JPS634498B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a cup-shaped (wide-mouthed) multilayer plastic container, and more particularly, a method for producing a cup-shaped multilayer plastic container that has excellent gas barrier properties, delamination resistance, appearance characteristics, and uniform wall thickness. Furthermore, the present invention relates to a method for manufacturing the multilayer plastic container with good molding workability. Conventionally, multilayer plastic containers have two surface layers made of olefin resin, an intermediate layer made of oxygen barrier resin such as ethylene vinyl alcohol copolymer, and an adhesive resin layer interposed between the two if necessary.
It has excellent oxygen barrier properties and moisture resistance,
It is well known as a container with excellent preservation of contents. Among these multilayer plastic containers, cup-shaped (wide-mouthed) containers are produced by vacuum forming heated multilayer sheets, plug-assisted vacuum forming, plug-assisted pressure forming, plug-assisted vacuum-pressure forming, twin-mold forming, slip forming, and air pressure forming. This cup-shaped container can be easily prepared by thermoforming by means such as molding or pressure forming, and has no seams in the container body, and can be heat-sealed to the lid member at the flange, making it suitable for various food packaging. It has come to be widely used in various fields. However, the manufacture of multilayer plastic cup containers presents several problems that are not present in the manufacture of single layer plastic cup containers. In other words, when thermoforming is performed at a relatively low temperature that can shorten the molding cycle, the oxygen barrier resin layer may break or crack at the bottom corner of the cup or the base of the flange, or cracks may occur at the interface between the layers. This tends to cause peeling of both surface layers, which causes deterioration of gas barrier properties, deterioration of appearance characteristics, and deterioration of drop impact strength.On the other hand, in relatively high temperature molding where such troubles can be avoided, the delamination of both surface layers It is unavoidable that uneven thickness, vertical streaks, etc. occur due to sagging, and the molding cycle becomes longer. The present inventors have discovered that when thermoforming such a multilayer sheet into a cup, the above-mentioned problems can be solved at once by creating a constant temperature gradient between the intermediate layer and both surface layers. I discovered that. That is, an object of the present invention is to provide a method for manufacturing a cup-shaped multilayer plastic container that is excellent in gas barrier properties, resistance to delamination, appearance characteristics, and uniformity of wall thickness. Another object of the present invention is to provide a method for producing the above-mentioned cup-shaped multilayer plastic container with good molding workability and a short molding cycle. According to the present invention, the oxygen permeability coefficient is 5.5×10 ^-12
A resin adhesive with a temperature conductivity lower than that of the olefin resin is used to connect the intermediate layer of oxygen barrier thermoplastic resin of cc・cm/cm ²・sec・cmHg (37℃) or less and both surface layers of olefin resin. The extruded multilayer sheet in a molten state is heated to a temperature higher than the melting point of the olefin resin constituting both surface layers of the sheet, and the temperature of the intermediate layer is both. 2 than the surface temperature of the surface layer
A method for manufacturing a multilayer plastic container is provided, which comprises slow cooling to a temperature condition of 80° C. higher, and then thermoforming the slow cooling sheet into a cup shape. In a preferred embodiment of the present invention, the above-described multilayered laminate is extruded into a sheet by simultaneous melt extrusion, the extruded sheet is slowly cooled until the temperature conditions described above are reached, and the slowly cooled sheet is then cut into pieces. Form into the shape of. Figure 1 of the accompanying drawings shows the temperature of both surface layers, the temperature of the intermediate layer, and the standing time when a co-melt extruded sheet comprising both surface layers of polypropylene and an intermediate layer of ethylene-vinyl alcohol copolymer is left to stand. Show relationships. The temperature of both surface layers of the simultaneously melt-extruded sheet can be determined by bringing iron-constantan thermocouples into contact with both surfaces of the sheet, and the temperature of the intermediate layer of this extruded sheet can be determined by punching this sheet into a disk shape and measuring the The measurement was performed by inserting the thermocouple into the layer portion. That is, the measured temperatures of both surface layers are the surface temperatures of the layers. Regarding the intermediate layer, since the layer is generally thinner than the surface layer and sandwiched between the high-temperature surface layers, the temperature gradient is hardly a problem, and the measurement location is can be any part. This first
Referring to the figure, the temperatures of both surface layers and the intermediate layer decrease exponentially with the passage of time, but at the beginning of the elapsed time, the decrease in the temperature of both surface layers is larger than the decrease in the intermediate layer temperature. It is understood that this can provide a temperature condition where the temperature of the middle layer of the multilayer sheet is higher than the temperature of both surface layers. According to the present invention, the multilayer sheet is prepared under a temperature condition in which the temperature is higher than the melting point of the olefin resin constituting both surface layers of the sheet, and the temperature of the intermediate layer is 2 to 80° C. higher than the temperature of both surface layers. It is thermoformed into a cup shape under elevated temperature conditions of 3 to 75°C. According to the present invention, by performing thermoforming with a temperature gradient within the above range between both surface layers and the intermediate layer, uneven thickness and vertical streaks due to sagging of both surface layers can be prevented, and in particular, Breakage of the oxygen barrier resin at the bottom corner of the cup or the base of the flange,
It is possible to prevent the occurrence of cracks or peeling at the interlayer interface, improve molding workability by reducing the pressure difference during molding, and shorten the molding cycle by shortening the cooling time on the mold. It becomes possible. In the most preferred embodiment of the present invention, a thermoplastic resin adhesive whose temperature conductivity is lower than that of the olefin resin of both surface layers is interposed between the oxygen barrier thermoplastic resin intermediate layer and the olefin resin surface layers. let In this specification, temperature conductivity (α) is a value defined by the following formula α=λ/Cd, where λ is electrical conductivity, C is specific heat, and d is density. The following dimension, that is, the formula α=Kcal/m・hr・℃／Kcal/Kg・℃×Kg/m ² = m ²
/hr. This value is
It relates to the temperature gradient during heat transfer, and the smaller the value, the larger the temperature gradient during heat transfer. Thus, in this embodiment of the invention, the resin adhesive layer not only serves to bond the intermediate layer to both surface layers, but also acts as a heat transfer barrier, further facilitating the formation of the aforementioned temperature gradients. In this specification, melting point refers to, for example, "CRYSTA-" by LeO Mandelkern.
