JPS6149178B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in biaxially stretched polyester carbonated beverage bottles, and more particularly, the present invention relates to improvements in biaxially stretched polyester carbonated beverage bottles, and more particularly, the present invention relates to polyester carbonated beverage bottles that suppress the transfer rate of carbon gas from the beverage liquid phase to the gas phase to a small level when the bottle is opened. Concerning bottles. Bottles made of polyethylene terephthalate formed by biaxial stretch blow molding are lighter than glass containers, and as described in U.S. Pat. No. 3,733,309, they have high pressure resistance, rigidity,
Because it has excellent transparency and low permeability to gases such as oxygen and carbon dioxide, it also has excellent preservability for the contents, and has come to be widely used as a storage container for carbonated beverages. While carbonated beverage bottles made of polyester have advantages not found in ordinary glass bottles, it has recently been discovered that they also have certain drawbacks not found in glass bottles. In other words, in bottled products in which a carbonated beverage is filled into a polyester bottle and then sealed with a lid, when the bottle is opened, the carbon dioxide dissolved in the beverage liquid phase is rapidly released into the gas phase. This causes a phenomenon in which the cap that is being removed flies off when the package is opened, ie, a cap missile. In addition, for large-capacity bottled products, only a portion of the beverage is dispensed outside the container and stored after being resealed in a cap. Since it moves from the liquid phase of the beverage to the gas phase, there is a problem in that the carbon dioxide concentration in the beverage significantly decreases, that is, air is removed, resulting in a deterioration in the flavor of the beverage. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a polyester carbonated beverage bottle in which the rate of transfer of carbon dioxide gas from the beverage liquid phase to the gas phase upon opening is suppressed to a small level. Another object of the present invention is to provide a polyester carbonated beverage bottle that prevents the aforementioned cap missile and suppresses a significant decrease in the carbon dioxide concentration in the beverage when the contents are repeatedly dispensed and resealed. be. Still another object of the present invention is to provide a polyester carbonated beverage container in which the above-described drawbacks of conventional polyester bottles are overcome without impairing the excellent pressure resistance, rigidity, transparency, and gas barrier properties. It is in. According to the present invention, there is provided a bottle formed by biaxial stretch blow molding of a polyester containing a surfactant and mainly composed of ethylene terephthalate units, wherein at least a body wall portion of the bottle has a density of 1.34 at 20°C. The surfactant is biaxially oriented so that the surface of the shell wall has ^a contact angle of 76 degrees or less with respect to water. Provided is a bottle for a carbonated beverage, characterized in that: The invention will now be described in detail with reference to the accompanying drawings. In FIG. 1 showing the overall structure of the carbonated beverage bottle of the present invention, this bottle consists of a body wall portion 1 integrally formed of polyester and a bottom portion 2 continuous to the lower end of the body wall portion. A frustum-shaped shoulder 3 and a substantially cylindrical neck 4 are provided at the upper end of the body wall 2 and connected thereto. A screw 6 is attached to the neck 4 to hold a lid (not shown) such as a cap or crown attached to the bottle opening 5 for sealing, or a ring 7 is provided to hold the bottle when filling or sealing the bottle. It is provided. This pressure-resistant bottle is formed by biaxially stretch blow-molding a parison or preform made of polyester mainly containing ethylene terephthalate units in a split mold with a cavity corresponding to the outer shape of the bottle. The polyester resin constituting part 1 has molecular orientation in two axial directions, that is, in the axial direction of the bottle and in the circumferential direction of the bottle. An important feature of the present invention is that the polyester constituting this bottle contains a surfactant, and at least the body wall of this bottle has a density of 1.34 g/cc.
