JPH0354156Y2 - - Google Patents

Description

[Detailed explanation of the idea]

<Industrial Application Field> The present invention relates to a nonwoven sheet that utilizes heat sealability and is used as a packaging material for bag making and filling. More specifically, it has excellent performance in terms of air permeability, water permeability, and mechanical properties, which are the characteristics of dry-processed nonwoven sheets, and its heat sealability is much better than conventional nonwoven sheets. The present invention relates to a nonwoven packaging sheet with heat sealability that can be usefully used as a packaging material. <Prior Art> Conventionally, paper, film, and paper laminated with film have been widely used as packaging materials. However, as the products to be packaged have diversified in recent years, the packaging materials used to package these products have also been required to have special functions. For example, the packaging material must have excellent heat sealability to be used in the form of a bag, be breathable or water permeable to protect the packaged product, and be strong so that the packaged product will not be damaged. There are packaging materials that are required to be flexible. To be more specific, bags for boiling green tea, bonito flakes, etc., so-called leather products such as shoes and bags, and light electrical products (cassettes, recorders, radios, etc.)
Bag-like packaging materials require the above-mentioned performance. However, the conventionally known packaging materials as described above cannot comprehensively satisfy these performances. <Problems that the invention aims to solve> For example, paper or wet non-woven sheets have traditionally been used for packaging bags for green tea, but these have too dense a structure and the components of green tea cannot be sufficiently eluted into hot water. There is a problem. As an alternative to this, it has recently been proposed to use a gauze fabric using monofilament, but this has the problem of being too coarse and causing green tea powder to spill outside. In addition, the former packaging material has poor heat-sealability, so it cannot be applied to a heating roll automatic filling machine, which is a general heat-sealing processing machine, and can only be used with a special fusing-sealing filling machine. have Alternatively, for a similar purpose, you can bag the stock of bonito flakes, dried sardines, or kelp in advance, place the bag in hot water to dissolve the stock extract, and then easily remove the stock after use. It's getting more and more. In this case, it is desirable to have a packaging material that can hold a larger amount of contents than a tie bag, and is stronger than conventional packaging materials because it does not tear when wet or dry, since force is applied in water or a hot bath. Furthermore, there is a desire for a packaging material that can be used in a similar manner for wheat tea boiled in a kettle, but no packaging material that satisfies this requirement has currently emerged. Furthermore, so-called leather products such as shoes and bags, as well as light electrical products, are packaged in the form of bags. These bag-shaped packaging materials are flexible and noble in order to prevent damage to the surface of the packaged products as much as possible, and have sufficient air permeability to maintain the quality of the packaged products during packaging and storage. There is a need for a material that is strong enough to be difficult to tear even when these packaged products having a certain weight are placed inside it, and is also inexpensive. Packaging materials that meet these requirements include dry-laid nonwoven sheets, especially spunbond nonwoven sheets. However, this dry nonwoven sheet has a problem that it cannot be provided at a low cost as a bag-shaped packaging material that satisfies the above-mentioned application fields because of its poor heat-sealability. Therefore, various methods have been proposed for imparting heat sealability to dry-laid nonwoven sheets. The first method is to laminate a perforated film onto a dry nonwoven sheet. The heat-sealing strength of the dry-laid nonwoven fabric sheet obtained by this method is generally not sufficient for practical use. Therefore, if the heat-sealing strength is increased by increasing the thickness of the film, the flexibility and air permeability of the dry-laid nonwoven sheet will deteriorate. come. The second method is to coat a dry nonwoven sheet with a hot melt resin to impart heat sealability. In this method, practically satisfactory heat sealing strength cannot be obtained unless the amount of resin is considerably increased. By increasing the amount of resin, air permeability becomes extremely low and the texture becomes hard. The third method is to use a mixed type dry-laid nonwoven sheet containing a low melting point polymer. In this case, the low melting point polymer is used to both act as an adhesive when manufacturing the nonwoven sheet and as a hot melt agent during heat-sealing, and the heat-sealability is slightly improved, but The proportion of low-melting point polymer fibers contributing to the strength of heat-sealing adhesion is considerably reduced due to the mixed weaving, and the degree of improvement in heat-sealability is not sufficient. There is also the problem of having to consider the balance between adjusting the strength, texture, etc. of the nonwoven sheet and adjusting the adhesion strength during heat sealing. It is extremely disadvantageous in terms of manufacturing, as it requires careful attention to the manufacturing process of the woven sheet. As described in detail above, it is no exaggeration to say that there is currently no packaging material that can satisfy the overall performance required for various types of boiling bags and bag-shaped packaging materials. The present invention solves the above-mentioned problems of conventionally known packaging materials, has excellent heat sealing properties, and can satisfy the overall performance of various boiling bags and bag-shaped packaging materials. The purpose is to provide woven sheets. <Means for solving the problem> The inventors of the present invention have developed a dry nonwoven sheet made of thermoplastic fibers while maintaining the excellent properties such as toughness, air permeability, and water permeability. In order to improve the heat-sealing performance of the dry-laid non-woven sheet, the dry-laid non-woven sheet is made into a two-tank structure, one layer of which is