JPH0752342A - Laminated sheet for molding - Google Patents

Abstract

PURPOSE:To obtain a molding laminated sheet based on a polypropylene resin not generating the wrinkles or thickness irregularity in a molded product due to sagging, excellent in thermal moldability and improved in gas barrier properties to a large extent. CONSTITUTION:In a molding laminated sheet wherein a polypropylene resin layer is laminated to at least the single surface of a gas barrier resin layer, the thermal shrinkage stress measured according to ASTM-D-1504 of the molding laminated sheet shows the max. value of 100-300g/cm<2> within the temp. range of the m.p. of a polypropylene resin - the m.p. +20 deg.C and the thickness ratio of the polypropylene resin layer with respect to the total thickness of the molding laminated sheet is 70% or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated sheet for gas barrier molding, which is mainly composed of polypropylene resin and is used for packaging of food etc. by molding it into a container by thermoforming such as vacuum forming or pressure forming. Regarding

[0002]

2. Description of the Related Art A laminated sheet for molding in which a polypropylene resin layer is laminated on at least one surface of a gas barrier resin layer such as a vinylidene chloride copolymer or an ethylene-vinyl alcohol copolymer with an adhesive layer, Molded into containers and the like by thermoforming such as molding and pressure molding, it is widely used for packaging foods and the like that require gas barrier properties.

Such a laminated sheet is generally produced by a coextrusion method or a heat laminating method. The co-extrusion method is a method in which resins are simultaneously extruded from a plurality of extruders and used for laminating T.
This is a method of stacking with a die to form a sheet and solidifying with a cast roller. The heat lamination method is to apply an adhesive to a gas barrier film that has been formed in advance,
In this method, a molten polypropylene resin layer extruded from a T-die is superposed on it.

This laminated sheet is in a substantially non-oriented state,
The laminated sheet has properties different from those of the stretch-oriented laminated sheet in that there is no dimensional change due to heat during thermoforming and a large elongation deformation along with the mold can be obtained. On the other hand, a problem in thermoforming the laminated sheet for molding is a defective phenomenon in which the sheet hangs down by its own weight during heating for molding, and this defective phenomenon is generally called sag. This sag
When this occurs, the molded product is wrinkled or the thickness of the molded product becomes uneven, which causes defective products. This phenomenon is generally observed in polypropylene-based molding sheets, but it is particularly noticeable in a laminated sheet with a gas barrier resin because the melt tension of the gas barrier resin is low. Moreover, in recent years, further improvement in gas barrier property is required due to long-term storage of foods and the like, and therefore, it is attempted to increase the thickness of the gas barrier resin layer, but as a result, sag becomes large. , Sag has been earnestly desired. As a measure to prevent this sag,
A method using a polypropylene resin having a high melt viscosity is proposed in Japanese Patent Laid-Open No. 61-79650.

[0005]

However, the high melt viscosity, for example, the melt flow rate (MFR) is 0.2 g.
When actually thermoforming a laminated sheet using a polypropylene resin having a value of / 10 minutes (ASTM-D-1238, 230 ° C), it is not always possible to sufficiently prevent sag, and therefore the molded product may be wrinkled. However, the thickness of the molded product is uneven and it is impossible to obtain a good product. Thus, the above-mentioned JP-A-6
It is considered that the proposal of Japanese Patent Laid-Open No. 1-79650 tries to utilize the low heat fluidity of the high melt viscosity resin for the sag prevention measure, but the low heat fluidity can suppress the size of sag. Is not a fundamental measure to prevent sag,
It is presumed that at the time of thermoforming, it becomes a cause of exacerbating the elongation deformation along the mold. In addition, since polypropylene resins having a high melt viscosity require a high extrusion processing temperature, there is a problem in that the gas barrier resin adjacent thereto has a thermal discoloration / deterioration.

The inventors of the present invention have conducted extensive studies to solve the above problems of the prior art, and as a result, did not cause deterioration or discoloration of the gas barrier resin, did not have molding defects due to sag in thermoforming, and reproduced the mold. It has been found that a laminated sheet for molding having excellent properties and improved gas barrier property is provided.