LLIZATION OF POLYMERS” (McGraw−
Hill Book Company, 1964), it is defined as the thermodynamic first dislocation point where the crystalline phase of a crystalline or semi-crystalline polymer melts.
It can usually be easily determined by methods such as differential thermal analysis, specific heat-temperature curve method, polarized light microscopy, X-ray diffraction, and infrared absorption spectroscopy. The oxygen barrier resin that makes up the intermediate layer has an oxygen permeability coefficient of 5.5×10 ^-12 cc・cm/cm ²・sec・cmHg
The thermoformable resin is selected to: Note that this oxygen permeability coefficient is not measured during thermoforming, but is measured under certain conditions (30° C., 0% RH) in the formed sheet state. Such resins are particularly ethylene-vinyl alcohol copolymers and nylon resins, and these resins contain polar groups such as hydroxyl groups and amide groups in the main chain or side chain of the polymer, and their melting points or softening points are It varies widely depending on the content of polar groups, changes in chemical composition, etc. More specifically, the ethylene-vinyl alcohol copolymer is composed of ethylene or a major portion of ethylene and a minor component of another olefin such as propylene, as described in U.S. Pat. Nos. 3,183,203 and 3,419,654. It can be obtained by saponifying a copolymer of a lower fatty acid with a vinyl ester such as vinyl formate, vinyl acetate, or vinyl propionate, particularly an ethylene-vinyl acetate copolymer. It has been found that the relationship between the melting point (Tm) of this ethylene-vinyl alcohol resin and the molar content (%) of ethylene according to differential thermal analysis etc. follows the following equation. Tm=1.64X+68 In the above formula, Tm represents the melting point of an ethylene-vinyl alcohol copolymer containing 0 to 80% ethylene, and X represents the mol% vinyl alcohol content. The polyamide resin is prepared according to the type of amino acid monomer for ring-opening polymerization type nylon, according to the type of acid and amine for condensation polymerization type nylon, according to the copolymerization composition for copolymerization type nylon, and according to the blend composition ratio for polymer blend, As shown in Table 1, it is known that the melting point varies according to differential thermal analysis.

【table】

[Table] As shown above, resins that have barrier properties against gases such as oxygen, such as ethylene-vinyl alcohol copolymers and nylon resins, have melting points and softening depending on the content of polar groups such as hydroxyl groups and amide groups, or chemical composition. The points change. Table 2 shows ethylene, which has excellent barrier properties against gases such as oxygen mentioned above, at 37°C and in an absolutely dry state.
The oxygen permeability coefficient (PO ₂ , cc·cm/cm ² ·sec·cmHg) of vinyl alcohol copolymer and polyamide is shown.

[Table] Ron 6)
Olefin resins include those whose main constituent monomer is olefin and are crystalline, such as low-, medium-, and high-density polyethylene, isotactic polypropylene, crystalline propylene-ethylene copolymer, crystalline Ethylene-butene copolymers, crystalline ethylene-propylene-butene copolymers, or blends thereof are used. Ethylene-vinyl acetate copolymer, ethylene-vinyl acetate copolymer and ethylene-vinyl acetate copolymer within the range that satisfies the condition of crystallinity.
