JPH09290865A - Packaging laminate film for fresh vegetable and its package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To securely execute a heat-sealing work to retain the freshness of food, by forming the external layer of a biaxially stretched film made of crystalline polypropylene and forming the innermost layer of a film made of olefin polymer having specified characteristics. SOLUTION: In a packaging laminate film constituted of at least two layers of the external layer A and the innermost layer B, the external layer A is a biaxially stretched film chiefly constituted of crystalline polypropylene to effectively retain the freshness of vegetable and increase non-permeability to water vapor and prevent drying and make the film tough for rapid and easy bagging. The innermost layer B is a film made of olefin polymer having a lower melting point than the external layer A by 10-90 deg.C and the layer B is easily and closely stuck to the external layer A. The heat-sealing is secured at a lower temperature. The thickness of the innermost layer B is 4-30μm and the surface relative roughness is made 0.5μm or smaller in the average roughness (Ra) at the central line. In this way, the decrease of the seal temperature caused by stuck water is made minimum to enable the high speed continuous heatsealing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated film for packaging fresh vegetables, and in particular, when packaging fresh vegetables that have been wet with water in a film bag for hermetically sealing and shipping, the hermetic packaging is quick and complete. The present invention relates to a laminated film for packaging fresh vegetables, which has been performed and has improved freshness retention.

[0002]

2. Description of the Related Art Generally, a packaging film is processed into a bag,
For example, confectionery, living foods (raw vegetables or fruits), etc. are put in this and used in a hermetically sealed method. The material used for the film, the form of the film (whether it is a single film or a laminated film) depends on the type of the object to be packaged, the purpose of packaging (for example, maintaining freshness, damage protection due to contact with the outside,
It is various depending on whether it is a design aspect or the overall purpose). Therefore, there are various materials for the film used therein. Generally, for example, polyolefins such as polyethylene, polypropylene and polybutadiene, polyvinyl chloride, polyvinylidene chloride, nylon, polyethylene terephthalate, polyvinyl alcohol, polystyrene, ethylene / vinyl acetate copolymer, polycarbonate and the like can be mentioned. And these are stretched or formed into a film in a non-stretched state, but when actually used as a packaging film, in accordance with the above purpose, as a single film or as a laminated film in which two or more kinds are laminated. used. In particular, in the case of having both functionality (especially gas barrier property against oxygen gas, nitrogen gas, carbon dioxide gas) and hermetic packaging property (heat sealing property), use in the form of a laminated film is common.

[0003] When the object to be packaged is a biological food, especially a fresh vegetable, the freshness of the product is remarkably deteriorated.
Furthermore, the time to reach the consumer needs to be shortened as much as possible. Therefore, first, when shipping from the production site, it is necessary to wash the harvested raw vegetables locally with water, put them in a film bag immediately without removing water sufficiently, immediately seal the opening part, and prepare for shipment. There is. Therefore, an automatic wrapping machine is used for raw vegetables that can be automatically wrapped. In the present step, since sealing is performed by fusion with a heat sealer, a single-layer film made of polyolefin having good heat-sealing property is often used as the film to be used.

[0004]

By the way, when fresh vegetables wet with water are put in a film bag and immediately heat-sealed, not only the raw material polymer other than the polyolefin but also the heat-sealing property is obtained. It has been found that even a film bag made of an excellent polyolefin has a serious problem that it is difficult to heat seal quickly and completely in a short time, and the fusion time of heat sealing is not constant but constantly changes. Probably the cause is
Maybe because the water adheres to the opening for heat sealing,
Or, it is considered that the degree of adhesion is large or small depending on the place.

Even if the product is sufficiently sealed and shipped, a considerable amount of time elapses before the product is lined up in the store and before it reaches the consumer. Therefore, deterioration in freshness due to the storage time cannot be avoided. Therefore, the measure against keeping the freshness for a longer time is extremely effective even if it is a slightly improved measure.

In view of the above, according to the present invention, even if fresh vegetables, that is, fresh vegetables that are still wet with water, are immediately put in a packaging film bag and the next heat sealing is immediately carried out, it is completely completed. In addition, it is an object of the present invention to provide a film for packaging raw vegetables, which can be surely processed and whose freshness (including taste) can be maintained for a long time. This could be easily achieved by the following means.