[0007]

The present invention is to solve the above problems. That is, the present invention relates to a molding laminated sheet in which a polypropylene resin layer is laminated on at least one side of a gas barrier resin layer via an adhesive layer, and the heat shrinkage measured by ASTM-D-1504 of the molding laminated sheet. The maximum stress is 100 g / cm ^{2 to} 3 in the temperature range of the melting point of polypropylene-based resin to the melting point + 20 ° C.
A value of 00 g / cm ² is shown, and the thickness ratio of the polypropylene resin layer to the total thickness of the molding laminated sheet is 70.
%, Which is a laminated sheet for molding.

The contents of the present invention will be described in detail below with reference to the drawings. The difference between the laminated sheet of the present invention and the conventional product is that the thermal shrinkage stress of the laminated sheet measured by ASTM-D-1504 is 100 g / cm ² of the maximum value in the temperature range of the melting point of the polypropylene resin to the melting point + 20 ° C. 300 g / cm
Indicate a value of ² .

The thickness ratio of the polypropylene resin layer to the total thickness of the laminated sheet is 70% or more. The need for is that even if the resin reaches a fluidized state during thermoforming,
This is to maintain tension and prevent the seat from hanging down due to its own weight. Heat shrinkage stress is 100 g / cm ^{2 to} 300
The need to show a value of g / cm ² is that if it is less than 100 g / cm ² , the tension cannot be maintained and the sheet hangs down due to its own weight, and if it is more than 300 g / cm ² , the elongation deformation along with the mold deteriorates. This is because a defect will occur. In addition, the thermal shrinkage stress is
The need to show the maximum value in the temperature range of melting point + 20 ° C is that if the maximum value is lower than the melting point of polypropylene resin, dimensional change due to heat during molding is large and molding becomes substantially impossible, and if it is higher than melting point + 20 ° C. This is because the tension state cannot be maintained during molding.

When the condition (1) is satisfied and the condition (2) is satisfied, good molding without sag becomes possible. That is, even a thermoplastic resin other than polypropylene resin, for example, a resin having poor thermoformability such as a gas barrier resin,
The total thickness may be less than 30% of the total thickness of the sheet. In the conventional laminated sheet, when the gas barrier resin layer is increased, the sag increases, so the thickness ratio could not exceed 3% at most, but in the sheet of the present invention, the gas barrier resin layer thickness ratio. Can be made 25% at maximum considering the interposition of the adhesive layer. This can significantly improve the gas barrier properties of the laminated sheet.

FIG. 1 is a conceptual diagram of a manufacturing process useful for obtaining the laminated sheet of the present invention. In FIG. 1, a method for producing a laminated sheet of the present invention (coextrusion method) is performed by melting a polypropylene resin from an extruder 1, an adhesive resin from an extruder 2, and a gas barrier resin from an extruder 3. Supply,
Combined with multi-layer T-die 4 and the layer structure is polypropylene resin / adhesive resin / gas barrier resin / adhesive resin /
The laminated sheet is made of polypropylene resin. T
The laminated molten resin that has been formed into a sheet by the die 4 is cooled and solidified by the cast roller 5 to form the laminated sheet 9.
The laminated sheet 9 passes through the take-up roller 6, the trim portion is cut by the trim cutter 7, and is wound into a cylindrical shape by the winder 8.

The important conditions in this case are, firstly, the T-die 4
By setting the ratio of the flow velocity of the resin flow passing through the lip portion of the cast roller 5 to the surface velocity of the roller first contacting the resin flow of the cast roller 5 to 1.5 to 3, and more preferably 2 to 2.5. is there. As a result, the resin molecules are stretched and oriented, and even the non-stretched sheet develops heat shrinkage stress. If the speed ratio is less than 1.5, the resin molecules are not sufficiently stretch-oriented, and the heat shrinkage stress of the sheet does not exceed 100 g / cm ² . Even if the speed ratio is larger than 3, the heat shrinkage stress is no longer large, but on the other hand, uneven thickness in the width direction of the sheet due to neck-in and uneven thickness in the width direction of each resin constituting the layer are generated.

