulp, fibers, superabsorbent resins, and membranes used in disposable products are recycled and reused in disposable products.

[0009] However, hook and loop fasteners used in such disposable products, especially male-type hook and loop fasteners, are difficult to crush directly while attached to the product and are also difficult to separate. Therefore, the presence of male-type hook and loop fasteners hinders the recycling and reuse of pulp, fibers, superabsorbent polymers, and films. If the used hook and loop fasteners could be easily removed from the raw materials through processes such as crushing, separation, washing, and sterilization, the recycling and reuse of pulp, fibers, superabsorbent polymers, and films would become very easy.

[0010] Existing technical documents

[0011] Patent documents

[0012] Patent Document 1: Japanese Patent Application Publication No. 09-313218 Summary of the Invention

[0013] The problem that the invention aims to solve

[0014] The present invention provides a male-type hook and loop fastener for use in such disposable products, which is not soluble in water at the temperature of bodily fluids excreted from the human body, but is easily soluble in water at the temperature of the water used when recycling used disposable products and separating and recycling used pulp, fiber, superabsorbent resin, membrane, etc., and will not become an obstacle when recycling raw materials such as pulp, fiber, superabsorbent resin, membrane, etc.

[0015] Furthermore, it is preferable to provide a warm water-soluble male hook and loop fastener that achieves high hook-and-loop strength (hereinafter, sometimes also referred to as hook-and-loop power). A more preferred objective is to provide a warm water-soluble male hook and loop fastener (hereinafter, sometimes referred to as a male-molded hook and loop fastener) that possesses both warm water solubility and high hook-and-loop strength. In addition, the male hook and loop element is soft, suppressing gelation and decomposition of the resin used in molding. As a result, breakage of the male hook and loop element or cracking of the base layer of the hook and loop fastener is virtually eliminated after molding. Moreover, a further preferred objective is to provide a male-molded hook and loop fastener that possesses both warm water solubility, high hook-and-loop strength, and excellent moldability, and that has a small male hook and loop element that provides excellent skin feel when worn.

[0016] Problem Solving Methods

[0017] That is, the present invention is a warm water soluble male hook and loop fastener, which has a base and a plurality of male hook and loop elements protruding from the surface of the base. The base and the male hook and loop elements both contain polyvinyl alcohol resin, and the base and the male hook and loop elements are soluble in warm water at any temperature in the range of 45 to 90°C, but not in water below 45°C.

[0018] Furthermore, it is preferable that in such a water-soluble male hook and loop fastener, a plurality of the aforementioned male hook and loop elements are arranged in a row, and the male hook and loop elements have a shape that stands upright from the surface of the base material, bends from the middle toward the row direction, and has its front end facing toward the surface of the base material; or the male hook and loop elements have a shape that stands upright from the surface of the base material, branches forward and backward from the middle toward the row direction and bends along the row direction, and has the front end of the branch facing toward the surface of the base material; in addition, both the base material and the male hook and loop elements are made of a polymer with a degree of polymerization of 300 to 700. The above-mentioned polyvinyl alcohol resin is formed in the range of 80 to 99 mol% saponification degree; in addition, the above-mentioned matrix and the above-mentioned male hook element are formed from a resin composition, wherein the above-mentioned resin composition contains 5 to 45 parts by weight of polyol or ethylene oxide polymer relative to 100 parts by weight of the above-mentioned polyvinyl alcohol resin; furthermore, the above-mentioned matrix and the above-mentioned male hook element are formed from a resin composition, wherein the above-mentioned resin composition contains 4 to 25 parts by weight of layered inorganic particles relative to 100 parts by weight of the above-mentioned polyvinyl alcohol resin.

[0019] Furthermore, in such a warm water-soluble male hook and loop fastener, when the male hook element has a shape that rises from the base surface, bends in the column direction from the middle, and has its front end facing towards the base surface, the height from the base surface of the male hook element to the top of the male hook element is 1.2 mm or less; when the male hook element has a shape that branches forward and backward in the column direction and bends in the column direction respectively, and the front end of the branch faces towards the base surface, the height from the base surface of the male hook element to the top of the male hook element is 0.6 mm or less.

[0020] In addition, it is preferable that in such a warm water-soluble male hook and loop fastener, the polyol or ethylene oxide polymer is polyethylene glycol and its number average molecular weight is in the range of 300 to 700; and the layered inorganic particles are talc.

[0021] Furthermore, the present invention is a combination of the aforementioned water-soluble male hook and loop fasteners and water-soluble loop fasteners. The water-soluble loop fasteners are composed of loop fibers containing polyvinyl alcohol resin that is dissolved in water at a temperature of 45 to 90°C but not in water below 45°C. Preferably, in such a combination, the water-soluble loop fasteners use non-woven or woven fabric as the base fabric and have loop fibers on its surface.

[0022] Furthermore, the present invention is a method for manufacturing a water-soluble male hook and loop fastener, the method comprising: passing a molten resin composition satisfying (1) and (2) below through the surface of a metal roller satisfying (A) below, pressing the molten material into a cavity in the shape of a male hook and loop element perforated on the surface of the metal roller, cooling and solidifying the molten material in this state, peeling it off from the surface of the metal roller, and extracting it from the cavity.

[0023] (A) The aforementioned metal roller is formed by stacking annular molds with multiple cavities engraved on the outer circumference. On the surface of such a metal roller, the multiple cavities are arranged in a row in the circumferential direction of the metal roller. The cavities bend in the direction of the row of cavities midway and their front ends are close to the surface of the metal roller, or they branch into two strands midway and bend in the direction of the row of cavities respectively, and their front ends are close to the surface of the metal roller.

[0024] (1) A resin composition comprising a polyvinyl alcohol resin, a polyol or an ethylene oxide polymer, and layered inorganic particles, wherein the mixing ratio of the resin composition is: 5 to 45 parts by mass relative to 100 parts by mass of the polyvinyl alcohol resin, and 4 to 25 parts by mass of the layered inorganic particles.

[0025] (2) The degree of polymerization of the above polyvinyl alcohol is 300-700, and the degree of saponification is 80-99 mol%.

[0026] Furthermore, in the preferred method of manufacturing such a water-soluble hook and loop fastener, when the cavity has a shape that bends in the direction of the column midway and its front end is close to the surface of the metal roller, the depth of the cavity from the surface of the metal roller is at most 1.2 mm or less; or, when the cavity has a shape that branches into two strands midway and bends in the direction of the column respectively and its front end is close to the surface of the metal roller, the depth of the cavity from the surface of the metal roller is at most 0.6 mm or less.

[0027] Moreover, the present invention is a disposable diaper or sanitary product, which is fitted with the aforementioned warm water-soluble male-type hook and loop fastener.

[0028] The effects of the invention

[0029] The water-soluble male hook and loop fastener of this invention (hereinafter sometimes referred to as male hook and loop fastener) has a water solubility temperature of 45-90°C and does not dissolve in water below 45°C. Existing known water-soluble hook and loop fasteners are designed to be flushed down the toilet and dissolved after use; therefore, it is important to consider that their water solubility temperature is equivalent to tap water at 10-25°C. The water solubility temperature of the water-soluble hook and loop fastener of this invention is much higher and is by no means suitable for flushing down the toilet and dissolving.

[0030] The water-soluble hook and loop fastener of the present invention has a water solubility temperature of any temperature between 45 and 90°C. Therefore, the water-soluble hook and loop fastener of the present invention is substantially insoluble in water below 45°C. "Substantially insoluble" here means that even if the surface layer dissolves when immersed in water, it will not dissolve into the interior, and its function as a hook and loop fastener will not be lost, or it will be substantially insoluble including the surface layer.

[0031] As a resin for male hook and loop fasteners that are soluble in warm water, polyvinyl alcohol resins can be cited as an example, considering both hook strength and solubility in warm water.

[0032] To clarify, resins like polyvinyl alcohol are special resins that, when made into fibers, yield much higher strength than ordinary fibers and are also water-soluble. The male hook and loop fastener of this invention comprises a polyvinyl alcohol-based resin, which is such a special resin, thereby obtaining a male hook and loop fastener that combines high hook-and-loop strength with warm water solubility.

[0033] As a male hook and loop fastener that combines high hook strength and warm water solubility, a male hook and loop fastener manufactured by injection molding is preferred. When manufactured by injection molding, a polyvinyl alcohol resin with a specific degree of polymerization and saponification is a suitable resin for the male hook and loop fastener. More preferably, a resin composition is formed by mixing a resin composition containing such a polyvinyl alcohol resin, a polyol or ethylene oxide polymer, and layered inorganic particles in a specific ratio. By using such a special resin composition, a male hook and loop fastener with high hook strength and rapid solubility in warm water at any temperature in the range of 45 to 90°C but not in water below 45°C can be easily obtained.