[0007]

Means for Solving the Problems That is, the raw vegetable packaging film of the present invention is a packaging laminated film comprising at least two layers of an outer layer (A) and an innermost layer (B), and the outer layer (A) is crystalline. A biaxially stretched film-like material having polypropylene as a main component, wherein the innermost layer (B) is a film-like material made of an olefin polymer having a melting point 10 to 90 ° C. lower than the melting point of the outer layer (A), The thickness of the innermost layer (B) is 4 to 30 μm, and the surface roughness is the center line average roughness (hereinafter R
Call a. ) Is 0.5 μm or less.
Hereinafter, the present invention will be described in more detail.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, first, the outer layer (A)
The polymer that forms the film is mainly composed of crystalline polypropylene. Therefore, it should not be an amorphous polyolefin or any other polymer. This is because it is a material that works most effectively to maintain the freshness of raw vegetables. Since it is made of crystalline polypropylene as the main component, it can be said that it is most desirable to use it alone. However, if the original properties of the polypropylene (melting point, hardness, strength, etc.) are not significantly changed, other components may be used. It may be added chemically or physicochemically. For example, the melting point (abbreviated as MP) of this range is 168 to 17 for the crystalline single polypropylene.
Since it is at 0 ° C, the lower limit is about 150 ° C, that is, 150 to 1
Those in the range of about 70 ° C. can be said to be in the category of polymers containing crystalline polypropylene as a main component.

The chemical addition specifically refers to copolymerization with propylene, and the monomer to be copolymerized is an α-olefin such as ethylene, butene-1, pentene-1,
Hexene-1,4-methyl-1-pentene and the like are preferable. One kind or two or more kinds of these monomers may be copolymerized at the same time, but the copolymer is preferably limited to about 5 mol% or less for the above reason.

Further, the physicochemical addition specifically includes
Blending other polymers with crystalline polypropylene. Preferred polymers to be blended are homopolymers or copolymers of α-olefins exemplified in the case of the copolymerization, or water additives of aliphatic or aromatic resins having a higher carbon number, that is, generally The hydrogenated petroleum resin mentioned can be mentioned. The hydrogenated petroleum resin includes an aliphatic system (chain-like, cyclic) obtained by hydrogenating the residual double bond of a polymer obtained by polymerizing a C5 olefin fraction produced by thermal decomposition of petroleum naphtha, and a C9 fraction. Of aromatic system obtained by hydrogenating double bond of aromatic ring of polymer obtained by polymerizing aromatic monomer
Kind. Among the above-mentioned examples, hydrogenated petroleum resins, particularly aliphatic resins are preferable. This is because the blending property is good, the water vapor transmission rate which will be described later can be further reduced, and the oxygen permeability can be appropriately controlled.

In the case of blending, M of the blended product
When P is measured by a differential thermal analyzer, the peak corresponding to MP is measured not only for the crystalline polypropylene that is the main component but also for the blend, so that common MP is often not shown. MP in such a case sees the highest peak,
Let it be all MPs. Therefore, in the case of blending, the rational mixing amount is not determined from the relationship with MP, but it is advisable to mix the required minimum amount in consideration of other hardness, strength and the like. Generally, in the case of blending, it is recommended to use about 25% by weight or less based on the crystalline polypropylene.

Next, the polymer forming the innermost layer (B) (the inner surface of the bag) will be described. First, the polymer here is 10 more than the MP shown by the polymer forming the outer layer (A).
It must be an olefinic polymer with a MP of ~ 90 ° C, preferably 20-70 ° C lower. This is because first of all, it can be easily and completely laminated (adhered) with the outer layer (A), and the heat sealing after inserting the raw vegetables can be performed very quickly and completely by fusing at a lower temperature. It is more desirable in that it has moisture permeability, works effectively to maintain the freshness of raw vegetables, and is softer than the polymer of the outer layer (A), which protects the raw vegetables after encapsulation from damage, etc. Is. Therefore, polymers other than olefin polymers are
Even if the MP conditions are satisfied, or if the olefin polymer is a polymer that does not satisfy the MP conditions, it does not relate to the present invention. Where 10
If the temperature is lower than ℃, it is not particularly satisfactory in the speed of heat sealing and protection from damage and the like. On the contrary, if it is higher than 90 ℃, the strength of the heat sealing part is particularly weak, and the lamination is difficult and difficult to perform easily. by. Here, “completely heat-sealed” means that the heat-sealed portion has a high strength, and the portion does not shrink, and is smooth.