Secondly, the elongation rate of the molten resin from the die exit of the T die 4 to the cast roller 5 is set to 5 or more. If the elongation rate is less than 5, the resin molecules are not sufficiently elongated and oriented, and it is difficult for the heat shrinkage stress of the sheet to reach 100 g / cm ² or more. The extension speed here means the ratio of the flow speed of the resin flow passing through the die lip portion of the T die 4 to the surface speed of the roller that comes into contact first with the distance from the outlet of the T die 4 to the cast roller 5 ( It is the value divided by m).

Thirdly, the surface temperature of the resin flow located 10 mmT from the point where the resin flow first contacts the cast roller 5 and the surface temperature of the resin flow, and cooling and solidification at a position moved 10 seconds downstream from that position. The difference from the surface temperature of the sheet is 100 ° C. or higher. If the temperature is lower than 100 ° C., the cooling rate is insufficient and stress relaxation occurs, so that the heat shrinkage stress of the sheet is hard to reach 100 g / cm ² or more. The resin flow and the surface temperature of the sheet are measured by a non-contact type thermometer using infrared rays.

As the gas barrier resin of the present invention, known resins can be used, but vinylidene chloride copolymers or ethylene-vinyl alcohol copolymers are preferred.
The vinylidene chloride copolymer referred to in the present invention is a copolymer containing vinylidene chloride as a main component and a monomer copolymerizable therewith, preferably vinylidene chloride / vinyl chloride copolymer or chloride. Vinylidene / methyl acrylate copolymer is used. The ethylene-vinyl alcohol copolymer referred to in the present invention is a vinyl alcohol unit obtained by saponification of a unit containing ethylene or ethylene as a main component and a small amount of an olefin such as propylene and a vinyl ester unit such as vinyl acetate. Is a copolymer having

MFR (ASTM-D-123) of polypropylene resins (including blended products) used in the present invention
8, 230 ° C.) is 0.3 g / 10 minutes to 3 g / 10 minutes, preferably 0.5 g / 10 minutes to 2 g / 10 minutes. This is because if it is less than 0.3 g / 10 minutes, extrusion molding becomes difficult, and if it exceeds 3 g / 10 minutes, it becomes difficult to make the value of the heat shrinkage stress of the sheet 100 g / cm ² or more.

In the present invention, the adhesive layer may be made of a known resin having adhesiveness to polypropylene resin and gas barrier resin, preferably ethylene vinyl acetate copolymer, unsaturated carboxylic acid modified polyolefin and the like. There is. The sheet of the present invention has a minimum structure in which a polypropylene resin layer is laminated on at least one surface of a gas barrier resin layer via an adhesive layer. Other resin layers may be provided as necessary. The laminating method is not necessarily the coextrusion method described above, and may be the thermal laminating method. In that case, the conditions for laminating the polypropylene resin layer may be the same as those described above in the coextrusion method.

The thickness of the laminated sheet of the present invention is not particularly limited, but 0.1 mm to 2 mm is preferable.

[0019]

EXAMPLES The present invention will be described below based on examples. The evaluation method and evaluation scale used in the present invention are shown below. (A) Sheet heat shrinkage stress measurement: ASTM-D-150
It measured based on 4. The measurement conditions are described below.

Sample distance between chucks: 100 mm Sample width: 20 mm The samples were sampled so that the sheet flow direction was the sample length direction. ○ Heating method: Silicone oil bath ○ Number of measurements: 10 times and averaged.

(B) Evaluation of sheet formability: Molding machine: FLV341 type molding machine [manufactured by Asano Laboratory Co., Ltd.] Molding method: Plug-assist vacuum molding ○ Shape of molding container: circular container with 70 mm diameter, high S: 2
0, 40, 60 mm ○ Number of containers molded at one time: 7 × 7 = 49 ○ Moldability evaluation method: 7 × 7 = 49 evaluation of the thickness distribution of the molded containers at the four corners (this position of the container is the thickest) Evaluation method for thickness distribution: The thickness at the middle of the container side wall, that is, at half the container height, is divided by the thickness of the center of the circle on the bottom surface of the container. The middle is the thinnest,
Since the center of the circle on the bottom is thickest, the closer it is to 1, the better the formability with less thickness unevenness.

