JPS627060B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a stretch-blown container for carbonated beverages coated with a multilayer film. More specifically, the present invention relates to a stretch-blown container for carbonated beverages coated with a multilayer film, and more specifically, a hydrophobic thermoplastic resin ( (hereinafter abbreviated as TP) layer (hereinafter abbreviated as TP layer) and a layer of ethylene-vinyl alcohol copolymer (hereinafter abbreviated as EVOH) (hereinafter abbreviated as EVOH)
A multilayer heat shrinkable film having two or more layers with excellent CO ₂ barrier properties, which has two or more layers (abbreviated as ``layer''), is bonded tightly by heat shrinking so that the TP layer is always the outermost layer. The present invention relates to a coated stretch-blown container for carbonated beverages. In recent years, with advances in blow molding methods, polypropylene (hereinafter abbreviated as PP) stretch-blown containers, polyethylene terephthalate (hereinafter abbreviated as PET)
PET stretch-blown containers are used for food packaging, and especially in the field of carbonated beverage containers (for colas), which have traditionally been dominated by glass containers, PET stretch-blown containers are becoming mainstream. is the current situation. However, PET and
While PP stretch-blown containers have excellent transparency, drop impact resistance, light weight, and low cost, they both have common drawbacks. In other words, the biggest drawback is that it has poor CO ₂ barrier properties, so when filled with carbonated drinks, CO ₂ easily permeates outside the container, resulting in a large pressure loss of CO ₂ inside the container. This is the problem. Furthermore, since carbonated beverages are distributed and sold for a relatively long period of time, the problem of pressure loss due to CO ₂ inside the container is the most critical issue. Since the surface area of the container becomes large, the pressure loss of CO ₂ becomes too large, making it difficult to put it into practical use. In the current carbonated beverage industry, the CO ₂ pressure loss when filling a carbonated beverage into a stretch-blown container with a large capacity of about 2 is within 15% over a period of approximately 3 months. However, it is not fully satisfied, and there is a problem that the above-mentioned tolerance standard is easily exceeded, especially in the case of a small volume size of about 500 ml. The inventors of the present invention have conducted extensive research in light of the above circumstances, and have found that not only stretch-blown containers with a large capacity of about 2,000 ml, but also stretch-blown containers with a small capacity of about 500 ml can reduce the CO ₂ pressure inside the container. They have succeeded in inventing a stretch-blown container for carbonated beverages that causes little loss and can be put to practical use even if the distribution period is extended over a long period of time. In general, gas permeation through plastic occurs in the direction of eliminating the concentration difference, that is, partial pressure difference, in a system separated by plastic, and this process is due to the dissolution and diffusion of gas into the plastic. It is known that Similarly, regarding stretch-blown containers filled with carbonated beverages, carbonated beverages that contain a large amount of CO ₂ are transferred to stretch-blown containers.
Since permeation occurs due to dissolution and diffusion of CO ₂ , the amount of CO ₂ decreases inside the container, resulting in a pressure loss of CO ₂ . Also, the solubility of CO ₂ in plastic is
It is known that under certain conditions it is constant for each plastic. Therefore, even in a stretch blow container filled with carbonated beverages, under certain conditions, the solubility of CO ₂ in the stretch blow container is constant, and the pressure loss of CO ₂ within the container is constant. Furthermore, it is known that the diffusion coefficient of CO ₂ to plastics is constant for each plastic under certain conditions. Therefore,
Even in stretch-blown containers filled with carbonated beverages, under certain conditions, the diffusion coefficient of CO ₂ to the stretch-blown container remains constant, and the amount of CO ₂ permeation increases over time, resulting in an increase in the pressure loss of CO ₂ inside the container. . That is, an analysis of the process of CO ₂ pressure loss in a stretch-blow container filled with carbonated beverages reveals the following. 1. CO ₂ from a carbonated beverage containing a large amount of CO ₂ was dissolved as it progressed into a stretched blow container.
CO ₂ begins to permeate out of the container. at this stage
Since the permeation of CO ₂ is in an unsteady state and the amount of CO ₂ permeation is small, the permeation of CO ₂ is not significantly related to the pressure loss of CO ₂ in the container, and is mainly due to the flow into the stretch blow container.
It involves the dissolution of _CO2 . 2 As the dissolution of CO ₂ in the container reaches a certain value, the permeation of CO ₂ increases and begins to shift to steady state permeation, which then becomes steady state. At this stage, the pressure loss caused by the dissolution of CO ₂ in the container becomes constant, and the pressure loss caused by the permeation of CO ₂ increases with the passage of time. As mentioned above, the causes of CO ₂ pressure loss in a stretch-blown container filled with carbonated beverages are the dissolution of CO ₂ into the stretch-blown container and the CO ₂ from the stretch-blown container.
