JP2008307469A - Filter for food product and food product-enclosing bag using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filter for food products excellent in powder leakage property, thermal seal processibility, seal strength, and toughness. <P>SOLUTION: The filter for food products is made of a laminated nonwoven fabric obtained by layering a first layer, a polyester type fiber layer; a second layer, a polyester type ultrathin fiber layer; and a third layer, a layer containing polyester type fibers having a melting point lower than the fibers composing the first layer by 30°C or more and uniting the layers by thermal pressure bonding and the laminated nonwoven fabric has weight per unit surface area (Metsuke) of 10 to 50 g/m<SP>2</SP>and hot-tack strength 1 N/25 mm or higher in a thermal sealing temperature range. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a food filter, and is particularly used for beverage extraction and soup extraction, has less powder leakage, has a wide heat seal temperature range, and has high hot tack and seal strength, and has a low melting point resin stain. The present invention relates to a food filter and a bag body that are excellent in bag-making processing, such as no sticking out and no adhesion of resin to a seal bar, and that have good shape retention and component extraction.

Thermoplastic synthetic fiber non-woven fabrics are widely used for extracting components of foods such as green tea, black tea, barley tea, oolong tea, regular coffee, koji soup and koji soup. Patent Document 1 proposes a specific polypropylene-based nonwoven fabric as a food extraction sheet, and Patent Documents 2 to 4 propose a nonwoven fabric using heat-adhesive conjugate fibers as a food extraction sheet.
The food extraction sheets described in these patent documents are excellent in heat sealability, dissolution property, taste, etc., but on the other hand, there are problems such as generation of fine particles, powder leakage, etc. .

Patent Documents 5 to 7 disclose the use of an ultrafine fiber nonwoven fabric obtained from a melt-blowing method, and proposes to solve the problem of powder leakage. However, a product that comprehensively satisfies the powder leakage property, the heat seal property, and the component extractability has not been obtained.
JP 2003-138460 A JP 2006-81777 A JP 2006-81779 A JP 2006-83496 A JP 2002-14299 A Japanese Patent Publication No. 60-11148 JP 2004-154760 A

  The object of the present invention is to solve the above-mentioned conventional problems, and it is difficult for powder to leak even in a powdery product or a fine particulate matter, and a food filter excellent in hot tack property, heat sealability, and component extractability and It is to provide the bag.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have conducted a combination of melting point difference of constituent fibers and difference in fiber diameter, and thereby, powder leakage property, hot tack property, heat seal property, and component extractability Has been found to be effective, and the present invention has been achieved. The invention claimed in the present application is as follows.
(1) A layer containing a polyester fiber having a melting point of 30 ° C. or more lower than the melting point of the constituent fibers of the first layer as a third layer, a polyester fiber layer of the first layer, a polyester extra fine fiber layer of the second layer , A laminated nonwoven fabric integrated by thermocompression bonding, wherein the laminated nonwoven fabric has a basis weight of 10 to 50 g / m ² and a hot tack strength of 1 N / 25 mm or more. Filter.
(2) The food according to (1) above, wherein an average fiber diameter of fibers constituting the first layer and the third layer is 10 to 30 μm, and an average fiber diameter of the second layer is 1 to 7 μm. Filter.
(3) The said (1) or (2) characterized by including the fiber whose melting | fusing point of the fiber which comprises the said 3rd layer is 30-150 degreeC lower melting | fusing point than the melting | fusing point of the fiber which comprises a 1st layer Filter for food as described in 4.
(4) The thermoplastic fiber of the third layer is a sheath-core type composite fiber, the core part is a high melting point component, and the sheath part component is 30 ° C. or more lower melting point than the core part. The food filter according to any one of (1) to (3) above.
(5) The content of the ultrafine fiber in the second layer is in the range of 10 to 35% by weight, and the basis weight of the ultrafine fiber layer in the second layer is 1.0 g / m ² or more ( The food filter according to any one of 1) to (4).
(6) The food filter as described in any one of (1) to (5) above, wherein the content of the low melting point fiber in the third layer is 20% by weight or more.
(7) The food filter according to any one of (1) to (6) above is overlapped with the third layer inside, heat sealed to form a bag, and extracted into the bag A food-enclosed bag body filled with a product and sealed.
(8) The food-enclosed bag according to (7), wherein the extract is selected from coffee powder, tea leaves, and soup stock.