The thickness ratio of the container is shown below and shown in Tables 1 and 2. Good range ... The thickness ratio of the container is 0.5 or more.

[0023]

Example 1 A polypropylene / polyvinylidene chloride laminated sheet was extruded into a film by the extrusion film forming apparatus shown in FIG. That is, in the extruder 1 [diameter 65 mm, L / D32], polypropylene resin [C resin = melting point: 165 ° C., MFR: 1
g / 10 minutes (230 ° C.)], extruder 2 [diameter 30 mm,
L / D28] is an ethylene-vinyl acetate copolymer resin [B resin = vinyl acetate content: 26%, MFR 4 g / 1.
0 minutes (190 ° C)], extruder 3 [diameter 30 mm, L / D
24], polyvinylidene chloride-based resin [A resin = vinylidene chloride component / vinyl chloride component: 90/10] is supplied and extruded, and they are merged by a multi-layer T die 4 [width 800 mm], and the resin composition and Composition ratio is C / B / A / B
/ C = 45/2/6/2/45 sheet-shaped melt was obtained, and cast roller 5 [diameter 300 mm, width 1000 m
m] to solidify by cooling to obtain a 5-layer sheet having a total thickness of 1.0 mm.

The extrusion film forming conditions at this time are as follows: total extrusion amount 50K
g / hour, resin temperature 220 ° C., lip interval of T die 4 is 2.0 mm, outlet of T die 4 and first pinch portion of cast roller 5, that is, a portion where the resin flow first contacts the cast roller 5. The distance was 200 mm, the surface speed of the cast roller was 1.13 m / min, and the surface temperature of the cast roller was 50 ° C.

The basic condition is that the ratio of the flow velocity of the resin flow passing through the lip portion of the T die 4 to the surface velocity of the resin flow on the cast roller 5 with which the resin flow first contacts is 2.0.
The value obtained by dividing the ratio with the surface speed by the distance from the outlet of the T die 4 to the cast roller 5, that is, the extension speed of the resin flow was set to 10. Further, the surface temperature of the resin flow located closer to the 10 mmT die 4 than the first pinch portion of the cast roller 5 is 200 ° C.
The surface temperature of the sheet at the position moved to the downstream side is 7 seconds.
It was 0 ° C, and the difference was 130 ° C.

Both sides of the sheet were cut by the trim cutter 6 so that the sheet width became 650 mm, and the sheet was wound into a cylindrical shape by the winder 8 to obtain the target sheet. AST
The heat shrinkage stress of the sheet measured according to MD-1504 reaches a maximum at 175 ° C., and the value is 160 g / cm ^2.
Met. The thickness ratio of the polypropylene resin layer to the total thickness of the laminated sheet is 90%.

[0027]

[Embodiment 2] The T die 4 has a lip interval of 1.5 mm,
The ratio of the flow velocity of the resin flow passing through the lip portion of the T die 4 to the surface velocity of the resin flow on the cast roller 5 with which the resin flow first contacts is set to 1.5, and the extension speed of the resin flow is set to 7. A five-layer sheet having a total thickness of 1.0 mm was obtained by the same configuration and manufacturing method as in Example 1 except that the thickness was set to 5.

The heat shrinkage stress of the sheet measured in accordance with ASTM-D-1504 reached its maximum at 175 ° C., and its value was 110 g / cm ² .

[0029]

Example 3 MFR 0.5 g / 10 min (230 ° C.), polypropylene having a melting point of 165 ° C. was used, the lip interval of the T die 4 was 3.0 mm, and the flow of the resin flow passing through the lip portion of the T die 4 The ratio of the speed to the surface speed of the resin flow on the cast roller 5 with which this resin flow first contacts is 3.0.
Then, a five-layer sheet having a total thickness of 1.0 mm was obtained by the same configuration and manufacturing method as in Example 1 except that the extension rate of the resin flow was set to 15.

The heat shrinkage stress of the sheet measured in accordance with ASTM-D-1504 reached its maximum at 170 ° C., and its value was 290 g / cm ² .

