JP2001171058A - Transparent freshness-retaining film and package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a freshness-retaining draw film which retains the freshness of raw vegetables and fruit or the like extending to a long period of time, and also, provide a package which is packaged with the film. SOLUTION: For this transparent freshness-retaining film, at least on one surface of a base material layer A comprising polypropylene, a heat-seal layer B with a thickness of 1 to 10 μm, containing 0.1 to 10 wt.% of a mixture of aluminum silicate, of which the average particle diameter is 0.5 to 5 μm, and magnesium oxide, of which the average particle diameter is 0.5 to 5 μm, is provided. Then, the haze value of the transparent freshness-retaining film is 1.0 to 12%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretch-preserving stretched film characterized by maintaining freshness of raw vegetables, fruits and vegetables for a long period of time, and a package packaged with the film.

[0002]

2. Description of the Related Art As a method for maintaining freshness of agricultural products such as fresh vegetables and fruits and vegetables, various freshness retaining films and freshness retaining sheets have been developed. As the freshness retaining film, a number of films formed by kneading an adsorbent for a gas harmful to agricultural products such as ethylene gas and ammonia gas and so on have been proposed.

[0003]

However, conventional adsorbent-kneaded films are often opaque or have a remarkably poor appearance. Agricultural products are packed at the production area and sold at retail stores as they are. However, in today's consumer-facing distribution formats, consumers or retailers are not always perfect in maintaining freshness or keeping freshness, or determining whether freshness is being maintained. . Moreover, even if a transparent freshness retaining film has been proposed, its effect is insufficient, or even if a film having a sufficient freshness retaining effect has been proposed, the blocking resistance is not only poor, but also when packaging agricultural products. There was a problem such as packaging loss.

[0004]

Means for Solving the Problems Accordingly, the present inventors have:
The present invention has eagerly developed a freshness maintaining film having a heat seal layer containing a specific amount of a specific adsorbent or the like, and has made it possible to increase the transparency and the blocking strength of the film to a certain value or less. The present invention includes the following items. Item 1. At least one surface of the base material layer A made of polypropylene contained 0.1 to 10 wt% of a mixture of aluminum silicate having an average particle size of 0.5 to 5 μm and magnesium oxide having an average particle size of 0.5 to 5 μm. The thickness is 1 to 1
It has a heat seal layer B of 0 μm and a haze value of 1.0 to
A transparent freshness retaining film which is stretched in at least one direction at 12%. Item 2. At least one surface of the base material layer A made of polypropylene has a thickness of 1 to 10 μm containing 0.1 to 10 wt% of aluminum silicate having an average particle size of 0.5 to 5 μm.
And a haze value of 1.0 to 12%
A transparent freshness maintaining film stretched in at least one direction. Item 3. Item 3. The transparent freshness retaining film according to Item 1 or 2, wherein a fatty acid glyceride and / or a fatty acid diethanolamine is coordinated on the surface of the heat seal layer B. Item 4. Heat seal layer B has an average particle size of 1.0 to 4.
0 μm silica particles or polymethyl methacrylate particles are mixed in an amount of 0.05 to 1.0 wt%, and the blocking strength at 40 ° C. between the layer B surfaces and between the layer B surface and the surface opposite to the layer B surface is 12N. Item 12. The transparent freshness retaining film according to any one of Items 1 to 3, wherein the thickness is not more than / 12 cm ² . Item 5. Item 5. A package obtained by packaging an agricultural product with the transparent freshness retaining film according to any one of Items 1 to 4.

[0005]

DETAILED DESCRIPTION OF THE INVENTION The adsorbent according to the present invention has the formula Al
_{2 0 3 · zSiO 2 · mH} 2 O ( wherein z represents a number of 1 to 20) is required to be a mixture of aluminum silicate or aluminum silicate and magnesium oxide represented by. The average particle size of the adsorbent is 0.5
５5 μm is preferred. If it is less than 0.5 μm, the particles tend to be enlarged due to secondary agglomeration of the adsorbent, and it becomes difficult to obtain desired transparency due to gels and buttery. On the other hand, if the average particle diameter exceeds 5 μm, the particle diameter becomes too large, and it is also difficult to obtain desired transparency. More preferably, the average particle size is from 1.0 μm to 4 μm.
m, and still more preferably 1.5 μm to 3 μm. Examples of the aluminum silicate include those represented by the above-mentioned formula.
It is preferable to have pores having a diameter of at most 5 nm inside, and more preferably to have pores having an average major axis of 5 nm or less. Still more preferably, it is preferable to have pores having an average major axis of 2 nm or less. The finer the pores inside are, the higher the adsorptivity is, and the desired freshness retention tends to be easily obtained.

