Method for manufacturing spunbond nonwoven fabric, as well as methods for manufacturing sanitary materials, masks, and protective clothing.

Abstract

To provide a manufacturing method that suppresses yarn breakage, improves spinnability, and allows for the production of spunbond nonwoven fabric at a high production rate and with high uniformity. [Solution] A method for manufacturing spunbond nonwoven fabric, comprising the steps of: supplying raw material resin to an extruder, melting and kneading it with a screw in the extruder, melting and extruding the melted and kneaded raw material resin from the discharge hole of a die, pulling and stretching the spun raw material resin to form fibers; depositing the fibers to form a fiber web composed of the fibers; and forming the fiber web into a sheet, wherein the raw material resin is a mixture of resin pellets A, which are obtained by kneading a polypropylene resin and an organic peroxide and pelletizing them so that the pellet size is within a specific range, and resin pellets B, which are obtained by pelletizing the polypropylene resin as is, and the ratio of the pellet size of resin pellets A to the pellet size of resin pellets B is within a specific range.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing spunbond nonwoven fabric, as well as a method for manufacturing sanitary materials, masks, and protective clothing. [Background technology]

[0002] Spunbond nonwoven fabrics made from polyolefins, particularly polypropylene spunbond nonwoven fabrics, are widely used in hygiene materials, masks, protective clothing, and other applications due to their low cost and excellent processability.

[0003] In the case of propylene polymers, which are the raw materials for polypropylene spunbond nonwoven fabrics, a common method for adjusting the melt viscosity of the resin is to control the molecular weight of the polymer by oxidative decomposition through heat treatment after polymerization by adding organic peroxides. In particular, when using propylene polymers for fiber molding or nonwoven fabric molding processes involving melt spinning, a low melt viscosity of the propylene resin is preferable for easier molding, and therefore, fluidity adjustment is performed using organic peroxides. Similarly, in injection molding, if it is necessary to improve the flowability of the resin depending on the product shape, fluidity adjustment is also performed using organic peroxides.

[0004] For example, Patent Document 1 proposes a method for producing a nonwoven fabric, in which a propylene polymer and an organic peroxide are supplied to an extruder equipped with a cross saw and a screw equipped with a Unimelt, the propylene polymer resin composition containing the propylene polymer and the organic peroxide in the extruder is melt-kneaded, and the melt-kneaded propylene polymer resin composition is spun and molded to produce a nonwoven fabric. It is stated that this invention provides a method for producing a nonwoven fabric in which yarn breakage is suppressed and spinnability is excellent.

[0005] Furthermore, Patent Document 2 proposes a resin composition comprising a propylene-α-olefin random copolymer polymerized with a metallocene catalyst, wherein the melt flow rate (MFR), molecular weight distribution, peak temperature of the melting curve obtained by differential scanning calorimeter, and α-olefin content are within a specific range, and a specific amount of organic peroxide is blended with this polymer, characterized in that the ratio of the MFR before and after vacuum constant-temperature drying of the resin composition is below a certain level, and a molded article (in Patent Document 2, this refers to fibers and nonwoven fabrics) containing the same. It is also stated that according to this invention, it can be used as a useful resin composition that can adjust the melt viscosity during molding by using it alone or in combination with other polypropylene resins as a masterbatch.

[0006] Furthermore, in order to enable the adjustment of melt viscosity over a wide range during the molding process, when attempting to produce a masterbatch of a propylene polymer containing a high concentration of organic peroxide, there is a problem that the peroxide reacts during melt mixing, making it impossible to obtain a masterbatch of a propylene polymer containing the desired high concentration of organic peroxide. For example, Patent Document 2 proposes a masterbatch based on a specific polypropylene polymerized with a metallocene catalyst. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2020 / 166013 [Patent Document 2] Japanese Patent Publication No. 2003-138075 [Overview of the project] [Problems that the invention aims to solve]

[0008] Typically, adjusting the fluidity of polypropylene using organic peroxides involves adding additives such as antioxidants and organic peroxides to the polymerized powder polymer at the polypropylene manufacturing plant, and then granulating it in an extruder to obtain polymer pellets with adjusted melt viscosity. However, when attempting to significantly lower the melt viscosity of propylene polymer, granulation at the manufacturing plant presents a problem: the low melt viscosity during the granulation process after adding the organic peroxide results in poor cutting, making it extremely difficult to obtain a stable pellet shape. Conversely, when fine-tuning the melt viscosity, granulation at the manufacturing plant presents a problem: even slight fluctuations in the amount of organic peroxide added cause large fluctuations in melt viscosity, making fine-tuning difficult. Furthermore, during the subsequent nonwoven fabric manufacturing stage, adding organic peroxides can cause pressure fluctuations in the extruder and spinneret, leading to yarn breakage and other difficulties in spinning.

[0009] In contrast, while the spinnability of spunbond nonwovens when organic peroxides are added is improved to some extent according to the technology proposed in Patent Document 1, when trying to obtain spunbond nonwovens with high uniformity, fine fiber diameter, low basis weight, or high production speed, which are required in recent years, spinning is still difficult due to pressure fluctuations in the extruder and spinneret, which can cause yarn breakage.

[0010] On the other hand, when attempting to produce a masterbatch of propylene polymer containing a high concentration of organic peroxides in order to enable wide-ranging adjustment of melt viscosity during the manufacturing stage of nonwoven fabrics, there is a problem that the peroxides react during melt mixing, making it impossible to obtain a masterbatch of propylene polymer containing the desired high concentration of organic peroxides.

[0011] In contrast, while the technology proposed in Patent Document 2 makes it easier to adjust the melt viscosity to some extent, it still presents problems in spinning, such as fluctuations in pressure within the extruder and spinneret, which can cause yarn breakage, when trying to obtain the spunbond nonwoven fabrics that are required in recent years.

[0012] Therefore, the object of the present invention is to provide a manufacturing method that suppresses the occurrence of yarn breakage and improves spinnability, thereby enabling the production of spunbond nonwoven fabrics with high production speed and high uniformity, not only for general spunbond nonwoven fabrics, but also for spunbond nonwoven fabrics in which the constituent fibers have a fine fiber diameter or a low basis weight. [Means for solving the problem]

[0013] As a result of diligent research to solve the above problems, the inventors have found that, at specific pellet sizes and pellet size ratios, pressure fluctuations within the extruder and spinneret do not occur, resulting in excellent spinnability, such as preventing yarn breakage.

[0014] This invention was completed based on these findings, and according to this invention, the following inventions are provided.

[0015] [1] A process of supplying raw material resin to an extruder, melting and kneading it with a screw inside the extruder, melting and extruding the melted and kneaded raw material resin from the discharge hole of the die, and pulling and stretching the spun raw material resin to form fibers, A step of depositing the aforementioned fibers to form a fiber web composed of the fibers, The process of forming the aforementioned fiber web into a sheet, A method for producing a spunbond nonwoven fabric having, The aforementioned raw material resin, Polypropylene resin and organic peroxide are kneaded together to form pellets of size L. A Resin pellets A, which are pelletized to be between 3.0 mm and 7.0 mm in size, Resin pellets B obtained by directly pelletizing a polypropylene-based resin, and are mixed, The pellet size L of the resin pellets A A (mm), the pellet size L of the resin pellets B B (mm), the ratio L A / L B is 0.8 or more and 1.2 or less, A method for producing a spunbond nonwoven fabric.

[0016] [2] A polypropylene-based resin and an organic peroxide are kneaded and pelletized so that the pellet size L A is 3.0 mm or more and 7.0 mm or less, resin pellets A, Resin pellets B obtained by directly pelletizing a polypropylene-based resin, are respectively supplied to an extruder and melt-kneaded by a screw in the extruder to obtain a raw material resin. Then, the melt-kneaded raw material resin is melt-extruded from a discharge hole of a die, and the spun raw material resin is drawn and stretched to form fibers; A step of depositing the fibers to form a fiber web composed of the fibers; A step of sheetifying the fiber web; A method for producing a spunbond nonwoven fabric having The pellet size L of the resin pellets A A (mm), the pellet size L of the resin pellets B B (mm), the ratio L A / L B is 0.8 or more and 1.2 or less, A method for producing a spunbond nonwoven fabric.

[0017] [3] The content of the organic peroxide in the resin pellets A is 1% by mass or more and 50% by mass or less. The method for producing a spunbond nonwoven fabric according to [1] or [2].

[0018] [4] The supply amount W per unit time of the resin pellets A A (g / min), the supply amount W per unit time of the resin pellets BB Ratio W to (g / min) A / W B A method for producing a spunbond nonwoven fabric according to any one of [1] to [3] above, wherein the ratio is 0.001 or more and 0.500 or less.

