JPS60105540A - Laminated film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laminated film suitable for food packaging. More specifically, the present invention relates to a laminated film with excellent gas and water vapor barrier properties suitable for vacuum packaging, which is a field of food packaging.

The vacuum packaging method referred to here means, for example, that packaging film (including sheets) is heated and softened in advance, then formed into a container shape that is larger than the item to be packaged, the item to be packaged is placed in the container, and then the packaging film (including sheet) is heated and softened. Either by sealing it with a lid material at the bottom to form a vacuum package, or by covering the packaged item placed on the composite material with a film that has been softened by heating, and deaerating the space between the composite material and the film. Refers to a packaging method that creates a vacuum package that is deformed according to the shape of the packaged material and attached to the composite material.

There has been a lot of research into using laminated films with enhanced gas barrier properties as packaging materials for vacuum packaging to improve the long-term shelf life of contents such as raw meats, processed meats, and fresh sweets. However, at present, there are no laminated films in the packaging field that have vinylidene chloride resin as a layer component, and in particular, there are no laminated films that satisfy all of the quality requirements in the packaging field.

The reason for this is that vinyl chloride IJ-based resin has high barrier properties against oxygen, water vapor, etc. (and is an excellent film material that is highly flexible), but it is necessary to make a laminated film using this as a layer component in the packaging field. When used for this purpose, a necking phenomenon as shown in Fig. 1bJ occurs, making it difficult to obtain a good quality package.
- This is because it may not even be able to exhibit its essential barrier properties.

This necking phenomenon is caused by, for example, when a multilayer film that has been subjected to heat is stretched, stretching spots that begin to appear in the vinylidene chloride resin layer propagate to other adjacent adhesive resin layers, surface layers, and heat seal resin layers. This is a phenomenon in which the multilayer film is not stretched uniformly as shown in Figure 1 (al), and uneven stretching occurs as shown in Figure 1 (bJ), resulting in the entire multilayer film having a striped appearance.

It is possible to prevent this necking phenomenon by changing the resin layers in the laminated combination, but it is extremely difficult to prevent this necking by achieving a high level of quality required in the packaging field. It will also happen.

The present invention has been made in view of the current situation.

The first object of the present invention is to use vinylidene chloride resin as a layer component of the laminated film for vacuum packaging, and to
Provides high gas barrier and water vapor barrier properties that are unaffected by the humidity of the packaged item and the environment.
The second purpose is to expand the range of application of vacuum packaging.
Necking resistance, whitening resistance, pinhole resistance, mold reversion resistance, shape retention, bending whitening resistance, wrinkle resistance, molded part toughness, curling resistance of sealed flange, shape reproducibility 1
An object of the present invention is to provide a film that achieves both high levels of surface gloss and molding temperature suitability.

The purpose of 1.2 above is to add the film of the present invention, i.e., a vinylidene chloride resin layer as a core layer, to the surface layer, heat seal I/L, with or without an adhesive resin layer, to the multilayer film structure.
(i) The surface layer is an impact-resistant methyl meccrylate resin with a heat deformation temperature of 90°C or less; (2) the heat seal resin layer is A composition mainly consisting of one selected from the group of low-density polyethylene with a thickness in the range of 30 to 100 microns, polypropylene, ethylene-vinyl acetate copolymer, ethylene autopropylene 1/1 copolymer, and ethylene-based ionomer 411j resin. (3) Between the thickness of the vinylidene chloride resin layer (TcJ and the thickness of the surface layer (TaJ), Ta is in the range of 5 to 35 microns, and 0.4 X Ta + 61B Tc, g 1.2
The relationship of This can be easily achieved by adopting the structure of a barrier laminated film with fa.

Hereinafter, the content of the present invention will be explained in detail using result tables and the like.