The food filter and the bag of the present invention are obtained by laminating a polyester fiber layer as a first layer, a polyester fiber layer containing a low melting point component as a third layer, and an ultrafine fiber layer as a second layer. Further, since the gap between the relatively thick fiber layers is covered with and / or laminated in the form of a film with an ultrafine fiber layer, the gap between the constituent fibers and the maximum pore diameter can be reduced, so that the leakage of fine particles can be prevented. Furthermore, by providing a difference in melting point between the first layer and the third layer and providing an ultrafine fiber layer, the low melting point resin does not bleed out, the adhesion of the resin to the seal bar is small and wide at the time of bag making processing, and wide Heat sealing can be performed in a temperature range, for example, 120 to 180 ° C., and a filter excellent in sealing strength and hot tack property can be obtained.
Therefore, the food filter and its bag according to the present invention are preferably used for tea, black tea, green tea, soup stock, boiled and dried soup, kelp, and other packaging materials.

  In the laminated nonwoven fabric forming the food filter of the present invention, the first layer is a polyester fiber having a high melting point component, the second layer is an ultrafine fiber, and the third layer is a polyester fiber having a melting point lower than the melting point of the first layer fiber. It has a structure where laminated fibers are laminated and integrated by thermocompression bonding.

  In particular, the present invention has a laminated structure in which the second layer of ultrafine fibers is interposed, firstly, the fiber gap can be reduced, and secondly, the interlayer bonding can be strengthened by partial thermocompression bonding. Thirdly, by providing a difference in melting point between the first layer and the third layer and interposing an ultrafine fiber layer, it is possible to prevent the low melting point resin from leaking out, and the heat sealing strength and temperature range can be widened. It is done.

  The small fiber gap, which is the first feature, is because the second layer of ultrafine fibers are coated and / or mixed into a relatively large fiber gap layer of the high melting point polyester fiber of the first layer and laminated. Furthermore, by making the lamination multi-layered, the fiber gap is further reduced, and a structure in which fine powder or the like is difficult to leak is obtained.

  According to the partial thermocompression bonding of the second feature, it is possible to set the pressure bonding temperature according to the melting point difference between the layers of the constituent fibers, and to strengthen the bonding between the layers, so that the rigidity and the peeling strength between the layers can be increased. .

  According to the heat sealing property of the third feature, since it has a laminated structure of polyester fibers having a melting point difference, the temperature range that can be heat sealed can be widened, hot tack strength and heat sealing strength are excellent, and at the time of heat sealing The adhesion of the molten resin to the hot plate can be reduced. In particular, since the melting point difference between the first layer and the third layer is provided, even when the low melting point polyester-based resin is melted during bag making, the ultrafine fiber layer and the high melting point fiber layer are not melted. It is possible to prevent the molten layer from seeping out of the resin, and the low melting point resin does not adhere to the seal bar, thereby enabling production and production with stable heat seal strength.

  The high-melting polyester fiber layer of the first layer used in the present invention is usually composed of thick fibers having a fiber diameter of 10 to 30 μm, preferably 12 to 25 μm, and has excellent strength and air permeability and high wear strength. preferable. Examples of such constituent fibers include polyester fibers such as polyethylene terephthalate, polybutylene terephthalate, and copolyester.

  The fiber layer containing the low melting point component of the third layer used in the present invention contains fibers having a low melting point of 30 ° C. or higher, preferably 30 to 150 ° C., that is, the heat sealing surface of the bag body. It becomes. The fiber diameter of the low melting point fiber is 10 to 30 μm, preferably 12 to 25 μm. As the constituent fibers, for example, an aromatic polyester copolymer obtained by copolymerizing polyethylene terephthalate with one or more compounds of phthalic acid, isophthalic acid, sebacic acid, adipic acid, diethylene glycol, 1,4-butanediol, Polyester fibers such as aliphatic polyester are used. Furthermore, a composite fiber composed of two components such as a core-sheath structure and side-by-side, for example, a composite fiber having a high melting point and a low melting point, specifically, polyethylene terephthalate, polybutylene terephthalate, copolymer polyester, etc. The high melting point fiber and the sheath are preferably low melting point fibers such as copolymer polyester and aliphatic polyester. In particular, these low melting point fibers exhibit excellent hot tack properties.