Specific examples of the olefinic polymer corresponding to the above are as follows. Polyethylene (MP about 100-125 ℃), polybutene (MP about 80 ℃), ethylene / propylene binary copolymer (MP
About 120 to 145 ° C.), an ethylene / propylene / butene-1 terpolymer (MP about 90 to 145 ° C.), an ethylene / vinyl acetate binary copolymer (MP about 80 to 100).
℃), ethylene / methacrylic acid binary copolymer (MP
80 ~ 100 ℃), 2 of ethylene-methyl acrylate
Binary copolymer (MP approximately 80-100 ° C), ethylene / methyl methacrylate (MP approximately 80-100 ° C)
° C), a binary copolymer with ethylene-4-methyl-pentene-1 (MP about 110 to 125 ° C), an ionomer (metal ion cross-linked polymer of ethylene / methacrylic acid) (MP
(About 100 to 120 ° C.) and the like. Among these, an ethylene / propylene binary copolymer or a terpolymer obtained by copolymerizing butene-1 with the binary copolymer is preferable. It should be noted that blended polymers obtained by appropriately blending the exemplified polymers are also acceptable.

As described above, the basic polymers forming the outer layer (A) and the innermost layer (B) have been described. However, it is not necessary that each layer be formed by simply using these polymers. It is necessary for each layer to further satisfy the following conditions, and by adding these conditions to the polymer, all the problems of the present invention can be solved.

The condition is that the outer layer (A) is as follows.
That is, the film-like material forming the film must be biaxially stretched in the longitudinal and lateral directions. This is especially effective in increasing moisture impermeable properties, that is, increasing the water vapor barrier property to protect raw vegetables from drying and reducing the loss of freshness due to storage, and strengthening the waist to increase the function as a support. The purpose is to make bagging of raw vegetables easy and quick. Therefore, the above effect cannot be obtained at a satisfactory level by unstretching or by stretching either one. Here, the stretching ratio is not particularly limited as long as it can be stretched, but is generally about 2 to 12 times in the length and width, preferably 3 to 10 times, and the same ratio in the length and width as much as possible.

Since the thickness of the outer layer (A) further promotes the effect of the biaxial stretching, it is preferable that the thickness of the innermost layer (B) is larger than that of the innermost layer (B). However, if it is too thick, the suitability of the automatic packaging machine will be poor, especially when automatically packaging fresh vegetables, which is not desirable. Considering various conditions, the preferable thickness is about 20 to 100 μm.
m can be illustrated. Therefore, the total thickness is about 24-130.
μm can be exemplified as a preferable thickness.

Next, the film-like material made of the polymer forming the innermost layer (B) needs to be specified in its thickness and surface roughness as described above. First, regarding the thickness, particularly 4 to 30 μm, preferably 8 to 2
It must be 0 μm. This is because the sealing method after inserting the raw vegetables into the film bag is the heat sealing method in the present invention, that is, it is desirable to perform the fusion sealing with only the innermost layer (B). The adhesive strength is weak and there is a high risk of breakage and opening during handling, and conversely, when it exceeds 30 μm, blocking becomes stronger. This results in delaying the opening work when making bags or inserting raw vegetables.

The surface roughness Ra is 0.5 μm or less,
It is preferably 0.3 μm or less, and as close as possible to 0 μm, especially on rough surfaces than 0.5 μm, especially raw vegetables harvested locally are washed with water and the wet raw vegetables are immediately put into a film bag. If you take the work step of inserting and immediately sealing (often using an automatic packaging system), heat it quickly, continuously, and completely under certain heat-sealing conditions (temperature and time). This is because sealing cannot be performed. Although the reason for this is not clear, it is considered that the surface roughness of the olefin-based polymer used for the innermost layer (B) in particular affects the adhesion of water. If raw vegetables wet with water are inserted into the film bag, water will inevitably adhere to the inner surface of the opening. If the inside of the opening is in a roughened state where water easily attaches, water naturally attaches to that portion. When heat sealing with water adhered is continuously performed at a particularly high speed, the sealing temperature is lowered, which makes it impossible. In the present invention, Ra is 0.5 μm as a boundary, and even if it is less than that, high-speed continuous heat sealing is possible.
It is extremely small, and it is considered that the heat sealability was not affected.