The content of these adsorbents in the heat seal layer B is preferably 0.1 to 10% by weight. 0.1wt
If the amount is less than 10% by weight, the admixture of the adsorbent is small, and the desired freshness retention property tends to be hardly obtained. . More preferably, the content of the adsorbent in the layer B is from 0.3 to 5 wt%, even more preferably from 0.5 to 2 wt%.

The thickness of the heat seal layer B according to the present invention is preferably 1 to 10 μm. If it is less than 1 μm, the expected heat seal strength cannot be obtained, and if it exceeds 10 μm, the transparency tends to decrease or the blocking strength tends to increase. The thickness of the layer B is more preferably 2 to 8 μm, and still more preferably 3 to 7 μm.

Various additives may be further mixed in the film of the present invention. For example, nucleating agents, anti-fog agents,
Examples include antioxidants, flame retardants, lubricants, antistatic agents, fillers, pigments, and the like. In particular, mixing an anti-fogging agent is useful for maintaining freshness. As the anti-fogging agent to be used, fatty acid glyceride, fatty acid diethanolamine, fatty acid ethanolamine monoester and the like are preferable.

It is preferable to add various antiblocking agents to the heat seal layer B of the present invention. Examples of the antiblocking agent include silica particles such as calcium carbonate, natural silica and synthetic silica, inorganic particles such as feldspar, and organic particles such as polymethyl methacrylate (hereinafter abbreviated as PMMA) particles, nylon particles, and urea resin. Although it is possible, silica particles and PMMA particles are particularly preferable, and when these are used, a system in which this adsorbent is mixed exhibits efficient antiblocking performance. Still more preferably,
An anti-blocking agent having a hydrophobic coating on the surface of silica particles and PMMA particles is more preferable. Further, when the average particle diameter of the anti-blocking agent is larger than the average particle diameter of the adsorbent, a more efficient anti-blocking effect can be obtained. The content of the antiblocking agent in the layer B is preferably 0.05 to 1.0 wt%. If it is less than 0.05% by weight, a desired anti-blocking effect tends to be hardly obtained, and if it exceeds 1.0%, transparency tends to be inhibited, and the performance of the adsorbent tends to be hardly exhibited, which is not preferable. The content is more preferably 0.1 to 0.8 wt%, and even more preferably 0.2 to 0.6 wt%.

Further, in order to achieve both the expected blocking property and transparency, the resulting film preferably has a haze value of 1.0 to 12%. If it exceeds 12%, the sense of see-through is very poor, and the freshness of the contents in the package displayed in a supermarket or the like tends to be difficult to recognize with the eyes of the consumer. Although it is very good, the blocking strength is very high, and the processability at the time of packaging tends to be extremely poor, which is not preferable. The haze value is more preferably 1.5 to 10%, still more preferably 2.0 to 8%, and still more preferably 3.0 to 7%.

Further, the lower the blocking strength of the obtained film, the better the processability at the time of packaging.
N / 12 cm ² or less is preferable. More preferably 10N
/ 12 cm ² or less, more preferably 8 N / 12 cm ²
The blocking strength is more preferably 7 N / 12 cm ² or less, even more preferably 2 N / 12 cm ² or less.

Further, the polypropylene according to the present invention comprises:
Any propylene-based polymer may be used, but in view of stretching stability, especially a propylene homopolymer having an MFR of 0.5 to 4 or a propylene-ethylene random copolymer having an ethylene content of 0.2 to 1.0 wt%. Etc. can be exemplified.

The contents of the package according to the present invention include:
Agricultural products such as raw vegetables and fruits and vegetables, for example, vegetables such as leek, sprouts, spinach, broccoli, peppers, cabbage, lettuce, or fruits such as strawberries, bananas, lemons, or enoki mushrooms, mushrooms, shimeji mushrooms And fungi such as shiitake mushrooms. In particular, a higher freshness preserving effect is observed in packaging of green onions, sprouts, and peppers.

As the resin for forming the heat seal layer B according to the present invention, an olefin polymer having a melting point of 140 ° C. or less is preferable. In particular, considering the sealing suitability at the time of packaging or the mechanical suitability at the time of packaging, Melting point is 120 ° C-1
A propylene ethylene copolymer having a temperature of 33 ° C. or a propylene ethylene butene copolymer having a melting point of 120 ° C. to 133 ° C. has good packaging suitability and is preferred.

Further, the base material layer A and the heat seal layer B according to the present invention need to be stretched at least uniaxially. If the film is not stretched, the desired freshness retention may not be obtained, which is not preferable. Further, it is more preferable that both the layers A and B are biaxially stretched. Examples of the stretching ratio are 4 to 6 times in the machine direction and 7 to 11 times in the direction perpendicular to the machine direction.