  In the food filter of the present invention, it is important that the fibers of the first layer and the third layer have a melting point difference. However, the melting point difference of the fibers constituting the third layer is preferably 30 ° C. or more, more preferably The temperature is preferably lower than that of the first layer in the range of 30 to 150 ° C. As a result, the roll temperature range during partial thermocompression bonding can be set wide. If the difference in the thermocompression roll temperature is too large, the low-melt fiber tends to deteriorate due to the influence of the roll temperature on the high melting point side. On the other hand, when the difference in melting point between the first layer and the third layer is too small, the thermocompression bonding temperature range is narrowed, and the strength and friction fluff strength are easily affected by the roll temperature conditions.

  The fiber diameter of the second layer ultrafine fiber of the present invention is preferably 7 μm or less, more preferably 1 to 5 μm, and has the role of reducing the fiber gap and the maximum opening diameter to reduce powder leakage. In particular, by laminating the fine fiber gaps so that the fine fibers are covered, the fiber gaps can be reduced with a small fine fiber ratio. If the fiber diameter is too large, the effect of covering the fiber gap is reduced.

Mass per unit area of the ultrafine fibers is preferably from 1 g / m ² or more, more preferably 1.5~10g / m ^2, more preferably from 2~7g / m ^2. If the basis weight of the ultrafine fibers is too small, the coverage of the interstices of the ultrafine fiber layer and the film formation are deteriorated.

  The content ratio of the ultrafine fibers of the second layer with respect to the entire laminated nonwoven fabric is usually 5 to 30% by weight, preferably 7 to 25% by weight. Examples of the ultrafine fiber include polyester fibers such as polyethylene terephthalate, polybutylene terephthalate, copolymerized polyester, and aliphatic polyester.

  The integration of the food filter of the present invention by thermocompression bonding means, for example, heating and pressure bonding between a known embossing roll and a smooth roll to join them. The heating temperature is a temperature range from the temperature above the softening temperature of the fiber to below the melting point. However, in consideration of thermal degradation of the low melting point fiber, the temperature difference between the upper and lower rolls is preferably 150 ° C. or less, preferably 130 ° C. or less. The pressure for thermocompression bonding is 10 to 1000 kPa / cm, preferably 50 to 700 kPa / cm.

  The area ratio of the thermocompression bonding of the laminated nonwoven fabric of the present invention is preferably 5 to 30%, more preferably 7 to 25%. If the pressure-bonding area ratio is too small, the bonding area decreases and the wear strength decreases. On the other hand, if it is too large, the wear strength increases, but the texture becomes paper-like.

  The bag-making process using the food filter of the present invention is performed by stacking the laminated nonwoven fabric with the third layer of the laminated nonwoven fabric on the inside, and sealing the end with a known sealing method as a heat seal. Is called. For example, it can be performed by a heat sealing method such as a three-pack sealing machine or a four-pack sealing machine, or an ultrasonic sealing method such as an ultrasonic sealing machine. Furthermore, it is possible to form a bag into two or more continuous continuous bags.

  The bag body of the present invention requires high sealing strength because, for example, the filling material filled in the bag does not drop or the bag is not broken when a heavy object is placed thereon. Accordingly, the sealing strength of the bag body is 1 N / 25 mm or more, preferably 1.5 N / 25 mm or more, more preferably 10 to 50 N / 25 mm. If the seal strength is too small, the seal portion is easily peeled off, causing problems such as leakage of contents to the outside.

  Furthermore, in order to carry out the bag forming process stably, it must have adhesive strength at the temperature immediately after heat sealing, that is, it has hot tack property, and the seal portion immediately after bag making may be bitten by a filler or torn. It is preferable because it does not occur and can be processed into a bag.

  The food filter of the present invention is characterized by excellent hot tack and a wide sealing temperature range. The hot tack strength is 1 N / 25 mm or more, preferably 5 N to 20 N / 25 mm.

  The heat seal temperature range of the present invention is preferably 120 to 220 ° C., more preferably 140 to 200 ° C. by providing a melting point difference between the first layer and third layer fibers. As shown in Table 2 of the present specification, even when the heat seal temperature is within this range, the heat seal strength is uniform, variation is small, and stable heat seal strength is obtained. In the examples of the present invention, the heat seal strength variation (R) is 3 N / 25 mm or less in the heat seal temperature range of 125 to 220 ° C.

As shown in Table 3 of the present specification, the suitable temperature range of the heat seal temperature is conventionally about 10 ° C., whereas in the present invention, the temperature range of the heat seal temperature is 110 to 200 ° C. (about 90 ° C. In this temperature range, the hot tack strength is stable, and a particularly stable hot tack strength is obtained when the heat seal temperature is 120 to 180 ° C.
Therefore, even when the surface temperature of the seal portion of the heat sealing machine changes due to changes with time, environment, etc., and it is difficult to perform heat sealing at a constant temperature, stable production with a constant seal strength can be achieved.