[0034] Furthermore, the male hook and loop fastener of the present invention is preferably obtained by the following method: a molten resin composition comprising the above-mentioned special resin composition, namely polyvinyl alcohol resin, polyol or ethylene oxide polymer, and layered inorganic particles, is passed through the surface of a metal roller as described above, and the molten material is pressed into a cavity in the shape of a male hook and loop element formed by rows and perforations on the surface of the metal roller. After the molten material is cooled and solidified in this state, it is peeled off from the surface of the metal roller and extracted from the cavity. The warm water-soluble male-shaped hook and loop fastener obtained by this method has multiple male hook elements arranged in a row. The male hook elements have a shape that stands up from the base surface, bends from the middle towards the row direction, and has its front end facing towards the base surface (hereinafter sometimes referred to as an inverted J-shape), or the male hook elements have a shape that stands up from the base surface, branches forward and backward in the middle towards the row direction and bends along the row direction, and has the front end of the branch facing towards the base surface (hereinafter sometimes referred to as a Y-shape).

[0035] The uniform bending direction of such male hook elements effectively resists tension from the direction of the male hook element row of the hooked object, making them less prone to breakage. Compared to cases where the head (hook-inflated head) of the male hook element extends along the direction intersecting with the male hook element row, or where the front end of the rod extends into an umbrella shape, higher hooking force can be easily obtained. In particular, in this invention, a low height of the male hook element is preferred. In this case, even when installed in a part that is likely to come into contact with the skin, such as in sanitary products or disposable diapers, the feeling of a foreign body can be suppressed, and even when in contact with the skin, it is less likely to cause skin roughness, and the time required for dissolution can be further shortened.

[0036] Furthermore, when the male hook element has an expansion head for hooking, such as a mushroom shape, it is preferable to use male hook elements to hook together raw materials uniformly.

[0037] Furthermore, the polyvinyl alcohol resins, polyols or ethylene oxide polymers, and layered inorganic particles that can constitute the water-soluble hook and loop fasteners of the present invention have been widely used for applications involving contact with human skin. Therefore, the water-soluble hook and loop fasteners of the present invention have minimal impact on the human body. Attached Figure Description

[0038] Figure 1 This is a perspective view of an example of the warm water-soluble male hook and loop fastener of the present invention.

[0039] Figure 2 This is a perspective view of another example of the warm water-soluble male hook and loop fastener of the present invention.

[0040] Figure 3 This is a photograph of an alternative drawing showing an example of the surface of the water-soluble hook and loop fastener of the present invention.

[0041] Symbol Explanation

[0042] 1: Male hook-and-loop element

[0043] 2: Matrix

[0044] T: Column direction of male hook element Detailed Implementation

[0045] Next, the warm water-soluble male hook and loop fastener of the present invention and its manufacturing method will be described in detail.

[0046] First, as described above, the water-soluble hook and loop fastener of the present invention has a water-soluble temperature range of 45 to 90°C. When the water-soluble temperature is below 45°C, especially below 40°C, the hook-and-loop force may disappear during wear due to bodily fluids. Furthermore, at temperatures exceeding 90°C, it may not dissolve during recycling or reuse processes. Preferably, the temperature range is 50 to 85°C, and more preferably 52 to 82°C.

[0047] It should be noted that the water dissolution temperature was determined using the following method.

[0048] [Water solubility temperature of male hook and loop fasteners (°C)]

[0049] A bath was prepared in 2000 ml of water by stirring with a heated stirrer (Advantech SRS316HA) at approximately 940 rpm using a 30 mm × 8 mm Φ stir bar, while maintaining the water temperature at a given level. Male hook and loop fasteners cut to 20 mm × 20 mm (weight per unit area: 0.1–0.2 g / 20 mm × 20 mm) were then added to this bath. The time required for the male hook and loop fasteners to completely dissolve was measured, and the lowest temperature at which complete dissolution occurred within 5 minutes was taken as the water dissolution temperature. It should be noted that initial measurements were taken at 5°C intervals to determine the approximate water dissolution temperature. Based on this result, further measurements were taken at 2°C intervals using water temperatures near the water dissolution temperature, and then at 1°C intervals using water temperatures near the water dissolution temperature to determine the final water dissolution temperature.

[0050] As a resin for male hook and loop fasteners that meets the water solubility temperature range of 45 to 90°C, polyvinyl alcohol (hereinafter referred to as PVA) resins can be cited from the aspects of water solubility, strength, moldability, and further from the aspect of obtaining high hook strength.

[0051] As a male hook and loop fastener that meets such a water solubility temperature, a so-called woven male hook and loop fastener is considered, which has a hook-shaped hooking element formed of coarse PVA water-soluble monofilament yarn on the surface of a base fabric made of a woven fabric made of PVA water-soluble fibers. Among such woven male hook and loop fasteners, PVA fibers can be cited as fibers that are both water-soluble and woven. In the aforementioned Patent Document 1, as a male hook and loop fastener that dissolves in room temperature water, it is also described that a hook-shaped male hook and loop fastener is made by cutting a loop that is protruding on a base fabric made of woven fabric or woven material.

[0052] However, in the case of woven hook and loop fasteners, those made of monofilament yarn formed from water-soluble PVA resin exhibit poor heat set. As a result, the hook shape easily stretches under light engagement, causing the hook to disengage and making it difficult to obtain sufficient hooking force. If coarse PVA monofilament yarn with high heat set is used to prevent the above situation, the resulting hook and loop fastener tends to be rigid and difficult to dissolve easily. In other words, it is difficult to obtain hook and loop fasteners that combine warm water solubility, high hooking force, and excellent skin feel. Furthermore, hook-shaped hooking elements formed from such rigid, coarse monofilament yarn tend to have reduced skin feel.

[0053] Therefore, from the above considerations, the warm water-soluble male hook and loop fastener of the present invention is more preferably a male-shaped hook and loop fastener obtained by injection molding or the like, compared with woven male hook and loop fasteners.

[0054] The resin constituting such a male-shaped hook and loop fastener (the resin constituting the matrix and the aforementioned male hook and loop elements) is preferably a PVA-type resin having a specific degree of polymerization and saponification, considering its strength, moldability, and solubility in warm water. More preferably, it is a resin composition in which polyols or ethylene oxide polymers are added to a PVA-type resin having such a specific degree of polymerization and saponification, or a resin composition in which layered inorganic particles are added to a PVA-type resin having such a specific degree of polymerization and saponification.

[0055] Regarding PVA-type resins, Patent Document 1 mentioned above also describes a water-soluble resin obtained by graft polymerization of a copolymer of polyoxyethylene with vinyl alcohol and allyl alcohol. However, such a complex copolymerized water-soluble resin is not currently commercially available and is not easily obtained. Furthermore, the hook and loop fasteners obtained using resins similar to this complex copolymer do not adequately meet requirements for formability, hooking force, hardness of the molded product, and surface stickiness. Moreover, the water-soluble resin described in Patent Document 1 is a resin that dissolves in water at room temperature, not a resin that dissolves in warm water (45–90°C) as targeted in this invention.

[0056] When manufacturing the water-soluble hook and loop fastener of the present invention by molding, the degree of polymerization of the PVA resin used (the degree of polymerization in this invention refers to the viscosity-uniform degree of polymerization, and is sometimes simply referred to as the degree of polymerization) is preferably in the range of 300 to 700. Considering that the degree of polymerization of PVA resins generally used for fiber applications is 1000 or more, for example, 1200 to 1800, the degree of polymerization of the PVA resin used in the present invention can be considered to be very low. As the resin for molding into hook and loop fasteners, from the viewpoint of hook strength, it is preferable to use a PVA resin with a high degree of polymerization, and from the viewpoint of moldability, it is preferable to use a PVA resin with a low degree of polymerization.

[0057] When the degree of polymerization is 300 or higher, the resulting male-shaped hook and loop fastener exhibits increased tensile strength. Conversely, when the degree of polymerization is 700 or lower, the melt viscosity does not become excessively high, resulting in good moldability, reduced gelation, and the ability of the molten resin to reach the front end of the cavity. Consequently, it is easy to obtain male-shaped hook and loop fasteners with male hook elements extending to the front end. The influence on moldability is particularly significant when the male hook element has a thin shape. A degree of polymerization in the range of 330 to 600 is particularly preferred, and more preferably in the range of 340 to 550.

[0058] It should be noted that the PVA resin used can be a mixture of two or more PVA resins with different degrees of polymerization, resulting in an average degree of polymerization of 300 to 700. However, since it is difficult to uniformly mix PVA resins with significantly different degrees of polymerization, when mixing two or more types, it is preferable to mix PVA resins with similar degrees of polymerization.