[0019] [5] Melting point Tm of the resin pellet A A (°C) and the melting point Tm of the resin pellet B. B Tm (difference from °C) B -Tm A A method for producing a spunbond nonwoven fabric according to any one of [1] to [4] above, wherein the temperature (°C) is 5.0°C or higher and 50.0°C or lower.

[0020] [6] A method for producing a spunbond nonwoven fabric, wherein the spunbond nonwoven fabric obtained by the method for producing a spunbond nonwoven fabric described in any of [1] to [5] above is immersed in a chloroform / methanol solvent in a volume ratio of 1:1 and subjected to sonication for 15 minutes at 45kHz and a solution temperature of 30°C, thereby extracting less than 100 ppm of organic peroxide.

[0021] [7] A method for producing a spunbond nonwoven fabric according to any one of [1] to [6], wherein the melt kneading is carried out for 0.5 minutes or more and 30.0 minutes or less.

[0022] [8] The length L of the screw C The diameter D of the screw (mm) C Ratio L to (mm) C / D C A method for producing a spunbond nonwoven fabric according to any one of the above [1] to [7], wherein the ratio is 15 or more and 50 or less.

[0023] [9] A step of cutting the spunbond nonwoven fabric obtained by the method for manufacturing spunbond nonwoven fabric described in any of [1] to [8] above to form nonwoven fabric parts, The process involves laminating and fixing the aforementioned nonwoven fabric parts and absorbent material, A method for manufacturing sanitary materials, including

[0024]

[10] A step of cutting the spunbond nonwoven fabric obtained by the method for manufacturing spunbond nonwoven fabric described in any of [1] to [8] above to form nonwoven fabric parts, The process of fixing the nonwoven fabric part and the string part, A method for manufacturing masks, including the method described above.

[0025]

[11] A step of cutting the spunbond nonwoven fabric obtained by the method for manufacturing spunbond nonwoven fabric described in any of [1] to [8] above to form nonwoven fabric parts, Sleeve portion including the aforementioned nonwoven fabric part, Body part including the aforementioned nonwoven fabric part, Leg portion including the aforementioned nonwoven fabric part, Head including the aforementioned nonwoven fabric part, A step of forming at least one part of, A step of joining the parts obtained by the above step together, and / or the parts obtained by the above step together with other parts, A method for manufacturing protective clothing, including [Effects of the Invention]

[0026] According to the manufacturing method of the present invention, the occurrence of thread breakage is suppressed, resulting in excellent spinnability. This allows for the production of high-quality spunbond nonwoven fabrics with high uniformity and high production speed, even if the constituent fibers have a fine diameter or a low basis weight, in addition to general spunbond nonwoven fabrics. Furthermore, by further processing the spunbond nonwoven fabric obtained by this manufacturing method, high-quality sanitary materials, masks, and protective clothing can be efficiently produced. [Modes for carrying out the invention]

[0027] The first embodiment of the method for producing spunbond nonwoven fabric of the present invention is as follows: The process involves supplying raw resin to an extruder, melting and kneading it with a screw inside the extruder, melting and extruding the melted and kneaded raw resin through the discharge hole of the die, and then pulling and stretching the spun raw resin to form fibers. A step of depositing the aforementioned fibers to form a fiber web composed of the fibers, The process of forming the aforementioned fiber web into a sheet, A method for producing a spunbond nonwoven fabric having, The aforementioned raw material resin, Polypropylene resin and organic peroxide are kneaded together to form pellets of size L. A Resin pellets A, which are pelletized to be between 3.0 mm and 7.0 mm in size, Resin pellet B, which is made by directly pelletizing polypropylene resin, It is a mixture of the following: The pellet size L of the aforementioned resin pellet A A (mm) Pellet size L of the resin pellet B B Ratio L to (mm) A / L B The value should be between 0.8 and 1.2.

[0028] Furthermore, a second embodiment of the method for producing spunbond nonwoven fabric of the present invention is: Polypropylene resin and organic peroxide are kneaded together to form pellets of size L. A Resin pellets A, which are pelletized to be between 3.0 mm and 7.0 mm in size, Resin pellet B, which is made by directly pelletizing polypropylene resin, The process involves supplying each of these to an extruder, melting and kneading them with a screw inside the extruder to form a raw material resin, then melting and extruding the melted and kneaded raw material resin through the discharge hole of the die, and then pulling and stretching the spun raw material resin to form fibers. A step of depositing the aforementioned fibers to form a fiber web composed of the fibers, The process of forming the aforementioned fiber web into a sheet, A method for producing a spunbond nonwoven fabric having, The pellet size L of the aforementioned resin pellet A A (mm) Pellet size L of the resin pellet B B Ratio L to (mm) A / L B The value should be between 0.8 and 1.2.

[0029] The components will be described in detail below, but the present invention is not limited in any way to the scope described below, as long as it does not exceed the spirit of the invention, and various modifications are possible without departing from the spirit of the invention.

[0030] In this invention, polypropylene-based resin means a resin having 50 mol% or more of propylene units as repeating units. Therefore, it may be a homopolymer of propylene, or a copolymer of propylene and various α-olefins. It may also be a mixture containing a certain amount of other thermoplastic resins, etc., as long as it contains 50 mol% or more of a homopolymer or copolymer of propylene and does not hinder the effects of this invention. Of course, it may also contain various additives such as antioxidants, weathering agents, light stabilizers, anti-fogging agents, blocking agents, lubricants, nucleating agents, and pigments such as titanium dioxide, as long as it does not hinder the effects of this invention. Hereafter, "...-based resin" refers to the same.

[0031] [First Embodiment] (I) Process of forming fibers In this process, first, the raw resin is supplied to the extruder. Then, the raw resin is... Polypropylene resin and organic peroxide are kneaded together to form pellets of size L. A Resin pellets A, which are pelletized to be between 3.0 mm and 7.0 mm in size, Resin pellet B, which is made by directly pelletizing polypropylene resin, It is a mixture of the following: The pellet size L of the aforementioned resin pellet A A (mm) Pellet size L of the resin pellet B B Ratio L to (mm) A / L BThe ratio is set to be between 0.8 and 1.2. By using a mixture of resin pellets A and B in this manner, resin pellets A and B can be uniformly mixed, making it possible to obtain a high-quality spunbond nonwoven fabric with high production speed and high uniformity. Details of each are explained below.

[0032] (I-1) Resin Pellet A The resin pellet A in this process is made by kneading a polypropylene resin and an organic peroxide, resulting in pellet size L. A These are pellets made to be between 3.0 mm and 7.0 mm in size.

[0033] This polypropylene resin is preferable because it has superior spinnability and strength characteristics compared to other polyolefin resins such as polyethylene resins.

[0034] Furthermore, the polypropylene resin mentioned above may be recycled resin. Using recycled resin can reduce the amount of virgin petrochemical raw materials used, thereby reducing the environmental impact during the manufacture of spunbond nonwoven fabrics.

[0035] On the other hand, as organic peroxides, those used as radical generators are preferred. Specifically, ketone peroxides such as "methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide," Diacyl peroxides such as "dibenzoyl peroxide, di-(3,5,5-trimethylhexanoyl) peroxide, dilauroyl peroxide, didecanoyl peroxide, di-(2,4-dichlorobenzoyl) peroxide," Hydroperoxides such as "t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide", Dialkyl peroxides such as "di-t-butyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexine-3, α,α'-bis(t-butylperoxy)diisopropylbenzene", Peroxyketals such as "1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 2,2-bis(t-butylperoxy)butane", Alkyl peresters such as "t-butyl peroxyoctoate, t-butyl peroxypivalate, t-butyl peroxyneodecanoate, t-butyl peroxybenzoate", Peroxycarbonates such as "di-(2-ethylhexyl) peroxydicarbonate, diisopropyl peroxydicarbonate, bis(4-t-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, t-butyl peroxyisopropyl carbonate," These are good examples of preferred materials. Among these, dialkyl peroxides are more preferred because they allow for easy control of the melt flow rate, Mw / Mn, or Mz / Mw ratio, as described later, when added in small amounts.

[0036] In this process, it is preferable that the organic peroxide content in resin pellet A be between 1% by mass and 50% by mass. By setting the lower limit of the organic peroxide content (by mass%) to preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more, it is easier to obtain an effect of lowering the melt viscosity, and a high-quality spunbond nonwoven fabric can be obtained at a high production rate and with high uniformity. On the other hand, by setting the upper limit of the organic peroxide content (by mass%) to preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, it is possible to uniformly mix the polypropylene resin used in resin pellet A, and also to uniformly mix resin pellet A and resin pellet B, so that a high-quality spunbond nonwoven fabric can be obtained at a high production rate and with high uniformity.