[0031]

[Comparative Example 1] The T die 4 has a lip interval of 1.4 mm,
The ratio of the flow velocity of the resin flow passing through the lip portion of the T die 4 to the surface velocity of the resin flow on the cast roller 5 with which the resin flow first contacts is set to 1.4, and the extension speed of the resin flow is set to 7. A 5-layer sheet having a total thickness of 1.0 mm was obtained with the same configuration and manufacturing method as in Example 1 except that the above-mentioned settings were made.

The heat shrinkage stress of the sheet measured in accordance with ASTM-D-1504 reached its maximum at 175 ° C., and the value was 90 g / cm ² .

[0033]

[Comparative Example 2] MFR 0.4 g / 10 min (230 ° C), polypropylene having a melting point of 165 ° C was used, and the lip interval of the T die 4 was set to 3.0 mm. The ratio of the flow velocity to the surface velocity of the resin flow on the cast roller 5 which first contacts the resin flow is 3.0.
Then, a five-layer sheet having a total thickness of 1.0 mm was obtained by the same configuration and manufacturing method as in Example 1 except that the extension rate of the resin flow was set to 15.

The heat shrinkage stress of the sheet measured in accordance with ASTM-D-1504 reached its maximum at 175 ° C., and its value was 310 g / cm ² .

[0035]

Comparative Example 3 A film (thickness 60 μm) formed by stretching a polyvinylidene chloride resin [vinylidene chloride component / vinyl chloride component: 90/10] at a longitudinal draw ratio of 3, a lateral draw ratio of 3.5, and a draw temperature of 35 ° C. ) Is coated with urethane adhesive of 20 μm on both sides, and polypropylene resin [melting point: 165
C, MFR: 1 g / 10 min (230 ° C.)] at a longitudinal stretching ratio of 3, a lateral stretching ratio of 4 and a stretching temperature of 150 ° C. A film (thickness 450 μm) laminated on both outer sides (90
It pressure-bonded at (degreeC) and obtained the 5-layer sheet of 1.0 mm in total thickness.
The heat shrinkage stress of the sheet measured according to ASTM-D-1504 reaches its maximum at 160 ° C, and the value is 15 kg.
Was / cm ² . The thickness ratio of the polypropylene resin layer to the total thickness of the laminated sheet is 90%.

(Evaluation of Effect of Heat Shrinkage Stress on Formability)
Value): for the laminated sheets of Examples 1 to 3 and Comparative Examples 1 to 3
Evaluate the formability by the evaluation method described in the text and display the results.
They are collectively described in 1. According to the results in Table 1, ASTM
-The heat shrinkage stress of the sheet measured according to D-1504
Is the melting point of polypropylene resin to the melting point + 20 ° C temperature range
Maximum of 100 g / cm²~ 300g / cm ²The value of
The laminated sheets of Examples 1 to 3 shown in the table have thickness ratios of containers (containers
The thickness at the middle of the side wall, that is, at the half height of the container,
The value obtained by dividing by the thickness of the center of the circle on the bottom of the vessel is 0.7 or more
Shows good moldability.

On the other hand, the heat shrinkage stress is 100 g / cm ²
In the smaller comparative example 1, the height of the container is 40, 60 mm.
In the case of a container having a high drawing ratio, that is, a large drawing ratio, the thickness ratio of the container becomes 0.4 or less, and only a molded container that cannot be practically used can be obtained. Further, in Comparative Example 2 in which the heat shrinkage stress is larger than 300 g / cm ² , the height of the container is as high as 40 and 60 mm. That is, in a container having a large drawing ratio, the elongation deformability that extends along with the mold is reduced, and a container having a shape as the mold cannot be obtained.

Further, in Comparative Example 3 in which the temperature at which the heat shrinkage stress is maximum is 5 ° C. lower than the melting point of the polypropylene resin, the sheet shrinks when heated to the molding temperature and cannot be molded. Taken together these results, good in maintaining moldability, heat shrinkage stress of the laminate sheet 100g / cm ² ~300g / cm ² of the maximum value in the temperature range of the melting point - mp + 20 ° C. of the polypropylene resin It turns out that it is necessary to be.