[0059] The degree of polymerization (viscosity-average polymerization degree) is a value obtained based on JIS K 6726:1994. Specifically, when the degree of saponification is less than 99.5 mol%, the viscosity-average polymerization degree (P) is calculated using the following formula, based on the limiting viscosity [η] (L / g) of PVA resin saponified to a degree of saponification of 99.5 mol% or more in water at 30°C.

[0060] P = ([η] × 10⁴ / 8.29)(1 / 0.62)

[0061] Furthermore, the degree of saponification of PVA resins also affects the hook-and-loop strength and warm water solubility of hook and loop fasteners, and consequently, their moldability. To meet these requirements, the degree of saponification of PVA resins is preferably in the range of 80 to 99 mol%. When the degree of saponification is 80 mol% or higher, the water solubility temperature becomes higher, making it easier to obtain PVA resins with a water solubility temperature range of 45 to 90°C. Conversely, when the degree of saponification is 99 mol% or lower, the water solubility temperature is less likely to exceed 90°C, which is suitable for economical pulp regeneration processes. In addition, it can dissolve quickly, and the moldability is not significantly reduced. A degree of saponification of 90 to 98.5 mol% is more preferred, and 93 to 97 mol% is most preferred.

[0062] The PVA resin used in this invention can be a mixture of two or more PVA resins with different degrees of saponification, wherein the average degree of saponification is 80-99 mol%. It should be noted that the degree of saponification is a value obtained based on JIS K 6726:1994.

[0063] In the case of PVA-based resins, increased saponification often leads to gelation. If used in injection molding, the molten resin cannot reach the ends of the cavity, making it difficult to obtain hook-and-loop fasteners with male hook elements extending to the front end. The effect of gelation is particularly pronounced when the male hook element is thin. Therefore, to prevent this problem, when using PVA-based resins with high saponification, it is preferable to select PVA-based resins with low polymerization, and then add the polyols or ethylene oxide polymers (described later), layered inorganic particles, and increase their addition amount to the PVA-based resin.

[0064] There are no particular limitations on the method for producing such PVA-based resins. They are generally manufactured through the hydrolysis or alcoholysis of polyvinyl acetate. In this invention, a saponified form of a homopolymer of vinyl acetate is sometimes preferred. Of course, within a range that does not severely impair the water solubility, moldability, etc., of the PVA-based resin, small amounts of other vinyl monomers can be copolymerized, such as vinyl formate, vinyl acetate, vinyl propionate, vinyl tert-carbonate, vinyl neopentanoate, and other α-olefins. Furthermore, polymers obtained by modifying the ends of the polymer can also be used. In addition, examples of polymerization methods for polyvinyl acetate include solution polymerization, bulk polymerization, bead polymerization, and emulsion polymerization. Furthermore, to increase the water solubility temperature of the resulting hook and loop fastener, a method can be used to crosslink the PVA-based resin present on the surface of the molded article intermolecularly.

[0065] Next, we will describe the preferred additives used to form the water-soluble male-shaped hook and loop fastener (forming the matrix and male hook element) of the present invention, such as polyols or ethylene oxide polymers.

[0066] Polyols or ethylene oxide polymers act as plasticizers during the molding of PVA resins. The melting temperature and thermal decomposition temperature of PVA resins are close, meaning that if PVA resins are melt-molded, thermal decomposition will occur during molding, making molding impossible. However, by adding polyols or ethylene oxide polymers to PVA resins, molding can be achieved.

[0067] The polyols used are aliphatic alcohols with three or more nucleotides. Specific examples include glycerol, pentaerythritol, and sorbitol, which can be used to add ethylene oxide, propylene oxide, and other alkyl oxides to their alcohol groups. Among these, the substance obtained by adding 2 to 10 moles of ethylene oxide to glycerol and sorbitol is preferred due to the high plasticizing effect of PVA resins.

[0068] In addition, polyethylene glycol is a specific example of ethylene oxide polymers. In particular, polyethylene glycol is preferred from the perspective of not easily leaching out, and also from the perspective of less vaporization when forming hook and loop fasteners so as not to cause a deterioration of the workplace environment. In particular, as polyethylene glycol, low polymers with a number average molecular weight of 300 to 700 are the most preferred among the above-mentioned polyols or ethylene oxide polymers.

[0069] By using polyethylene glycol with such a low number-average molecular weight, the moldability of PVA-based resins (resin compositions comprising PVA-based resins and polyethylene glycol) can be further improved, thereby making the resulting hook-and-loop fasteners more flexible. In particular, when the number-average molecular weight is 300 or higher, polyethylene glycol is less likely to seep out onto the surface of the resulting hook-and-loop fastener, and the surface is less sticky. Furthermore, when the number-average molecular weight is 700 or lower, the moldability is even better. A number-average molecular weight of 350 to 500 is more preferred, and particularly preferred is 370 to 450. It should be noted that a small amount of epoxyalkane, such as propylene oxide, may be copolymerized in the polyethylene glycol.

[0070] The number-average molecular weight of the polyethylene glycols used in this invention is measured as follows. In a stoppered flask, 1 g (weighed to the nearest 0.1 mg) of the polyethylene glycol sample to be tested is added to 25 mL of accurately weighed phthalic anhydride pyridine solution. The flask is then stopped, heated in a boiling water bath for 2 hours, and allowed to cool to room temperature. Next, 50 mL (accurately weighed) of 0.5 mol / L sodium hydroxide aqueous solution and 10 drops of phenolphthalein solution for titration are added to the flask. The liquid in the flask is titrated with the 0.5 mol / L sodium hydroxide aqueous solution, and the endpoint is defined as the point at which the liquid remains red for 15 seconds. Based on the titration amount M (mL) obtained in this experiment, and the titration amount R (mL) obtained by performing a blank test similarly to the above (excluding the use of a polyethylene glycol sample), the number-average molecular weight is calculated using the formula: _(polyethylene glycol sample volume (g)) × 4000 _(MR) × 0.5 (mol / L) _(MR)_.

[0071] The amount of such polyols or ethylene oxide polymers (sometimes these compounds are also representatively referred to as polyethylene glycols) added is preferably in the range of 5 to 45 parts by weight relative to 100 parts by weight of PVA resin. At less than 5 parts by weight, the added effect of polyethylene glycol, namely, the improvement in moldability and the softness of the molded article, cannot be obtained. At more than 45 parts by weight, the polyethylene glycol seeps into the surface of the resulting hook-and-loop fastener, making the surface sticky. Furthermore, the hook-and-loop fastener element of the resulting hook-and-loop fastener does not have sufficient breaking strength. More preferably, it is in the range of 10 to 40 parts by weight, and particularly preferably in the range of 12 to 38 parts by weight.

[0072] Furthermore, it is preferable to add layered inorganic particles to the raw materials (resin composition) constituting the water-soluble male-shaped hook and loop fastener of the present invention. That is, it is preferable to add layered inorganic particles to the raw materials (resin composition) constituting the matrix and the male hook and loop element. The layered inorganic particles can reduce the stickiness of the surface of the obtained male-shaped hook and loop fastener. In addition, since the layers are arranged parallel to the flow direction of the resin during molding, the fluidity of the melt is not seriously impaired even with the addition of solid substances, and the obtained molded product (water-soluble male-shaped hook and loop fastener) can be endowed with excellent tensile strength, etc.

[0073] Furthermore, when manufacturing the hook-and-loop fastener by pressing molten resin into a cavity shaped like a male hook-and-loop element that passes through the surface of a metal roller, allowing the resin melt to cool and solidify in this state, and then peeling it off from the surface of the metal roller, the layers of layered inorganic particles added to the resin melt are arranged parallel to the flow direction of the resin melt. As a result, when the cooled and solidified hook-and-loop fastener is extracted from the cavity, it can prevent the hook-and-loop element from breaking or tearing midway through the cavity, thus preventing cracks. Furthermore, when the hook-and-loop fastener of the resulting hook-and-loop fastener is hooked and then peeled off from the loop fastener, it can also prevent the hook-and-loop fastener from breaking or tearing. In addition, since the layers of layered inorganic particles are arranged parallel to the surface of the molded product (warm water-soluble hook-and-loop fastener), it is easy to prevent polyethylene glycol from seeping from the interior of the molded product to the surface. On the other hand, when the inorganic particles have a needle-like or granular shape, it is difficult for layered inorganic particles to prevent seepage.

[0074] Specific examples of layered inorganic particles include kaolin, halloysite, talc, pyrophyllite, montmorillonite, vermiculite, and mica, with talc being the preferred choice. Talc is a pulverized form of hydrated magnesium silicate and has the following effects: it improves the formability of the male-shaped hook and loop fastener during molding, increases the strength of the resulting male-shaped hook and loop element, and makes the surface of the resulting male-shaped hook and loop fastener non-sticky.