made of fibers that soften or melt easily at relatively low temperatures, and the other layer of which is made of fibers that easily soften or melt at relatively low temperatures. If a dry non-woven sheet is made from fibers that soften or melt at higher humidity, the heat-sealed area will be less likely to become transparent when the dry non-woven sheet is heat-sealed, achieving strong adhesion. As a result of intensive research, we have arrived at the present invention. That is, the object of the present invention is to provide a composite nonwoven sheet in which two types of dry nonwoven sheets are laminated and partially bonded by point bonding, in which the nonwoven sheet of one layer is made of thermoplastic material that softens or melts at a relatively low temperature. The nonwoven sheet in the other layer is made of thermoplastic fibers that soften or melt at a higher temperature than the fibers constituting the nonwoven sheet, and is characterized by having a sublimeness of 5.3 cm ³ /g or more. This is achieved by a composite nonwoven sheet for packaging that has heat sealability. The fibers forming one dry-laid nonwoven sheet of the composite nonwoven sheet according to the present invention are fibers that soften or melt at relatively low temperatures. The fiber is made from a polymer that can form fibers, and the polymer is
Olefin systems such as polyethylene and polypropylene, polyamide systems such as nylon 6, nylon 66, and nylon 610, or copolymer polyamide systems,
Various polymers can be used, such as. This dry nonwoven sheet contributes to strong adhesion during heat sealing, so depending on the purpose of use, the type of raw material,
It is formed by appropriately selecting the basis weight, etc. of the nonwoven sheet. The raw material for the other dry-laid nonwoven sheet is selected so that it softens or melts at a higher temperature than the first dry-laid nonwoven sheet. Next, the fiber types of the two types of non-woven sheets to be laminated and the basis weight of the non-woven sheets can be freely selected depending on the purpose of use. I can handle it. What is required when selecting the fibers of the two types of nonwoven sheets is that the fibers of the two types of nonwoven sheets have a difference in softening point and melting point of 30° C. or more. More preferably, there is a difference of 50°C or more. The reason for this is that if there is variation in humidity control during heat sealing, a difference of 30°C or less may affect the variation in adhesive strength due to temperature variation, and if the softening point and melting point are 30°C or more. If there is a difference, even if there is some temperature variation, it will hardly affect the heat-sealing adhesive strength and it can be processed to provide high adhesive strength. The first two types of nonwoven sheets may be made by any manufacturing method as long as they are dry nonwoven sheets. That is, it may be a non-woven sheet produced by a spunbond method or a non-woven sheet produced by a needle punch method. Further, it may be either a long fiber nonwoven sheet or a short fiber nonwoven sheet.
However, it is more preferable to use a spunbond nonwoven sheet that can be produced relatively inexpensively, has air permeability or water permeability, and is strong and flexible. Next, the two types of nonwoven sheets can be laminated and bonded together using heat, resin, and mechanical entanglement. What is important at this time is to partially adhere the two nonwoven sheets in as few areas as possible in order to maintain the feel and breathability of the nonwoven sheets as much as possible. The area ratio of the bonded area of the two types of nonwoven sheets to the total area is as follows:
5-30% is preferred. In this way, it is possible to impart adhesive strength sufficient to withstand heat sealing. Various methods can be used for bonding. For example, when the embossing is performed between a pair of rolls, the embossing roll is passed between an embossing roll with a dotted or linear convex pattern and a roll with a smooth surface. The roll temperature at this time is higher than the softening point of the lower fiber and lower than the melting point. Adhesion may be performed using ultrasonic waves, high frequencies, or the like. In this case, a large number of generator heads are arranged,
By passing the nonwoven sheet between the lower rotating rolls, which are paired with dotted or linear protrusions, the nonwoven sheet is compressed by the roll protrusions and the oscillation head. Bonding is performed by generating heat. Further, when adhesion is performed using a resin, it is preferable to use a hot melt adhesive. As for the method of applying the adhesive, it is preferable to apply it in dots using a dot method. Alternatively, two nonwoven sheets may be partially bonded together by mechanical interlacing using needle punching. When the composite nonwoven sheet according to the present invention is used for packaging and heat sealed, the heat during the heat sealing process causes the fibers in the dry nonwoven sheet made of two types of thermoplastic fibers to deform and melt, causing the fibers to interact with each other. Glue to. That is, when fibers with a low softening point or a low melting point are heated to their melting point, the fibers melt, and a molten substance collects at the junction of the fibers with a high softening point or a high melting point, bonding the fibers together. Cooling solidifies the melt, resulting in the formation of a stable bond and excellent heat sealing. By using two types of dry non-woven sheets made of thermoplastic fibers with a softening point or melting point difference of 30°C or more, a strong heat-sealed bond can be obtained without the heat-sealed part becoming transparent. Incidentally, non-woven sheets made by mixing (mixing, laminating) thermoplastic fibers and non-thermoplastic fibers are known, but when these non-woven sheets are heat-sealed, the adhesion is caused by the melted part of the thermoplastic fibers being non-thermoplastic. Non-thermoplastic fibers do not soften or melt even when heated, so their adhesion is weak. must be interposed with adhesive. An example of the structure of the composite nonwoven sheet of the present invention thus obtained is shown in FIGS. 1 and 2. As shown in FIG. 1, the composite nonwoven sheet 11 of the present invention consists of a portion 12 where two nonwoven sheets are not bonded together, and a portion 13 where the two nonwoven sheets are partially bonded in dots by heat or resin. Looking at this in FIG. 2, which is a cross-sectional view of the composite nonwoven sheet shown in FIG. 1, the composite nonwoven sheet 1