Acrylic ester copolymers and ionically crosslinked olefin copolymers (ionomers) may also be used alone or in combination with other olefinic resins. As the resin adhesive having a lower temperature conductivity than the olefin resin, a thermoplastic resin known per se that exhibits adhesiveness to both the olefin resin layer and the oxygen barrier resin is used. As already mentioned above, a suitable resin adhesive has a lower temperature conductivity than the olefinic resin in contact with it. Such a resin adhesive is an acid- or acid-anhydride-modified olefin resin, and this modified olefin resin has an ethylenically unsaturated carboxylic acid or its anhydride unit introduced by means such as grafting or terminal treatment. Relatedly, they exhibit lower thermal conductivity than olefinic resins. Suitable examples of ethylenically unsaturated carboxylic acids or their anhydrides include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, crotonic acid, aconitic acid, itaconic acid,
Itaconic anhydride, citraconic acid, citraconic anhydride, tetrahydrophthalic anhydride, etc., and the main olefinic resin may be the olefinic resin exemplified above, such as polyethylene, polypropylene, etc. The amount of acid or anhydride contained in the modified olefin resin is 0.1 to 25% by weight, particularly 0.3 to 20% by weight.
It is desirable that the amount is within the range of % by weight. A suitable resin adhesive has a thermal conductivity that is at least 0.05×10 ⁻⁴ m ² /hr or more, particularly 0.1×10 ⁻⁴ m ² /hr or more lower than the temperature conductivity of the olefinic resin with which it is combined. The simplest means to lower the temperature conductivity of acid- or acid anhydride-modified olefin resin is to blend this resin with a thermoplastic resin and a rubbery substance (hereinafter referred to as rubbery substance) having elastomeric properties. It is. Such rubbery substances include:
Ethylene-propylene copolymer with an ethylene content of 65 to 98% by weight, ethylene-propylene rubber (EPR), ethylene-propylene-nonconjugated diene rubber (EPDM), polyisobutylene, butyl rubber, polybutadiene, polyisoprene, styrene-butadiene rubber, Thermoplastic elastomers such as nitrile-butadiene rubber, styrene-butadiene block copolymers, polyester elastomers, polyurethane elastomers, vinyl chloride elastomers, and EPR and EPDM modified with acids or acid anhydrides. Can be used.
These rubbery substances are present in an amount of 2 to 50% by weight, especially 5 to 50% by weight, based on the acid or acid anhydride modified olefin resin.
It is blended in an amount of 40% by weight. According to the present invention, the above-mentioned oxygen barrier thermoplastic resin is used as an intermediate layer, olefin resin is used as both surface layers, and a resin adhesive layer having a temperature conductivity lower than that of the olefin resin is interposed between these layers. and co-melt extrusion through a multi-layer die to form a multi-layer sheet. Simultaneous melt extrusion is well known per se, and can be carried out in the present invention using well known equipment and under known conditions. Generally, it is preferable to carry out extrusion at a pressure of 80 to 300 kg/cm ² with a die outlet temperature of 120 to 260°C. In addition to the five-layer structure, the layer structure of the multilayer sheet is such that blends of various resins such as burrs produced by-product during molding are removed between the intermediate layer and both surface layers, or between the adhesive layer and both surface layers. It is also possible to create a structure with a larger number of layers by interposing the two layers. The overall thickness of the multilayer sheet ranges from 0.1 to 5.0 so that various containers ranging from so-called flexible cup-shaped containers to rigid cup-shaped containers can be manufactured.
It can be varied within the range of mm. In addition, the thickness ratio of the intermediate layer A and both surface layers B is A:B=1:500 to 1:1, especially 1:50 to 1:1, so as to obtain an optimal combination of oxygen barrier properties and moisture resistance. It is preferable that the ratio be within the range of 1:5, while the ratio of the adhesive layer C and both surface layers B is B:C=1:600 to 1:5, and it is particularly preferable that the ratio is within the range of 1:150 to 1:10. desirable. According to the present invention, a multilayer sheet in a molten state as extruded is slowly cooled under the already detailed temperature conditions, that is, a temperature higher than the melting point of the olefin resin constituting both surface layers of the multilayer sheet. However, it is thermoformed into a cup shape under a temperature condition in which the temperature of the middle layer is 2 to 80° C. higher than the temperature of both surface layers. At this time, the temperature of both surface layers made of olefin resin should be 10 to 50 degrees Celsius higher than the melting point of the olefin resin, from the viewpoint of molding workability, prevention of uneven thickness, shortening of molding cycle, etc. desirable. The oxygen barrier resin in the intermediate layer has a melting point much higher than that of the olefin resin, generally 5 to 90°C.
Although it has a high melting point, the difference in cooling rates between the intermediate layer and both surface layers keeps the intermediate layer at a temperature above its melting point. Slow cooling of an extruded multilayer sheet generally involves leaving the sheet in air or an inert atmosphere, or
Alternatively, it can be carried out by contacting with these air currents, but in the former case, the contact is carried out for a period of 3 seconds to 10 minutes, particularly 5 seconds to 6 minutes, depending on the overall thickness and layer thickness ratio. The time during which the temperature gradient described above is formed may be determined experimentally from the standing time. In the latter case, the cooling time for forming a predetermined temperature gradient may be determined by taking into consideration the temperature and flow rate of the gas. Thermoforming into a cup can be easily carried out by means known per se such as vacuum forming, plug-assisted vacuum forming, plug-assisted pressure forming, plug-assisted vacuum-pressure forming, mold-to-mold forming, slip forming, wind forming, and pressure forming. Can be done. The female mold used in this thermoforming may be cooled naturally or forced, but according to the present invention, in either case, the temperature of both surface layers is maintained at a relatively low temperature. Since cup molding is possible, the cooling time on the female mold can be significantly shortened.