First, we will discuss the premise of the present invention, that is, a film with a 3 to 5 layer structure in which a core layer is a vinylidene chloride resin layer, and a surface layer and a heat seal resin layer are provided with or without an adhesive resin layer. This is an essential requirement for imparting barrier properties to the film and achieving the first objective of the present invention, and the level of gas barrier required in the packaging field requires that the vinylidene chloride resin layer This can be sufficiently achieved by setting the thickness to 2 microns or more.

Therefore, the important constituent requirements of the present invention are: (1) the surface layer is made of impact-resistant methyl methacrylate resin with a heat distortion temperature of 90C or less; (2) the heat seal resin layer is of low density with a thickness in the range of 30-100 microns. The resin has a composition mainly consisting of a part selected from the group of polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, and ethylene-based ionomer resin; ■ The cyclized vinylidene-based resin layer The TIL between the thickness (Tc) and the thickness (T'a) of the surface layer is in the range of 5 to 35 microns, and 0.4 X Ta + 6-4 Tel, 1.2 X
It is a combination of the above requirements q) to ② that the relationship of Ta + 12 is maintained;

The reason why this is necessary is to combine and design the unknown characteristics of the laminated filter produced by the combination of the resin layers in order to solve the problems specific to the vacuum packaging method, and as a result, the second aspect of the present invention The purpose of Zunawa is to provide a high level of quality required in the vacuum packaging field.

It is inherently difficult to analyze the above requirements individually;
Furthermore, although it is quite possible that this may lead to misunderstandings, we will attempt to analyze each requirement below in order to clarify each tendency.

First, the necessity of requirement ① is shown in Table 2.

From the results in Table 2, for example, if the surface layer resin of the laminated film is replaced with another resin, such as a similar high-impact polystyrene resin, polystyrene/polymethyl methacrylate, or crystalline polyamide or polypropylene, the resin composition Not only will the balance be lost and a part of the required quality will be lost, but even worse, molding will not be possible at all. Furthermore, even if the same impact-resistant methyl methacrylate resin is used, if the heat deformation temperature of the resin is too high (over 90C), the molded part may lose its gloss, cause whitening when folded, or reduce mold reproducibility. The result is a loss of 5. Furthermore, research conducted by the present inventors has revealed that a material f having a heat distortion temperature of 55° C. can be used.

Considering the results in 1-1 below, among the surface layer resins used in the evaluation, styrene resins, polypropylene, etc. are considered to have extremely small dimensional changes and stress/generation due to changes in temperature and humidity. This can also be seen from the low hygroscopicity of the resin. On the other hand, it is well known that polyamides, methyl methacrylate resins, etc. have hygroscopic properties, and there is a correlation between dimensional changes and moisture absorption rates of these resins. However, there is a large difference in curl variability due to changes in temperature and humidity exhibited by molded articles having surface layers made of these two types of resins. In other words, those with a surface layer made of polyamide suffer from severe curl fluctuations and poor appearance, making them difficult to put into practical use.On the other hand, those with a surface layer made of methyl methacrylate resin have a surface layer made of the above-mentioned styrene resin or polypropylene. It was found that the behavior was similar to that of the conventional one, and there was almost no curl variation. Here, the uniqueness of the impact-resistant methyl methacrylate-based imj11, which is difficult to imagine based on conventional knowledge, is revealed and is very interesting.

The heat deformation temperature of impact-resistant methyl methacrylate resin can be changed by selecting the grade of the base methyl methacrylate resin, the grade of rubber added, and its concentration, but it is If it is too high, the effect of improving impact resistance is poor and although it has high rigidity, it becomes brittle, making it difficult to use in this field. If the temperature is too low (over 55°C), the influence of the rubber will be strong and the impact resistance will be further improved, but on the other hand, the rigidity will decrease and shrinkage after molding will gradually appear, especially when molded elongation. Some large corners tend to shrink (
There is a possibility that mold reproducibility will be lost on the child side.

Next, the necessity of component (■) is to ensure sealing performance with the lid material and mixture material to be combined, as well as to facilitate ripening in vacuum packaging, and the relationship is shown in Table 3. It is shown.