  The food filter of the present invention can have a wide sealing temperature range, and can obtain hot tackiness and high and stable sealing strength. This is because the difference between the melting points of the first layer and the third layer is 30 ° C. or more, so that even if the fibers of the low melting point are softened or melted, the ultrafine fiber layer and the high melting point fiber layer are in a predetermined state. This is because the fiber shape is maintained. Accordingly, the melted fiber does not adhere to the seal bar during bag making.

In the present invention, the food filter and its bag body can reduce fine particle powder leakage, and the powder leakage rate is preferably 5% or less, more preferably 3% or less, particularly preferably 2% or less, High sealing strength, excellent rigidity and component extractability. The basis weight of the filter material is 10 to 50 g / m ² , preferably 12 to 40 g / m ² . If the basis weight is too small, it is easy for powder to leak, and the seal strength, rigidity, etc. are reduced. On the other hand, if it is too large, powder leakage will be difficult and seal strength and rigidity will be increased, but the component extractability will be reduced.

  In the present invention, the maximum opening diameter of the food filter is 50 μm or less, preferably 40 μm or less, more preferably 1 to 30 μm. When the maximum opening diameter is too large, the fiber gap is large, so that powder leakage is likely to occur, and particularly when the granular material is finely broken, powder leakage is likely to occur.

  The extract to be filled in the bag of the present invention is not particularly limited as long as it is a solid such as a powder shape or a granular sheet. For example, tea leaves such as green tea, oolong tea, barley tea, black tea, etc. for liquor drinks, regular coffee fine ground, medium ground, coarse ground powder, etc. Such mixed powders.

The present invention will be described based on examples.
The measurement method is as follows.
(1) Weight per unit area (g / m ² ): A sample of 20 cm in length × 25 cm in width is cut out at three places, the weight is measured, and the average value is calculated by converting to mass per unit. (JIS-L-1906)
(2) Average fiber diameter (μm): Take a 500 times magnified photograph with a microscope, and obtain the average value of 10 fibers.
(3) Breathability: Conforms to JIS-L-1906 Frajour method.
(4) Powder leakage rate (%): About 10g of 7 kinds of dust for JIS-Z-8901 test, measure the weight W1 accurately, cut a 25cm square sample, attach it to the vibrator, and vibrate for 10 minutes The dust weight W2 that the sample has passed through is measured and obtained from the following formula.
Powder leakage rate (wt%) = W2 / W1 x100
(5) Average flow pore size (μm): A palm porometer model CFP-1200AEX manufactured by PMI is used. The average flow hole diameter is DIAMETER with a CUMULATIVE FILTER FLOW value of 50% in the CUMULATIVE FILTER FLOW VS DIAMETER graph. For the measurement, Pyr Sylwick was used as the immersion liquid. The sample is immersed in the immersion liquid and thoroughly deaerated before measurement.
(6) Seal strength (N): Using a constant-length tensile tester, cut a sample width of 25 mm and a length of 200 mm, peel the heat seal part up and down about 50 mm, and attach each so that it peels 180 degrees. The peel strength was measured at 3 points each at a tensile rate of 10 cm / min and indicated by the average value of the maximum strength.
However, the seal temperature was 150 ° C., the time was 1 second, the pressure was 5500 kPa, the seal area was 25 mm × 25 mm (measured after being immersed in boiling liquid for 10 minutes as a hot water treatment).
(7) Hot tack strength (N / 25mm)
Cut a sample with a width of 25 mm and a length of 400 mm, and heat seal it with a hot tack tester (Theller Model HT) from HWThellsr Inc at a die seal area of 0.25 cm ² , a seal pressure of 5000 kPa, and a seal measurement time of 500 msec. The instantaneous peel strength was measured.