[0037] Furthermore, in this process, the resin pellet A has a pellet size L A These pellets are made to have a size of 3.0 mm to 7.0 mm. This pellet size L A Regarding the range (mm), by setting the lower limit to 3.0 mm or more, preferably 4.0 mm or more, the supply of the resin pellets A into the extruder becomes smoother, allowing for high production speed and high uniformity, resulting in a high-quality spunbond nonwoven fabric. On the other hand, the pellet size L A By setting the upper limit of the (mm) range to 7.0 mm or less, preferably 6.0 mm or less, it becomes easier to uniformly mix resin pellet A and resin pellet B, allowing for high production speed and high uniformity, resulting in a high-quality spunbond nonwoven fabric.

[0038] Note that the pellet size L of resin pellet A. A (mm) refers to a value measured and calculated by the following method: Pellet size L of resin pellet B, which will be described later. B (mm) refers to the value measured and calculated in the same manner, replacing "resin pellet A" with "resin pellet B". (i) Take out 30 resin pellets A at random. (ii) For the extracted resin pellet A, measure the diameter of the smallest circumscribed circle in the image obtained by observing it from directly above with a microscope (for example, a "VW-9000" manufactured by Keyence Corporation). (iii) The remaining 29 samples are measured in the same manner, and the arithmetic mean (mm) of the diameter of their smallest circumscribed circle is calculated and rounded to two decimal places.

[0039] Of course, the resin pellet A used in the present invention may contain pigments for coloring, antioxidants, lubricants such as polyethylene wax and fatty acid amide compounds, and heat stabilizers, to the extent that they do not impair the effects of the present invention.

[0040] (I-2) Resin Pellet B The resin pellet B used in this process is made by pelletizing polypropylene resin as is. This polypropylene resin may be the same as the polypropylene resin used in resin pellet A, or it may be a different polypropylene resin.

[0041] Of course, the resin pellet B used in the present invention may also contain pigments for coloring, antioxidants, lubricants such as polyethylene wax and fatty acid amide compounds, and heat stabilizers, to the extent that they do not impair the effects of the present invention.

[0042] (I-3) Raw resin In this process, the raw resin supplied to the extruder is a mixture of resin pellet A and resin pellet B (hereinafter sometimes simply referred to as "mixture"). By using such a mixture, the homogeneity of the material can be easily improved, and a high-quality spunbond nonwoven fabric can be obtained at a high production speed and with high uniformity. Here, in order to mix resin pellet A and resin pellet B, for example, a method can be adopted in which each is supplied to separate hoppers, weighed, and then supplied to the extruder through the same piping.

[0043] Of course, the raw material resin used in the present invention may also contain additives, namely pigments for coloring, antioxidants, lubricants such as polyethylene wax and fatty acid amide compounds, and heat stabilizers, to the extent that they do not impair the effects of the present invention. Whether or not resin pellets A and B contain these additives, they can be added to the mixture in this step.

[0044] And the pellet size L of the resin pellet A. A (mm) Pellet size L of the resin pellet B B Ratio L to (mm) A / L B The ratio L shall be between 0.8 and 1.2. A / L BBy setting the lower limit of the range to 0.8 or higher, preferably 0.9 or higher, it is possible to obtain a high-quality spunbond nonwoven fabric with high production speed and high uniformity. On the other hand, the ratio L A / L B By setting the upper limit of this range to 1.2 or less, preferably 1.1 or less, it is possible to obtain a high-quality spunbond nonwoven fabric with high production speed and high uniformity.

[0045] Note that the above ratio L A / L B This refers to the pellet size L obtained by measuring and calculating by the method described above. A The pellet size L (mm) was obtained by measuring and calculating it using the same method. B Divide by (mm) and round to two decimal places to calculate the result.

[0046] In this process, the amount of resin pellet A supplied per unit time W A The amount of resin pellet B supplied per unit time (g / min) W B Ratio W to (g / min) A / W B It is preferable that the ratio W is between 0.001 and 0.500. Here, in this first embodiment, the ratio W A / W B This refers to the ratio of the content of resin pellet A (g / min) to the content of resin pellet B (g / min) in the mixture supplied to the extruder per unit time (1 minute).

[0047] The ratio W mentioned above A / W B Regarding the range, by setting the lower limit preferably to 0.001 or higher, more preferably to 0.002 or higher, and even more preferably to 0.003 or higher, a high-quality spunbond nonwoven fabric can be obtained with a high production rate and high uniformity. On the other hand, the above ratio W A / W BBy setting the upper limit of the range preferably to 0.500 or less, more preferably to 0.400 or less, and even more preferably to 0.300 or less, it is possible to obtain a high-quality spunbond nonwoven fabric with high production speed and high uniformity.

[0048] In this process, the melting point Tm of the resin pellet A A (°C) and the melting point Tm of the resin pellet B. B Tm (difference from °C) B -Tm A It is preferable that the temperature (°C) be between 5.0°C and 50.0°C.

[0049] The difference Tm B -Tm A Regarding the range of (°C), by setting the lower limit preferably to 5.0°C or higher, more preferably to 7.0°C or higher, and even more preferably to 10.0°C or higher, the mixing state is more likely to become uniform, allowing for a high production rate and high uniformity, resulting in a high-quality spunbond nonwoven fabric. On the other hand, the difference Tm B -Tm A By setting the upper limit of the (°C) range to preferably 50.0°C or lower, more preferably 40.0°C or lower, and even more preferably 30.0°C or lower, stable mixing can be achieved, resulting in a high production rate, high uniformity, and a high-quality spunbond nonwoven fabric.

[0050] Note that the melting point Tm of resin pellet A as referred to here is... A (°C) is a value measured and calculated by the following procedure: Melting point Tm of resin pellet B. B (°C) refers to the value measured and calculated in the same manner, replacing "resin pellet A" with "resin pellet B". (i) Take a 2.0 mg sample from resin pellet A and place it in a differential scanning calorimeter (for example, TA Instruments "DSC Q2000"). (ii) Differential scanning calorimetry is performed under nitrogen conditions, with a heating rate of 16°C / min and a measurement temperature range of 50°C to 230°C. (iii) Calculate the peak top temperature (°C) of the largest endothermic peak in the DSC curve. (iv) For each level, three measurements are taken by changing the sampling site of the test specimen, and the arithmetic mean is rounded to the first decimal place.

[0051] In this process, when supplying the raw resin to the extruder, resin pellets A and B can be used as a pre-mixed material. However, if a pre-mixed material is not used, it is preferable to supply both resin pellets A and B from the main feeder's inlet. This allows the pellets to mix together during supply, facilitating uniform mixing and enabling the production of high-quality spunbond nonwoven fabric with high production speed and high uniformity. Furthermore, when using equipment with a side feeder, it is also preferable to supply resin pellet A from the side feeder.

[0052] Examples of extruders to which the raw material resin is supplied include single-screw and twin-screw extruder types.

[0053] Next, the raw material resin is melted and kneaded by a screw inside the extruder, and then extruded through the discharge hole of the die.

[0054] When melting and kneading with a screw inside an extruder, the shape of the screw is not particularly limited, but in this process, the length L of the screw is C The diameter D of the screw (mm) C Ratio L to (mm) C / D C It is preferable to set the ratio L to 15 or more and 50 or less. C / D C Regarding the range, by setting the lower limit preferably to 15 or more, and more preferably to 20 or more, a good mixing state can be obtained, thus enabling the production of high-quality spunbond nonwoven fabric with high production speed and high uniformity. On the other hand, the above ratio L C / D CBy setting the upper limit of the range preferably to 50 or less, and more preferably to 40 or less, stable processing becomes possible, allowing for the production of high-quality spunbond nonwoven fabrics with high production speed and high uniformity.

[0055] In addition to a standard constant-pitch screw, the screw structure may also incorporate some dam flight, fluted, or cross saw elements.

[0056] In this process, it is preferable to perform the melt kneading for 0.5 minutes or more and 30.0 minutes or less. By setting the lower limit of the melt kneading time range to preferably 0.5 minutes or more, and more preferably 1.0 minute or more, a good mixing state can be obtained, thus enabling the production of a high-quality spunbond nonwoven fabric with high production speed and high uniformity. On the other hand, by setting the upper limit of the melt kneading time range to preferably 30.0 minutes or less, and more preferably 20.0 minutes or less, stable processing is possible, thus enabling the production of a high-quality spunbond nonwoven fabric with high production speed and high uniformity.