[0075] That is, the male-shaped hook and loop fastener of the present invention is preferably manufactured by extracting the male hook element from the cavity of the mold. By adding the above-mentioned layered inorganic particles to the molding material, it has the following advantages: it can reduce the tearing of the male hook element in the cavity during extraction, and it can reduce the tearing of the molded male hook element during use. In addition, the surface of the resulting male-shaped hook and loop fastener does not become sticky even under high humidity conditions. The average particle size of such layered inorganic particles is preferably in the range of 0.1 to 100 μm, and particularly preferably in the range of 1 to 20 μm. The "average particle size" mentioned here refers to the 50% particle size (D50), which can be measured by a particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., Nanotrac (registered trademark) particle size distribution measuring device UPA-EX150) using laser Doppler method.

[0076] Furthermore, the amount of such layered inorganic particles added is preferably 4 to 25 parts by weight relative to 100 parts by weight of PVA resin. When the amount added is less than 4 parts by weight, the effect of adding layered inorganic particles as described above cannot be sufficiently obtained; conversely, when it exceeds 25 parts by weight, the resin's fluidity decreases, impairing its moldability. Preferably, it is in the range of 5 to 20 parts by weight, and within the range of 1 / 3 to 2 / 3 of the amount of polyethylene glycol added; particularly preferably, it is in the range of 7 to 15 parts by weight, and within the range of 2 / 5 to 3 / 5 of the amount of polyethylene glycol added.

[0077] The male-type hook and loop fastener of the present invention is preferably molded from a resin composition comprising PVA-type resin, polyethylene glycol-type resin, and layered inorganic particles as described above. In addition, other substances may be added within the range that does not impair moldability or the strength, water solubility, and other effects of the present invention of the resulting male-type hook and loop fastener. For example, by including colorants such as pigments and dyes, the dissolution of the hook and loop fastener in water can be easily observed with the naked eye. Furthermore, reinforcing fillers, deodorizing agents, mildew inhibitors, antibacterial agents, etc., may also be added.

[0078] The total amount of PVA-type resin, polyethylene glycol, and layered inorganic particles in the material constituting the male-shaped hook and loop fastener is preferably 80% by mass or more, more preferably 90% by mass, further preferably 95% by mass or more, and for example, 100% by mass.

[0079] For water-soluble male hook and loop fasteners, from the viewpoint of obtaining high hook-and-loop force, it is preferable that the male hook and loop elements are arranged in a row, and that the male hook and loop elements have a shape that stands up from the base surface, bends from the middle towards the row direction, and has its front end facing towards the base surface, or that the male hook and loop elements have a shape that stands up from the base surface, branches forward and backward from the middle towards the row direction and bends along the row direction, and has the front end of the branch facing towards the base surface.

[0080] It should be noted that the "middle part" mentioned above refers to the part of the male hook element that contacts the substrate surface and extends to the front end of the male hook element.

[0081] Next, a method for molding hook and loop fasteners from such a water-soluble resin composition containing PVA resin will be described.

[0082] As a specific method for manufacturing a water-soluble male-shaped hook and loop fastener suitable for use as the present invention, the following method can be used: a molten resin composition is flowed into a sheet on the surface of a metal roller having cavities in the shape of male hook elements, and the molten material is pressed into the cavities. After cooling and solidification, it is peeled off from the surface of the metal roller and simultaneously extracted from the cavities, thereby manufacturing a sheet having multiple male hook elements on the surface.

[0083] That is, the method for manufacturing the water-soluble male hook and loop fastener of the present invention is as follows: a molten resin composition satisfying (1) and (2) below is passed through the surface of a metal roller satisfying (A) below, and the molten material is pressed into a cavity in the shape of a male hook and loop element formed by perforation on the surface of the metal roller. After the molten material is cooled and solidified in this state, it is peeled off from the surface of the metal roller and extracted from the cavity.

[0084] (A) The metal roller is formed by stacking annular molds with the cavities engraved on the outer circumference. On the surface of the metal roller, the cavities are arranged in a row in the circumferential direction of the metal roller. The cavities bend in the direction of the row of cavities in the middle and their front ends are close to the surface of the metal roller, or they branch into two strands in the middle and bend in the direction of the row respectively, and their front ends are close to the surface of the metal roller.

[0085] (1) A resin composition comprising polyvinyl alcohol resin, polyol or ethylene oxide polymer and layered inorganic particles, wherein the mixing ratio of the resin composition is: 5 to 45 parts by mass relative to 100 parts by mass of polyvinyl alcohol resin and 4 to 25 parts by mass of layered inorganic particles.

[0086] (2) The degree of polymerization of the above polyvinyl alcohol is 300-700, and the degree of saponification is 80-99 mol%.

[0087] The manufacturing method is described in more detail. A mold roller is prepared by sequentially stacking a ring-shaped mold with a thickness of 0.2 to 0.5 mm, on the outer circumference of which are engraved cuts in the shape of male hook elements such as inverted J or Y, with a metal ring without such cuts. The mold roller has multiple cavities with cuts in the shape of male hook elements on its outer circumference surface.

[0088] It should be noted that, in the case of male-type hooking elements, such as the inverted J-shaped element, where the hooking direction is unidirectional, it is preferable to replace half of the aforementioned ring-shaped mold with an inverted J-shaped cut that has a thickness of 0.2 to 0.5 mm and an inverted J-shaped cut carved on its outer circumference in the opposite direction to the inverted J-shaped shape. In this case, the inverted J-shaped ring mold bending in the opposite direction and the inverted J-shaped ring mold bending in the forward direction can be alternated, and more than two pieces can be used alternately.

[0089] On the surface of such a metal roller, multiple cavities curved in the circumferential direction are arranged in rows in the circumferential direction. Furthermore, multiple such rows exist parallel to each other in the width direction of the metal roller. In the case of an inverted J-shape, the curvature of the cavities is reversed either in units of one row or multiple rows. In this case, whether in the case of an inverted J-shape or a Y-shape, the cavities taper from the surface of the metal roller to the front end, and gradually bend in the circumferential direction of the metal roller in the middle (between the surface of the metal roller and the front end), with the front end facing the direction closer to the surface of the metal roller.

[0090] As a specific method for passing the molten resin composition satisfying (1) and (2) above through the surface of a metal roller and molding it, the molten material is extruded into the gap between the metal roller and other drum rollers located in opposite positions and pressed, thereby filling the cavity with the molten material and forming a sheet with a uniform thickness on the roller surface. During the rotation of the mold roller, the molten material in the cavity is cooled and solidified using a refrigerant that circulates continuously inside the roller. At the same time, it is stretched using a pressure roller with the gap adjusted to make the substrate of the resulting male-shaped hook and loop fastener a uniform thickness. Then, the cooled sheet is peeled off from the surface of the mold roller, and the male hook and loop elements are extracted from the cavity. Thus, a sheet with multiple male hook and loop elements on the surface, i.e., a male-shaped hook and loop fastener, is obtained.

[0091] In the warm water-soluble male-shaped hook and loop fastener of the present invention obtained by such method, a plurality of male hook elements are arranged in a row, each hook element having a shape that stands up from the base surface, bends from the middle towards the row direction, and has its front end facing towards the direction close to the base surface (inverted J-shape), or each hook element having a shape that stands up from the base surface, branches forward and backward in the middle towards the row direction and bends along the row direction, and has the front end of each branch facing towards the direction close to the base surface (Y-shape).

[0092] With such a shape, the male hook element is not easily collapsed by pressure from above, and multiple male hook elements work together to resist the tensile force in the direction of the hook element row of the ring hook element of the hooked object. Therefore, a high hook force can be obtained.

[0093] It should be noted that in this invention, the male hook element can stand upright directly from the substrate surface or from the ridge-like protrusions formed on the substrate surface. When the male hook element stands upright from the ridge-like protrusions, the rate of dissolution in water is accelerated, which is therefore preferable. The height of the ridge-like protrusions is preferably in the range of 1 / 20 to 1 / 3 of the substrate thickness from the substrate surface. To make the male hook element stand upright from the ridge-like protrusions, methods such as making the diameter of the aforementioned cavity-filled annular mold slightly smaller than the adjacent cavity-free annular mold, or making the center of the cavity-filled annular mold offset from the center of the adjacent annular mold, can be cited. It should be noted that it is not necessary for all the male hook elements to stand upright from the ridge-like protrusions; even if only a portion stands upright, the desired effect can be obtained.

[0094] Figure 1 The male-shaped hook and loop fastener shown is composed of multiple male hook elements (1) arranged in a row. Each hook element has a shape (inverted J-shape) that stands upright from the surface of the base (2), bends in the column direction (T) from the middle, and has its front end facing the direction close to the surface of the base. Figure 2 The male-shaped hook and loop fastener shown is a combination of multiple male hook and loop elements (1) arranged in a row, each hook and loop element having a shape (Y-shaped shape) that stands up from the surface of the base (2), branches in the middle of the column direction (T) and bends along the column direction, and the front ends of each branch face the direction close to the surface of the base.