[Example 1]
The third layer of the laminated nonwoven fabric of the present invention is an average fiber having a core-sheath structure in which a core is polyethylene terephthalate (PET) and a sheath is a copolymer polyester (Co-PET, melting point 210 ° C.) from a two-component spinneret for spunbond. A composite fiber web with a diameter of 17 μm and a basis weight of 6 g / m ² was prepared. Using a second layer of polyethylene terephthalate (PET, solution viscosity ηsp / c 0.50), a spinning temperature of 300 ° C. and heating air at 320 ° C. At 1000 Nm ³ / hr, an ultrafine fiber web with an average fine diameter of 2 μm and a basis weight of 3 g / m ² is ejected and laminated, and a general polyethylene terephthalate (PET) of the first layer is spun onto the spunbond spinneret. A thermoplastic fiber web having an average fiber diameter of 14 μm and a basis weight of 6 g / m ^{2 at} a spinning temperature of 300 ° C. is laminated as a laminated fiber web on a collection net, and further has a crimp area ratio of 25% embossed roll, linear pressure 350 N / cm, Thermocompression bonding at a vertical temperature of 230 ° C / 145 ° C The food filter of Example 1 (weighing 15 g / m ² ) was obtained.

[Example 2]
The third layer of the filter material of the present invention is an average fiber having a core-sheath structure in which a core is polyethylene terephthalate (PET) and a sheath is a copolyester (Co-PET, melting point 160 ° C.) from a two-component spinneret for spunbond. A composite fiber web with a diameter of 18 μm and a basis weight of 16 g / m ² was prepared. Using a second layer of polyethylene terephthalate (PET, solution viscosity ηsp / c 0.50), a spinning temperature of 300 ° C. and heating air at 320 ° C. At 1000 Nm ³ / hr, an ultrafine fiber web with an average fine diameter of 2 μm and a basis weight of 2 g / m ² is ejected and laminated, and a general polyethylene terephthalate (PET) of the first layer is spun onto the spunbond spinneret. average at a spinning temperature of 300 ° C. fiber diameter 14 [mu] m, by laminating a basis weight 12 g / m ² amount varying thermoplastic fiber webs as the laminated fiber web on the collecting net, further crimping area ratio, 25% embossing roll linear pressure 350N / Cm, the vertical temperature is 230 ℃ / 115 ℃ To obtain a food filter of Example 1 (basis weight 30 g / m ²⁾ by thermal compression bonding.

[Example 3]
The third layer of the filter material of the present invention is an average fiber having a core-sheath structure in which a core is polyethylene terephthalate (PET) and a sheath is a copolymer polyester (Co-PET, melting point 135 ° C.) from a two-component spinneret for spunbond. A composite fiber web having a diameter of 18 μm and a basis weight of 17 g / m ² was prepared. Using a second layer of polyethylene terephthalate (PET, solution viscosity ηsp / c 0.50), a spinning temperature of 300 ° C. and heating air at 320 ° C. in 1000 nm ³ / hr, the average fiber diameter 2 [mu] m, are laminated by ejecting the ultra fine fiber web basis weight 6 g / m ^2, average fiber diameter of the copolyester of the first layer (Co-PET, melting point 210 ° C.) thereon 15μm from the spinneret for spun bond the average fiber diameter 15μm at a spinning temperature of 260 ° C., by laminating a basis weight 17 g / m ² amount varying thermoplastic fiber webs as the laminated fiber web on the collecting net, further crimping area ratio , 25% embossed roll, linear pressure 350N / cm, vertical temperature To obtain a food filters of Example 1 and thermo-compression bonding (basis weight 40 g / m ²⁾ at 230 ℃ / 115 ℃.

The food filter of the first to third embodiments of the present invention has excellent hot tack property and heat sealability in a wide temperature range, no adhesion of resin on the heat seal bar, and low filterability such as powder leakage. Excellent performance was obtained.
The results of Examples 1 to 3 are shown in Tables 1 to 3.

[Comparative Example 1]
Using general polyethylene terephthalate (PET), a thermoplastic fiber web having an average fiber diameter of 14 μm and a basis weight of 30 g / m ² at a spinning temperature of 300 ° C. was prepared on a collection net by the same spunbond method as in Example 1. A nonwoven fabric was obtained by thermocompression bonding with an embossing roll having a crimping area ratio of 15%, a linear pressure of 350 N / cm, and an upper and lower temperature of 230 ° C / 235 ° C. As shown in Table 1, the obtained filter had greatly reduced powder leakage and was inferior in filter performance.