[0057] In this process, the molten and kneaded raw resin is extruded through the discharge hole of the spinneret. Specifically, the molten and kneaded raw resin passes through piping, is measured by a metering device such as a gear pump, passes through a filter to remove foreign matter, and is then guided to the spinneret. At this time, the temperature from the resin piping to the spinneret (spinning temperature) is preferably between 180°C and 280°C. By keeping the spinning temperature within the above range, a stable molten state is achieved, and yarn breakage during spinning can be suppressed, resulting in a spunbond nonwoven fabric with fewer defects.

[0058] In this process, the die hole used for melt extrusion has a die hole diameter D P It is preferable that the length be between 0.1 mm and 0.6 mm, and the land length L of the nozzle hole. P (The length of the straight section having the same diameter as the hole in the nozzle) is defined as hole diameter D P L is defined by the quotient obtained by dividing by P / D PIt is preferable that the value be between 1 and 10.

[0059] In this process, the single-hole discharge rate of the melt-kneaded raw material resin according to this embodiment, that is, the amount of raw material resin discharged from one hole of the die, is preferably 0.15 g / (hole / min) or more and 2.50 g / (hole / min) or less. By setting the lower limit of the single-hole discharge rate range of the melt-kneaded raw material resin to preferably 0.15 g / (hole / min) or more, and more preferably 0.20 g / (hole / min) or more, a high-quality spunbond nonwoven fabric can be obtained at a high production rate and with high uniformity. On the other hand, by setting the upper limit of the single-hole discharge rate range of the melt-kneaded raw material resin to preferably 2.50 g / (hole / min) or less, and more preferably 2.00 g / (hole / min) or less, a high-quality spunbond nonwoven fabric can be obtained at a high production rate and with high uniformity.

[0060] Next, the spun raw resin is stretched and pulled.

[0061] Before this pulling and stretching, the spun raw resin can also be cooled. Methods for this include, for example, forcibly blowing cold air, natural cooling at ambient temperature, and adjusting the distance between the spinneret and the pulling equipment. Furthermore, these methods can be combined. The cooling conditions can be appropriately adjusted and adopted considering the discharge rate per single hole of the spinneret, the spinning temperature, and the ambient temperature.

[0062] Furthermore, it is preferable to stretch and draw the cooled and solidified raw material resin using an air-flow traction device at a spinning speed of 2000 m / min to 6000 m / min. This is because a spinning speed of 2000 m / min to 6000 m / min results in high productivity, promotes the orientation and crystallization of the fibers, and allows for the production of high-strength fibers.

[0063] (II) Process of forming a fiber web In this process, the fibers are deposited to form a fiber web composed of the fibers. More specifically, for example, the fibers can be opened by passing them through an opening section that reduces the ambient air flow velocity, and then collected on a moving net to obtain a fiber web.

[0064] Before the step of sheet-forming the fiber web described later, it is also a preferred embodiment to temporarily bond the fiber web by bringing a heat flat roll (a roll having a heating mechanism and a smooth surface (without unevenness for embossing)) into contact with the upper surface of the fiber web while the fiber web is placed on the moving net. By doing so, it is possible to prevent the surface layer of the non-woven fiber web from being turned up or blown away during conveyance on the moving net, which would deteriorate the appearance, and to improve the conveyance property from when the yarns are collected until heat crimping.

[0065] Here, regarding the temporary bonding, the temperature of the heat flat roll is set to be not lower than 30°C lower than the melting point Tm PP (°C) of the polypropylene-based resin used and not higher than 10°C higher than Tm PP (°C), that is, preferably not lower than (Tm PP - 30)°C and not higher than (Tm PP + 10)°C. Regarding the range of the surface temperature of the heat flat roll, by setting the lower limit to be preferably not lower than -30°C with respect to the melting point of the polypropylene-based resin ((Tm PP - 30)°C or higher), it is possible to prevent the surface layer of the non-woven fiber web from being turned up or blown away during conveyance on the moving net, which would deteriorate the appearance, and to improve the conveyance property from when the yarns are collected until heat crimping. Also, regarding the range of the surface temperature of the heat flat roll, by setting the upper limit to be preferably not higher than +10°C with respect to the melting point of the polypropylene-based resin ((Tm PP + 10)°C or lower), excessive heat adhesion can be suppressed, and appropriate flexibility suitable for use in disposable diapers, especially as a spunbond non-woven fabric for sanitary materials, can be obtained.

[0066] Furthermore, in temporary bonding, it is preferable to set the linear pressure of the heat flat roll to 0.5 N / cm or more and 50 N / cm or less. By setting the lower limit of the linear pressure range of the heat flat roll to preferably 0.5 N / cm or more, and more preferably 1 N / cm or more, it is possible to prevent the surface layer of the nonwoven fiber web from peeling or being blown away while being transported on a moving net, thereby preventing deterioration of the fabrication, and to improve transportability from the collection of yarn to heat-seal bonding. On the other hand, by setting the upper limit of the linear pressure range of the heat flat roll to preferably 50 N / cm or less, and more preferably 40 N / cm or less, it is possible to obtain a spunbond nonwoven fabric for sanitary materials that has appropriate flexibility, particularly suitable for use in disposable diapers.

[0067] (III) Process of forming a fiber web into a sheet In this process, the fiber web is formed into a sheet. "Forming into a sheet" here means making the fiber web into a state that can be easily transported, such as by heat bonding as described later. More specifically, for example, the fiber web can be heat-bonded to form fused and unfused portions. Here, in the present invention, "fused portion" refers to the portion where the convex portions of the upper roll and the lower roll overlap and contact the fiber web when heat bonding is performed using a pair of rolls with irregularities, and the portion where the convex portions of the roll with irregularities contact the fiber web when heat bonding is performed using a roll with irregularities (embossed roll) and a flat roll. In other words, the portion where the convex portions of the roll with irregularities contact the fiber web, causing the fibers in that area to partially melt and the fiber intersections to fuse together is the "fused portion," and the portion where this does not occur is the "unfused portion." On the other hand, when heat bonding is performed using a pair of upper and lower flat (smooth) rolls, substantially only fused portions are formed. Furthermore, in the case of ultrasonic bonding, the part that is heat-welded by ultrasonic processing (the part that the oscillating horn contacts) becomes the fused part.

[0068] There are no particular limitations on the method of forming the fiber web into a sheet, but examples include methods of heat fusion using various rolls, such as a heat embossing roll in which a pair of upper and lower roll surfaces are engraved (with raised and recessed areas), a heat embossing roll consisting of a combination of a roll with one flat (smooth) surface and a roll with an engraved (raised and recessed area) surface, and a heat calender roll consisting of a combination of an upper and lower pair of flat (smooth) rolls, a method of heat fusion using ultrasonic vibration of a horn, and a method of penetrating the fiber web with hot air to soften or melt the surface of the fibers and heat fusion the fiber intersections.

[0069] In particular, it is preferable to use a heat embossing roll in which a pair of upper and lower roll surfaces are each engraved (with raised or recessed areas), or a heat embossing roll consisting of a combination of a roll with one flat (smooth) surface and a roll with an engraved (raised or recessed area) surface. By doing so, it is possible to provide both a fused section that improves the strength of the spunbond nonwoven fabric and a non-fused section that improves the texture and feel, while maintaining high productivity.

[0070] Regarding the surface material of the rolls, it is preferable that the materials of both rolls have the same hardness in order to prevent the engraving (recessed portion) of one roll from being transferred to the surface of the other roll. Furthermore, it is preferable that the materials of both rolls are made of metal in order to appropriately fuse the fibers together.

[0071] In this process, when sheet-forming is performed using the heat embossing roll as described above, it is preferable that the adhesion area ratio be 5% or more and 30% or less. By setting the adhesion area ratio preferably at 5% or more, more preferably at 8% or more, and even more preferably at 10% or more, the strength that can be put to practical use as a spunbond nonwoven fabric can be obtained. On the other hand, by setting the adhesion area ratio preferably at 30% or less, more preferably at 25% or less, and even more preferably at 20% or less, appropriate flexibility suitable for use particularly in the application of disposable diapers can be obtained as a spunbond nonwoven fabric for sanitary materials. Even when ultrasonic adhesion is used, it is preferable that the adhesion area ratio be within the same range.