The means for obtaining the predetermined thickness of the innermost layer (B) and the means for obtaining the surface roughness Ra ≦ 0.5 μm are not specified. For example, for a predetermined thickness, the lip width of a die generally attached to an extruder is adjusted, and when stretching is performed, whether it is uniaxial or biaxial and the stretching ratio in that case is also taken into consideration. By calculating in advance, a desired thickness can be obtained.

On the other hand, the surface roughness can be exemplified by the following method, which is a preferable method. This is a method of quenching immediately after melt extrusion from a die, regardless of the film forming means, and the cooling temperature is set to about -20 ° C / sec or less, preferably -30 ° C / sec or less. Is good.
It is considered that at least the olefin-based polymer of the innermost layer (B) is formed into a film-like substance with fine crystals by this rapid cooling, and a smooth surface having a surface roughness Ra ≦ 0.5 μm is obtained. This quenching is preferably performed by a cooling roll cooled to a predetermined temperature. This is performed immediately after being extruded from the die by first contacting the cooling roll and then performing the rapid cooling.

Since the surface roughness of the roll may affect the surface roughness of the innermost layer (B), the roll should be mirror-finished so that it is as smooth as possible. good. Further, in the case of rapid cooling, a small amount of the nucleating agent is mixed in the polymer, which may have a promoting effect of further reducing the surface roughness of the innermost layer (B) to be obtained. The nucleating agent is generally used in the case of an olefin polymer, for example, talc, adipic acid or a sodium salt of benzoic acid,
The amount of addition is suitably selected within the range of about 0.01 to 0.8% by weight.

Next, the stretching means will be described. As described above, at least the outer layer (A) requires biaxial stretching,
The innermost layer (B) may or may not be stretched. Therefore, the innermost layer (B) is not stretched, or even when it is stretched, when the conditions are different from those of the outer layer (A) (uniaxial stretching or when the outer layer (A) and the biaxial stretching ratio are different). Will be stretched separately and then laminated.

The method for stretching at least the outer layer (A) is not particularly limited, but basically, after the melt extrusion into a film, at least the Vicat softening temperature (based on ASTM 1525) of the polymer used for the outer layer (A) once. A method of cooling and solidifying to (heat deformation temperature) and heating to the stretching temperature again (after the rapid cooling when accompanied by the innermost layer (B)) is adopted. The stretching temperature here is of course required to be lower than the melting point of the polymer, but the preferable temperature is in the range of + 10 ° C to -40 ° C centering on the Vicat softening temperature (TB). The biaxial stretching is preferably performed by a stretching roll in the longitudinal direction and then a tenter in the transverse direction.

When the outer layer (A) and the innermost layer (B) are laminated at the same time as the melt extrusion by the coextrusion method described later, the subsequent stretching must be performed simultaneously for both layers and at the same ratio in the length and width directions. Therefore, regarding the stretching temperature in such a case,
The innermost layer (B) is set at a stretching temperature. The stretching temperature at this time is, of course, lower than the MP of the olefin polymer used in the innermost layer (B), but the preferable temperature is within the range of ± 15 ° C. around TB of the polymer.

The outer layer (A) and the innermost layer (B) may be laminated by any of the dry lamination method, the coextrusion method and the extrusion lamination method which are generally used, among which the latter two methods are used. The method is preferred.
This is because the adhesion between the outer layer (A) and the innermost layer (B) is extremely excellent, and thus the dry lamination method using an adhesive is not necessary. The outer layer (A) and the innermost layer (B) are used according to whether the co-extrusion method or the extrusion lamination method is used properly.
Depending on the stretching conditions. That is, when both layers are biaxially stretched in the longitudinal and transverse directions at the same rate, it is effective to use the coextrusion method. However, whether the innermost layer (B) is unstretched or uniaxially stretched,
Alternatively, when the stretching ratio is different from that of the outer layer (A), it is preferable to carry out the extrusion lamination method.

There are no particular restrictions on the addition of additives to each layer polymer during lamination. For example, antioxidants, heat stabilizers, antifogging agents, antistatic agents, antiblocking agents and the like which are generally used in relation to packaging polyolefin films can be mentioned. These additives may be added to only the outer layer (A), only the innermost layer (B), or both layers, if necessary, but the addition amount of each is limited to about 2% by weight or less.

