JPH0515546B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention absorbs or exhausts water vapor generated by foods such as leafy vegetables (spinach, broccoli, etc.), fruits (pears, etc.), mushrooms (enoki mushrooms, etc.), and thereby maintains the freshness of foods. Concerning possible sheets. Traditionally, low-temperature storage methods and gas-controlled storage methods have been used to maintain the freshness of leafy vegetables, fruits, and mushrooms (hereinafter collectively referred to as "fruits and vegetables"), and depending on the type, they can be very effective. giving. However, in reality, there are many types of fruits and vegetables, and each type has different properties, so it is often difficult to obtain sufficient effects. For example, for items that breathe very rapidly and cause a large amount of water transpiration, the gas may be controlled using polyethylene film packaging to suppress the amount of respiration, but in such cases the humidity inside the packaging is 100% (relative humidity). ), resulting in condensed water adhering to the fruits and vegetables themselves and the inside of the packaging. This condensed water serves as a breeding ground for microorganisms and contaminates fruits and vegetables. Furthermore, if there is a large amount of condensed water, the fruit or vegetables cannot breathe in that area, and as a result of anaerobic respiration, phenomena such as physiological softening and discoloration occur that impair quality. On the other hand, phenomena such as withering and discoloration caused by too little moisture are also great enemies of fruits and vegetables. In other words, since fruits and vegetables continue to live after harvest, it is inconvenient to have too much or too little moisture, so it is important to adjust the moisture appropriately. Up until now, the applicant has been using a sheet made by coating a water-impermeable sheet with water-absorbing resin powder and adhesive and pasting paper on it to prevent fruits and vegetables from withering and wilting. provides a method. However, although this sheet has a very good ability to absorb liquid water, it has a low ability to absorb water vapor. As mentioned above, condensation on the surface of fruits and vegetables can cause various problems such as anaerobic respiration, so it is not enough to simply absorb the water condensed on the sheet, and to this day, it has not been effective in keeping fruits and vegetables sufficiently fresh. In many cases, it was not. Therefore, it is important to adjust the humidity of the atmosphere rather than adjusting the moisture content of fruits and vegetables. The present invention solves all of the above-mentioned problems and provides a water vapor regulating sheet that has the function of absorbing and exhausting water vapor, which has been impossible until now. The present invention will be explained in detail below. The present invention is a laminated sheet characterized in that, as shown in FIG. 1, a water/hygroscopic resin layer 3 is provided between a highly hygroscopic resin film 1 and a highly vapor impermeable resin film 2. This is a water vapor regulating sheet that can be mainly used to maintain the freshness of fruits and vegetables. In addition, without impairing the purpose of improving the water vapor regulating function, which is the main function of the present invention, the resin film 2 with high vapor impermeability can be placed between the highly hygroscopic resin film 1 and the water/hygroscopic resin layer 3, or between the highly hygroscopic resin film 1 and the water/hygroscopic resin layer 3. It is also possible to laminate a non-sized processed base paper with high water resistance between the water-absorbing and hygroscopic resin layer 3. The highly hygroscopic resin film 1 of the present invention only needs to be sensitive to moisture and have the ability to absorb moisture; for example, ordinary cellophane, polyamide resin,
Films such as polyvinyl alcohol and saponified ethylene-vinyl acetate copolymers can be used. Further, the vapor-impermeable film 2 of the present invention is not particularly limited, and may be any hydrophobic film such as a polyethylene film, a polypropylene film, or a polyester film. Furthermore, the water-absorbing/hygroscopic resin used as the intermediate layer is usually a mixture containing the following water-absorbing resin powder and desiccant powder such as calcium oxide, calcium chloride, zeolite, or silica gel. That is, the water-absorbing resin specifically includes:
Water-soluble resins are partially cross-linked to make them water-insoluble, including starch-sodium acrylate graft polymers, starch-acrylonitrile graft polymer hydrolysates, and partially cross-linked starch-poly(meth)acrylic acid copolymers. Starch-graft polymer systems such as coalesced or partially cross-linked starch-polymethyl methacrylate hydrolyzates and salts of the above substances, or cross-linked products typified by methacrylic acid-vinyl acetate copolymer hydrolyzates. Synthetic resin materials can be used. These can absorb and retain water tens to thousands of times their own weight, and in the present invention, they are used in a fine powder state.
After uniformly blending with the desiccant powder described above and, if necessary, an alkali hydroxide compound, etc., it is made into a coating liquid together with a non-aqueous resin binder. The mixing ratio of the water-absorbent resin powder and the desiccant powder varies depending on the type of fruits and vegetables to be mixed, but it is generally preferably a weight ratio of 10:1 to 10:10. The water absorbent resin powder and the desiccant powder each have a mesh size of 35 or less, preferably 100 mesh or less, and preferably have a shape close to a sphere of 50μ or more. The non-aqueous resin binder is preferably a flexible resin that has low solubility in water and exhibits effective adhesive properties despite the increase in volume of the water-absorbing resin powder upon absorption of water and moisture, such as ethylene-vinyl acetate copolymer, Examples include, but are not limited to, chlorinated polypropylene, urethane resin, and linear thermoplastic polyester resin. The water-absorbing resin powder and desiccant powder must be mixed in a total of at least 100 parts by weight, preferably 500 to 900 parts by weight, with respect to 100 parts by weight of this resin binder. This mixture of resin binder, water-absorbing resin powder, desiccant powder, alkali hydroxide, etc. is heated to melt the resin binder, and in this molten state,
It can be applied to a hygroscopic resin film 1 or a vapor-impermeable resin film 2. Alternatively, this mixture is dissolved or dispersed in a solvent such as alcohols, acetic esters, ketones, or hydrocarbon solvents to form a coating liquid, and coated on the hygroscopic resin film 1 or the vapor-impermeable resin film 2.
It can also be applied by a gravure method, a roll coating method, a silk screen method, a knife coating method, etc. When this coating is applied to the hygroscopic resin film 1, it is necessary to laminate the vapor-impermeable resin film 2 on top of this, and when this coating is applied to the vapor-impermeable resin film 2, it is necessary to laminate the hygroscopic resin film 2 on top of this. It is necessary to laminate the plastic films 1, and this laminate is done through an adhesive 4, but partial pattern adhesion is preferred in order to increase the efficiency of water vapor absorption. A general urethane adhesive can be used as the adhesive, and lamination can be done by dry lamination. The present invention will be explained in more detail below using examples. <Example 1> After applying the following water-absorbing and hygroscopic resin (,,,) layer (30g/m2 ⁾ to ordinary cellophane #300 using a knife coater, 10g/ ^m2 of urethane adhesive was applied in a grid pattern. A water vapor control sheet of the present invention was completed by laminating a biaxially stretched polypropylene film (20μ).