[0072] The adhesion area ratio (%) referred to here means the area ratio of the above-mentioned fused portion in the entire spunbond nonwoven fabric. Specifically, it is shown by the following formula Adhesion area ratio (%) = {Area of fused portion (mm 2 )} / [{Area of fused portion (mm 2 )} + {Area of non-fused portion (mm 2 )}] × 100 ··· (Formula) = {Area of fused portion (mm 2 )} / {Area of spunbond nonwoven fabric (mm 2 )} × 100 ··· (Formula) The shape of the fused portion formed by sheet-forming is not particularly limited. For example, a circle, an ellipse, a square, a rectangle, a parallelogram, a rhombus, a regular hexagon, a regular octagon, etc. can be used. Further, it is preferable that the fused portions uniformly exist at regular intervals in the longitudinal direction (transport direction) and the width direction of the spunbond nonwoven fabric. By doing so, the variation in the strength of the spunbond nonwoven fabric can be reduced.

[0073] In this process, when a roll heated during sheet-forming is used, the surface temperature of the roll is 30°C lower than the melting point Tm PP (°C) of the polypropylene-based resin used or higher and 10°C higher than Tm PP (°C) or lower, that is, (Tm PP - 30)°C or higher and (Tm PPIt is preferable that the temperature be below +10°C. Regarding the range of the roll's surface temperature, the lower limit is preferably -30°C or higher relative to the melting point of the polypropylene resin ((Tm). PP By setting the temperature to -30°C or higher, strong heat bonding can be achieved, and a spunbond nonwoven fabric with sufficient strength for practical use can be obtained. Furthermore, regarding the range of the surface temperature of the roll, the upper limit is preferably +10°C or less relative to the melting point of the polypropylene resin ((Tm PP By keeping the temperature below +10°C, excessive heat bonding is suppressed, and a moderate flexibility is obtained, making it suitable for use as a spunbond nonwoven fabric for sanitary materials, especially in disposable diapers.

[0074] In this process, when a heated roll is used during sheet formation, the linear pressure of the roll is preferably between 50 N / cm and 500 N / cm. By setting the lower limit of the linear pressure range of the roll to preferably 50 N / cm or more, more preferably 100 N / cm or more, and even more preferably 150 N / cm or more, a spunbond nonwoven fabric with sufficient strength for practical use through strong heat bonding can be obtained. On the other hand, by setting the upper limit of the linear pressure range of the roll to preferably 500 N / cm or less, more preferably 400 N / cm or less, and even more preferably 300 N / cm or less, a spunbond nonwoven fabric with appropriate flexibility suitable for use in sanitary materials, particularly in disposable diapers, can be obtained.

[0075] Furthermore, in this process, to adjust the thickness of the resulting spunbond nonwoven fabric, heat bonding can be performed using a thermal calender roll consisting of an upper and lower pair of flat rolls before and / or after the sheet formation process. The upper and lower pair of flat rolls are metal rolls or elastic rolls with no irregularities on the surface of the rolls, and can be used in pairs of metal rolls or metal rolls and elastic rolls. Here, an elastic roll is a roll made of a material that has elasticity compared to a metal roll. Examples of elastic rolls include so-called paper rolls such as paper, cotton, and aramid paper, as well as resin rolls made of urethane resin, epoxy resin, silicone resin, polyester resin, hard rubber, and mixtures thereof.

[0076] (IV) Other post-processing steps The material obtained by performing the above steps may be used as spunbond nonwoven fabric, but further post-processing can be performed depending on the intended use.

[0077] For example, a chemical solution can be applied to a sheeted fiber web to give it new functionality. Methods for applying this chemical solution include roll coating, gravure printing, flexographic printing, and spray coating, in which the solution is drawn up from a chemical solution tank using a metal roll rotating in the tank, and the sheeted fiber web is brought into contact with the metal roll above it, thereby transferring the liquid to the surface of the sheeted fiber web. Among these, the roll coating method is preferred because it offers excellent productivity, allows for uniform application of the solution, allows for easy adjustment of the amount of liquid applied, and allows the liquid to be applied to only one side of the laminated nonwoven fabric.

[0078] Examples of chemical solutions and their functionalities include antibacterial and antiviral agents (antibacterial and antiviral properties), hydrophilic agents (hydrophilic properties), water repellents (water repellency), oil repellents (oil repellency), antistatic agents (antistatic properties), deodorants (deodorant properties), fragrances (fragrance properties), and cooling agents (cooling properties).

[0079] Other post-processing options such as hole punching, printing, and film lamination are also available.

[0080] [Second Embodiment] The first and second embodiments use the same resin pellets A and B, but they differ in that in the first embodiment, a mixture of resin pellets A and B is used as the raw material resin and supplied to the extruder, whereas in the second embodiment, resin pellets A and B are supplied to the extruder separately and melt-kneaded in the screw inside the extruder to form the raw material resin. The second embodiment will be described below, focusing on the differences.

[0081] (I) Process of forming fibers In this process, first, Polypropylene resin and organic peroxide are kneaded together to form pellets of size L. A Resin pellets A, which are pelletized to be between 3.0 mm and 7.0 mm in size, Resin pellet B, which is made by directly pelletizing polypropylene resin, Each of these is supplied to an extruder, where it is melted and kneaded by the screw inside the extruder to obtain the raw resin. Then, The pellet size L of the aforementioned resin pellet A A (mm) Pellet size L of the resin pellet B B Ratio L to (mm) A / L B The ratio shall be between 0.8 and 1.2. As stated above, the resin pellets A and B in this process are the same as those shown in (I-1) and (I-2) of the first embodiment, respectively. Also, the pellet size L of resin pellet A A (mm) Pellet size L of the resin pellet B B Ratio L to (mm) A / L B The point that it should be between 0.8 and 1.2 is the same as that shown in (I-3) of the first embodiment.

[0082] In addition, at least the following points are the same as those of the first embodiment. • Amount of resin pellet A supplied per unit time W A The amount of resin pellet B supplied per unit time (g / min) W B Ratio W to (g / min) A / W B • Melting point Tm of the resin pellet A A (°C) and the melting point Tm of the resin pellet B. B Tm (difference from °C) B -Tm A (℃) Furthermore, examples of extruders that supply resin pellets A and B include single-screw and twin-screw extruder types.

[0083] On the other hand, in this embodiment, in this process, resin pellet A and resin pellet B are supplied to an extruder, and melt-kneaded by the screw in the extruder to form the raw resin. By supplying resin pellet A and resin pellet B to the extruder separately in this way, supply irregularities can be reduced, and a high-quality spunbond nonwoven fabric can be obtained at a high production speed and with high uniformity. Here, in order to supply resin pellet A and resin pellet B separately, for example, one resin pellet can be fed in from the main supply port and the other resin pellet can be fed in from the side feeder.

[0084] Of course, additives, namely pigments for coloring, antioxidants, lubricants such as polyethylene wax and fatty acid amide compounds, and heat stabilizers, may be supplied separately to the extruder, as long as they do not impair the effects of the present invention. Whether or not resin pellets A and B contain these additives, they can be added in this process.

[0085] Next, the raw material resin is melted and kneaded by a screw inside the extruder, and then melted and kneaded and extruded through the discharge hole of the die. Here, at least the shape and structure of the extruder screw, as well as the time for melting and kneading, are the same as in the first embodiment.

[0086] In this process, the molten and kneaded raw material resin is extruded through the discharge hole of the die, and the spun raw material resin is pulled and stretched to form fibers. Here, at least the spinning temperature, the structure of the die hole used for melt extrusion, the single-hole discharge amount of the molten and kneaded raw material resin, the method of cooling the spun raw material resin, the cooling conditions, and the spinning speed are the same as in the first embodiment.

[0087] (II) Process of forming a fiber web (III) Process of forming a fiber web into a sheet (IV) Other post-processing steps These three steps are the same as in the first embodiment.

[0088] [Obtained spunbond nonwoven fabric] Further explanation will be given regarding the spunbond nonwoven fabric obtained by the method for manufacturing the spunbond nonwoven fabric according to the first embodiment and the second embodiment (hereinafter sometimes simply referred to as "the spunbond nonwoven fabric according to this embodiment").

[0089] First, the fibers constituting the spunbond nonwoven fabric according to this embodiment preferably have an average single fiber diameter of 8 μm or more and 25 μm or less. By setting the lower limit of the average single fiber diameter range preferably at 8 μm or more, and more preferably at 10 μm or more, a decrease in spinnability during the manufacturing stage can be prevented, and production stability can be enhanced, resulting in a spunbond nonwoven fabric of superior quality. On the other hand, by setting the upper limit of the average single fiber diameter range preferably at 25 μm or less, and more preferably at 20 μm or less, a spunbond nonwoven fabric with a superior feel, uniform texture, and superior strength can be obtained. The average single fiber diameter can be controlled by spinning temperature, single-hole discharge rate, spinning speed, etc.