[0039]

[Table 1]

[0040]

[Embodiment 4] The resin composition ratio of the laminated sheet is C / B / A /
Example 1 except that B / C = 40/2/16/2/40
A 5-layer sheet having a total thickness of 1.0 mm was obtained with the same configuration and manufacturing method as described above. The heat shrinkage stress of the sheet measured according to ASTM-D-1504 becomes maximum at 175 ° C.,
The value was 140 g / cm ² . The thickness ratio of the polypropylene resin layer to the total thickness of the laminated sheet is 80.
%.

[0041]

[Embodiment 5] The resin composition ratio of the laminated sheet is C / B / A /
B / C = 35/3/24/3/35, the lip interval of the T die 4 is 2.2 mm, and the resin flow rate passing through the lip portion of the T die 4 and this resin flow come into contact first. The ratio of the surface velocity of the resin flow on the cast roller 5 to 2.
A 5-layer sheet having a total thickness of 1.0 mm was obtained with the same configuration and manufacturing method as in Example 1 except that the stretching speed of the resin flow was set to 11.

The heat shrinkage stress of the sheet measured in accordance with ASTM-D-1504 reached its maximum at 175 ° C., and its value was 140 g / cm ² . The thickness ratio of the polypropylene resin layer to the total thickness of the laminated sheet is 70%.

[0043]

Comparative Example 4 The resin composition ratio of the laminated sheet is C / B / A / B.
/ C = 33/4/26/4/33, the lip spacing of the T die 4 is 2.4 mm, the flow velocity of the resin flow passing through the lip portion of the T die 4 and the cast at which this resin flow first comes into contact. The ratio of the resin flow on the roller 5 to the surface velocity is 2.2.
And the total thickness of 1. was obtained by the same configuration and manufacturing method as in Example 1 except that the extension rate of the resin flow was set to 11.
A 0 mm 5-layer sheet was obtained.

The heat shrinkage stress of the sheet measured in accordance with ASTM-D-1504 reached its maximum at 175 ° C., and the value was 140 g / cm ² . The thickness ratio of the polypropylene resin layer to the total thickness of the laminated sheet is 66%. (Evaluation of influence of thickness ratio of polypropylene resin layer on moldability): Moldability of the laminated sheets of Examples 4 and 5 and Comparative Example 4 was evaluated by the evaluation method described in the text, and the results are summarized in Table 2. Described. According to the results of Table 2, the laminated sheets of Examples 4 and 5 in which the polypropylene resin layer has a thickness ratio of 70% or more, the container has a thickness ratio of 0.6 or more, which indicates good moldability.

On the other hand, in the laminated sheet of Comparative Example 4 in which the thickness ratio of the polypropylene resin layer is less than 70%, the height of the container is as high as 60 mm. That is, in a container having a large drawing ratio, the thickness ratio of the container is 0.4, and only a molded container that cannot be used practically can be obtained. From the above results, it can be seen that in order to maintain good moldability, the thickness ratio of the polypropylene resin layer to the total thickness of the laminated sheet needs to be 70% or more.

[0046]

[Table 2]

[0047]

The present invention has the above configuration,
There is no wrinkling or uneven thickness of the molded product due to the sag, and the thermoformability is excellent. As a result, there is an advantage that it is possible to supply a molding laminated sheet having a significantly improved gas barrier property, which is an industrially useful invention.

[Brief description of drawings]

FIG. 1 is a manufacturing process 1 for obtaining a molding laminated sheet of the present invention.
It is a conceptual diagram which shows an example.

[Explanation of symbols]

 1 Extruder 1 2 Extruder 2 3 Extruder 3 4 Multi-layer T-die 5 Cast roller 6 Take-off roller 7 Trim cutter 8 Winder 9 Laminated sheet

Claims (1)

[Claims] 1. A molding laminated sheet in which a polypropylene-based resin layer is laminated on at least one surface of a gas barrier resin layer with an adhesive layer interposed between the gas barrier resin layer and the AST of the molding laminated sheet.
The heat shrinkage stress measured by MD-1504 has a maximum value of 1 in the temperature range of the melting point of the polypropylene resin to the melting point + 20 ° C.
200 g / cm ² represents the value of to 300 g / cm ^2, forming laminated sheet, wherein the thickness ratio of the polypropylene-based resin layer in the total thickness of the laminated sheet for the molding of at least 70%.