One example is that this is due to permeation due to diffusion. Therefore, there are the following two methods for preventing CO ₂ pressure loss in a stretch blow container filled with carbonated beverages. (1) A method of reducing the solubility of CO ₂ in a stretch blow container. (2) A method of reducing permeation by diffusion of CO ₂ from a stretch blow container. Generally, if (1) is satisfied, (2) can also be satisfied in many cases, but (1) or (1)
A method to satisfy (2) is to use a multilayer stretch blow container whose layer component is a thermoplastic resin that has low CO ₂ solubility and low permeability due to CO ₂ diffusion, such as EVOH. However, these containers are difficult to manufacture, require coextrusion, and are extremely costly, making them impractical.Furthermore, if the adhesiveness between the inner and outer layers is poor, the adhesive layer may also be difficult to manufacture. There is a problem in that this further increases the cost since it has to be provided. Taking these circumstances into consideration, the inventors of the present invention have conducted intensive research on a low-cost and simple method for reducing the pressure loss _of CO ₂ in stretch-blown containers for carbonated beverages. It was discovered that if the permeation of CO ₂ in the container was prevented, the pressure loss of CO 2 in the container would be caused only by the dissolution of CO ₂ into the stretch-blow container, and the pressure loss of CO ₂ in the container could be reduced. did. That is, the present inventors have discovered that by preventing the permeation of CO ₂ from a stretch blow container due to diffusion, the inside of the container can be improved.
As a result of researching ways to reduce CO ₂ pressure loss, we decided to heat-shrink a heat-shrinkable film with excellent CO ₂ barrier properties to the entire area around the body of a stretch-blow container, or from the top of the shoulder to the bottom. This method can almost prevent CO ₂ from permeating through diffusion.
It has been found that the pressure loss of CO ₂ inside the container can be reduced. This is because the stretch blow container has relatively thick walls from the mouth to the shoulders and bottom, so CO ₂ permeation from these parts is low, and most of the permeated CO ₂ comes from the body. It showed that. Note that EVOH is suitable as the resin for the heat-shrinkable film with excellent CO ₂ barrier properties used in the present invention, but the CO ₂ barrier properties of the EVOH layer decrease with increased humidity, so it is difficult to avoid the effects of moisture. So as not to accept it,
It is necessary to laminate the TP layer on at least one side so that the TP layer is always the outermost layer. That is, the present invention provides for the entire area around the body of a stretch blow container or the entire area around the body from the top of the shoulder to the bottom.
A stretch blow container for carbonated beverages with low pressure loss of CO ₂ inside the blow container because the multilayer heat shrinkable film with excellent CO ₂ barrier properties, consisting of two or more layers consisting of a TP layer and an EVOH layer, is tightly bonded through heat shrinkage. This is what we provide. In addition, the present invention uses a multilayer heat-shrinkable film with excellent CO ₂ barrier properties used in stretch-blown containers for carbonated beverages to adhere tightly through heat shrinkage. A stretch-blown beverage container is provided. That is, the present invention provides excellent adhesion by simply heat-shrinking a multilayer heat-shrinkable film with excellent CO ₂ barrier properties to a stretch-blow container for carbonated beverages.
The object of the present invention is to provide a stretch-blown container for carbonated beverages that is easy to manufacture and has excellent productivity. In addition, when carrying out the present invention, if necessary,
By printing on a multilayer heat-shrinkable film with excellent CO ₂ barrier properties, it can be used as a label with excellent aesthetic appeal, making it possible to provide a stretch-blown container for carbonated beverages that is beautiful and has high commercial value. . In other words, printed heat-shrinkable labels are currently used for stretch-blown containers, and in the above case, it is only necessary to change the heat-shrinkable labels to heat-shrinkable labels that have excellent CO ₂ barrier properties, making the process easier. There is no need to change or increase equipment, and it is very simple and low-cost to reduce CO ₂
It can be used as a label to prevent pressure loss. FIG. 1 shows a cross section of a stretch-blown container for carbonated beverages in which the entire circumference of the body is covered with a multilayer film. A cross section of is shown in Fig. 2. Further, cross-sections of a multilayer heat-shrinkable film with excellent CO ₂ barrier properties are shown in FIGS. 3 to 5. In the figure, numeral 1 is a stretch blow container, 2
is a multilayer heat shrink film. Furthermore, 3 is
The EVOH layer, 4 represents the TP layer, and 5 represents the adhesive layer. The stretch-blown containers used in the present invention include PET stretch-blown containers and PP stretch-blown containers, which have the following characteristics in terms of transparency, gloss, rigidity, etc.