The packaging film of the present invention may basically be composed of two layers, an outer layer (A) and an innermost layer (B), but between the layers or the outermost layer of the outer layer (A). As a result, there is no restriction in providing an auxiliary layer made of another polymer. However, a nylon layer having high moisture permeability, a polyvinyl alcohol layer, etc. are not preferable. Further, an auxiliary layer made of a material having extremely small oxygen permeation, such as polyvinyl alcohol, polyvinylidene chloride, nylon or polyester, is not preferable.

Further, the kind of raw vegetables to be packaged in the present invention is not particularly limited, but among them, bean sprouts and green onions are preferable, and most preferable are bean sprouts whose freshness decreases quickly.

As described above, the effect that the continuous heat-sealing can be carried out completely and quickly even with fresh vegetables whose bag made of the film of the present invention is wet with water is one of the effects other than this heat-sealing. The reason why it is also excellent in freshness retention is considered to be due to the following action.

Vegetables are generally called bio-foods and have a respiratory action for a while even after harvesting. This respiratory action depends on water and oxygen. Therefore, the loss of water causes the raw vegetables to wither in the film bag, and the commercial property is lost. Retention of water is extremely important. On the other hand, with respect to oxygen, the presence of oxygen is likely to cause the wear of components related to taste, and therefore it is said that the absence of oxygen is better. In contrast to this relationship, the laminated film according to the present invention has the following characteristics. First, the water vapor transmission rate related to water retention is about 10g / m2 ・ 2
It is 4 hours or less. And for oxygen related to taste,
Its transmittance is about 400-2500cc / m2 ・ 24hr
・ Atm. Here, the water retention property is far superior to that of any other film. This is very effective for the raw vegetables to breathe longer. However, oxygen is inferior to other films and is likely to exist at a high concentration. In other words, the deterioration of taste will be accelerated. However, when the bean sprouts and leaf scallions were actually sealed and packaged in a laminated film bag according to the present invention together with water, and the time-dependent changes in taste were checked, it was found that the taste was particularly good after harvest and within the fresh period without feeling wilted. I don't feel the difference. Given this,
Rather, it is considered that the presence of oxygen in an appropriate range together with the water acts to maintain the freshness for a longer time without adversely affecting the taste.

[0031]

Next, the present invention will be described in more detail with reference to Examples together with Comparative Examples. Ra, water vapor transmission rate, and oxygen permeability shown in the text and the examples are values measured by the following methods. Ra: Surface roughness profile measuring machine based on JIS B-0601, Surcom 570A type (manufactured by Tokyo Seimitsu Co., Ltd.),
The values measured with a cutoff value of 0.8 mm and a measurement length of 5 mm are shown in μm. Moisture vapor transmission rate: The value measured under the condition [B] of JIS Z-0208 (measurement temperature 40 ° C, RH 90%) is g / m2 · 2.
It is shown in units of 4 hr. Oxygen permeability: The value measured by an oxygen permeability measuring device (isobaric pressure method, JIS K-2126) manufactured by MOCON Co., is cc
/ M2 · 24 hr · atm · 23 ° C.

Example 1 First, a film-like material as the outer layer (A) was formed by the following method. MP 163 ℃ polypropylene (TB = 15
T-die (2 ° C) at 200-250 ° C (barrel temperature)
(10 ° C.), melt-extruded into a film form, contacted with a cooling roll, cooled to 70 ° C., and then passed through a heating roll heated to 150 ° C., while raising the surface temperature of the film-like product to 140 ° C. Then, the film was stretched 5 times in the longitudinal direction with a stretching roll, further sent under a heating atmosphere of 150 ° C., stretched 8 times in the transverse direction with a tenter, and contacted with a cooling roll to obtain a final film-like product, It was wound into a shape. The obtained product was a biaxially stretched polypropylene film having a uniform surface and a thickness of 24 μm.

Then, using the obtained film of the outer layer (A) as a substrate, the innermost layer (B) was extruded on the substrate and laminated by the following method to obtain a laminated film. First, the roll-shaped outer layer (A) film-like material is
The terpolymer of propylene, ethylene, and butene-1 at MP130 ° C., which forms the innermost layer (B) on this surface, is heated to 150 ° C.
0 ° C (barrel temperature), lip width 800 μm T-die (1
(85 ° C), spit out, and immediately the innermost layer (B)
The surface was sent out so as to contact a cooling roll (temperature 20 ° C., Ra 0.1 μm), and was rapidly cooled at a cooling rate of −40 ° C./sec. The total thickness of the obtained laminated film was 30.5 μm, therefore the innermost layer (B) was 6.5 μm, and the surface roughness Ra of the (B) was 0.30 μm.