[0090] In this invention, the average single fiber diameter (μm) of the fiber is a value measured and calculated by the following procedure. (i) Take 10 small samples (100 x 100 mm) randomly from the obtained spunbond nonwoven fabric. (ii) Take surface photographs at 500 to 2000x magnification using a microscope (e.g., Keyence Corporation's "VW-9000") or a scanning electron microscope (e.g., Keyence Corporation's "VHX-D500"), and measure the width (diameter) of 10 non-fused fibers from each sample, for a total of 100 fibers. If the cross-section of the fiber is irregular, measure the cross-sectional area and determine the diameter (equivalent circle diameter) of a perfect circle with the same cross-sectional area. (iii) Calculate the arithmetic mean of the diameter values ​​(μm) of the 100 measured samples and round to two decimal places.

[0091] Furthermore, the basis weight of the spunbond nonwoven fabric according to this embodiment is 5 g / m². 2 More than 100g / m 2 The following is preferable: Regarding the range of basis weight, the lower limit is preferably 5 g / m². 2 Above, a comfortable 10g / m 2 More preferably 15 g / m² 2 As a result of the above, a spunbond nonwoven fabric with mechanical strength suitable for practical use is obtained. On the other hand, regarding the range of basis weight, the upper limit is preferably 100 g / m². 2 More preferably 50g / m 2 More preferably 30 g / m 2 The following conditions result in a spunbond nonwoven fabric with appropriate flexibility suitable for practical use.

[0092] In this invention, the basis weight of the spunbond nonwoven fabric shall be determined in accordance with JIS L1913:2010 "General Nonwoven Fabric Testing Methods" "6.2 Mass per Unit Area", and the value obtained by the following procedure shall be adopted. (i) From the spunbond nonwoven fabric, take three 20cm x 25cm test pieces randomly for every 1m of sample width. (ii) Measure the mass (g) of each under standard conditions (20°C, 65% relative humidity). (iii) The arithmetic mean is 1m 2 Mass per unit (g / m³) 2 It is expressed as ) and rounded to the first decimal place.

[0093] Furthermore, the thickness of the spunbond nonwoven fabric according to this embodiment is preferably 0.05 mm or more and 1.50 mm or less. By having a lower limit of the thickness range preferably 0.05 mm or more, more preferably 0.08 mm or more, and even more preferably 0.10 mm or more, or by having an upper limit of the thickness range preferably 1.50 mm or less, more preferably 1.00 mm or less, and even more preferably 0.80 mm or less, a spunbond nonwoven fabric with flexibility and appropriate cushioning properties that is suitable for practical use is obtained.

[0094] Furthermore, the thickness (mm) of the spunbond nonwoven fabric shall be the value obtained by measuring according to Method A of "6.1 Thickness (ISO method)" in JIS L1913:2010 "General Test Methods for Nonwoven Fabrics".

[0095] Furthermore, it is preferable that the amount of organic peroxide extracted by immersing the spunbond nonwoven fabric according to this embodiment in a chloroform / methanol solvent in a volume ratio of 1:1 and sonicating it for 15 minutes at 45 kHz and a solution temperature of 30°C (hereinafter sometimes simply referred to as "the organic peroxide content of the spunbond nonwoven fabric") be less than 100 ppm. This is because a concentration of less than 100 ppm makes it less likely for performance to deteriorate during use and storage.

[0096] In this invention, the organic peroxide content of the spunbond nonwoven fabric refers to the value measured and calculated by the following method. (i) Take five random 25 mg samples from the area of ​​the spunbond nonwoven fabric, excluding the edges. The edges of the spunbond nonwoven fabric refer to the 10% area at both ends of the fabric's width. (ii) The test specimen obtained in (i) is immersed in a chloroform / methanol solvent in a volume ratio of 1:1 and sonicated for 15 minutes at 45 kHz to dissolve it. For this sonication, for example, an ultrasonic cleaner such as AS ONE Corporation's "VS-100 III" can be used. The amount of solvent relative to the mass of the test specimen shall be 0.8 mL of solvent per 1 mg of test specimen. (iii) The sonicated solution obtained in (ii) is filtered through a polytetrafluoroethylene (PTFE) filter (hereinafter sometimes simply referred to as "PTFE filter"; pore size: 0.45 μm) to obtain the sample solution. Here, a PTFE filter such as "T010A" manufactured by Advantec Toyo Co., Ltd. can be used. (iv) Dissolve 0.1 g of organic peroxide in 10 mL of a chloroform / methanol solution in a volume ratio of 1:1 to prepare a standard stock solution (10 μg / mL). Then, dilute this standard stock solution with the aforementioned chloroform / methanol solution to prepare standard solutions of various concentrations (0.1 μg / mL, 0.2 μg / mL, 0.5 μg / mL, 1.0 μg / mL). The organic peroxides listed above are listed below, and a standard solution of each concentration is prepared for each. Furthermore, if it is clear, or at least suspected, that the mixture contains organic peroxides other than those listed below that have the structure shown in general formula (1) or (2) by other methods (e.g., iodine titration, polarography, etc.), a standard solution of that organic peroxide is also prepared. • Di-t-butyl peroxide • Dicumyl peroxide 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane 2,5-Dimethyl-2,5-bis(t-butylperoxy)hexyn-3 • α,α'-Bis(t-butylperoxy)diisopropylbenzene • 1,1-Bis(t-butylperoxy)-3,3,5-trimethylcyclohexane 2,2-Bis(t-butylperoxy)butane (v) The sample solution described above is subjected to liquid chromatography-mass spectrometry (LC / MS / MS) under the following conditions. • High-performance liquid chromatography (HPLC): For example, the "LC-20A" manufactured by Shimadzu Corporation. • Mass spectrometer (MS): For example, Sciex API 4000. • Column: ODS type column (for example, "SUMIPAX ODS A series" manufactured by Sumika Analysis Center Co., Ltd.) Mobile phase: 0.1% formic acid aqueous solution + methanol (gradient extraction conditions) ·Injection volume: 5μL • Ionization: Electrospray ionization (ESI) (vi) Identify the organic peroxide from the mass spectrum (MS) of each sample solution, and quantify the amount of organic peroxide (ppm) from the peak area using a calibration curve obtained from the standard solutions of the organic peroxides. (vii) For each test specimen, round the arithmetic mean (ppm) of the measured values ​​to the first decimal place to obtain the amount of organic peroxide (ppm).

[0097] The melt flow rate (MFR) of the spunbond nonwoven fabric according to this embodiment is preferably 10 g / 10 min or more and 400 g / 10 min or less, more preferably 20 g / 10 min or more and 300 g / 10 min or less, and even more preferably 30 g / 10 min or more and 200 g / 10 min or less. This is because a melt flow rate of 20 g / 10 min or more results in a spunbond nonwoven fabric with excellent flexibility, and a melt flow rate of 400 g / 10 min or less increases the mechanical strength of the embossed portion of the spunbond nonwoven fabric, resulting in a spunbond nonwoven fabric with high tensile strength.

[0098] In this invention, the MFR of the spunbond nonwoven fabric is determined in accordance with JIS K7210-1:2014 "Plastics - Method for determining melt mass flow rate (MFR) and melt volume flow rate (MVR) of thermoplastic plastics - Part 1: Standard test methods," Chapter 8, Method A: Mass measurement method. Five 20g test pieces are randomly selected from the area excluding the edges of the spunbond nonwoven fabric. For each test piece, the arithmetic mean of the measured value (g / 10 min) under conditions of a load of 2160g and a temperature of 230°C is rounded to the first decimal place to determine the MFR (g / 10 min). The edges of the nonwoven fabric refer to the 10% area at both ends of the fabric's width. For measurement, for example, a melt indexer "F-F01" manufactured by Toyo Seiki Seisakusho Co., Ltd. can be used.

[0099] Furthermore, the melt flow rate (MFR) of spunbond nonwoven fabrics can be controlled by the weight-average molecular weight of the polypropylene resin. The higher the weight-average molecular weight of the polypropylene resin, the lower the melt flow rate. The weight-average molecular weight can be controlled by the weight-average molecular weight of the raw material resin and the amount of organic peroxide added.

[0100] [Manufacturing methods for sanitary materials, masks, and protective clothing] The spunbond nonwoven fabric according to this embodiment is suitable for a wide range of applications, including sanitary materials such as diapers and sanitary napkins, masks and protective clothing, due to its high production rate, high uniformity, and high quality, even if the constituent fibers have a fine fiber diameter or a low basis weight, as well as being a general spunbond nonwoven fabric. The term "protective clothing" as used herein refers to clothing worn when engaging in work involving acids, alkalis, organic chemicals, other gases and liquids, as well as particulate chemicals, and biologically hazardous substances such as pathogens and biologically derived materials that can harm humans, and is used to prevent the permeation and / or penetration of chemical substances.