The film according to the present invention can be subjected to various surface treatments. For example, corona treatment,
A flame treatment, a plasma treatment and the like can be exemplified, but it is particularly preferable to perform a corona treatment on the heat seal layer B side because the effect of maintaining freshness tends to increase. On the other hand, heat seal layer B
When corona treatment is applied to the surface side, depending on the treatment strength,
It is preferable that the processing strength is reduced as long as the blocking tends to be severe and an excellent freshness retaining effect can be maintained. Preferably, the corona treatment strength is 30 w · mi.
n / m ² or less, more preferably 20 w · min / m ² or less, even more preferably 10 w · min / m ² or less.

The moisture permeability of the film according to the present invention is 10 g / m ² .multidot.
It is preferably at most d. If it exceeds 10 g / m ² · d, moisture evaporating from the contents permeates to the outside of the package, and the freshness of the contents tends to decrease, which is not preferable.
The moisture permeability of the film is more preferably 8 g / m ² ·
d or less, still more preferably 7 g / m ² · d or less.

The oxygen permeability of the film according to the present invention is preferably 4000 to 20000 ml / m ² · d · MPa. Oxygen permeability is 4000ml / m ²・ d ・ MPa
When the amount is less than the above, the supply amount of oxygen to the contents is insufficient, and depending on the contents of the package, the respiration is significantly inhibited, and the desired freshness retention tends to be hardly obtained. Also 20000
If it exceeds ml / m ² · d · MPa, the oxygen supply becomes excessive and the contents are in a state of hyperventilation, so that the degree of aging or deterioration is severe, and a desired freshness retention property tends not to be obtained. More preferably 6000 to oxygen permeability
19000 ml / m ² · d · MPa, even more preferably 7000 to 18000 ml / m ² · d · MPa.

[0019]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. The evaluation method is as follows. [Haze value] Haze value was measured according to JIS K 7105. [Moisture Permeability] Measured in accordance with JIS Z 0208 condition B. [Oxygen permeability] According to JIS K 7126 method A, 10 ° C, 65%
It was measured under the condition of RH. [Blocking strength] Two films of 3 cm × 10 c
m, and the two test pieces were overlapped by 3 cm × 4 cm so that the measurement surfaces faced each other. Then, a load of 600 g was applied on the overlapped 12 cm ² part, and 40 ° C. for 24 hours. After storage, the shear strength in the longitudinal direction of the test piece was measured by a peeling tester. still,
The tensile speed of the peel tester was measured at 200 mm / min. [Freshness retention period] A bag of 200 cm x 250 cm was prepared from a film, and 100 g of soybean sprouts were packed and stored at 10 ° C to investigate the freshness retention period. The freshness of soybean sprouts was judged from the appearance such as color and hardness, and the odor.

Example 1 A layer A composed of a propylene homopolymer (MFR = 2.0 g / 10 min) having a melting point of 165 ° C. and propylene ethylene having a melting point of 130 ° C. and an ethylene content of 2 wt% and a butene content of 9 wt% 0.7 wt% of aluminum silicate having pores with an average particle diameter of 2 μm and an average long diameter of 3.4 nm as an adsorbent was 0.7 wt% with respect to a butene copolymer (MFR = 6.0 g / 10 min). Was mixed with 0.7 wt% of magnesium oxide of 2 μm and mixed with 0.3 wt% of silica particles having an average particle diameter of 3 μm as a blocking inhibitor, and then co-extruded, and then 4.5 times in the longitudinal direction, at right angles thereto. Stretched 9 times in any direction, and furthermore, treatment strength of both sides A and B was 20 w · min / m
² is subjected to corona treatment, layer A is 20 μm, layer B is 5 μm
With this, a transparent freshness retaining film having a total thickness of 25 μm was obtained. The evaluation results of this film are shown in Table 1.

Example 2 0.5% by weight of stearyl monoglyceride and 0.5% of stearyl ethanolamine monostearate as antifoggants were added to a propylene homopolymer (MFR = 2.0 g / 10 min) having a melting point of 165 ° C.
layer A with a melting point of 130 ° C. and an ethylene content of 2
wt%, a propylene ethylene butene copolymer having a butene content of 9 wt% (MFR = 6.0 g / 10 min), a silica having pores having an average particle diameter of 2 μm and an average major axis of 3.4 nm as an adsorbent. Aluminum oxide 0.7
0.2% by weight of magnesium oxide having an average particle size of 2 μm.
After co-extrusion of layer B in which 7 wt% was mixed and 0.3 wt% of silica particles having an average particle diameter of 3 μm were mixed as an antiblocking agent, it was stretched 4.5 times in the longitudinal direction and 9 times in the direction perpendicular thereto, Further, the processing strength of both A surface and B1 surface is 20 w
・ Corona treatment at min / m ² , layer A is 20 μm,
A transparent freshness retaining film having a layer B of 5 μm and a total thickness of 25 μm was obtained. The evaluation results of this film are shown in Table 1.