The moisture permeability of the laminated film is 7 g / m.
2/24 hours, oxygen permeability 1400cc / m2 / 24
It was hr.atm.23 ° C.

Next, using the above-mentioned laminated film, a bag of 180 × 250 mm in size (one side is opened) is prepared, the harvested sprouts are immediately washed with water, and the wet sprouts are manually inserted in advance. Then, the mixture was supplied to an automatic heat sealer heated to 155 ° C., and heat sealing was continuously performed at a heating time of 0.3 seconds / bag. Obtained 300
The heat-sealed portion of the bag was checked. As a result, it was confirmed that all were completely heat-sealed, the sealing strength was sufficient, and that they were not damaged during handling.

Finally, 5 bags of the above-obtained bean sprouts were left in an atmosphere of RH 35% and a temperature of 20 ° C. for 4 days, and the 5 bags were opened to check the odor. Compared with the odor, the odor was slightly changed, but the odor was felt, but it was not at a level not acceptable as a product. Also, as a whole, the hardness of the bean sprouts did not change and there was no discoloration.

Comparative Example 1 (Ra of the innermost layer (B) was 0.5 μm)
Example of exceeding m) In Example 1, the laminated film was formed under exactly the same conditions except that the temperature of the cooling roll was set to 70 ° C., the cooling rate was −10 ° C./sec, and the cooling was performed under slow cooling conditions. The total thickness of the obtained laminated film was 30.5 μm, and the innermost layer (B) was 5.
And the surface roughness Ra of the (B) is 0.7.
It was 1 μm.

Next, using the laminated film, a bag was prepared under the same conditions as described in Example 1, and was sealed with bean sprouts for continuous heat sealing. As a result, 48 out of 300 bags were incompletely heat-sealed, and when the sealed portion was checked in detail, they were not partially fused. It is considered that Ra was large (rough surface) as compared with Example 1, and therefore some water remained and was scattered in the heat-sealed portion when the wet sprouts were inserted.

Example 2 As a polymer for the outer layer (A), a propylene copolymer at MP160 ° C. obtained by copolymerizing 0.5 mol% of ethylene with propylene was used, and as a polymer for the innermost layer (B),
Biaxially stretched laminated film using the ethylene / propylene copolymer (TB = about 117 ° C.) at MP132 ° C. obtained by copolymerizing ethylene with 6.5 mol% of ethylene in propylene by the following coextrusion method. Was molded. That is, first, one T die for coextrusion adjusted to 220 ° C. was attached to the discharge ports of two extruders whose barrel temperatures were adjusted to 200 to 250 ° C., and immediately after the T die, in Example 1, The chill roll used, and then the heating roll, then the tenter, and finally the take-up roll were arranged. In the T die, the lip width of the merging discharge port is 2000.
It was set to μm. The temperature of the cooling roll is 15 ° C., and the temperature of the heating roll is 127 ° C. higher than the TB of the innermost layer (B) by 10 ° C.
Set to ° C. This is one in which the film temperature of the innermost layer (B) is made to reach a surface temperature of 120 ° C. and then the whole is stretched. The ambient temperature of the tenter was set to 150 ° C.

Next, the two extruders are laminated so that the polymer of the outer layer (A) is on the lower side and the polymer of the innermost layer (B) is on the upper side (in contact with the cooling roll). Each was fed and melt extrusion started. The extrusion rate was adjusted so that the quenching rate by the cooling roll at this time was −38 ° C./sec. After the rapid cooling, first, while heating the laminated film to the above temperature with a heating roll, first stretch 7 times in the longitudinal direction and then 8 times in the transverse direction with a tenter, cool to room temperature and finish the entire winding process. did.

The biaxially stretched laminated film thus obtained had a total thickness of 60 μm, the innermost layer (B) had a thickness of 21 μm, and Ra.
Was 0.27 μm. The moisture vapor transmission rate is 7g / m2 ・ 2
4hr, oxygen permeability is 1550cc / m2 ・ 24hr ・
It was atm · 23 ° C.

Next, using the obtained laminated film,
200 bags of size 60 x 600 mm (opening on one side) were made, and washed manually with water immediately after harvesting in this bag, and the leaf leek in a wet state was inserted, and this was put into an automatic heat sealer (set temperature). 160 ℃), heating time 0.4
Heat sealing was performed continuously as seconds / bag. 2 obtained
When the sealed portion of 00 bags was checked, it was confirmed that all of 200 bags were completely fused and sealed. Of course, it was confirmed that the heat-sealing strength was high and there was no problem in practical use.