[Table] Cut this sheet into 8 x 10 cm ² and make 12 x 20 cm ² made of unstretched polypropylene film with a thickness of 40μ.
After filling and sealing a bag with 150 g of enoki mushrooms, the storage status of the enoki mushrooms was checked at room temperature for up to 3 days (Table 2). For comparison, a conventional water-absorbing sheet (60 g/m ² of unsized processed base paper / 30 g/m ² of water-absorbing resin / 8 x 10 cm ² of biaxially oriented polypropylene film (20μ)) was filled and sealed in the same way, and a sheet was not inserted. were tested simultaneously.

[Table] 〓×: Discoloration and soft rot 〓
As described above, it has been found that in the present invention, there is almost no dew condensation inside the packaging, and the water vapor inside the packaging of enoki mushrooms is well controlled. <Example 2> A sheet of the present invention was prepared in the same manner as in <Example 1> using a 15μ polyvinyl alcohol film as the first highly hygroscopic film layer. The 50 x 50 cm ² sheet was filled in a bag made of 30 μm polyethylene film with 10 kg of new water pears, which tend to develop sunspots during storage, and the opening was closed and stored in a refrigerator at approximately 2 to 5°C for 4 months, and the storage status was evaluated over time. investigated. The results were as shown in Table 3. The conventional product is the same as (Example-1), and the sheet area is 50×
It was set to ^50cm2 .

[Table] 〓○：No discoloration 〓

Claims (1)

[Claims] 1. A water-absorbing/hygroscopic resin layer made of a mixture containing a water-absorbing resin powder and a desiccant is provided between a highly hygroscopic resin film and a highly vapor-impermeable resin film. Water vapor adjustable seat. 2 The composition ratio of water absorbent resin and desiccant is
The water vapor adjustable sheet according to claim 1, characterized in that the water vapor content is 10:1 to 10:10.