[0095] In particular, in the present invention, when the male hook element has a shape that stands upright from the base surface, bends in the midway direction, and has its front end facing towards the base surface (inverted J-shaped shape), the height from the base surface of the male hook element to the top of the male hook element is preferably 1.2 mm or less. In addition, when the male hook element has a shape that branches forward and backward in the midway direction and bends in the midway direction, and the front end of each branch faces towards the base surface (Y-shaped shape), the height from the base surface of the male hook element to the top of the male hook element is preferably 0.6 mm or less.

[0096] Generally speaking, the height of the male hook-and-loop fastener element in male-shaped hook and loop fasteners is often 1.5 mm or more, and usually has a height of about 2 to 3 mm. However, in this invention, considering both water solubility and application (skin feel), a height of 1.2 mm or less or 0.6 mm or less, which is lower than such conventional heights, is preferred.

[0097] That is, with such a low height of the male hook element, combined with the softness of the male hook element, even when installed on a part that is easy to come into contact with the skin, like a sanitary product, it can suppress the feeling of foreign body, and even when in contact with the skin, it is not easy to cause skin roughness, and it can further shorten the time required for dissolution.

[0098] There is no particular limitation on the lower limit of the height of the male hook element; for example, it can be 0.1 mm or more, or 0.2 mm, or 0.4 mm. When the male hook element is inverted J-shaped, the lower limit of the height of the male hook element can be, for example, 0.4 mm, 0.6 mm, or 0.8 mm.

[0099] From the viewpoint of water solubility, the length from the top of the male hook element to the front end (the bent portion) is preferably 0.15 to 0.55 mm.

[0100] From the perspective of water solubility, the width of the male hook element is preferably 0.15 to 0.3 mm.

[0101] To obtain such a low-height hook and loop fastener, it is achieved by using a metal roller that does not carve the cavity too deeply from the surface of the metal roller. Specifically, when manufacturing a hook and loop fastener with a shape (inverted J-shape) where the hook and loop fastener stands upright from the base surface, bends in the mid-course direction, and has its front end facing towards the base surface, it can be easily obtained by using a metal roller with the cavity's depth from the metal roller surface being at most 1.2 mm or less. In addition, when manufacturing a hook and loop fastener with a shape (Y-shape) where the hook and loop fastener branches forward and backward in the mid-course direction and bends in the course direction, and each branch's front end faces towards the base surface, it can be easily obtained by using a metal roller with the cavity's depth from the metal roller surface being at most 0.6 mm or less.

[0102] Furthermore, in the water-soluble hook and loop fastener of the present invention, the thickness of the base layer is preferably in the range of 0.15 to 0.3 mm, considering both rapid water solubility and the breaking strength of the hook and loop fastener.

[0103] Furthermore, in the water-soluble male-shaped hook and loop fastener of the present invention, the element density of the male hook and loop elements is preferably 60 to 160 elements / cm². 2 .

[0104] Furthermore, for the water-soluble male hook and loop fastener of the present invention, the same water-soluble male hook and loop fastener can be bonded to the back side by heat pressing or by using a water-soluble adhesive, etc., to produce a double-sided hook and loop fastener with male hook elements on both the front and back sides. Additionally, to ensure that male hook elements are present on the back side during molding, a metal roller with a cavity on the surface of the metal roller on the back side can be used to produce a double-sided hook and loop fastener with male hook elements on both the front and back sides. Furthermore, a loop material (hook and loop fastener with loop hook elements) formed from a water-soluble woven fabric or nonwoven fabric with loop fibers on the surface can also be integrated with the back side to produce a water-soluble double-sided hook and loop fastener with male hook elements on the surface and loop hook elements on the back side. Of course, the male hook and loop material do not necessarily have to be sandwiched between the various base materials and integrated back to back. As long as they are joined in such a way that the side with the male hook element is the surface side and the side with the fiber loop is the back side, other overlapping methods can be used. Alternatively, they can be joined in such a way that the fiber loop is located at the back side away from the part with the male hook element.

[0105] The water-soluble male hook and loop fastener of this invention dissolves rapidly upon contact with water at 45–90°C, eliminating its hooking ability. Furthermore, since the male hook and loop fastener itself completely dissolves and ceases to exist, any hook and loop fastener that can be used for hooking can be used, as long as it is not a low-temperature soluble hook and loop fastener such as one that dissolves in room temperature water. Therefore, the hook and loop fastener used for hooking does not need to be water-soluble, but by also making the hook and loop fastener water-soluble, the entire hook and loop fastener can be dissolved and eliminated during recycling / reuse.

[0106] Furthermore, if the hook and loop fasteners to which they are hooked also dissolve in the same way as the water-soluble male hook and loop fasteners when in contact with warm water at 45–90°C, it is preferable to improve the reliability of the loss of hook and loop fasteners in warm water by connecting these hook and loop fasteners to each other, and to ensure that they dissolve substantially completely at the same time as the water-soluble male hook and loop fasteners.

[0107] As a water-soluble hook and loop fastener used for such hooking, it is preferable to be a hook and loop fastener made of fibers that can dissolve in water at or near the same temperature as male hook and loop fasteners. In particular, PVA-type resins are preferred as water-soluble fibers due to their excellent tensile strength and excellent processability. Examples include: warm water-soluble PVA fibers (Kuralon K-II (registered trademark) WN-4~8, WQ-9) sold by Kuraray Co., Ltd., obtained by dissolving PVA resin with a saponification degree of 88-98 mol% and a polymerization degree of 1500-2000 in dimethyl sulfoxide and performing dry-wet or wet spinning of the resulting spinning solution in a methanol bath; warm water-soluble PVA fibers obtained by mixing polyethylene glycol and sorbitol ethylene oxide adducts with PVA resin with a saponification degree of 89-97.5 mol% and a polymerization degree of 300-450 and performing melt spinning; and warm water-soluble PVA fibers obtained by dissolving PVA resin with a saponification degree of 88-98 mol% in water and performing wet spinning of the resulting spinning solution in a saturated sodium sulfate aqueous solution bath.

[0108] Examples of loop fasteners formed from such water-soluble PVA fibers include nonwoven fabrics formed from such water-soluble fibers, and nonwoven fabrics with loops (hooking elements) formed from such water-soluble fibers on the surface of the woven fabric.

[0109] Specifically, in the case of nonwoven fabrics, the following nonwoven fabrics can be cited: nonwoven fabrics made by forming a web of warm water soluble fibers and binding them together by needle punching or the like, and making the surface napped as needed, so that loops (hooking elements) formed by the warm water soluble fibers exist on the surface of the nonwoven fabric.

[0110] In the case of woven fabrics, examples include fabric-type hook and loop fasteners and knitted hook and loop fasteners. The fabric-type hook and loop fasteners use water-soluble fibers as yarns, which are then used as both warp and weft yarns to create the fabric. These yarns are then woven into the fabric parallel to the warp yarns, protruding in loops on certain parts of the fabric surface. The knitted hook and loop fasteners use yarns formed from these water-soluble fibers to create the knitted fabric, and the surface of the knitted fabric is napped using a needle cloth or similar method, resulting in loops formed from the water-soluble fibers on the fabric surface. Alternatively, multifilament yarn can be used as the water-soluble fiber. This multifilament yarn is used as both warp and weft yarns to create the fabric, and the loop-shaped hook and loop elements are then woven into the fabric parallel to the warp yarns, protruding in loops on certain parts of the fabric surface, thus creating fabric-type hook and loop fasteners. Furthermore, to prevent the loop-shaped hook and loop elements from being pulled out during hook-and-loop separation, it is preferable to coat the back of the resulting fabric with a water-soluble resin.

[0111] In addition, the multifilament yarn, which is a warm water soluble fiber, can be nonwoven by spunbonding and its surface can be made to be napped, so that the loops formed by the warm water soluble fiber protrude on its surface.

[0112] It should be noted that, as described above, the water-soluble male hook and loop fastener of the present invention can be made into a water-soluble hook and loop fastener with a male hook and loop element on the surface and a female hook and loop element (hereinafter referred to as a loop hook and loop element) on the back side (hereinafter referred to as water-soluble loop hook and loop fastener).

[0113] Specifically, a hook and loop fastener is made by overlapping a water-soluble male hook and loop fastener back-to-back with the hook elements on the outside, and then bonding the two together in some parts or on the entire surface using a water-soluble adhesive and heat pressing.

[0114] Alternatively, the end of a water-soluble hook and loop fastener with a loop hook element on the back can be overlapped with the end of a water-soluble male-shaped hook and loop fastener with a male hook element on the surface, with the side having the male hook element as the surface side and the side having the loop hook element as the back side side. The two are then joined together by hot pressing with a water-soluble adhesive. The hook and loop fasteners are joined together with the male hook element as the surface side and the loop hook element on the back side away from the part where the male hook element is located (i.e., the part where the male hook element is located and the part where the loop hook element is located are not back to back, but sandwiched and joined together and extending away from that part respectively). This is how the hook and loop fastener is obtained.