Example 3 1.4 wt% of aluminum silicate having an average particle diameter of 2 μm and an average long diameter of 1.4 nm was mixed as an adsorbent in the layer B, and the average particle diameter was 2. 0.3wt of 5μm PMMA particles
%, A transparent freshness retaining film was obtained in the same manner as in Example 2. The evaluation results of this film are shown in Table 1.

Example 4 Hydrophobic silica particles having an average particle diameter of 2.5 μm (Silohobic # 200, manufactured by Fuji Silysia Chemical Ltd.) treated with an organosilicon compound as a blocking inhibitor in Layer B were added to 0.1%. A transparent freshness retaining film was obtained in the same manner as in Example 2 except that 3 wt% was mixed. The evaluation results of this film are shown in Table 1.

Example 5 Corona treatment strength was 8 w · mi
A transparent freshness retaining film having a total thickness of 30 μm was obtained in the same manner as in Example 4 except that the thickness was changed to n / m ² and the thickness of the layer A was changed to 25 μm. Table 1 shows the evaluation results of this film.
It was shown to.

[0025]

[Table 1]

Comparative Example 1 A film was obtained in the same manner as in Example 2 except that the adsorbent, the antiblocking agent and the antifogging agent were not mixed into the layer B. The freshness retention period of this film was 5 days, which was problematic in practical use.

Comparative Example 2 6 wt% of aluminum silicate having pores having an average particle diameter of 2 μm and an average long diameter of 3.4 nm and 6 wt% of magnesium oxide having an average particle diameter of 2 μm were used as adsorbent in layer B. A film was obtained in the same manner as in Example 2 except that the mixture was carried out by%. The haze value of this film was 23.0%, which was problematic in practical use.

Comparative Example 3 A film was obtained in the same manner as in Example 2 except that 1.4% of a synthetic zeolite having an average particle diameter of 3 μm was mixed in Layer B as an adsorbent. The freshness retention period of this film was 5 days, which was problematic in practical use.

Comparative Example 4 A film was obtained in the same manner as in Example 2 except that 1.4% of calcium hydroxide having an average particle diameter of 3 μm was mixed in Layer B as an adsorbent. The freshness retention period of this film was 5 days, which was problematic in practical use.

Comparative Example 5 A film was obtained in the same manner as in Example 2 except that 1.4% of calcium oxide having an average particle diameter of 2.5 μm was mixed in Layer B as an adsorbent. The freshness retention period of this film was 5 days, which was problematic in practical use.

[0031]

According to the present invention, in particular, when packaging agricultural products, by mixing a specific adsorbent etc. while maintaining transparency and satisfying anti-blocking properties and ensuring sufficient packaging suitability. , Freshness retention can be enhanced.

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Claims (5)

[Claims] 1. A mixture of aluminum silicate having an average particle diameter of 0.5 to 5 μm and magnesium oxide having an average particle diameter of 0.5 to 5 μm is coated on at least one surface of a base material layer A made of polypropylene. A transparent freshness retaining film having a heat seal layer B having a thickness of 1 to 10 μm containing 10 to 10 wt% and having a haze value of 1.0 to 12% and stretched in at least one direction. 2. A base material layer A made of polypropylene having a thickness of 0.1 to 1 wt% containing 0.1 to 10 wt% of aluminum silicate having an average particle size of 0.5 to 5 μm on at least one surface.
It has a heat seal layer B of 0 μm and a haze value of 1.0 to
A transparent freshness retaining film which is stretched in at least one direction at 12%. 3. The transparent freshness retaining film according to claim 1, wherein fatty acid glyceride and / or fatty acid diethanolamine are coordinated on the surface of the heat seal layer B. 4. The heat seal layer B has an average particle size of 1.0
0.05 to 1.0 wt% of silica particles or polymethyl methacrylate particles having a particle size of from 4.0 to 4.0 [mu] m, and blocking strength at 40 [deg.] C. between the layers B and between the layers B and the side opposite to the layer B. Is 12 N / 12 cm ² or less, respectively. 5. A package, wherein an agricultural product is packaged with the transparent freshness retaining film according to any one of claims 1 to 4.