The results in Table 3 show that the thickness of the sealing layer required for the film of the present invention is in the range of 3o-ioo microns.

This phenomenon is presumed to facilitate heating in the thickness direction in order to impart thermoformability to the individual surface layer resin whose moldability temperature range is higher than that of the heating side surface layer resin. Furthermore, the resin used for the sealing layer is sufficient as long as it has sealing properties with the lid material and the cover, and the resin layer and resin composition are selected depending on the other resin to be sealed, but it is widely used in the field. The main resin is selected from the group consisting of low-density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, and ethylene-based ionomer resin. It is presumed that any resin composition can meet this evaluation quality as long as it is within the above thickness range.

Next, the reason why configuration requirement (2) is necessary is shown in FIG.

This figure 2 shows the hypothesis of the present inventors, that is, the % quality of the film of the present invention is determined by the thickness (Tc) of the vinylidene chloride resin layer.
Thickness of impact-resistant methyl methacrylate resin layer (Ta)
It is an analytical diagram of a laminated film created based on the hypothesis that it is determined by a certain relationship between This figure is a rectangular coordinate with (TC) on the vertical axis and (Ta) on the horizontal axis.
The symbols of the overall evaluation in the table are plotted. In other words, we need a film that has the highest standards of properties such as reversion resistance, pinhole resistance, curl resistance, content deformation resistance, thickness distribution, molded part wrinkle resistance, and whitening resistance. Items that are not included are marked with an ◎ mark, and items that are not included are collectively indicated.

According to the results in Figure 2, there is a tendency for those marked with ◎ to be in the center and those marked with . Items with good evaluations are concentrated inside the quadrilateral that connects each item with a straight line.

By the way, point a (35, 54) corresponds to experiment Nl130, and point β
(5, 18) corresponds to experiment No. 50, and point γ (5, 8) corresponds to experiment N.
159, and the point δ(35, 20) is the experiment Na, respectively.
The overall thickness of the film is approximately 140 microns, and the factor of overall thickness has been eliminated.

Therefore, the straight line αβ is represented by Te=1.2 XTa+12, and the straight line γδ is represented by Tc=0.4 XTa+6.

Therefore, in order to provide the film of the present invention with the desired properties of the present invention, the relationship between (Tc) and (Ta) is as follows:
At least (Ta) is in the range of 5 to 35 microns, and 0.4XTa-to 13 6TC! ,,-1-2X
This indicates that it is necessary to satisfy the relational expression Ta+1 2.

The inventors' hypothesis in designing the experiment shown in Figure 2 (Table 4) was that in applying the resin composition of the film layer of the present invention in this application, temperature unevenness due to heating (i.e., layer thickness and Temperature unevenness in the thickness direction that occurs as a result of specific heat is unavoidable, and therefore the properties of each resin that would be exhibited under such conditions were considered to be more suppressed than they were in essence. For example, the quality of the film that is the object of the present invention must be maximized under the suppressed conditions, and the relationship between the combination of (Tc) and (1'a) must be the original one. is considered to occur with some other regularity.

Although this hypothesis was generally correct, it did not necessarily work out as expected in the details.

For example, in terms of pinhole resistance, whitening resistance, molding temperature suitability, etc., adaptability to the range of (Ta) > o-4 (TC-6), that is, adaptability to thicken Ta, inhibits flexibility. This has not only been refuted, but the suppression of characteristics due to insufficient temperature, as hypothesized, has been demonstrated.

On the other hand, the adaptability to the range of (Te) > 1.2 This has been refuted by the tendency of (Tc) to play an interesting role in this field.

This phenomenon is generally considered to be a phenomenon in which the heat shrinkability and weakness of (Te) are balanced by the rigidity and toughness of (Ta).