4 is a nonwoven sheet 15 made of fibers with a lower softening point or melting point, and a nonwoven sheet 16 made of fibers with a higher softening point or melting point than the fibers of the previous nonwoven sheet 15.
are laminated, and nonwoven sheets 15 and nonwoven sheets 16 are bonded at a plurality of positions indicated by 17. FIG. 3 shows a schematic diagram when the composite nonwoven sheet according to the present invention is used as a packaging material. A composite nonwoven sheet 18 in which a nonwoven sheet 20 made of fibers with a lower softening point or melting point is partially adhered in a dotted manner to a nonwoven sheet 19 made of fibers with a higher softening point or melting point. Two sheets are prepared and stacked one on top of the other with the respective nonwoven sheets 20 facing inside.
Since the nonwoven sheets 20 made of fibers with lower softening or melting points are in contact with each other, the ends 21
By heat sealing, the ends of the two composite nonwoven sheets can be easily and reliably integrated. Therefore, a bag for brewing can be made by placing the object to be packaged 22, for example, green tea, inside two composite nonwoven sheets and heat sealing the entire outer periphery. If it is heat-sealed, it can be made into bag-shaped packaging materials for so-called leather products and light electrical products. The composite nonwoven sheet according to the present invention may be used by selecting the type of fiber, the type of nonwoven sheet, the basis weight, etc., depending on the purpose. Note that the basis weight of each nonwoven sheet to be laminated is preferably 10 to 100 g/m ² , but is not particularly limited. As detailed above, since the composite nonwoven sheet according to the present invention is composed of two types of dry nonwoven sheets,
It has a thickness that cannot be obtained with non-woven sheets made with low melting point fibers as a binder, has excellent flexibility and sublime properties, and has extremely high air permeability and water permeability, as well as excellent performance in preventing powder leakage. . Therefore, the composite nonwoven sheet of the present invention can be used to make bags for boiling green tea, bonito flakes, etc., deodorant bags, desiccant bags,
It is usefully used for bags for brewing green tea, bonito flakes, etc., so-called leather products such as shoes and bags, and bag-shaped packaging materials for light electrical appliances. Furthermore, since it has excellent heat-sealability, it can be widely used as a packaging material for everyday materials such as cushion inner bags, bedding and blanket packaging, confectionery packaging, and shopping bags. Furthermore, since the composite nonwoven sheet of the present invention has excellent heat-sealing properties, it can be used to manufacture bags or fill products to be packaged using an automatic bag making machine or an automatic filling machine. <Examples> Hereinafter, the present invention will be specifically explained by giving examples. The definitions and measurement methods of the characteristics described in Examples are shown below. - Fabric weight: Take a 20cm x 20cm sample and convert the weight to the fabric weight.・Tensile strength and elongation: Take a sample of 3 cm x 20 cm both vertically and horizontally, using a constant speed extension type tensile tester (Shimadzu Autograph DSS-2000 model universal tensile tester)
Measurements were made using a grasping length of 10 cm and a pulling speed of 20 cm/min. - Heat seal adhesive strength: Shown as the maximum value measured in the same manner as the above tensile strength and elongation at a grip length of 5 cm and a tensile speed of 20 cm/min. (After boiling for 5 minutes when wet) - Air permeability: Conforms to JIS-L-1096 A method.・Water permeability: According to JIS-A-1218 (soil permeability test method). Water permeability (/m ² /sec) = Q ^/ (S The volume per unit weight is determined from the thickness value and expressed. - Powder retention: Put 10g of Japanese seasoning manufactured by Shimaya Co., Ltd. into an 8cm x 10cm pouch, boil in 500cc of boiling water for 5 minutes, and judge by powder leakage. ○...There is almost no powder. △...There is some powder, but it is not noticeable. ×...A lot of powder is noticeable. Examples 1 to 3, Comparative Examples 4 to 6 In Examples 1 to 3, polypropylene spunbond, nylon 6 spunbond, and polyester spunbond long fiber nonwoven sheets were prepared by melt-spinning by a known method. . As shown in Table 1, in Examples 1 and 2, polypropylene spunbond was selected for the low melting point layer and polyester spunbond was selected for the high melting point layer (melting point difference of about 90°C) as two types of configurations.
In Example 3, polypropylene spunbond was selected for the low melting point layer and nylon 6 spunbond (melting point difference of about 50°C) was selected for the high melting point layer. These selected nonwoven sheets were bonded together by thermocompression bonding. The composite nonwoven sheet of the present invention was obtained by passing it between an embossing roll with a circular convex shape of 1.0 mmφ and a pressure bonding area ratio of 8% and a roll with a smooth surface and partially adhering it. On the other hand, in Comparative Examples 4 and 5, polyethylene film was laminated onto paper and wet-laid nonwoven sheets. In Comparative Example 6, the performance of each ester spunbond made of a blend of low melting point fibers as a binder was compared. The results are shown in Table-1. Examples 1 to 3 are thick and sublime, and have very high heat seal adhesive strength. As a result, a strong composite nonwoven sheet with high air permeability and water permeability, good powder retention, and strength could be obtained. On the other hand, Comparative Examples 4 and 5 have heat-sealing properties, but have no air permeability and are not thick, and Examples 1 to 5 have heat sealability.
It had a harder texture than No. 3, and was not the object of the present invention. Furthermore, Comparative Example 6 showed good heat-sealability, air permeability, and tough physical properties, but the thickness was small and the quality was poor, the texture was hard, and there were many micro holes, so the powder retention was poor. It was. As mentioned above, Comparative Examples 4 to 6 could not satisfy the performance aimed at by the present invention.