The aperture ratio of the cup, that is, the ratio of cup height (H) to cup opening diameter (D), is preferably in the range of 1/100 to 5/1, particularly 1/50 to 3/1. According to the present invention, even when this drawing ratio is increased, the tendency of delamination at the base of the flange can be effectively prevented. In this case, the shape of the cup (wide mouth container) can be any geometric shape as long as it has an opening, such as cylindrical, conical, triangular, square, pentagonal, hexagonal, star-shaped, hemispherical, etc. It may be in the form of In the present invention, it is advantageous from the point of view of thermoeconomics to use the melt-extruded multilayer sheet for thermoforming into cups immediately after it has been slowly cooled. However, even if a multilayer sheet is formed in advance using the T-die method, the multilayer sheet is reheated, the multilayer sheet is subjected to the temperature gradient described above, and then thermoformed into a cup, the same result occurs. Those skilled in the art will appreciate that significant advantages are achieved. The invention is illustrated by the following example. In addition, various measurements in each example were performed according to the following methods. (i) Uniformity of body wall thickness (WTV): Using a point micrometer, the thickness was measured at 12 points in the circumferential direction of the central part of each cup body at a temperature of 25°C for 3 cups each. . The value of WTV was determined according to the following formula. WTV=100×Standard Deviation/Average Thickness (ii) Appearance Characteristics (App): The presence or absence of streaks in the vertical direction of the cup was mainly determined by visual judgment by a panel of 5 people. In each table in Examples, ◯ means no vertical streaks (good), and × means vertical streaks observed (bad). (iii) Peeling strength (Sp) of the lower base of the flange: 4 points in the circumferential direction under the flange of the cup, width 10
mm, cut out 20mm in length and use a tensile tester to test 20
The peel strength (Sp) was determined at a peel rate of 100 mm/min in an atmosphere of 60% RH at ℃. The results are the average values of the peel strength (12 points each) between the inner surface layer and the intermediate layer and between the outer surface layer and the intermediate layer. (iv) Oxygen permeability (Qo ₂ ) Measured based on ASTM-D-1434. That is, the wall portion of the sheet or cup to be measured was cut into a predetermined size, and the sheet was used for measurement. A gas permeability tester manufactured by Toyo Tester Kogyo Co., Ltd. was used for the measurement. This converts the sample to 2
After fixing it between two chambers, vacuum the chamber until the pressure in one chamber reaches a low pressure of 10 ^-2 mmHg or less (low pressure side). After that, the other chamber (high pressure side) was replaced with oxygen gas dehumidified with calcium chloride so that the pressure became 1 atm, and then the temporal change in pressure increase on the low pressure side was read with a recorder, and the oxygen gas permeability Qo ₂ was determined. It is a method of measurement. The temperature was 37℃ and 20℃, and the humidity on the high pressure side was 0%RH and 60% using calcium chloride.
This was done under RH conditions. (v) Oxygen permeability coefficient (PO ₂ ) Oxygen permeability coefficient (PO ₂ ) is calculated from the oxygen excess using the following formula. PO ₂ = 1.52×10 ^-15 ×h×Qo ₂ (cc・cm/cm ²・sec・cmHg) In the formula, h is the thickness of the measurement sample (μ), and Qo ₂ is the oxygen permeability of the measurement sample (cc / ^m2・
day・atm). Example 1 An extruder for both surface layers was equipped with a metering type screw having a screw diameter of 90 mm and an effective length of 1980 mm, and a metering type screw having a screw diameter of 32 mm and an effective length of 640 mm. A built-in extruder for the adhesive layer, an extruder for the intermediate layer with a built-in metering type screw with a screw diameter of 40 mm and an effective length of 880 mm, and 5 similar to those described in JP-A-51-68670.
Using a layered die, the ethylene content is 30 mol%,
Vinyl alcohol content is 70 mol%, heating rate is
Melting point measured by differential thermal analysis (DTA method) at 10°C/min is 182°C, temperature is 37°C, and relative humidity is 0%.