[0115] In the case of a water-soluble hook and loop fastener that is joined together by having a loop hook and loop element on the back side of the part that is separated from the part containing the male hook and loop element, it is required that the water-soluble loop hook and loop fastener also have sufficient tensile strength on its own. Therefore, as a water-soluble loop hook and loop fastener, it is preferable to have a water-soluble loop hook and loop fastener with a loop of water-soluble fiber on the surface of a warp-knitted fabric formed of water-soluble fibers.

[0116] The water-soluble male hook and loop fastener obtained by this invention has sufficient hook-and-loop force and the property of not dissolving in room temperature water but rapidly dissolving in warm water of any temperature range of 45-90°C. Furthermore, no substances harmful to the human body are added. Therefore, the water-soluble male hook and loop fastener can be used alone or in combination with the water-soluble female hook and loop fastener as a fastening material for securing sanitary products to underwear, as a waist fastening material for disposable diapers, or as a fastening material for other disposable products.

[0117] Furthermore, by introducing a used disposable product equipped with the water-soluble hook and loop fastener of the present invention into a process for recycling pulp, fiber, superabsorbent resin, and film from a used disposable product equipped with the water-soluble hook and loop fastener of the present invention using warm water, the hook and loop fastener immediately dissolves and disappears in the presence of warm water, and the presence of the hook and loop fastener of the present invention does not hinder the recycling of pulp, fiber, superabsorbent resin, film, etc.

[0118] Example

[0119] The present invention will be described below through examples. In the examples, for hook-and-loop fasteners, E40000 (manufactured by Kuraray Fastener Co., Ltd.) was used as the hook-and-loop fastener, and the initial hook-and-loop fastener and the hook-and-loop fastener after 10 repeated hook-and-loop peeling were measured in accordance with JIS L3416:2000.

[0120] In addition, regarding whether the surface of the hook and loop fastener is sticky, after placing the obtained hook and loop fastener at a temperature of 30°C and a humidity of 100% for 4 hours, touch the surface of the hook and loop fastener and judge whether it is sticky by its feel.

[0121] Example 1

[0122] As a mold, a ring-shaped mold with a thickness of 0.30 mm and a diameter of 212 mm, having hook-shaped hook elements (inverted J-shaped hook elements) with a depth of 0.90 mm engraved on its outer circumference, a metal ring with a thickness of 0.30 mm and a diameter of 212 mm without such engraving, a ring-shaped mold with a hook-shaped hook element with a thickness of 0.30 mm and a diameter of 212 mm engraved on its outer circumference facing the opposite direction of the aforementioned hook-shaped hook element, and a metal ring with a thickness of 0.30 mm and a diameter of 212 mm without such engraving are sequentially stacked to prepare a mold roller with a width of 120 mm and multiple cavities with inverted J-shaped hook element shapes on its outer circumference surface and cavities with hook element shapes facing the opposite direction. It should be noted that the diameter of the ring-shaped mold with hook-shaped hook elements engraved on its outer circumference is slightly smaller than the diameter of the rings adjacent to it on both sides (to the extent of forming a ridge-like protrusion with a height of 0.03 mm, as described later).

[0123] 100 parts by mass of a PVA resin with a degree of polymerization of 345 and a degree of saponification of 93 mol% (formed from 50 parts by mass of a PVA resin obtained by saponifying vinyl acetate with a degree of polymerization of 300 to a degree of saponification of 88 mol% and 50 parts by mass of a PVA resin obtained by saponifying vinyl acetate with a degree of polymerization of 390 to a degree of saponification of 98 mol%), 25 parts by mass of polyethylene glycol with a number average molecular weight of 400 and 12 parts by mass of talc (average particle size: 4 μm) were mixed, and the resulting resin composition a-1 was melted at 190°C. The molten material is extruded into the gap between the aforementioned die roller and other drum rollers located in opposite positions. It is pressed by the die roller and drum rollers, thereby filling the cavity with the molten material and forming a sheet with a uniform thickness on the roller surface. The molten material in the cavity is cooled by water that is continuously circulated during the rotation of the die roller. It is then stretched by a pressure roller with the gap adjusted to a base thickness of 0.20 mm. The cooled and solidified sheet is then peeled off from the surface of the die roller, thus manufacturing a water-soluble hook and loop fastener (water-soluble hook and loop fastener).

[0124] In the obtained warm water-soluble male-shaped hook and loop fastener, multiple male hook elements are arranged in a row. Each male hook element has a shape (inverted J-shape) that rises from a ridge-like protrusion (0.03 mm high) formed on the substrate surface, bends from the middle in the row direction, and has its front end facing towards the substrate surface. Its height is 0.94 mm, and the element density is 110 elements / cm³. 2 In addition, the thickness of the substrate is 0.21 mm.

[0125] The properties of the obtained water-soluble male-shaped hook and loop fasteners are shown in Table 1 below. According to the table, it is clear that the water dissolution temperature is much higher than the 55°C temperature required for dissolving in room temperature water. The hook-and-loop force, softness, and surface stickiness are essentially unaffected, making it suitable for use as a waist fastening material for disposable diapers. In particular, even when used as a waist fastening material for disposable diapers, it will not dissolve in urine during wear, posing no usability issues. After use, the disposable diaper is folded into a ball, and the water-soluble male-shaped hook and loop fasteners attached to the diaper are used to secure the fold. Then, the diaper is immersed in 80°C stirred warm water. The result is that the hook and loop fasteners immediately dissolve and disappear, and the disposable diaper unfolds from its folded state, becoming easy to handle subsequently.

[0126] Furthermore, as the hooking material for such water-soluble male-shaped hook and loop fasteners, a web is made of water-soluble PVA fiber (Kuralon K-II (registered trademark) WN-6, 1.7 dtex, 51 mm in length) manufactured by Kuraray Co., Ltd., which is soluble in water at 60°C. This web is then needle-punched to bind the fibers together, and the surface is then napped using a needle cloth to create loops formed by the fibers on the surface, with a weight of 200 g / m² per unit area. 2 The nonwoven fabric was used as the hook-and-loop fastener. The hook-and-loop force was high, slightly weaker than that of male-type hook-and-loop fasteners, but the hook-and-loop performance was excellent. Then, a 2cm square was cut while the water-soluble male-type hook-and-loop fastener was hooked together with the nonwoven fabric made of water-soluble fibers. This square was then immersed in 75°C water being stirred, and the dissolution was observed. The result was that the hook-and-loop fastener peeled off in 30 seconds, and both the hook-and-loop fastener and the nonwoven fabric completely dissolved in 4 minutes and 35 seconds.

[0127] [Table 1]

[0128]

[0129] Examples 2-6

[0130] In Example 1 above, the PVA resin used for molding was changed to PVA1 to PVA5 and resin compositions a-2 to a-6 were manufactured. Otherwise, five types of warm water soluble male-type hook and loop fasteners (warm water soluble male-type hook and loop fasteners) were manufactured in the same manner as in Example 1.

[0131] [PVA1: Example 2] A PVA resin with a degree of polymerization of 330 and a degree of saponification of 91.3 mol% (formed from 67 parts by mass of a PVA resin obtained by saponifying vinyl acetate with a degree of polymerization of 300 to a degree of saponification of 88 mol% and 33 parts by mass of a PVA resin obtained by saponifying vinyl acetate with a degree of polymerization of 390 to a degree of saponification of 98 mol%)

[0132] [PVA2: Example 3] A PVA resin with a degree of polymerization of 360 and a degree of saponification of 94.7 mol% (formed from 33 parts by mass of a PVA resin obtained by saponifying vinyl acetate with a degree of polymerization of 300 to a degree of saponification of 88 mol% and 67 parts by mass of a PVA resin obtained by saponifying vinyl acetate with a degree of polymerization of 390 to a degree of saponification of 98 mol%)

[0133] [PVA3: Example 4] PVA resin with a degree of polymerization of 390 and a saponification degree of 98.5 mol%.

[0134] [PVA4: Example 5] PVA resin with a degree of polymerization of 372 and a saponification degree of 96.2 mol%.

[0135] [PVA5: Example 6] PVA resin with a degree of polymerization of 381 and a saponification degree of 97.1 mol%.

[0136] The obtained water-soluble male-shaped hook and loop fasteners are all the same as those in Example 1, with multiple male hook and loop elements arranged in a row. Each male hook and loop element has a shape (inverted J-shape) that rises from a ridge-like protrusion (0.03 mm high) formed on the substrate surface, bends from the middle in the row direction, and has its front end facing towards the substrate surface. Its height is 0.94 mm, and the element density is 110 elements / cm³. 2 In addition, the thickness of the substrate is 0.21 mm.