PET stretch-blown containers are superior. In addition, typical methods for manufacturing stretch blow containers include injection stretch blow molding method and extrusion stretch blow molding method.
An example of the injection stretch blow molding method is a method in which a bottomed parison made of a thermoplastic resin is injection molded into a mold, cooled to room temperature, then reheated to the stretching temperature, and stretch blow molded. Next, the multilayer heat-shrinkable film with excellent CO ₂ barrier properties used in the present invention will be explained. As the CO ₂ barrier layer, an EVOH layer is used. EVOH preferably has an ethylene content of 20 to 60 mol% and a degree of saponification of 90% or more, preferably an ethylene content of 20 mol%.
If it is below, moldability becomes difficult, and if the ethylene content is 60 mol % or more and the degree of saponification is 90% or less, the CO ₂ barrier property decreases, so it is preferably within the above range. Furthermore, as shown in Table 1, the CO ₂ permeability of a multilayer heat-shrinkable film with excellent CO ₂ blocking properties is 20 c.c./m ² day (30°C, 67% RH) or less, especially 10 c.c. /m ² day (30°C, 67%RH) or less. In other words, the CO ₂ permeability is 20 c.c./m ²
day (30℃67%RH) or less, the
This is because the effect of blocking the permeation of CO ₂ and reducing the pressure loss of CO ₂ inside the container becomes greater.

[Table] Use of stretch blow container Furthermore, CO ₂ permeability is 20c.c./m ² day (30℃67
%RH), the thickness of the EVOH layer must be 2.
It is good if it is at least μ, but a range of 3 to 20 μ is preferable from the viewpoints of molding processability, uniformity of film formation, and practicality. On the other hand, the TP used in the present invention includes polyethylene, PP, polybutene-1, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-
Acrylic acid ester copolymers, polyolefin resins such as ionomers, polystyrene, impact-resistant polystyrene, acrylonitrile-butadiene-
Polystyrene resins such as styrene terpolymer,
Polyvinylidene chloride resins such as polyvinylidene chloride, vinyl chloride-vinylidene chloride copolymer, acrylonitrile-vinylidene chloride copolymer, acrylic acid ester-vinylidene chloride copolymer, polyvinyl chloride, vinyl chloride and other vinyl monomers Polyvinyl chloride resins such as copolymers with polymers, PET, polybutylene terephthalate, dehydrated condensates of ethylene glycol and cyclohexanedimethanol with terephthalic acid, transesterified products of dimethyl terephthalate and polytetramethylene ether glycol, etc. polyester resin, nylon-6,
Examples include polyamide resins such as nylon 6.6, and polycarbonate resins, and these may be used alone or as a mixture of two or more. Also, these
Additives such as lubricants, antioxidants, antistatic agents, ultraviolet absorbers, and colorants are added to the TP as necessary. Furthermore, an adhesive layer can be provided between the TP layer and the EVOH layer, if necessary. Therefore, the composition is TP layer/EVOH layer, TP layer/adhesive layer/EVOH layer, TP layer/EVOH layer/TP layer, TP layer
layer/adhesive layer/EVOH layer/adhesive layer/TP layer. The adhesive layer differs depending on the manufacturing method of the multilayer heat-shrinkable film; in the case of dry lamination, for example, a two-component reactive polyurethane adhesive is used, and other anchor coating agents for extrusion lamination are used, but coextrusion In the case of molding, maleic anhydride graft-modified polyolefins and partially saponified ethylene-vinyl acetate copolymers are used. Next, to explain the heat shrinkability of the multilayer heat shrinkable film used in the present invention, the heat shrinkable layer may be the EVOH layer, the TP layer, or both layers may be heat shrinkable. The multilayer heat shrinkable film may have a property of 3 to 30% in the longitudinal direction (hereinafter referred to as MD), preferably 5 to 15% in the transverse direction (hereinafter referred to as TD) in hot air at 100°C for 5 seconds. but
It is desirable to have a heat shrinkability of 10 to 50%, preferably 20 to 40%, from the viewpoint of conformability to a stretch blow container. The film is manufactured using EVOH that has been uniaxially or biaxially stretched by a known method.