Oxygen permeability coefficient at RH is 0.07×10 ^-12 cc・cm/cm ²・
The intermediate layer is an ethylene/vinyl alcohol copolymer with sec/cmHg, and the adhesive layer is isotactic polypropylene grafted with maleic anhydride (grafting rate: 3%, thermal conductivity: 2.54×10 ^-4 m ² /hr). Density is 0.912g/cc, thermal conductivity is 2.86×10 ^-4
m ² /hr A multilayer sheet having a five-layer structure having both surface layers made of isotactic polypropylene having a melting point of 167° C. was melt-extruded. The extrusion conditions and die temperature of each of these extruders were as follows: 1. Extruder for both surface layers; Feed section temperature: 180°C Metering section temperature: 219°C Screw rotation speed: 30 rpm 2. Extruder for adhesive layer ; Feed section temperature: 168℃ Metering section temperature: 196℃ Screw rotation speed: 7rpm 3 Extruder for intermediate layer; Feed section temperature: 179℃ Metering section temperature: 234℃ Screw rotation speed: 10rpm 4 Multilayer die indicated temperature: 212℃ 5 Total extrusion amount: 85 Kg/hr The 5-layer sheet melt-extruded under the above extrusion conditions was molded using a known vacuum forming method to form a sheet with a mouth diameter of 71 mm and a height of 36 mm.
A mm round cup was molded. The temperature of each layer of the sheet during cup forming after being left for 50 seconds after being discharged from the die lip was 198°C on both surface layers.
℃, and the middle layer was 209℃. The total thickness of the resulting five-layer cup was 0.31 mm, and the composition ratio of outer surface layer:adhesive layer:intermediate layer:adhesive layer:inner surface layer was 15:0.1:1:0.1:15. The five-layer cup thus obtained is hereinafter referred to as A. Next, we will examine the A cup's (i) body wall thickness uniformity (WTV), (ii) appearance characteristics (App), (iii) peel strength of the base under the flange (Sp), and (iv) the bottom of the cup. Oxygen permeability (Qo ₂ ) was measured according to each method described in the specification. The results are shown in Table-3. For comparison, the extruders, multilayer dies, and synthetic resins described above were used under the following extrusion conditions: 1 Extruder for both surface layers; Feed section temperature: 180°C Metering section temperature: 231°C Screw rotation speed : 26rpm 2 Extruder for adhesive layer; Feed section temperature: 168℃ Metering section temperature: 196℃ Screw rotation speed: 7rpm 3 Extruder for intermediate layer; Feed section temperature: 179℃ Metering section temperature: 234℃ Screw rotation speed: 10rpm 4 Multilayer die temperature: 217℃ 5 Total extrusion amount: 86Kg/hr The 5-layer sheet melt-extruded under the above extrusion conditions was molded using a known vacuum forming method to form a sheet with a mouth diameter of 71mm and a height of 36mm.
A circular cup of mm was molded. The temperature of each layer of the sheet during cup forming after being left for 50 seconds after being discharged from the die lip was 208°C on both surface layers.
℃, and the middle layer was 209℃. The total thickness of the resulting five-layer cup was 0.31 mm, and the composition ratio of outer surface layer:adhesive layer:intermediate layer:adhesive layer:inner surface layer was 15:0.1:1:0.1:15. The five-layer cup thus obtained is hereinafter referred to as B. Next, we will examine the B cup's (i) body wall thickness uniformity (WTV), (ii) appearance characteristics (App), (iii) peel strength of the base under the flange (Sp), and (iv) the bottom of the cup. Oxygen permeability (Qo ₂ ) was measured according to the method described in each specification. The results are also shown in Table 3. From Table 3, the temperature difference between the surface of both surface layers and the intermediate layer is
It is known that Cup A, which was manufactured under conditions where the temperature was maintained at 11°C, was clearly superior to Cup B, which was molded under the same conditions where the temperature difference was 1°C, in the above-mentioned performances.

[Table] Example 2 Using the three extruders and multilayer die described in Example 1, the ethylene content was 45 mol%, the vinyl alcohol content was 55 mol%, and the
The melting point according to the DTA method is 158℃, and the oxygen permeability coefficient (37℃, 0%RH) is 0.3×10 ^-12 cc・cm/cm ²・
sec/cmHg ethylene/vinyl alcohol copolymer as the middle layer, ethylene/propylene copolymer modified with maleic anhydride (ethylene content: 7% by weight, modification rate: 10%, temperature conductivity: 3.06×
10 ^-4 m ² /hr) as adhesive layer, density 0.90g/cc,
The melting point is 153℃ and the thermal conductivity is 4.77×10 ^-4 /hr.