Finally, for the 5 bags of the above-mentioned leaf green onion bag,
It was left for 4 days under the conditions described in Example 1, and 5 bags were opened to check the freshness. Regarding the odor, there was no difference between immediately after the harvest and no leaves wilting, and it was in a fresh state, maintaining sufficient freshness.

Example 3 As the polymer for the outer layer (A), MP160 was obtained by blending 20% by weight of hydrogenated petroleum resin (dicyclopentadiene hydrogenated resin manufactured by Exxon Chemical Co., product number Escoletz 5320) with polypropylene. ℃ blended polypropylene is used, the innermost layer (B), polybutene-
Blend type ethylene / propylene copolymer obtained by blending 30% by weight of 1 and 0.1% by weight of talc fine powder as a nucleating agent with the ethylene / propylene copolymer at MP 132 ° C. used in Example 2. Except that (TB = 108 ° C.) was used, in the same manner as in Example 1, coextrusion molding was performed to form a biaxially stretched laminated film having a length of 6 times and a width of 8 times. The total thickness of the obtained laminated film was 58 μm, the innermost layer (B) was 19 μm, and Ra was 0.1 μm. The moisture vapor transmission rate is 2g / m2 · 24hr and the oxygen transmission rate is 500c.
It was c / m2 · 24 hr · atm · 23 ° C.

Using the biaxially stretched laminated film obtained above, a bag having a size of 180 × 250 mm (one side is opened) 50
0 sheets were prepared, and washed immediately with water after harvesting in the bag, wet bean sprouts were manually inserted in advance, and then this was sent to an automatic heat sealer (set temperature 160 ° C.) for a heating time of 0. Heat sealing was performed continuously for 33 seconds / bag. When the heat-sealed portion of the obtained 500 bags was checked, it was confirmed that all were completely firmly fused and sealed. The freshness check by storage was also performed under the same conditions as in Example 1, and the same results were obtained.

Comparative Example 2 (Example in which a polymer other than the present invention was used as the innermost layer (B)) Polypropylene of MP163 ° C. was used as the polymer of the outer layer (A), and MP134 ° C. of 6.12 was used as the innermost layer (B). Copolymerization was carried out under exactly the same conditions as in Example 2 except that each nylon copolymer was used to obtain a biaxially stretched laminated film. The total thickness of the obtained film was 58.5 μm,
The innermost layer (B) was 19.8 μm and Ra was 0.2 μm. The water vapor transmission rate was 15 g / m2 · 24 hr, and the oxygen permeability was 180 cc / m2 · 24 hr · atm · 23 ° C.

Then, using the obtained laminated film, 200 bags having the same size as in Example 1 were prepared, and then, as in the above example, bean sprouts were inserted and heat sealing was performed continuously. As a result, 30 bags were incompletely heat-sealed. This is probably because the hydrophilicity of nylon itself affected the retention of water on the heat seal surface. Then, the 5 completely sealed bags were similarly left for 4 days in an atmosphere of RH 35% and 20 ° C., then opened and checked for odor.
It had a stronger odor than that of and had a slight discoloration. This was ineligible for commercial value. It is considered that it was affected by moisture permeability and oxygen permeability.

Comparative Example 3 (Example in which Innermost Layer (B) Is Made of Olefin Polymer Other Than the Present Invention) Polypropylene of MP163 ° C. as the polymer of the outer layer (A) and ethylene of MP160 ° C. as the polymer of the innermost layer (B) Extrusion lamination was performed under the same conditions as in Example 1, using a propylene copolymer (ethylene is 0.5 mol% copolymer) and an MP63 ° C. ethylene / vinyl acetate copolymer, respectively. Got However, in the case of the ethylene / propylene copolymer, the barrel temperature is 160 to
200 ℃, T die temperature 190 ℃, and ethylene
In the case of vinyl acetate copolymer, barrel temperature 100 to 15
The temperature was 0 ° C. and the T-die temperature was 140 ° C.