By imparting biaxial molecular orientation as described above,
Furthermore, the surfactant is distributed on the surface of the body wall so that the contact angle with water on the surface of the body wall is 76 degrees or less, as shown in FIG. According to the present invention, this feature suppresses the transfer of carbon dioxide gas from the beverage liquid phase to the gas phase upon opening of the bottled carbonated beverage to a rate significantly lower than that of conventional polyester bottles, and as a result, It is possible to effectively eliminate the danger caused by cap missiles and the loss of flavor due to lack of flavor. The reason why polyester bottles have a significantly higher rate of carbon dioxide gas transfer from the beverage liquid phase to the gas phase when opened than in ordinary glass bottles has not yet been clarified, but the present invention According to research conducted by et al., one reason may be that polyester bottles are much less wettable with carbonated beverages than glass bottles. According to the present invention, by setting the contact angle of at least the surface of the body wall of the polyester bottle to water at 23°C to 76 degrees or less, particularly 72 degrees or less, carbon dioxide gas is transferred from the beverage liquid phase to the gas phase when the bottle is opened. It has been unexpectedly discovered that the migration rate of polyester bottles can be suppressed to a significantly lower level than that of conventional polyester bottles. In the present invention, in relation to the above-mentioned objects,
A surfactant is contained in the polyester that forms the bottle, and at least the body wall of the bottle is
Density at °C is 1.34 g/cc or more, especially 1.345 to
It is important to orient the molecules biaxially so that the weight is 1.40 g/cc. Generally, the phenomenon in which foreign components mixed in a plastic material to be molded migrate to the surface of the molded product is known as blooming or immigration. According to the present invention, by blending a surfactant into polyester and giving a unique molecular orientation to the side wall of the bottle made of the surfactant-containing polyester, the pressure resistance and rigidity required for the body wall are achieved. In addition to imparting transparency and gas barrier properties, it has become possible to distribute the surfactant on the surface of the body wall so that the contact angle with water on the surface of the body wall falls within the above-mentioned range. . The reason for this is probably that the increase in density due to the biaxial molecular orientation of the polyester significantly promotes the blooming or immigration of the surfactant onto the surface of the shell wall. As a surfactant, the temperature is 25℃ and the concentration is 0.1%.
Measured according to the JIS K3362 method for a solution, if the foaming force is at least 10 mm, especially 50 to 250 mm, and the specific surface tension is less than 0.95, especially within the range of 0.30 to 0.75, the bubble blowing phenomenon can be prevented. Based on this knowledge, nonionic, anionic or amphoteric surfactants are preferably used for the purpose of the present invention. Preferred examples of such surfactants include the following, but the present invention is of course not limited thereto. Nonionic surfactants Glycerin fatty acid (C ₈ - C ₂₂ ) ester, sorbitan fatty acid (C ₈ - _{C 22} ) ester, propylene glycol fatty acid ester, sucrose fatty acid ester, citric acid mono (di or tri) stearyl ester, Pentaerythryl fatty acid (C ₈ - C ₁₈ ) ester, polyglycerin fatty acid (C ₈ - _{C 22} ) ester, polyoxyethylene (20) glycerin fatty acid (C ₁₂ - _{C 18} ) ester, polyoxyethylene (20) sorbitan Fatty acid ( _C12 - _C18 ) ester, polyethylene glycol fatty acid ( _C8 - _C18 ) ester, polypropylene glycol fatty acid ( _C8 - _C18 )
Ester, polyoxyethylene aliphatic alcohol (C ₁₁ ~