[0101] Furthermore, the method for manufacturing the sanitary material according to this embodiment includes the step of cutting the spunbond nonwoven fabric obtained by the method for manufacturing the spunbond nonwoven fabric to form nonwoven fabric parts, The process involves laminating and fixing the aforementioned nonwoven fabric parts and absorbent material, It is preferable to include the above. By manufacturing the sanitary material in this manner, the effects of the spunbond nonwoven fabric can be further enhanced. Here, "fixing" means to integrate the nonwoven fabric part and the absorbent material, and specifically, this can be done by fixing them using adhesive or adhesive tape, or by melting a part of the nonwoven fabric part and fusing it to the absorbent material.

[0102] Furthermore, the method for manufacturing a mask according to this embodiment includes the step of cutting the spunbond nonwoven fabric obtained by the method for manufacturing the spunbond nonwoven fabric to form nonwoven fabric parts, The process of fixing the nonwoven fabric part and the string part, It is preferable to include the above. By manufacturing the mask in this manner, the effects of the spunbond nonwoven fabric described above can be more fully realized. Here, "fixing" means to integrate the nonwoven fabric part and the string part, and specifically, this can be done by fixing them with an adhesive or by melting a part of the nonwoven fabric part and fusing it to the string part. The "string part" refers to the part of the mask that can be put over the ears. In the present invention, the component constituting the "string part" does not refer only to string-shaped objects, but may also be a band-shaped object or a sheet-shaped object with an opening, as long as it can be put over the ears when made into a mask.

[0103] Furthermore, the method for manufacturing protective clothing according to this embodiment includes the step of cutting the spunbond nonwoven fabric obtained by the method for manufacturing spunbond nonwoven fabric to form nonwoven fabric parts, Sleeve portion including the aforementioned nonwoven fabric part, Body part including the aforementioned nonwoven fabric part, Leg portion including the aforementioned nonwoven fabric part, Head including the aforementioned nonwoven fabric part, A step of forming at least one part of, A step of joining the parts obtained by the above step together, and / or the parts obtained by the above step together with other parts, It is preferable to include the above. By manufacturing protective clothing in this manner, the effects of the spunbond nonwoven fabric can be more fully realized. Here, "joining" means to integrate parts such as sleeves, torso, legs, and head, which include nonwoven fabric parts, with other parts, or with other components. Specifically, this can be done by fixing them with adhesive or adhesive tape, sewing them together, or melting a part of the sleeve or other part to fuse it with other components.

[0104] Furthermore, a sheet such as a film can be laminated onto the spunbond nonwoven fabric before cutting. This allows for the creation of protective clothing with higher barrier properties. [Examples]

[0105] Next, the present invention will be specifically described based on examples. However, the present invention is not limited to these examples.

[0106] [Measurement method] The evaluation methods and measurement conditions used in the examples are described below. Unless otherwise specified, the measurements of each physical property were performed based on the methods described above.

[0107] (1) Average single fiber diameter (μm) of the fibers constituting the spunbond nonwoven fabric: The measurements and calculations were performed using the VHX-D500 electron microscope manufactured by Keyence Corporation, according to the method described above.

[0108] (2) Melting point Tm of resin pellet A A (°C), Melting point Tm of resin pellet B B (°C): A TA Instruments "DSC Q2000" differential scanning calorimeter was used, and measurements and calculations were performed according to the method described above.

[0109] (3) Content of organic peroxides in spunbond nonwoven fabric (ppm): The organic peroxide content in the spunbond nonwoven fabric was measured and calculated using the method described above.

[0110] (4) Pellet size (mm): The pellet size was measured and calculated using the method described above.

[0111] (5) Weight (g / m 2 ): The basis weight of the spunbond nonwoven fabric was measured and calculated using the method described above.

[0112] (6) Number of times the thread broke: As part of the evaluation of uniformity, we assessed yarn breakage during spinning. This is because the number of yarn breaks is one of the factors that greatly affects the uniformity of spunbond nonwoven fabrics. The evaluation involved measuring the number of yarn breaks over 10 minutes at one-hour intervals using a counter, for a total of five measurements over 50 minutes. This was then converted to the number of yarn breaks per 100 holes.

[0113] (7) Uniformity of the ground surface (points): As an evaluation of uniformity, the uniformity of the weave of the obtained spunbond nonwoven fabric was assessed. Samples measuring 100 mm x 100 mm were randomly taken from the spunbond nonwoven fabric, placed on black cardboard (AC card black #350), and 20 panelists evaluated the uniformity of the weave of the spunbond nonwoven fabric using the following five-point scale. Subsequently, the scores judged by each panelist were totaled to determine the uniformity of the weave of the spunbond nonwoven fabric, with a score of 80 points or higher being considered a passing grade. A uniformity of weave of 85 points or higher is preferable, and a score of 90 points or higher is more preferable. • 5 points: Excellent (The fibers are evenly distributed, and there is almost no variation in shade (black or white).) 4 points: Good (between 5 and 3 points) • 3 points: Average (There is little tangling of fibers (thread bundles), but variations in shade (black and white) are visible.) • 2 points: Poor (between 3 and 1 point) • 1 point: Very poor (Many tangles (thread bundles) in the fibers, and strong contrasts (black and white) are visible).

[0114] [Polypropylene resins, polypropylene masterbatches, organic peroxides] The polypropylene resin used in the examples and comparative examples, and the polypropylene resin mixed with organic peroxide (polypropylene masterbatch) are as follows.

[0115] (Polypropylene resin A) This is a polypropylene homopolymer obtained using a Ziegler-Natta catalyst, with a pellet size of 4.5 mm and an MFR of 2 g / 10 min. It is a polypropylene-based resin that does not contain organic peroxides. In the table, it is abbreviated as "PP-A".

[0116] (Polypropylene resin B) This polypropylene homopolymer, obtained using a Ziegler-Natta catalyst, has a pellet size of 7.0 mm and an MFR of 2 g / 10 min. It is a polypropylene-based resin that does not contain organic peroxides. In the table, it is abbreviated as "PP-B".

[0117] (Polypropylene Masterbatch α) "VMPP10X" manufactured by Polytechs (a compound of polypropylene resin and organic peroxide, containing 10% by mass of 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane as the organic peroxide). The pellet size is 5.0 mm. It is abbreviated as "MB-α" in the table.

[0118] (Polypropylene Masterbatch β) "VMPP5X" manufactured by Polytechs (a compound made by kneading polypropylene resin and organic peroxides, containing 5% by mass of 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane as the organic peroxide). In the table, it is abbreviated as "MB-β".

[0119] (Polypropylene Masterbatch γ) This is a propylene homopolymer obtained using a metallocene catalyst. It is obtained by melting, kneading, cooling, and cutting polypropylene with an MFR of 30 g / 10 min, so that it contains 10% by mass of the organic peroxide: 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane. The pellet size is 7.5 mm. It is abbreviated as "MB-γ" in the table.

[0120] [Example 1] (a) Process of forming fibers Fibers were formed using the method described in the first embodiment. First, a mixture of resin pellets A and B was used as the raw material resin. • Resin pellet A: Polypropylene masterbatch α • Resin pellet B: Polypropylene resin A In this mixing process, the amount of resin pellet A supplied per unit time is W. A The amount of resin pellet B supplied per unit time (g / min) W B Ratio W to (g / min) A / W B The ratio was set to 0.015. Then, a mixture of resin pellet A and resin pellet B (a chip blend, abbreviated as "mixture" in the table) was supplied from the main feeder to a single-screw extruder type extruder, and the screw inside the extruder (screw length L) was used. C Screw diameter D (mm) C Ratio L to (mm) C / D C (of which there are 30) is melt-kneaded at 230°C for 5.0 minutes, and the melt-kneaded raw material resin is given a pore size D P The diameter is 0.40mm, and the land length is L P 0.8mm (L P / D PThe raw material resin was melt-extruded from the discharge hole of the spinneret (2) at a spinning temperature of 235°C. Subsequently, the spun raw material resin was cooled and solidified by blowing cold air (12°C air, wind speed 30 m / min) onto it. This was then pulled and stretched using compressed air with an airflow traction device (ejector) at a spinning speed of 3400 m / min to form fibers. The average single fiber diameter of the obtained fibers was 18 μm.

[0121] (b) process of forming a fiber web The fibers obtained by the above method were opened by passing them through a fiber-opening section where the surrounding airflow velocity was reduced, and then the fibers were deposited on a net conveyor that was sucked in by air from the back side to form a fiber web composed of these fibers.