However, if the container is formed into a container shape and then filled with the contents and vacuum sealed, the shrinkage must be suppressed until the container is filled with the contents.
In the process after deaeration, the margin in the size of the container relative to the contents must be overcome by shrinkage, and furthermore, the contents are coated in a deaerated state and deformed to match the external shape of the contents. In this case, when the contents are coated, it is in a malleable state, and the coating wave is 1&! At this temperature, the contents must be bound with a certain degree of shrinkage without causing deformation of the contents.

We must also satisfy these five contradictory demands (
・. In addition, when sealing with the lid material 2 composite material, the seal is formed in such a way that a part that is not subjected to forming stress remains thick and a part of the wall thickness is brought into the forming part and becomes thinner. The phenomenon is not the same as the balance problem that is commonly thought of, such as the tendency for distortion to occur due to t.

In particular, an unusual phenomenon that was found in the study of the present invention and which was extremely difficult was that when the lid material 9 composite material was sealed, the flange part did not become flat as shown in the third factor, but was curved. There is a curling phenomenon at the flange part. This phenomenon occurs in the form of a mixture of downward curves and upward curves, as shown in Figure 4, 111, tbl, and in various parts of the combinations of (Ta) and (Tc). This was a difficult phenomenon to occur. in the end.

The present invention, which defines the relationship between (Ta') and (Te),
When this 5-pit phenomenon was resolved, an unexpected effect was also demonstrated.

Next, the reason for the necessity of component (2) is shown in Table 5.

From the results in Table 5, in order to achieve the characteristics such as molded part toughness, molded part wrinkle resistance, and molding temperature suitability for this application,
This indicates the need for an overall film thickness in the range of 6.0 to 170 microns.

This phenomenon is caused by the characteristics of vacuum packaging applications, that is, when the laminated film is softened and deformed by heating from one side of the surface for a short time (especially heating from the sealing resin layer side), the resin composition of the present invention, that is, the rigidity Molding a barrier resin layer that is small and difficult to thermoform due to the large temperature dependence of flow deformation with a surface layer that is relatively rigid and has high flow viscosity and is flexible and has low temperature dependence of flow deformation. In order to bring out the characteristics of the laminated film, which is sandwiched between the ground layer and the ground layer, which is rich in properties, and somehow achieves harmony, it is necessary to heat each resin layer uniformly within a temperature range that allows it to be molded and deformed. Until the end of the molding process, it is important to maintain the temperature of each resin layer within its temperature range, and in reality, the resin layer with the lowest temperature that can be thermally deformed must be higher (heated) than the other resin layers. It is presumed that this phenomenon occurs because the heating direction is reversed.It is of critical technical significance to apply this type of reverse thermoforming to vacuum packaging.

The laminated film of the present invention having such structural requirements exhibits superior quality performance compared to commercially available vacuum packaging films and comparative products.

In Table 6, (XI, IYI, [Z+ are currently commercially available products, sample NfL 10.

27, 37, 62, 73 are comparative products, N[L21,
Nos. 44, 55, and 65 are the laminated films of the present invention (including range confirmation), and are compared in °C based on comprehensive evaluation.

According to the results in Table 6, the film of the present invention exhibits an outstanding effect of satisfying all Revision 111b JJt requirements with a high level of quality, and is classified better than any of the current commercially available products and comparative products. .

The film of the present invention, which has excellent quality performance as described above, can exhibit the barrier properties of vinylidene chloride resin against light, so it is beneficial for the shelf life of contents and expands the scope of application of vacuum packaging. be able to.

The beylidene resin used in the present invention is mainly composed of vinylidene chloride and is a copolymer of vinyl chloride, methacrylnitrile, acrylonitrile, vinyl acetate, acrylic acid, etc.

The impact-resistant methyl methacrylate-based resin used in the present invention includes, for example, a center layer made of a hard polymer mainly composed of methyl methacrylate, and an alkyl acrylate whose alkyl group has 1 to 8 carbon atoms. A composition basically having a three-layer structure consisting of an intermediate layer made of a soft polymer and an outermost layer made of a hard polymer whose main component is methyl methacrylate (for example, JP-A-52-58150). .53
-58554゜57-200411. 57-200
412. 5B-62046 isobarically disclosed composition) and a polymer whose main component is methyl methacrylate.