[Table] Example 7 Two nonwoven sheets of the same type as in Example 1 were stacked and pasted together by passing between rolls having 30 protrusions/cm ² with a diameter of 1.0 mm on the head that oscillates ultrasonic waves. Ta. Two of the resulting composite nonwoven sheets were heat-sealed using two sheets with the polypropylene spunbond placed on the inside. (The processing conditions were the same as in the previous example.) The heat seal adhesive strength was 3.8
Kg/3cm was obtained. A sachet was made from this, and 10g of Japanese seasoning made by Shimaya Co., Ltd. (8cm x 10cm sachet) was boiled in 500cc of boiling water for 5 minutes. Good results were obtained, with sufficient dashi and no powder leakage. Comparative Example-8 Using the sample of Comparative Example-6, a sachet was made in the same manner as in Example-7, and 10 g of Japanese seasoning was put inside and boiled in boiling water for 5 minutes. However, the seasoning powder leaked and the results were not satisfactory. <Effects of the invention> Since the composite nonwoven sheet according to the invention is configured as described above, it has excellent heat-sealability, sublime properties, good air permeability, water permeability, and good powder retention. In addition, since it is made only from dry-laid non-woven sheets, it has a soft texture, unlike when laminated with films, and because it is made from two types of dry-laid non-woven sheets made of thermoplastic fibers, it is strong and has great elongation. It is hard and strong. Therefore, it can be used in a wide range of applications as a packaging material for various kinds of boiling bags and bag-shaped packaging materials.

[Brief explanation of drawings]

Fig. 1 is a plan view showing an embodiment of the composite nonwoven sheet according to the present invention, Fig. 2 is a plan view of the composite nonwoven sheet shown in Fig. 1, and Fig. 3 is a plan view showing an embodiment of the composite nonwoven sheet according to the present invention. FIG. 2 is a cross-sectional view showing an example of a package made by heat sealing using two composite nonwoven sheets. 11, 14, 18... Composite nonwoven sheet, 12...
...Non-adhesive part, 13, 17...Adhesive part, 15, 20
...Nonwoven sheet made of fibers with a low softening point and melting point, 16,19...Nonwoven sheet made of fibers with a high softening point and melting point, 21...Heat-sealed part, 22...Packaged object .

Claims (1)

[Scope of utility model registration request] In a composite nonwoven sheet in which two types of dry nonwoven sheets are laminated and partially bonded at points,
The nonwoven sheet of one layer is made of thermoplastic fibers that soften or melt at a relatively low temperature, and the nonwoven sheet of the other layer is made of thermoplastic fibers that soften or melt at a higher temperature than the fibers that make up the nonwoven sheet. 5.3
A composite nonwoven sheet for packaging with heat sealability, characterized by having bulkiness of cm ³ /g or more.