[Comparative Example 2]
As the thermoplastic fiber web, a composite fiber web with an average fiber diameter of 16 μm and a basis weight of 30 g / m ² is collected for the spunbond composite fiber whose core is polyethylene terephthalate (PET) and whose sheath is high-density polyethylene (PE). A nonwoven fabric (30 g / m ² ) was obtained by thermocompression bonding with an embossing roll having a pressure bonding area ratio of 25%, a gland pressure of 350 N / cm, and a vertical temperature of 120 ° C./110° C.
As shown in Table 1, the obtained filter has a hot tack property in which the powder leakage property is greatly reduced and the heat seal temperature range is narrow, the heat seal strength is high, but the low melting point fiber resin oozes out, and the seal bar The filter performance was inferior, such as adhering to the fusion resin.

[Example 4] (Coffee filter)
Using a tetrahedral three-dimensional heat sealing machine, slit the food filter of Example 3 into a tape with a width of 150 mm, and then bond the 760 dtex polypropylene yarn and the tag at a temperature of 180 ° C. Fold 150mm, use an ultrasonic horn with a seal width of 3mm at the end, and first ultrasonically seal the bottom of the cylinder at intervals of 70mm to form a bag, then place it in the bag regularly. 10g of fine ground coffee powder was added, and the bag opening was similarly ultrasonically sealed in a direction perpendicular to the bottom every 70mm length to obtain a tetrahedral coffee tetrapack with a side of 70mm ( Seal strength 18N / 25mm).

  The coffee tetra pack of the present invention has a rigidity capable of holding the shape and was able to hold the shape well even when extracted with a mug. About 150 cc of hot water was poured into a commercially available mug, and the obtained coffee tetra pack of the present invention was put in. The components were extracted for about 60 seconds, and then the tetra pack was taken out. When I drank coffee, I was able to drink fragrant and delicious coffee. Little powder remained at the bottom of the cup.

[Example 5] (Dashi bag)
The filter material of Example 1 was slit into a tape having a width of 220 mm. A three-sided heat sealer was used to fold the filter material in half. To. After that, the bottom of the tube is heat-sealed over a width of 10 mm at intervals of 140 mm to form a bag shape, and then 20 g of dashi powder containing cocoons, rice cakes, boiled raisins, rice cakes, and the like as components. After that, the upper part of the bag was heat-sealed over a width of 10 mm to obtain a dashi bag sealed in three directions of 140 mm in length and 110 mm in width.
About 700 cc of water was poured into a pan containing the bag of the present invention, soaked for 15 to 30 minutes, boiled as it was, extracted components, and then the bag was taken out. When I drank this dashi soup, there was a flavor and I was able to drink delicious dashi soup. Almost no dashi powder remained at the bottom of the pan (initial seal strength 8 N / 25 mm, seal strength after extraction 7 N / 25 mm).

  The food filter material of the present invention and the bag body thereof are excellent in powder leakage, heat seal processability, seal strength, rigidity, etc., and thus have wide applications as packaging materials for extracts such as powder and granular materials, for example, It can be preferably used for extraction of ingredients for beverages and for soup stock.

Claims (8)

A polyester-based fiber layer of the first layer, a polyester-based ultrafine fiber layer of the second layer, and a layer containing polyester-based fibers having a melting point of 30 ° C. or more lower than the melting point of the constituent fibers of the first layer as the third layer; A food filter comprising a laminated nonwoven fabric laminated and integrated by thermocompression bonding, wherein the laminated nonwoven fabric has a basis weight of 10 to 50 g / m ² and a hot tack strength of 1 N / 25 mm or more.   2. The food filter according to claim 1, wherein an average fiber diameter of fibers constituting the first layer and the third layer is 10 to 30 μm, and an average fiber diameter of the second layer is 1 to 7 μm.   The food filter according to claim 1 or 2, comprising a fiber having a melting point of 30 to 150 ° C lower than a melting point of the fiber constituting the first layer. .   The thermoplastic fiber of the third layer is a sheath-core type composite fiber, the core part is a high melting point component, and the sheath part component has a low melting point of 30 ° C or more from the core part. The filter for foodstuffs in any one of 1-3. The content of the ultrafine fiber in the second layer is in the range of 10 to 35% by weight, and the basis weight of the ultrafine fiber layer in the second layer is 1.0 g / m ² or more. The filter for foodstuffs in any one of.   The food filter according to any one of claims 1 to 5, wherein the content of the low melting point fiber in the third layer is 20% by weight or more.   The food filter according to any one of claims 1 to 6, wherein the third layer is overlapped and heat-sealed to form a bag, the bag is filled with an extract, and sealed A food encapsulating bag characterized by the above.     8. The food-enclosed bag according to claim 7, wherein the extract is selected from coffee powder, tea leaves, and soup powder.