[0137] It should be noted that the hook-and-loop fasteners made of PVA3 and PVA5, which are water-soluble, exhibit hook-and-loop fasteners that clearly only extend halfway through the process. In particular, the hook-and-loop fasteners made of PVA3 show very obvious incomplete hook-and-loop fasteners. This can be attributed to the resin not being fully filled into the front part of the cavity during molding, but the hook-and-loop strength is not significantly reduced as a result.

[0138] The properties of the five types of water-soluble hook and loop fasteners obtained above are shown in Table 2 below. According to this table, it is clear that the water solubility temperature of the water-soluble hook and loop fastener obtained from PVA1 in Example 2 is much higher than the 50°C temperature required for dissolving in room temperature water. Furthermore, the water solubility temperature of the water-soluble hook and loop fastener obtained from PVA2 in Example 3 is 62°C; the water solubility temperature of the water-soluble hook and loop fastener obtained from PVA3 in Example 4 is 80°C; the water solubility temperature of the water-soluble hook and loop fastener obtained from PVA4 in Example 5 is 70°C; and the water solubility temperature of the water-soluble hook and loop fastener obtained from PVA5 in Example 6 is 77°C. All of these have water solubility temperatures much higher than the temperature required for dissolving in room temperature water.

[0139] Furthermore, the water-soluble hook-and-loop fasteners obtained in Examples 2-6 all exhibit no problems in terms of hooking force, softness, or surface stickiness, making them suitable as waist-fastening materials for disposable diapers. Moreover, they do not dissolve due to urine during wear, posing no usability issues. After use, these disposable diapers are folded into balls, and the folds are secured using the water-soluble hook-and-loop fasteners attached to the diapers. Then, in this state, they are immersed in stirred warm water at 80°C. The hook-and-loop fasteners immediately dissolve and disappear, allowing the disposable diapers to unfold from their folded state, facilitating subsequent processing.

[0140] [Table 2]

[0141]

[0142] Furthermore, as the hooking object for each of these water-soluble hook and loop fasteners, a loop nonwoven fabric made of PVA fibers soluble in water at 60°C was manufactured in the same manner as in Example 1 above, and hooking was performed using this nonwoven fabric as the hooking object. As a result, all water-soluble hook and loop fasteners exhibited high hooking force and excellent hooking properties. Then, a 2cm square was cut from the hooked water-soluble hook and loop fastener and the aforementioned nonwoven fabric made of water-soluble fibers, and immersed in warm water at 75°C (80°C for the water-soluble hook and loop fasteners in Examples 4 and 6) while being stirred. The dissolution state was observed, and the hook and loop fasteners peeled off in 10–30 seconds, and both the hook and loop fasteners and the nonwoven fabric completely dissolved in 2 minutes 25 seconds to 4 minutes 6 seconds. Additionally, the hook and loop fasteners in the examples did not dissolve when the water temperature was below 49°C.

[0143] Comparative Examples 1-3

[0144] In Example 1 above, the PVA resin used for molding was changed to any PVA from PVA6 to 7 described below, and resin compositions b-1 to b-3 were manufactured. Otherwise, a warm water-soluble hook-and-loop fastener was manufactured in the same manner as in Example 1. It should be noted that with PVA6, the hook-and-loop element has low strength and is prone to breakage during molding. Furthermore, with PVA8, the melt viscosity is too high, causing gelation within the mold, preventing the molten resin from reaching the front end of the cavity. As a result, a good hook-and-loop fastener could not be manufactured. On the other hand, with PVA7, there were no problems with molding, and a hook-and-loop fastener with the same shape as in Example 1 was obtained.

[0145] [PVA6: Comparative Example 1] A PVA resin with a degree of polymerization of 250 and a saponification degree of 74 mol%.

[0146] [PVA7: Comparative Example 2] A PVA resin with a degree of polymerization of 500 and a saponification degree of 75 mol%.

[0147] [PVA8: Comparative Example 3] PVA resin with a degree of polymerization of 1200 and a saponification degree of 99.9 mol%.

[0148] The water solubility temperatures of the defective male-shaped hook and loop fasteners obtained from PVA8 and the warm water-soluble male-shaped hook and loop fasteners obtained from PVA7 were measured. The results showed that the water solubility temperature of the hook and loop fasteners obtained from PVA8 was 97℃, the water solubility temperature of the hook and loop fasteners obtained from PVA7 was 27℃, and the water solubility temperature of the hook and loop fasteners obtained from PVA6 was 25℃.

[0149] It is known that when the water dissolution temperature is high, as in the case of the male-shaped hook and loop fastener formed from PVA8, a large amount of water at very high temperatures is required in the process of recycling pulp from disposable products and then wet-processing it into nonwoven fabric. Therefore, it is not feasible from an economic point of view.

[0150] Conversely, hook and loop fasteners made of PVA7 have a risk of dissolving in urine when used in disposable diapers if the water solubility temperature is too low. To avoid this problem, a special structure that does not come into contact with urine is required, which makes them unsuitable for general use.

[0151] Example 7

[0152] In Example 1 above, an annular mold with a cavity depth of 1.2 mm and a thickness of 0.3 mm engraved on its surface was used as the molding roller, and the same resin composition a-1 as in Example 1 was used to manufacture a water-soluble male-shaped hook and loop fastener. The resulting water-soluble male-shaped hook and loop fastener had an element density of 136 pieces / cm³. 2 It features a male hook-and-loop fastener element with a height of 1.26 mm. The surface of this hook and loop fastener is as follows: Figure 3 As shown, the product has multiple male hook-and-loop fasteners arranged in a row. Each hook-and-loop fastener is shaped like an inverted J, rising from the surface of the base and bending in the row direction, with its front end facing towards the surface of the base. The thickness of the base is 0.23 mm. The properties of the resulting water-soluble male hook-and-loop fastener are shown in Table 3 below.

[0153] The resulting male-shaped hook and loop fastener has a large male hook element. Compared with the case of Example 1, although it is somewhat inferior in terms of the speed of dissolving in warm water, it has no problems in any aspect of hook force and surface stickiness.

[0154] When used as an attachment material for disposable diapers, sanitary products, and other intimate apparel, the skin feel is poor, requiring considerable effort in its installation. However, the resulting male-shaped hook and loop fasteners, when used as a waist fastening material for disposable diapers, do not dissolve due to urine during wear. After use, similar to Example 1, the disposable diaper is folded into a ball, and the folded state is secured using the warm water-soluble male-shaped hook and loop fasteners attached to the diaper. Then, the diaper is immersed in 80°C stirred warm water, resulting in the male-shaped hook and loop fasteners dissolving and disappearing. The disposable diaper is then released from its folded state and unfolded, becoming easy for subsequent processing. Furthermore, the hook and loop fasteners in the examples did not dissolve at water temperatures below 49°C.

[0155] Example 8

[0156] In Example 1 above, as the shape of the cavity for the molding roller, an annular mold with a thickness of 0.3 mm and Y-shaped cuts with a depth of 0.55 mm engraved on its outer circumference was used, and the same resin composition a-1 as in Example 1 was used to manufacture a water-soluble male-shaped hook and loop fastener. The resulting water-soluble male-shaped hook and loop fastener has male hook elements arranged in a row on its surface. Each hook element has a shape that rises from the base surface, branches forward and backward in the column direction, bends along the column direction, and the front ends of each branch face towards the direction close to the base surface, i.e., it has a Y-shaped shape with a height of 0.55 mm. Furthermore, the element density is 147 elements / cm². 2 The thickness of the substrate is 0.18 mm. The properties of the obtained warm water soluble hook and loop fasteners are shown in Table 3 below.

[0157] The resulting male-shaped hook and loop fastener exhibits the same excellent warm water solubility and hook-and-loop force as the hook and loop fastener of Example 1. Furthermore, regarding surface stickiness, it is completely imperceptible, just as in Example 1, making it excellent in terms of ease of use. Moreover, even for applications involving skin contact, it is soft and has an excellent feel against the skin, and it does not dissolve in urine during wear, posing no usability problems whatsoever.

[0158] After use, the disposable diaper is folded into a ball, and then secured in this folded state using the warm water-soluble hook-and-loop fasteners attached to the diaper. Next, the diaper is immersed in 80°C warm water with stirring. As a result, the hook-and-loop fasteners immediately dissolve and disappear, releasing the diaper from its folded state and allowing it to unfold, making it easier for subsequent processing. Furthermore, the hook-and-loop fasteners in these examples did not dissolve at water temperatures below 49°C.