The sealing resin used in the present invention includes, for example, low-density polyethylene, ethylene-vinyl acetate copolymer (with a vinyl acetate content of 0.3 to 40%), Kochile 7 series-RIA zimmer resin, ethylene・It refers to a composition whose main component is one selected from propylene copolymers, borig sigma pyrene, etc.

In the present invention, the heat distortion temperature refers to a load of 1 & 6 kl/l according to ASTM, D-648, and a heating rate of 2°C.
Measured under conditions of 7 minutes.

The evaluation method and scale used in the present invention are as follows.

■] The film to be evaluated for moldability is supplied in a continuous state with the Nour layer on the top, heated from the top with an impulse heater, and the mold placed on the bottom of the film is depressurized, while at the same time pressurized air is introduced from the top to form a container. After forming the product into a shape and filling it with the contents, the lid material is placed over the top and vacuum packaged, and then the flange is heated and sealed from the top using an infrared heater.
((Ten) Molded using a vacuum packaging machine PF537 manufactured by Shin-Daigo Iron Works, and its molding properties are necking resistance and puncture resistance.

The items of mold reversion resistance, molding temperature suitability, mold reproducibility, and molded part 4 wrinkling were evaluated according to the evaluation method and evaluation scale shown below, and samples marked with ◎ and Q were judged to have excellent molding suitability.

Water injection Judgment was made based on the discoloration of the thermolabel (manufactured by Tika Sangyo Co., Ltd.) attached to the surface layer of the film.

(11 Molding Temperature Appropriate Depth 15% L Using a mold with an inner diameter of 95 mm, the heating time of the impulse heater was changed from 0.6 to 1.6 seconds by 6 ranks at 0.2 second intervals, and the obtained Visually observe whether there are any defects in the appearance of the container shape, such as a torn film or poor shape.

(2; Mold reproducibility The obtained container shape is measured using a curvature gauge that measures the curvature of a part of the corner in the cross section of the molded container shown in FIG.

(3) Resistance to mold reversion For the obtained container shape, measure L and L in the cross section of the molded container shown in Figure 6 (phantom), and compare this with D' and L' in the cross section of the mold shown in Figure 6 (bl). Then, calculate P using the formula below.

(4) Six-morning resistance Film heating rank...(0.8 seconds) to 20% depth.

Using a molded product with an inner diameter of 95%, 20 molded bodies are created for each of the films to be evaluated, and whether or not the resulting container shape has holes is visually observed.

(5) Necking resistance Using a mold with a depth of 20% and an inner diameter of 95 mm, the film to be evaluated is molded across 6 film heating ranks, and whether or not necking patterns occur in the resulting container shape. Observe with the naked eye.

(6) Molding part 1 Using a mold with a wrinkle depth of 15% and an inner diameter of 95%, the film to be evaluated was molded at a film heating rank of n (o, s seconds), and the resulting container shape was molded with a diameter of 94%. After stuffing sliced ham with a thickness of 149 cm and vacuum packaging, wrinkles in the film that enters the bottom of the container are observed with the naked eye.

■] The film to be evaluated for practical suitability was formed into a container shape using a vacuum packaging machine PF537 manufactured by Shin-Daigo Iron Works. The toughness of the molded part was evaluated according to the evaluation method and scale shown below, and the molded container was stuffed with sliced ham and vacuum packaged. The samples were evaluated according to the evaluation method and scale shown in , and the samples marked with ◎ and () were judged to have excellent practical suitability.

(1) For each film to be evaluated for pinhole resistance, 20 packages were placed in a cardboard box (inner dimensions: height 1.40 yen).

After placing the cardboard box in a box (150% vertically and 400% horizontally), the horizontal sides of the cardboard box were clamped and rotated for 5 minutes at a speed of 601 mm. Visually observe whether vacuum return occurs in the removed package.