[0122] (c) Process of forming a fiber web into a sheet The fiber web obtained above was heat-fused using a pair of upper and lower heat-embossing rolls consisting of the following upper and lower rolls (upper roll: a metal embossing roll with a diamond pattern engraved (the raised parts are rhombus-shaped), where the area of ​​the raised parts is 11% of the total surface area of ​​the roll, surface temperature: 140°C; lower roll: a metal flat roll, surface temperature: 140°C) to obtain a spunbond nonwoven fabric having fused and unfused sections. The evaluation results are shown in Table 1.

[0123] [Example 2] A spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that step (a) was modified as follows. The evaluation results are shown in Table 1.

[0124] (a) Process of forming fibers Fibers were formed using the method described in the second embodiment. First, the following resin pellets A and B were used. • Resin pellet A: Polypropylene masterbatch α • Resin pellet B: Polypropylene resin A Then, resin pellet B was supplied from the main feeder and resin pellet A was supplied from the side feeder to a single-screw extruder type extruder. At this time, the supply rate W of resin pellet A per unit time was A The amount of resin pellet B supplied per unit time (g / min) W B Ratio W to (g / min) A / W B The value was set to 0.015. Then, the screw inside the extruder (screw length L) C Screw diameter D (mm) C Ratio L to (mm) C / D C (of which there are 30) is melt-kneaded at 230°C for 5.0 minutes, and the melt-kneaded raw material resin is given a pore size D P The diameter is 0.40mm, and the land length is L P 0.8mm (L P / D P The raw material resin was melt-extruded from the discharge hole of the spinneret (2) at a spinning temperature of 235°C. Subsequently, the spun raw material resin was cooled and solidified by blowing cold air (12°C air, wind speed 30 m / min) onto it. This was then pulled and stretched using compressed air with an airflow traction device (ejector) at a spinning speed of 3400 m / min to form fibers. The average single fiber diameter of the obtained fibers was 18 μm.

[0125] [Example 3] In process (a), resin pellet A is replaced with polypropylene masterbatch β, and specific W A / W B A spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that the value was changed to 0.031. The evaluation results are shown in Table 1.

[0126] [Example 4] In process (a), ratio W A / W B A spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that the value was changed to 0.051. The evaluation results are shown in Table 1.

[0127] [Example 5] In step (a), a spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that the number of discharge holes in the spinneret was increased fivefold while keeping the single-hole discharge rate unchanged, and the kneading time was changed to 1.0 minute. The evaluation results are shown in Table 2.

[0128] [Example 6] In step (a), the spinning temperature was changed from 230°C to 200°C, but otherwise the spunbond nonwoven fabric was obtained in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0129] [Comparative Example 1] In step (a), a spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that resin pellet A was replaced with polypropylene masterbatch γ. The evaluation results are shown in Table 2.

[0130] [Comparative Example 2] In process (a), a spunbond nonwoven fabric was obtained in the same manner as in Comparative Example 1, except that resin pellet B was replaced with polypropylene resin B. The evaluation results are shown in Table 2.

[0131] [Table 1]

[0132] [Table 2]

[0133] The spunbond nonwoven fabrics of Examples 1-6 are of the pellet size L of resin pellet A. A (mm) is 3.0 mm or more and 7.0 mm or less, the pellet size L of the resin pellet B. B Ratio L to (mm) A / L B With a ratio between 0.8 and 1.2, the number of yarn breaks during spinning was 7 or less, demonstrating excellent spinnability. This allowed for the production of highly uniform spunbond nonwoven fabrics at a high production rate.

[0134] On the other hand, the pellet size L of resin pellet AA In Comparative Examples 1 and 2, where the (mm) was greater than 7.0 mm, the spunbond nonwoven fabrics experienced a high number of yarn breaks during spinning, and it was not possible to obtain a highly uniform spunbond nonwoven fabric. In particular, the pellet size ratio L A / L B Comparative Example 1, where the ratio was greater than 1.2, experienced a higher number of thread breakages.

Claims

1. The process involves supplying raw resin to an extruder, melting and kneading it with a screw inside the extruder, melting and extruding the melted and kneaded raw resin through the discharge hole of the die, and then pulling and stretching the spun raw resin to form fibers. A step of depositing the aforementioned fibers to form a fiber web composed of the fibers, The process of forming the aforementioned fiber web into a sheet, A method for producing a spunbond nonwoven fabric having, The aforementioned raw material resin, Polypropylene resin and organic peroxide are kneaded together to form pellets of size L. Ａ Resin pellets A, which are pelletized to have a size of 3.0 mm or more and 7.0 mm or less, Resin pellet B, which is made by directly pelletizing polypropylene resin, It is a mixture of the following: The pellet size L of the resin pellet A Ａ (mm) Pellet size L of the resin pellet B Ｂ Ratio L to (mm) Ａ / L Ｂ The value shall be between 0.8 and 1.

2. A method for manufacturing spunbond nonwoven fabric.

2. Polypropylene resin and organic peroxide are kneaded together to form pellets of size L. Ａ Resin pellets A, which are pelletized to have a size of 3.0 mm or more and 7.0 mm or less, Resin pellet B, which is made by directly pelletizing polypropylene resin, The process involves supplying each of these to an extruder, melting and kneading them with a screw inside the extruder to form a raw material resin, then melting and extruding the melted and kneaded raw material resin through the discharge hole of the die, and then pulling and stretching the spun raw material resin to form fibers. A step of depositing the aforementioned fibers to form a fiber web composed of the fibers, The process of forming the aforementioned fiber web into a sheet, A method for producing a spunbond nonwoven fabric having, The pellet size L of the resin pellet A Ａ (mm) of the pellet size L of the resin pellet B Ｂ Ratio L Ａ / L Ｂ is set to be 0.8 or more and 1.2 or less, A method for manufacturing spunbond nonwoven fabric.

3. A method for producing a spunbond nonwoven fabric according to claim 1 or 2, wherein the content of organic peroxide in the resin pellet A is 1% by mass or more and 50% by mass or less.

4. The amount of resin pellet A supplied per unit time W Ａ The amount of resin pellet B supplied per unit time (g / min) W Ｂ Ratio W to (g / min) Ａ / W Ｂ A method for producing a spunbond nonwoven fabric according to claim 1 or 2, wherein the ratio is 0.001 or more and 0.500 or less.

5. The melting point Tm of the resin pellet A. Ａ (°C) and the melting point Tm of the resin pellet B. Ｂ Difference Tm from (°C) Ｂ -Tm Ａ A method for producing a spunbond nonwoven fabric according to claim 1 or 2, wherein the temperature (°C) is 5.0°C or higher and 50.0°C or lower.

6. A method for producing a spunbond nonwoven fabric, comprising immersing the spunbond nonwoven fabric obtained by the method for producing a spunbond nonwoven fabric according to claim 1 or 2 in a chloroform / methanol solvent in a volume ratio of 1:1, and ultrasonically treating it for 15 minutes at 45 kHz and a solution temperature of 30°C, thereby extracting less than 100 ppm of organic peroxides.

7. A method for producing a spunbond nonwoven fabric according to claim 1 or 2, wherein the melt kneading is performed for 0.5 minutes or more and 30.0 minutes or less.

8. The length L of the aforementioned screw Ｃ The diameter D of the screw (mm) Ｃ Ratio L to (mm) Ｃ / D Ｃ A method for producing a spunbond nonwoven fabric according to claim 1 or 2, wherein the ratio is 15 or more and 50 or less.

9. A step of cutting the spunbond nonwoven fabric obtained by the method for manufacturing spunbond nonwoven fabric according to claim 1 or 2 to form nonwoven fabric parts, The process involves laminating and fixing the aforementioned nonwoven fabric parts and absorbent material, A method for manufacturing sanitary materials, including

10. A step of cutting the spunbond nonwoven fabric obtained by the method for manufacturing spunbond nonwoven fabric according to claim 1 or 2 to form nonwoven fabric parts, The process of fixing the nonwoven fabric part and the string part, A method for manufacturing masks, including the method described above.

11. A step of cutting the spunbond nonwoven fabric obtained by the method for manufacturing spunbond nonwoven fabric according to claim 1 or 2 to form nonwoven fabric parts, Sleeve portion including the aforementioned nonwoven fabric part, Body part including the aforementioned nonwoven fabric part, Leg portion including the aforementioned nonwoven fabric part, Head including the aforementioned nonwoven fabric part, A step of forming at least one part of, A step of joining the parts obtained by the above step together, and / or the parts obtained by the above step together with other parts, A method for manufacturing protective clothing, including

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