[0159] [Table 3]

[0160]

[0161] Example 9

[0162] In Example 1 above, the polyethylene glycol mixed in the PVA resin was replaced with a 2 mol% ethylene oxide adduct of sorbitol to produce resin composition a-7. Otherwise, a warm water-soluble male-type hook and loop fastener was manufactured in the same manner as in Example 1. The resulting male-type hook and loop fastener is similar to that of Example 1, with multiple male hook and loop elements arranged in a row. Each male hook and loop element has a shape (inverted J-shape) that rises from a raised portion (0.03 mm high) formed on the substrate surface, bends in the row direction from the middle, and has its front end facing towards the substrate surface. Its height is 0.94 mm, and the element density is 110 elements / cm². 2 Additionally, the substrate thickness is 0.21 mm. The properties of the resulting water-soluble hook and loop fasteners are shown in Table 4 below.

[0163] It possesses the same excellent warm water solubility and hook-and-loop force as the hook and loop fastener of Example 1. Furthermore, regarding surface stickiness, it is completely non-sticky, just like the hook and loop fastener of Example 1, making it excellent in terms of ease of use. In addition, even when used in contact with the skin, it is soft and has an excellent feel against the skin, and it does not dissolve in urine during wear, posing no problems in its use.

[0164] [Table 4]

[0165]

[0166] Examples 10-13

[0167] In Example 1 above, the resin composition a-1 used for molding was changed to the following resin compositions a-8 to a-11. Otherwise, four types of warm water soluble male-type molding hook and loop fasteners were manufactured in the same manner as in Example 1.

[0168] [Resin Composition a-8: Example 10] In Example 1 above, the amounts of polyethylene glycol and talc added were changed to 38 parts by weight of polyethylene glycol and 22 parts by weight of talc, relative to 100 parts by weight of PVA resin. Otherwise, it was manufactured in the same manner as in Example 1.

[0169] [Resin Composition a-9: Example 11] In Example 1 above, the amounts of polyethylene glycol and talc added were changed to 10 parts by weight of polyethylene glycol and 5 parts by weight of talc, relative to 100 parts by weight of PVA resin. Otherwise, it was manufactured in the same manner as in Example 1.

[0170] [Resin Composition a-10: Example 12] In Example 1 above, the added polyethylene glycol was changed to polyethylene glycol with a number average molecular weight of 600, otherwise it was manufactured in the same manner as in Example 1.

[0171] [Resin Composition a-11: Example 13] In Example 1 above, the added talc was changed to talc with an average particle size of 1.5 μm; otherwise, it was manufactured in the same manner as in Example 1.

[0172] In Example 10, the melt flow of the resin composition a-8 used for molding the male hook and loop fastener was slightly low, and a small number of male hook elements were observed that were thought to have not reached the front end of the cavity by the melt. Furthermore, in Example 11, a very small number of male hook elements were torn off midway when being withdrawn from the cavity. However, the male-molded hook and loop fasteners obtained through Examples 10 and 11 did not have any product-related problems, and a soft hook and loop fastener with hook-shaped male hook elements faithfully conforming to the cavity was obtained. In contrast, in Examples 12 and 13, there were no molding or product-related problems. The performance of the male-molded hook and loop fasteners obtained in Examples 10 to 13 is shown in Table 5 below.

[0173]

[0174] The water-soluble male hook and loop fasteners of Examples 10-13 described above all possess the same excellent water solubility and hook-and-loop force as the hook and loop fastener of Example 1. Furthermore, regarding surface stickiness, except for Example 10, they are completely imperceptible like Example 1, making them excellent in terms of ease of use. Additionally, while the water-soluble male hook and loop fastener of Example 10 has a slight surface stickiness, it is not a problem during use. Moreover, even for applications involving skin contact, the water-soluble male hook and loop fastener of Example 11 is slightly less flexible, but the water-soluble male hook and loop fasteners of the other examples are all soft and gentle.

[0175] Even when these male-shaped hook and loop fasteners are used as fasteners for disposable diapers, the fasteners do not dissolve due to urine during wear, posing no usability issues. Furthermore, when a disposable diaper with these male-shaped hook and loop fasteners attached is folded into a ball, and in this state is secured using warm water-soluble male-shaped hook and loop fasteners attached to the disposable diaper (the hooking object is a non-woven fabric with loops on the surface of the disposable diaper), and then immersed in stirred warm water at 80°C, the male-shaped hook and loop fasteners immediately dissolve and disappear, releasing the disposable diaper from its folded state and allowing it to unfold, making it easy to proceed with subsequent processing (sizing and reuse). Additionally, the hook and loop fasteners of these embodiments do not dissolve in water at temperatures below 50°C.

Claims

1. A warm water-soluble male hook and loop fastener, comprising a substrate and a plurality of male hook and loop elements protruding from the surface of the substrate. Both the matrix and the male hook-and-loop element contain polyvinyl alcohol resin, and both the matrix and the male hook-and-loop element are soluble in warm water at a temperature of 45~90℃ but not in water below 45℃. Both the matrix and the male hooking element are formed from polyvinyl alcohol resins with a degree of polymerization ranging from 300 to 700 and a degree of saponification ranging from 80 to 99 mol%. The matrix and the male hooking element are formed of a resin composition, wherein the resin composition contains 5 to 45 parts by weight of a polyol or ethylene oxide polymer relative to 100 parts by weight of the polyvinyl alcohol resin. The matrix and the male hooking element are formed of a resin composition, wherein the resin composition contains layered inorganic particles in a polyvinyl alcohol resin at a mass ratio of 4 to 25 parts by mass relative to 100 parts by mass of the polyvinyl alcohol resin. The layered inorganic particles are talc.

2. The warm water-soluble male hook and loop fastener according to claim 1, wherein, Multiple male hook elements are arranged in a row. The male hook elements have a shape that stands upright from the base surface, bends from the middle towards the row direction, and has its front end facing towards the base surface. Alternatively, the male hook elements have a shape that stands upright from the base surface, branches forward and backward from the middle towards the row direction and bends along the row direction, and has the front end of the branch facing towards the base surface.

3. The warm water-soluble male hook and loop fastener according to claim 2, wherein, When the male hook element has a shape that rises from the base surface, bends in the column direction from its middle, and has its front end facing towards the base surface, the height from the base surface of the male hook element to the top of the male hook element is 1.2 mm or less. When the male hook element has a shape that branches forward and backward in the column direction from its middle and bends in the column direction respectively, and has the front end of the branch facing towards the base surface, the height from the base surface of the male hook element to the top of the male hook element is 0.6 mm or less.

4. The warm water-soluble male hook and loop fastener according to claim 1, wherein, The polyol or the ethylene oxide polymer is polyethylene glycol, with a number-average molecular weight in the range of 300 to 700.

5. A combination of a water-soluble male hook and loop fastener according to any one of claims 1 to 4 and a water-soluble loop fastener, wherein the water-soluble loop fastener is composed of loop fibers containing a polyvinyl alcohol resin that is soluble in warm water at a temperature of 45 to 90°C but not in water at a temperature below 45°C.

6. The combination according to claim 5, wherein, Water-soluble hook and loop fasteners use non-woven or woven fabric as the base material, with loop fibers on the surface.

7. A method for manufacturing a warm water-soluble male hook and loop fastener, the method comprising: A molten resin composition satisfying (1) and (2) below is passed through the surface of a metal roller satisfying (A) below, and the molten material is pressed into a cavity in the shape of a male hook-and-loop element that is perforated on the surface of the metal roller. After the molten material is cooled and solidified in this state, it is peeled off from the surface of the metal roller and extracted from the cavity. (A) The metal roller is formed by stacking annular molds with multiple cavities engraved on their outer circumference. On the surface of the metal roller, the multiple cavities are arranged in a row in the circumferential direction of the metal roller. The cavities bend in the direction of the row of cavities midway and their front ends are close to the surface of the metal roller, or they branch into two branches midway and bend in the direction of the row of cavities respectively, with their front ends close to the surface of the metal roller. (1) A resin composition comprising a polyvinyl alcohol resin, a polyol or an ethylene oxide polymer, and talc, wherein the mixing ratio of the resin composition is: 5 to 45 parts by weight of the polyol or the ethylene oxide polymer and 4 to 25 parts by weight of the talc relative to 100 parts by weight of the polyvinyl alcohol resin. (2) The degree of polymerization of the polyvinyl alcohol resin is 300~700 and the degree of saponification is 80~99 mol%.

8. The method for manufacturing the warm water-soluble male hook and loop fastener according to claim 7, wherein, When the cavity has a shape that bends midway in the direction of the column and its front end is close to the surface of the metal roller, the depth of the cavity from the surface of the metal roller is less than 1.2 mm at its deepest point, or When the cavity has a shape that branches into two strands midway and bends toward the column direction respectively, with its front end close to the surface of the metal roller, the depth of the cavity from the surface of the metal roller is less than 0.6 mm at its deepest point.

9. A disposable diaper or sanitary product, wherein the diaper is fitted with a warm water-soluble hook and loop fastener as described in any one of claims 1 to 4.

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