_C20 ) ether, polyoxyethylene alkyl (C7 _or higher) phenyl ether, N-N'-bis(2-hydroxyethyl) aliphatic ( _C8 - _C18 ) amine, fatty acid ( _C12 - _C18 ) and Condensation product with diethanolamine, polyoxypropylene-polyoxyethylene block copolymer, polyethylene glycol (molecular weight 200 or more), polypropylene glycol (molecular weight 200 or more), anionic surfactant Alkyl (C ₁₀ - _{C 20} ) sulfonate ( Na, K,
NH ₄ ), alkyl (C ₈ - C ₂₀ ) benzene sulfonate (Na, K, NH ₄ ), alkylnaphthalene sulfonate (Na), naphthalene formaldehyde condensate sulfonate (Na), sodium alkyl ( _C4 , _C5 , _C6 , _C8 , _C13 ), alphosuccinate, alkyl ( _C8 - _C20 ) sulfate (Na, K,
NH ₄ ), polyoxyethylene fatty alcohol (C ₁₂ ~
C ₂₀ ), ether sulfate (Na, NH ₄ ), polyoxyethylene alkyl (C ₇ or higher) phenyl ether sulfate (Na, NH ₄ ), natural fatty acid salt (Na, K, NH ₄ ), rosin (non-carbon) (equalized or hydrogenated) soaps (Na, K), copolymers of styrene and maleic acid and their alkali salts, cationic surfactants dimethyl dialkyl ( _C12 - _C18 ) ammonium chloride, these surfactants alone It can be used alone or in combination of two or more, and if desired, the following additives or builders, namely polyvinylpyrrolidone, methylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, polyvinyl alcohol, carboxymethylcellulose and its sodium salt , polyacrylic acid and its sodium salt, phosphates (Na, K, Mg), sodium tripolyphosphate, These can be used in combination. Particularly suitable surfactants for the purposes of the present invention are glycerin fatty acid monoesters, sorbitan fatty acid monoesters, propylene glycol fatty acid monoesters, polyoxyethylene glycerin fatty acid esters. These are polyoxyethylene sorbitan fatty acid ester and polyglycerin fatty acid ester. In the present invention, polyethylene terephthalate is preferably used as the polyester, but
Isophthalic acid p
-β-oxyethoxybenzoic acid/naphthalene 2/
6-dicarboxylic acid・diphenoxyethane-4・
Dicarboxylic acid components such as 4'-dicarboxylic acid, 5-sodium sulfoisophthalic acid, adipic acid, sebacic acid or their alkyl ester derivatives, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexylene Glycol, cyclohexanedimethanol,
Copolyesters containing glycol components such as ethylene oxide adducts of bisphenol A may also be used. Furthermore, this polyester can also contain additives such as coloring agents such as pigments and dyes, ultraviolet absorbers, and antistatic agents. The polyethylene terephthalate used has an intrinsic viscosity [η] of 0.5 or more, particularly 0.6 or more, from the viewpoint of mechanical strength of the stretch blow container. According to the present invention, the surfactant is preferably added to the polyester in an amount of 10 ppm or more per polyester.
It is contained in an amount of 100 to 5000 ppm. The carbonated beverage bottle of the present invention uses polyester blended with the above-mentioned surfactant, and the degree of molecular orientation of the polyester constituting the body wall of the bottle has a density of 1.34 g/cm ³ or more as described above. It can be obtained by a stretch blow molding method which is known per se, except that the molding is carried out so as to become as follows. That is, in one embodiment of the present invention, a polyester parison containing a surfactant and mainly composed of ethylene terephthalate units is heated to a stretching temperature, and the heated parison is applied to the body wall of the container and its continuous parts. Within the cavity of the mold defined by the wall surface corresponding to the bottom wall, the containers are stretched in the axial direction of the container simultaneously or in this order, and a fluid is blown into the interior of the mold to expand and stretch the container in the circumferential direction. Compound polyester parisons include bottomed parisons manufactured by injection molding of surfactant-containing polyester, and pipes obtained by extrusion molding of compound polyester, cut to specified dimensions, and one end closed by compression molding. A bottom parison or the like may be used.