(2) Heating the film with an impulse heater to rank n for shape retention evaluation
(o, s seconds) using a mold to a depth of 159 and a diameter of 9.5 mm, place the container with the bottom side up on a solid flat surface, and pour hard salt onto the bottom to a thickness of l. Bisito (vertical 100)
5% x horizontal 1009) and place a load (weight) on top of it.
Place the container gently on the container and visually observe the deformation of the container shape.

Impulse heater heating rank n for the film to be evaluated
(o, s seconds) to a depth of 15, sandwiching the four sides of the container-shaped flange formed with a mold with a diameter of 95% with iron clamps,
It was fixed at the height SCa. Inside this container is a diameter of 94t.
, insert a cylindrical paper tube with a wall thickness of 59 mm and a height of 209 mm, place a 29 mm thick iron plate on top of this paper tube, and drop an iron ball (weight 3 ooys) from the iron plate J: 0.3 m. The container was dropped repeatedly until it burst.

(4) Heating the film with an impulse heater to rank n
(Mold using a mold with a depth of 15 mm and a diameter of 95 mm in seconds, fill this container with sliced ham of 141 mm in thickness and 94 mm in diameter, overlap the lid material, vacuum pack it, and top it up. Then, the film is heated by radiant heat using an infrared heater until the film temperature reaches 100°C to seal it.

The adhesive strength between the film to be evaluated and the lid material of the obtained molded body is measured using an Instron type tester (tensile speed 100/min, sample 1J 15%).

The Ti material used here is a laminate film having the structure described in 1 above.

Outside Seal side O P /pvDc=+-tocellophane/EVA (VA 5%) 20μ 23μ
The sealing layer of the 40 μ laminated film was made of an ionomer resin, and the sealing side resin of the lid laminated film was made of an ionomer resin.

■] The film to be evaluated for appearance quality was placed in a mold with a depth of 1 x 1 and a diameter of 95 holes using impulse heater heating rank II (0.8 seconds) using a vacuum packaging machine PF537 manufactured by Shin-Daigo Iron Works. Filled with shaped sliced ham (height: 41. Diameter: 94), layered with a commercially available lid material and vacuum-packed with flange fsI~
The packages obtained by heat-sealing with a suitable infrared heater are evaluated as shown below regarding surface gloss, transparency, g-shaped part whitening resistance, bending whitening resistance, curling resistance, and curling resistance. Evaluation was made according to the method and evaluation scale, and those marked with ◎ and Q were judged to have excellent appearance quality.

(1) Surface gloss The bottom film of the resulting package was cut out, and the surface gloss of the film was measured using the JIS, Z8/741 method (
The angle of incidence is 45°).

121 After cutting out the bottom film of the resulting transparent package and wiping off the dirt from the ham juice on the inside with ethanol, the degree of haze was measured according to the method of ASTM I003, and h = haze degree after molding - haze before molding. Evaluate by degrees.

(3) Resistance to whitening of molded part The resulting package was placed on a matte black mount and observed with the naked eye to see if it had whitened or not.

(4) 7-rank part of the package with bending resistance to whitening: vertical 2 o λX horizontal 201
The film was cut to a size of 1, with folds made in two directions perpendicular to the machine direction and the machine direction, and observed with the naked eye on a black matte mount.

t5J Displacement from the horizontal position of the rank 7 part of the package that has achieved curl resistance (
Figure 7 (II, II' of allbl) is measured.

(67 Curl resistance) After leaving the resulting package in a refrigerator at a temperature of 5C and a humidity of 80%, measure the curl property !, 2', and compare it with !, 4' before storing in the refrigerator. The value of r; average value after storage in the refrigerator - average value before storage in the refrigerator A flat film having the layer arrangement and thickness shown in the table and adjusted to 5 was formed.