A method of laminating TP by extrusion coating or dry lamination, a method of laminating TP on the EVOH side of the laminate by extrusion coating or dry lamination, or a method of laminating EVOH on TP that has been uniaxially or biaxially stretched by a known method. A method of laminating by extrusion coating or dry lamination method, a method of laminating TP on the EVOH side of the laminate by extrusion coating or dry lamination method, or a method of laminating TP on uniaxially stretched EVOH by extrusion coating or dry lamination method. , a method of stretching in other directions, and a method of stretching the laminate in another direction.
A method in which TP is laminated on the EVOH surface by extrusion coating or dry lamination, or a method in which EVOH is laminated on uniaxially stretched TP by extrusion coating or dry lamination and then stretched in the other direction, and the EVOH surface of the laminate is laminated in the other direction. TP is laminated by extrusion coating or dry lamination, or an unstretched laminate of two or more layers of EVOH and TP is created by coextrusion or dry lamination, and then uniaxial or dry lamination is performed by a known method. There are methods such as biaxial stretching, which are not particularly limited, but in consideration of economic efficiency, lamination stretching by coextrusion is preferable. Further, the shape of the multilayer heat-shrinkable film in the present invention includes a cylindrical film and a flat film, but a cylindrical film is preferable from the viewpoint of appearance and strength. However, in the case of a cylindrical film,
Since printing is difficult, a method is used that prints on a flat film and then seals it. In addition, the sealing methods include hot plate seals, impulse seals, fusing seals, high frequency seals, ultrasonic seals, etc.
There is also a method of making adhesive tape into a cylindrical shape, and there are also other sticker forms such as gassho stickers, envelope stickers,
One example is inserting a sheet of paper and sealing it.
In terms of workability and appearance, envelope stickers are preferable. Therefore, the structure of the multilayer heat-shrinkable film is preferably TP layer/EVOH layer/TP layer or TP layer/adhesive layer/EVOH layer/adhesive layer/TP layer. However, in the case of a combination of nylon-6 and EVOH, they have excellent mutual thermal adhesion, so even with a two-layer structure, envelope stickers with excellent envelope pasting properties and aesthetic appearance are possible. After heat shrinking, the cylindrical multilayer heat shrink film thus created is cut to fit the entire circumference of the body from the upper shoulder to the bottom of the stretched blow container. A stretch-blown container for carbonated beverages coated with the multilayer film of the present invention is manufactured by placing the container over the container, feeding it into a shrink tunnel, and bonding it tightly by heat shrinking. As described above, the present invention makes it possible to prevent CO ₂ pressure loss inside the container by using a multilayer heat shrink film with excellent CO ₂ barrier properties in place of the currently used heat shrink labels. Moreover, since there is no need to change the process or increase equipment, it has the advantage of being extremely simple and low-cost to use, and its significance to the carbonated beverage industry is extremely large. Examples will be described below. Example 1 Nylon - 6 layers, 10μ thickness/ethylene content 33
An EVOH layer with mol% and saponification degree of 99% was coextruded and laminated and stretched using the tubular method to a thickness of 10μ, and printing was applied to the EVOH surface to create a multilayer film with a total thickness of 20μ. The heat shrinkage rate of this multilayer film is MD: 10%, TD: 20% in hot air at 100℃ for 5 seconds.
The CO ₂ permeability is 4.1cc/m ² day (30℃67%
RH). Using this multilayer film,
Paste and seal the envelope so that the EVOH surface becomes the inner surface and the diameter is slightly larger than the diameter of the PET stretched blow container, and after heat shrinking, the inner volume will be reduced.