From the viewpoint of moldability and transparency, it is desirable that the parison used is rapidly cooled to become substantially amorphous after molding. The basis weight of the container and therefore the parison, that is, the ratio of parison weight (g)/container volume (cc) varies depending on the degree of pressure resistance required, but is generally 0.01 to 0.08 g/cc, particularly 0.02 to 0.08 g/cc. It is desirable that it be in the range of 0.06g/cc. The polyester parison is preheated to the stretching temperature prior to stretch blowing. This stretching temperature is a temperature lower than the crystallization temperature of the polyester used and at which the polyester parison can be stretched, specifically 90 to 130°C, especially
Temperatures between 90 and 110°C are used. Stretch blow molding of preheated parison is
This can be carried out by means known per se, such as sequential stretch blow molding or simultaneous stretch blow molding. For example, in the former case, the parison is stretched axially under fluid injection at a relatively low pressure (pre-blowing) and then stretched by circumferential expansion of the container under fluid injection at a relatively high pressure. Let's do it. In the latter case, stretching in the circumferential direction and stretching in the axial direction are simultaneously performed by blowing fluid at high pressure from the beginning. The parison is stretched in the axial direction by, for example, holding the neck of the parison between a mold and a mandrel.
This can be easily done by applying a stretching rod to the inner surface of the bottom of the parison and stretching the stretching rod. In order to provide the molecular orientation with the density specified in the present invention, at the above-mentioned stretching temperature, the stretching ratio in the axial direction and the circumferential direction of the parison must be set to 1.5 to 1.5, respectively.
It is desirable to set it to 2.5 times (in the axial direction) and 1.7 to 4.0 times (in the circumferential direction). The carbonated beverage to be filled in the container of the present invention may be any carbonated beverage known per se, such as cider,
Ramune, cola, plain soda, ginger ale, carbonated synthetic colored drinks, carbonated fruit juice drinks,
Carbonated soft drinks such as carbonated vitamin- or amino acid-enriched drinks; beer, sparkling fruit liquor,
Examples include highballs, gin fizz, and other carbonated cocktails. The excellent effects of the present invention will be explained in detail in the following examples. Example 1 0.4 parts by weight of each of the five types of surfactants shown in Table 1 were added to 100 parts by weight of polyethylene terephthalate having an intrinsic viscosity of about 0.96, mixed uniformly, and then molded into a hollow cylindrical amorphous shape by injection molding. Create a parison with a bottom and blow mold at 100℃ to determine the inner volume.
A cylindrical hollow blow bottle with a size of 1020 ml and a weight of 55 g was prepared. A polyethylene terephthalate bottle containing no surfactant was also molded as a control product. Also, the density of the body wall of the bottle is 1.34 (g/cm ³ )
The molecules were oriented biaxially so that the molecular weight was in the range of ~1.40 (g/cm ³ ). For these bottles, the contact angle of the body wall of the PET bottle was measured. In addition, a commercially available carbonated drink Sprite was cooled to 5℃ in each bottle, and 1
A filled product (head space 20ml) and a 750ml filled product (bed space 270ml) were prepared, sealed with a 38mm aluminum PP cap, and left indoors for one month. The sample bottle was shaken vigorously for 2 minutes, and after being left for 10 minutes, the cap was carefully opened and examined to see if it felt like the cap was flying off in the hand. As a result, as shown in Table 2, the product of the present invention, in which a surfactant was added to a biaxially oriented PET bottle with a density of 1.35, was better than the PET bottle with a density of 1.337, in which no surfactant was added. As a result, I didn't get the feeling that the cap would fly off when I opened it.

【table】

【table】

[Table] Example 2 Polyethylene glycol lauryl ether was added as a surfactant in varying amounts to 100 parts by weight of polyethylene terephthalate having an intrinsic viscosity of about 0.96, and bottles were molded in the same manner as in Example 1. After cooling the liquid temperature of commercially available carbonated cider (3.2 VoL) to 5°C, it was gently filled into these trial bottles. The filling amount of cider is 1 filling (head
The space was 20ml), sealed with a 38mm aluminum PP cap, and left indoors for 3 months. This sample bottle was shaken vigorously for 2 minutes, opened immediately and after being left for 2 minutes, and the amount of cider overflowing from the bottle mouth was measured. As a result, when no surfactant was added or when the amount added was small, cider overflowed from the bottle mouth. Similarly, after shaking the sample bottle, the sample bottle was left to stand quietly for 2 minutes, then opened, and after 5 minutes, the loss volume was measured after the bottle was sealed, and the amount of surfactant added was determined.