The obtained films (Samples N11l to 14) were evaluated according to the evaluation method described in the text for each item of surface gloss, transparency, molded part wrinkle resistance, bending whitening resistance, mold reproducibility, and curling variability. The results are shown in Table 2.

Based on the NY value results, it was found that if the surface layer was replaced with another resin, molding would become impossible, wrinkles would appear in the molded part, and transparency would be impaired.
:C51,c which leads to the following drawbacks.

Furthermore, even if the same impact-resistant methyl methacrylate resin is used, if the heat deformation temperature of the resin exceeds 90°C, defects will occur in surface gloss, whitening on bending, and mold reproducibility. After all, surface gloss, transparency, molded part wrinkle resistance, bending resistance to whitening, and mold reproducibility.

It has been found that in order to exhibit a high degree of curl resistance, an impact-resistant methyl methacrylate resin having a heat deformation temperature of 90° C. or lower is used for the surface layer on one side of the laminated film.

Example 2 Using the resins A to D shown in Table 1, a flat film was formed by coextrusion from a T-die using four extruders and adjusted to have the layer arrangement and thickness structure shown in Table 3. It was filmed.

The obtained films (Samples N115 to 27) were evaluated for sealing properties, anti-necking properties, and anti-whitening properties according to the evaluation method described in the text, and the results are shown in Table 3.

From this evaluation result, when the thickness of the seal layer is less than 30 microns, defects tend to occur in the sealing performance with the mating material. Furthermore, if the thickness exceeds 100 microns, necking is likely to occur, and the film on the molded part becomes white. It has been found that in order to achieve a high degree of performance, the thickness of the sealing layer should be in the range of 30 to 1()0 microns.

Example 3 Using resins A to D shown in Table 1, coextrusion was carried out using four extruders through T-dies so that the overall thickness of the layer arrangement and thickness structure shown in Table 4 was approximately 140 microns. A flat film adjusted to the above was formed.

The obtained films (Samples N128 to 61) were evaluated for size resistance, shape retention, remolding resistance, whitening resistance, pinhole resistance, curl resistance, mold reproducibility, and molding temperature suitability. It was evaluated according to the evaluation method shown in Table 1 and the results are shown in table wJ4.

The design of Example 3 is based on the hypothesis of the present inventors, that is, in applying the film layer resin structure of the present invention to vacuum packaging applications,
Temperature unevenness that occurs in the thickness direction of the film layer cannot be avoided (
Therefore, the characteristics of each resin that would be exhibited in that state are suppressed from their essential properties, and the thickness (Ta) of the impact-resistant methyl methacrylate resin layer
This is based on the hypothesis that the relationship between the combination of and the thickness (Tc) of the vinylidene chloride resin layer has a regularity different from the original one.

However, nothing can be deciphered from Table 4 of the enumerated results. Therefore, in the evaluation in Table 4, the items in which all the evaluation items were evaluated at the highest level are marked with ◎, and those that do not meet the conditions are shown with * to stratify them, and the stratification symbols are shown in Figure 2. The results were plotted and analyzed.

The analytical diagram in Figure 2 shows (Tc) on the vertical axis and (Ta) on the horizontal axis.
) are rectangular and angular coordinates.

According to the second plot distribution, there is a tendency for the distribution to curve around the area marked with ◎ and the area marked with . Considering the classification of the two, the coordinate points a, β
, γ, and δ can be defined as one area by a quadrilateral connecting them with straight lines. By the way, the locus-like point α (:3 s, 54) points to the sample ridge 30,
β(5,18) is the sample Ugly 50, r(5,8) is the sample m59, and J(35,20) is the sample N149.

Therefore, the straight line aβ is Te = 1.2 X Ta + 1
2. The straight line ya is 'l'e = 0.4 X Ta +
It can be expressed as 6.

Also, since the overall thickness of the film is set to 6140 microns, this can be eliminated as a factor.