A cylindrical film was cut to a certain length so as to fit the entire circumference of the body from the top of the shoulder to the bottom of a 500ml PET stretch blow container with a body wall thickness of 0.4 mm.The film was placed over the body of the container and heated at 100℃. The material was introduced into the Shrink tunnel for 5 seconds and bonded tightly by heat shrinkage. Fill this container with 100ml of water and the CO ₂ pressure inside the container will be 2.8
CO ₂ was sealed at a concentration of kg/cm ² and stored at 30°C for 3 and 6 months. The pressure loss of CO ₂ in the container after 3 months was 8.5%, and the pressure loss after 6 months was 9.1%. Example 2 Nylon - 6 layers, 10μ thickness/ethylene content 33
A multilayer film with a total thickness of 25μ is obtained by co-extrusion lamination and stretching using the tubular method so that the EVOH layer with mole% and saponification degree of 99% is 5μ thick and the nylon 6 layer is 10μ thick.The 6 sides of the nylon are printed. It was created. The heat shrinkage rate of this multilayer film is MD: 14%, TD: 25% in 100℃ hot air for 5 seconds, and CO ₂
The permeability was 7.3 cc/m ² day (30°C, 67% RH). The following steps were carried out in the same manner as in Example 1. The CO ₂ pressure loss after 3 months was 9.2%, 6
The pressure loss after several months was 9.8%. Example 3 PP layer 8μ thick/maleic anhydride modified PP layer 2μ
Thickness/ethylene content 33 mol%, saponification degree 99%
EVOH layer 5μ thickness/maleic anhydride modified PP layer 2
Coextrusion lamination and stretching was carried out using the tubular method so that the thickness was μ/PP layer 8μ, and printing was applied to the PP surface to create a multilayer film with a total thickness of 25μ. The heat shrinkage rate of this multilayer film in hot air at 100℃ is
MD: 12%, TD: 23%, _CO2 permeability is 2.8
cc/m ² day (30°C, 67%RH). The following steps were carried out in the same manner as in Example 1. The pressure loss of CO ₂ after 3 months was 6.9%, 6.
The pressure loss after several months was 7.4%. Example 4 A 10μ thick EVOH layer with an ethylene content of 33 mol% and a saponification degree of 99% was biaxially stretched by the tubular method, and a low density film was coated with a two-component reactive polyurethane anchor coating layer on both sides. Polyethylene was extrusion coated to a thickness of 15μ to create a multilayer film with a total thickness of 40μ. The heat shrinkage rate of this multilayer film is MD: 11% and TD: 23% in 5 seconds in hot air at 100°C.
The CO ₂ permeability was 1.3 cc/m ² day (30°C, 67% RH). The following steps were carried out in the same manner as in Example 1. The pressure loss of CO ₂ after 3 months is 6.3%, 6
The pressure loss after several months was 6.6%. Example 5 A 10μ thick film biaxially stretched by the tubular method.
Printing is performed on PP film, a two-component reactive polyurethane anchor coating is applied to the printed surface, and EVOH with an ethylene content of 33 mol% and a saponification degree of 99% is applied.
Extrusion coating was performed to a thickness of 10μ, and then a 10μ thick biaxially stretched PP film was laminated on the EVOH surface by dry lamination to create a multilayer film with a total thickness of 30μ. The heat shrinkage rate of this multilayer film is MD: 14%, TD: 25 in hot air at 100℃ for 5 seconds.
%, and the CO ₂ permeability is 3.2cc/m ² day (30℃67%
RH). The following steps were carried out in the same manner as in Example 1. The pressure loss of CO ₂ after 3 months was 7.3%, 6
The pressure loss after several months was 7.8%. Comparative example Nylon biaxially stretched by tubular method
6. A 15μ thick film was printed and extrusion coated with low density polyethylene to a thickness of 15μ on both sides via a two-component reactive polyurethane anchor coating layer to create a multilayer film with a total thickness of 45μ. The heat shrinkage rate of this multilayer film is
MD: 15%, TD: 24 in 5 seconds in hot air at 100℃
%, and the CO ₂ permeability is 96c.c./m ² day (30℃67%
RH). The following steps were carried out in the same manner as in Example 1. The CO ₂ pressure loss after 3 months was 17.8%, 6
The pressure loss after several months was 25.3%.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of a stretch blow container for carbonated beverages coated with a multilayer film according to an embodiment of the present invention, and FIGS. 3 to 5 are multilayer heat-shrinkable containers used in an embodiment of the present invention. FIG. 3 is a cross-sectional view of the film. 1...Stretch blow container, 2...Multilayer heat shrink film, 3...EVOH layer, 4...TP layer, 5...Adhesive layer.

Claims (1)

[Claims] 1. Two or more layers comprising a hydrophobic thermoplastic resin layer and an ethylene-vinyl alcohol copolymer layer on the entire circumference of the body of the stretch blow container or on the entire circumference of the body from the top of the shoulder to the bottom. A stretch blow for carbonated beverages coated with a multilayer film, characterized in that the multilayer heat shrinkable film with excellent CO ₂ barrier properties is adhered by heat shrinking with the hydrophobic thermoplastic resin layer being the outermost layer. container. 2 CO ₂ permeability of multilayer heat shrink film is 20 c.c./m ²
A stretch blow container for carbonated beverages coated with the multilayer film according to claim 1, characterized in that the temperature is less than 1 day (30° C., 67% RH).