A multilayer sheet with a five-layer structure having both surface layers of ethylene-propylene copolymer was melt-extruded. The extrusion conditions and die temperature of each of these extruders were as follows: 1. Extruder for both surface layers; Feed section temperature: 165°C Metering section temperature: 202°C Screw rotation speed: 34 rpm 2. Extruder for adhesive layer ; Feed section temperature: 158℃ Metering section temperature: 185℃ Screw rotation speed: 9rpm 3 Extruder for intermediate layer; Feed section temperature: 166℃ Metering section temperature: 215℃ Screw rotation speed: 11rpm 4 Multilayer die temperature: 197℃ 5 Total extrusion amount: 87 Kg/hr The five-layer sheet melt-extruded under the above extrusion conditions was molded into a rectangular cup with a mouth width of 115 x 115 mm and a height of 38 mm using a known vacuum forming method. The temperature of each layer of the sheet during cup forming 40 seconds after being discharged from the die lip is such that both surface layers are
The temperature was 184°C, and the middle layer was 191°C. The total thickness of the resulting five-layer cup was 0.45 mm, and the composition ratio of outer surface layer: adhesive layer: intermediate layer: adhesive layer: inner surface layer was 20:0.1:1:0.1:20. The five-layer cup thus obtained is hereinafter referred to as C. Next, we will examine the C cup's (i) uniformity of body wall thickness (WTV), (ii) appearance characteristics (App), (iii) peel strength (Sp) of the root part under the flange, and (iv) of the bottom of the cup. Oxygen permeability (Qo ₂ ) was measured according to each method described in the specification. The results are shown in Table 4. For comparison, the extruders, multilayer dies, and synthetic resins described above were used under the following extrusion conditions: 1 Extruder for both surface layers; Feed section temperature: 166°C Metering section temperature: 202°C Screw rotation speed : 32 rpm 2 Extruder for adhesive layer; Feed section temperature: 158℃ Metering section temperature: 185℃ Screw rotation speed: 9 rpm 3 Extruder for intermediate layer; Feed section temperature: 166℃ Metering section temperature: 204℃ Screw rotation speed: 13 rpm 4 Multilayer die indicated temperature: 195℃ 5 Total extrusion amount: 85Kg/hr The five-layer sheet melt-extruded under the above extrusion conditions was molded using a known plug-assisted vacuum forming method to reduce the outer diameter of the mouth.
A rectangular cup measuring 115 x 115 mm and 38 mm in height was molded. The temperature of each layer of the sheet during cup forming 40 seconds after being discharged from the die lip was 184°C for both surface layers and 183°C for the middle layer. The total thickness of the resulting five-layer cup was 0.44 mm, and the composition ratio of outer surface layer: adhesive layer: intermediate layer: adhesive layer: inner surface layer was 20:0.1:1:0.1:20. The five-layer cup thus obtained is hereinafter referred to as D. Next, we will examine the D-cup's (i) uniformity of body wall thickness (WTV), (ii) appearance characteristics (App), (iii) peel strength of the base under the flange (Sp), and (iv) of the bottom of the cup. Oxygen permeability (Qo ₂ ) was measured according to the method described in each specification. The results are also shown in Table-4. From Table 4, it is clear that Cup C, which was manufactured under conditions where the temperature difference between the surfaces of both surface layers and the intermediate layer was maintained at 7°C, had better performance than Cup D, which was molded under the same conditions where the temperature difference was 1°C. Known to be excellent.

[Table] Example 3 An extruder for both surface layers equipped with a built-in metering-type screw having a screw diameter of 65 mm and an effective length of 1430 mm, having the same shape and dimensions as above, and eliminating burrs generated during cup molding. An extruder for the repro layer to form the layer to be recovered (hereinafter referred to as the repro layer), an extruder for the adhesive layer with a built-in metering-type screw having a screw diameter of 45 mm and an effective length of 900 mm, and adhesive. An extruder for intermediate layer having the same shape and dimensions as the extruder for layer, and 7 similar to that described in JP-A No. 51-68670.
Using a layered die, the ethylene
A vinyl alcohol copolymer is used as an intermediate layer, and a maleic anhydride-grafted polypropylene described in Example 1 is used as an adhesive layer. Isotactic polypropylene described in Example 1: Maleic anhydride-grafted polypropylene: Ethylene-vinyl alcohol copolymer Mixture with a combined mixing ratio of 16:0.2:1
Low-density polyethylene with a density of 0.922 g/cc and a thermal conductivity of 5.69 x 10 ^-4 m ² /hr per 100 parts by weight.