Therefore, the relationship between (Tc) and (Ta) for the film of the present invention to achieve the object of the present invention is such that (T&) is at least in the range of 5 to 35 microns and 0.4 Ta 4-64 Tel, 1. 2
This shows that the relational expression of X Ta + 1 2 must be simple. This relationship shows the correctness of the hypothesis of the present inventors.

Example 4 The A-DO) resin shown in Table 5 was coextruded from a T-die using four extruders to form a flat film with a 11v arrangement so that the layer arrangement and n-shape structure shown in Table 5 were obtained. It was filmed.

The obtained films (Samples N162 to 73) were evaluated in terms of molded part toughness, molded part wrinkle resistance, and molding temperature suitability according to the evaluation method described in the text, and the results are shown in Table 5.

From this evaluation result, if the overall thickness is less than 60 microns, the toughness of the molded part is likely to be insufficient (or wrinkled), and the molding temperature suitability is narrowed. If it is too thick, it will warp and the molding temperature suitability will be narrowed, and large wrinkles will easily form.

After all, in order to achieve a high level of quality in terms of toughness of the molded part, wrinkle resistance of the molded part, and molding temperature suitability, the overall thickness must be between 60 and 17 mm.
It can be seen that the film should be in the 0 micron range.

Example 5 Three types of commercially available films shown below were purchased, and (3
), (η, ri; symbols are attached.

Symbol Manufacturer Total thickness Layer composition (X) Company X 148μ See Table 6 (Y) Company Y 158μ See Table 6 (Z) Company X 100μ See Table 6. Representative samples from this series 1.11-j are 21, 44, 55, 65. Representative samples of comparative products [1
, 27, 37, 62, and 73 were selected and evaluated for all items of moldability, practical Jability, and appearance quality as defined in the present invention using the methods described in the text, and the results are shown in Table 6.

According to the evaluation results, it can be seen that the film of the present invention is the only film that satisfies all the evaluation items of the present invention at a high level.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the necking phenomenon, [a2 is a cross-sectional view of the laminated film in a good stretched state without the necking phenomenon;
(bl is a cross-sectional view of the laminated film in which the necking phenomenon occurred. Figure 2 is an analysis diagram. Figure 3 is a diagram showing a package with no curl in the 7 rank part. Figure 4 is a diagram showing the 7 rank part of the package without curling. This indicates a package with a curled part.
(&) shows a state in which it is curled upward, and (b) shows a state in which it is curled downward. FIG. 5 is an explanatory diagram of measurement sites in U non-tax assessment. Figure 6 is an explanatory diagram of the measurement site in the evaluation of mold reversion resistance.
a) is a diagram showing the measurement site of the molded container, (bl is a diagram showing the measurement site of the molded product. Figure 7 is an explanatory diagram of the measurement site in curl resistance evaluation. Patent applicant Asahi Kasei Industries, Ltd. Figure 1 (a) (b) Fig. 2 A scrap/l thickness, I+ (To), thickness 0 Fig. 3 Fig. 4 (a) (b) Fig. 5 Fig. 6 (a) (b) Fig. 7 (a) (b)

Claims (1)

[Scope of Claims] 1. A film with a 3-5 layer structure in which a vinylidene chloride resin layer is a core layer and a surface layer and a heat seal resin layer are provided thereon with or without an adhesive resin layer, (11) The surface layer is an impact-resistant methyl methacrylate resin with a heat deformation temperature of 90°C or less; (2) the heat-sealing resin layer is low-density polyethylene or polypropylene with a thickness in the range of 3 () to 100 microns; (3) Thickness (Tc) of the vinylidene chloride resin layer; (3) Thickness (Tc) of the vinylidene chloride resin layer; and,
The thickness of the above surface layer (between TaJ and Ta is in the range of 5 to 35 microns, 0.4 x 1'a → 64 Tc 41.2 x Ta
+12 relationship is maintained; (4) the overall thickness of the film is in the range of 60 to 170 microns; and the above conditions (II to (4)) are satisfied. Barrier laminated film