Then, the innermost layer (B) in the obtained laminated film
Of an ethylene / propylene copolymer having an MP of 160 ° C. (hereinafter referred to as a 160B film) and an innermost layer (B) made of an ethylene / vinyl acetate copolymer having an MP of 68 ° C. (hereinafter referred to as a 68B film). Each 100-sheet bag (one side is opened) was produced. Then, water-washed bean sprouts were manually inserted into each bag in a wet state and sent to an automatic heat sealer to try continuous heat sealing. Here, the heat sealing conditions were as follows. First, in the case of a bag made of 160B film, the fusing temperature is set to 16
When the temperature was set to 5 ° C., the innermost layers (B) were finally fused in one minute. Since this is extremely slow and is not suitable for automatic heat sealing, when the temperature was further raised to 180 ° C and heat sealing was performed, the fusing time was 1 second, and although speeding up was possible, the fusing seal sealed by fusing did not However, when it comes into contact with an external object, that part is directly touched, and it is liable to be damaged, so it is not a desirable heat seal.

On the other hand, in the case of the bag made of 68B film, when the fusing temperature was set to 100 ° C., it was completely fused in 0.2 seconds, so that there is no problem in the suitability for automatic heat sealing. However, a slight wrinkle pattern was observed on the heat-sealed portion, the surface was not a smooth sealing surface, and a drop test showed that the heat-sealed portion was partially damaged in 40 bags.

Comparative Example 4 (Example in which the thickness of the film-like material of the outermost layer (B) is out of the range) In Example 1, except that the layer thickness of the terpolymer of the innermost layer (B) was changed. Extrusion lamination was performed under exactly the same conditions to form a film in which the outer layer (A) was biaxially stretched and the innermost layer (B) was unstretched. The total thickness of the laminated film is 26 μm, and the thickness of the innermost layer (B) is 2 μm.
Ra was 0.2 μm in m (hereinafter referred to as 2B film). Similarly, by changing the layer thickness and the total thickness of the innermost layer (B), the total thickness was 62 μm, so that the innermost layer (B) had a thickness of 38 μm and an Ra of 0.4 μm (hereinafter Is called a 38B film).

Using the obtained 2B film and 38B film, 200 sheets each (opening on one side) were prepared in the same manner as in Example 1. And first, manually insert the wet bean sprouts from the 2B film bag,
Then, it is supplied to an automatic heat sealer, and the heating time is 0.
Heat sealing was performed continuously for 2 seconds / bag. Although the obtained 200 bags were completely heat-sealed, the seal strength was tested by dropping, but 150 bags partially damaged the heat-sealed portion.

That is, it can be seen that when the thickness of the innermost layer (B) is less than 4 μm, the heat sealing strength is weak and it cannot be put to practical use. On the other hand, with the bag made of 38B film, the manual opening performed before inserting the bean sprouts was not smooth, and it took time to open the bag. That is, the innermost layers (B) were blocked from each other, and the separation was poor.

[0054]

Since the present invention is as described above, it has the following effects. In the film for packaging raw vegetables of the present invention, this is used as a packaging bag, raw vegetables wet with water are put in the packaging bag, and immediately heat-sealed, even if it is continuously and automatically packaged for a short time, it adheres to the innermost layer (B). It is possible to completely and surely carry out the seal packaging without being affected by the moisture.

As to the freshness and taste of the vegetables during storage in a bag, even fresh vegetables such as bean sprouts can be kept fresh for a longer period of time, and the deterioration of taste is small. In addition, since the innermost layer (B) is a film bag which is softer than the outer layer (A), it has an effect of further reducing the occurrence of scratches during the handling of raw vegetables, which also contributes to maintaining freshness. ing.

Claims (3)

[Claims] 1. A packaging laminated film comprising at least two layers of an outer layer (A) and an innermost layer (B), wherein the outer layer (A) is a biaxially stretched film-like material containing crystalline polypropylene as a main component, The innermost layer (B) is a film-like material made of an olefin polymer having a melting point 10 to 90 ° C. lower than the melting point of the outer layer (A), and the innermost layer (B)
Is 4 to 30 μm, and the surface roughness is 0.5 μm or less in terms of center line average roughness. 2. The innermost layer (B) is formed of a film of a binary copolymer of ethylene and propylene or a ternary copolymer of ethylene, propylene and butene-1.
The laminated film for packaging raw vegetables according to. 3. A raw vegetable package, wherein the laminated film for packaging raw vegetables according to claim 1 or 2 is used to hermetically package raw vegetables having water droplets on the surface thereof.