A mixture of 23.5 parts mixed in is used as a repro layer, and a mixture of the isotactic polypropylene described in Example 1 and the low density polyethylene in a ratio of 80:20 is used as an inner and outer layer, and outer surface layer/repro layer/adhesive layer/ A multilayer sheet with a seven-layer structure consisting of an intermediate layer/adhesive layer/repro layer/inner surface layer was melt-extruded. The extrusion conditions of each of these extruders and the indicated temperature of the die section were as follows: 1. Extruder for both surface layers Feed section temperature: 175°C Metering section temperature: 215°C Screw rotation speed: 45 rpm 2. Extrusion for repro layer Machine Feed section temperature: 175℃ Metering section temperature: 215℃ Screw rotation speed: 21rpm 3 Adhesive layer extruder Feed section temperature: 170℃ Metering section temperature: 195℃ Screw rotation speed: 7rpm 4 Intermediate layer extrusion machine Feed section temperature : 180℃ Metering part temperature: 235℃ Screw rotation speed: 10rpm 5 Multilayer die indicated temperature: 209℃ 6 Total extrusion amount: 65Kg/hr The 7-layer sheet melt-extruded under the above extrusion conditions was once slowly cooled to room temperature. . Then the said sheet
After heating at 200° C. for 2 minutes, the mixture was left at room temperature for 10 seconds, and a rectangular cup (square wide-mouth container) with a mouth width of 246×186 mm and a height of 40 mm was formed using a known plug-assisted vacuum forming method. The temperature of the sheet layer during cup forming was 195°C for both surface layers and 198°C for the intermediate layer. The total thickness of the resulting 7-layer container was 1.35 mm, and the composition ratio of outer surface layer: repro layer: adhesive layer: intermediate layer: adhesive layer: repro layer: inner surface layer was 10:5:
It was 0.1:1:0.1:5:10. The seven-layer container thus obtained will be referred to as E hereinafter. For comparison, immediately after heating the sheet at 200° C. for 2 minutes, a square cup (square wide-mouthed container) having the same shape, dimensions, and composition ratio as above was obtained by the method described above. In this case, the temperature of the layers of the sheet during cup forming is
The temperature in the middle layer was 199°C. The seven-layer container thus obtained is hereinafter referred to as F. Next, for each container E and F, (i) uniformity of body wall thickness (WTV), (ii) appearance characteristics (App), (iii) peel strength of the root part under the flange (Sp), (iv ) The oxygen permeability (Qo ₂ ) at the bottom of each cup was measured according to the method described in the specification. The results are also shown in Table-5. From Table 5, it can be seen that the container E manufactured under the condition that the temperature difference between the surfaces of both surface layers and the intermediate layer was maintained at 3°C has the above-mentioned performance than the wide-mouth container F manufactured under the condition that the temperature difference between both layers is 0. It is known to be clearly superior.

[Table] Example 4 Using the three extruders and multilayer die described in Example 1, the ethylene content was 55 mol%, the vinyl alcohol content was 45 mol%, and the
The melting point according to the DTA method is 144℃, and the oxygen permeability coefficient (37℃, 0%RH) is 3.8×10 ^-12 cc・cm/cm ²・
The middle layer is ethylene/vinyl alcohol copolymer with sec/cmHg, and the adhesive layer is high-density polyethylene modified with maleic anhydride (modification rate: 1.4%, temperature conductivity: 6.14×10 ^-4 m ² /Hf). and the density is
0.958g/cc, melting point is 132℃, temperature conductivity is
A multilayer sheet with a five-layer structure having both surface layers of high-density polyethylene of 7.66×10 ^-4 m ² /hr was melt-extruded. The extrusion conditions and die temperature of each of these extruders were as follows: 1. Extruder for both surface layers; Feed section temperature: 140°C Metering section temperature: 165°C Screw rotation speed: 47 rpm 2. Extruder for adhesive layer ; Feed section temperature: 135℃ Metering section temperature: 161℃ Screw rotation speed: 8 rpm 3 Extruder for intermediate layer; Feed section temperature: 160℃ Metering section temperature: 201℃ Screw rotation speed: 30rpm 4 Multilayer die indicated temperature: 172℃ 5. Total extrusion rate: 65 Kg/hr The five-layer sheet melt-extruded under the above extrusion conditions was molded into a circular cup with a mouth diameter of 93 mm and a height of 53 mm using a known plug-assisted vacuum-pressure forming method.
The temperature of each layer of the sheet at the time of cup forming, 1 minute and 30 seconds after being discharged from the die lip, was 152°C for both surface layers and 171°C for the middle layer. The total thickness of the resulting five-layer cup was 0.50 mm, and the composition ratio of outer surface layer:adhesive layer:intermediate layer:adhesive layer:inner surface layer was 5:0.1:1:0.1:5. The five-layer cup thus obtained is hereinafter referred to as G. Next, G shows the cup's (i) body wall thickness uniformity (WTV), (ii) appearance characteristics (App), (iii) peel strength of the base under the flange (Sp), and (iv) cup bottom. The oxygen permeability (Qo ₂ ) of each sample was measured according to each method described in the specification. The results are shown in Table-6. For comparison, the extruders, multilayer dies, and synthetic resins described above were used under the following extrusion conditions: 1 Extruder for both surface layers; Feed section temperature: 140°C Metering section temperature: 194°C Screw rotation speed : 44rpm 2 Extruder for adhesive layer; Feed section temperature: 135℃ Metering section temperature: 161℃ Screw rotation speed: 8rpm 3 Extruder for intermediate layer; Feed section temperature: 160℃ Metering section temperature: 201℃ Screw rotation speed: 30rpm 4 Multilayer die temperature: 184℃ 5 Total extrusion amount: 66Kg/hr The 5-layer sheet melt-extruded under the above extrusion conditions was molded using a known vacuum forming method to form a sheet with a mouth diameter of 0.50mm and a height.
A 53mm circular cup was molded. The temperature of each layer of the sheet during cup forming 1 minute and 30 seconds after being discharged from the die lip was 172°C on both surface layers.