The rosvolium value was especially low when it was in the range of 10PPM to 5000PPM.

[Table] Example 3 To 100 parts by weight of polyethylene terephthalate having an intrinsic viscosity of about 0.96, 0.3 parts by weight of each of the various surfactants shown in Table 1 were added, and after uniformly mixing, the same method as in Example 1 was used. The bottle was molded. Also, the body of the bottle has a density of 1.34g/cm ³ ~
The molecules were oriented biaxially so that the weight was within the range of 1.40 (g/cm ³ ). These sample bottles were filled with 750 ml of commercially available carbonated beverage cola cooled to 5°C (head space: 270 ml), sealed with 38 mm aluminum PP caps, and left indoors for one month. After that, gently shake this sample bottle once or twice.
After 5 minutes, the aluminum cap was opened, and after being allowed to stand for 5 minutes, the cap was sealed. Using this method, the same sample was repeatedly tested for 3 consecutive days by repeatedly opening and sealing the cap once a day. Further, the loss volume at that time was measured using a master volume gauge. the result,
When the cap is opened, the carbon dioxide gas contained in carbonated drinking water escapes, but the way it escapes is when a surfactant is added to make the surface of the PET bottle easier to wet. It was slow and LossVoL was low.

【table】 [Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing the overall structure of the carbonated beverage bottle of the present invention, and FIG. 2 is a partial cross-sectional view showing the relationship between the body wall containing the surfactant and the contact angle with water according to the present invention. FIG. 3 is a partial cross-sectional view showing the relationship between the shell wall portion to which no surfactant is added and the contact angle with water. Reference number 1 is the trunk wall, 2 is the bottom wall, 3 is the shoulder,
4 indicates the neck, 5 indicates the bottle mouth, and 6 indicates the screw.

Claims (1)

[Scope of Claims] 1. A bottle formed by biaxial stretch blow molding of a polyester containing a surfactant and mainly composed of ethylene terephthalate units, wherein at least the body wall of the bottle has a density at 20°C.
The molecules are oriented in biaxial directions so that the weight is 1.34 g/cm ³ or more, and the surfactant is distributed on the surface of the body wall so that the contact angle with water on the surface of the body wall is 76 degrees or less. A carbonated drink bottle that is characterized by 2. The bottle according to claim 1, wherein the surfactant is contained in an amount of 10 ppm or more per polyester. 3. The bottle according to claim 1, wherein the surfactant is a nonionic or anionic surfactant. 4 Regarding sample concentration 0.1% solution at test temperature 25℃
The bottle according to claim 1, which contains a nonionic or anionic surfactant having a foaming force of at least 5 mm as measured in accordance with JIS K3362 and a specific surface tension of less than 0.95. 5. Add surfactant to 100 to 100% per polyester.
The bottle according to claim 1, containing the content in an amount of 5000 ppm. 6. The bottle according to claim 1, wherein the surfactant is a glycerin fatty acid ester. 7. The bottle according to claim 1, wherein the surfactant is a sorbitan fatty acid ester. 8. The bottle according to claim 1, wherein the surfactant is a propylene glycol fatty acid ester. 9. The bottle according to claim 1, wherein the surfactant is polyoxyethylene glycerin fatty acid ester or polyoxyethylene sorbitan fatty acid ester. 10. The bottle according to claim 1, wherein the surfactant is a polyglycerin fatty acid ester. 11. The bottle according to claim 1, wherein the molecules of the body wall portion are oriented such that the density thereof is 1.345 to 1.40 g/cm ³ . 12. The bottle of claim 1, wherein said bottle has a container weight/container volume ratio of 0.01 to 0.08 g/cc.