℃, and the middle layer was 172℃. The total thickness of the resulting five-layer cup was 0.50 mm, and the composition ratio of outer surface layer:adhesive layer:intermediate layer:adhesive layer:inner surface layer was 5:0.1:1:0.1:5. The five-layer cup thus obtained is hereinafter referred to as H. Next, we will look at the H cup's (i) uniformity of the body wall thickness (WTV), (ii) appearance characteristics (App), (iii) peel strength of the root part under the flange (Sp), and (iv) cup bottom. The oxygen permeability (Qo ₂ ) of each sample was measured according to the method described in the specification. The results are also shown in Table-6.

[Table] Example 5 An extruder for an inner surface layer equipped with a metering type screw having a screw diameter of 65 mm and an effective length of 1430 mm, an extruder for an outer surface layer having the same shape and dimensions as above, and a screw Diameter is 45mm,
Using an adhesive layer extruder with a built-in metering screw with an effective length of 900 mm, an intermediate layer extruder with the same shape and dimensions as the adhesive layer extruder, and a 5-layer T-die. , a nylon 6-6/6 copolymer with a nylon 6/6 content of 10 mol% (melting point 181°C, thermal conductivity 3.40×10 ^-4
m ² /hr) was used as the intermediate layer, and the maleic anhydride grafted polypropylene described in Example 1 and the density were 1.18.
g/cc, and a thermoplastic polyurethane with a temperature conductivity of 1.56×10 ^-4 m ² /hr in a weight ratio of 60:40 was used as the adhesive layer, and the isotactic polypropylene (PP) described in Example 1 was used as the adhesive layer. A five-layer structure consisting of outer layer (PP)/adhesive layer/intermediate layer/adhesive layer/inner layer (HDPE) with one surface layer and the high-density polyethylene (HDPE) described in Example 4 as the other surface layer. We performed melt extrusion molding of multilayer sheets. The extrusion conditions and die section temperature for each of these extruders were as follows: 1. Extruder for outer surface layer Feed section temperature: 180°C Metering section temperature: 220°C Screw rotation speed: 25 rpm 2. Extrusion for inner surface layer Machine Feed section temperature: 140℃ Metering section temperature: 165℃ Screw rotation speed: 30rpm 3 Adhesive layer extruder Feed section temperature: 135℃ Metering section temperature: 160℃ Screw rotation speed: 7rpm 4 Intermediate layer extrusion machine Feed section temperature : 180℃ Metering part temperature: 235℃ Screw rotation speed: 10rpm 5 Multilayer die indicated temperature: 208℃ 6 Total extrusion amount: 66Kg/hr The 5-layer sheet melt-extruded under the above extrusion conditions was formed by known plug-assisted vacuum pressure forming. A circular cup with a mouth diameter of 62 mm and a height of 36 mm was molded using the method.
The temperature of each layer of the sheet during cup forming after being left for 6 minutes after being discharged from the die lip was 175℃ for one surface layer (PP) surface, 174℃ for the other surface layer (HDPE) surface, and 191℃ for the middle layer. It was warm at ℃. The total thickness of the resulting five-layer cup was 0.25 mm, and the composition ratio of outer surface layer: adhesive layer: intermediate layer: adhesive layer: inner surface layer was 20:0.1:1:0.1:15. The five-layer cup thus obtained is hereinafter referred to as I. For comparison, the extrusion conditions were the same as above except that the temperature of the metering part of the extruder for the intermediate layer was 200°C and the screw rotation speed was 12 rpm (however, the indicated temperature of the die part was 207°C). ) The same five-layer sheet as above was melt-extruded, and a circular multilayer cup having the same shape, dimensions, and composition ratio as above was obtained by the same molding method as above. In this case, the temperature of each layer of the sheet during cup forming after being left for 6 minutes after being discharged from the die lip was 175°C on the surface of the outer surface layer and 175°C on the surface of the inner surface layer.
The temperature was 174°C, and the middle layer was 175°C. Hereinafter, this cup will be referred to as J. Next, for each cup of I and J, (i) uniformity of body wall thickness (WTV), (ii) appearance characteristics (App), (iii) peel strength of the root part under the flange (Sp), (iv ) The oxygen permeability (Qo ₂ ) at the bottom of each cup was measured according to the method described in the specification. The results are shown in Table 7.

【table】 [Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the standing time and the temperature of both surface layers and the intermediate layer of a multilayer sheet.

Claims (1)

[Claims] 1 Oxygen permeability coefficient is 5.5×10 ^-12 cc・cm/cm ²・sec・
A sheet is formed by simultaneous melt extrusion of an intermediate layer of thermoplastic resin with oxygen barrier properties of cmHg (37℃) or less and both surface layers of olefin resin via a resin adhesive layer that has a lower temperature conductivity than the olefin resin. The extruded multilayer sheet in a molten state is heated to a temperature higher than the melting point of the olefinic resin constituting both surface layers of the sheet, and the temperature of the intermediate layer is 2 to 2 times higher than the surface temperature of both surface layers. A method for producing a multilayer plastic container, which comprises slow cooling until the temperature is 80°C higher, and then thermoforming the slow cooling sheet into a cup shape.