JP3794305B2 - Manufacturing method of heat-resistant bottle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a heat-resistant bottle. More specifically, in the two-stage blow molding method, the heat shrinkage performed before the secondary blow molding can be performed stably, and in the circumferential direction and the height direction. The present invention relates to a method for producing a heat-resistant bottle capable of providing a bottle having a substantially uniform orientation and excellent mechanical strength.
[0002]
[Prior art]
Biaxial stretch blow molded containers of thermoplastic polyester resin such as polyethylene terephthalate have excellent transparency, surface gloss, impact resistance, rigidity and gas barrier properties required for bottles. It is used as a bottling container.
[0003]
In general, when manufacturing a bottling product, it is necessary to heat sterilize or sterilize the contents after hot filling or filling the contents in order to enhance the storage stability of the contents. However, polyester bottles have the disadvantage of inferior heat resistance, causing heat deformation and shrinkage deformation of the contents when hot-filling the contents, so heat setting after forming the biaxially stretched blow container (heat set) An operation is being performed.
[0004]
As a manufacturing method of this heat-fixed biaxial stretch blow-molded container, there are known a one-mold method in which heat setting is performed simultaneously with blow molding and a two-mold method in which blow molding and heat setting are performed in separate molds. Furthermore, a two-stage blow molding method is also known in which the first stage blow-molded product is subjected to heat shrinkage and heat fixation and then subjected to final blow molding. This two-stage blow molding method has a short occupation time in the mold and is excellent in productivity.
[0005]
Japanese Patent Laid-Open No. 5-200839 discloses (a) a cavity having a vertical direction of 1.0 to 1.3 times and a horizontal direction of 0.6 to 1.0 times the final bottle size. A primary blow molding step of stretching and blowing the body and bottom portion from the neck portion to the base portion by 4 to 22 times in terms of area magnification using the primary blow molding mold, and (b) a primary blow molded product formed by the primary blow molding. And a secondary blow molding step of blow molding after heating at 110 to 255 ° C., and a method for forming a bottle having heat resistance and pressure resistance to be molded.
[0006]
[Problems to be solved by the invention]
Containers with a hemispherical bottom that has been thinned by stretching, especially where the center of the bottom is crystallized, have excellent heat and pressure resistance, and are filled with contents that are subject to internal pressure such as carbonated beverages. Although it can sufficiently withstand the heat sterilization treatment with flowing hot water (regularly at 65 ° C. for 10 minutes or longer), a base cup separate from the container is manufactured as described in the above-mentioned Japanese Patent Application Laid-Open No. 5-200249, and this is put into the container. There is an annoyance that must be fixed by bonding or the like.
[0007]
In addition, since the heat shrinkage is performed by taking it out from the blow mold, the workability is inferior and the dimensional stability due to the heat shrinkage is poor.
Accordingly, an object of the present invention is to stably perform heat shrinkage in a method for producing a heat-resistant bottle by two-stage blow molding, and to orient substantially evenly in the circumferential direction and the height direction to obtain mechanical strength. It is providing the manufacturing method of the heat resistant bottle which can provide the outstanding bottle.
[0008]
[Means for Solving the Problems]
According to the present invention, a preform of thermoplastic polyester is subjected to primary stretch blow molding using a primary blow mold, and the resulting primary bottle is subjected to in-mold shrinkage using a heated primary blow mold, and then to primary. In a heat- resistant bottle manufacturing method comprising heat- treating a heat-treated primary bottle taken out from a blow mold outside the mold under a condition allowing shrinkage, and performing secondary blow molding of the secondary bottle with a secondary blow mold The temperature of Tg + 30 ° C. to Tg + 80 ° C. (T ₁ ) based on the glass transition point (Tg) of polyester. ) In the mold so that the ratio of the heat-treated primary bottle surface area / primary blow mold surface area (R ₁ ) is 0.6 to 0.8 using the heated primary blow mold, There is provided a method for producing a heat-resistant bottle, characterized by performing heat treatment outside the mold such that the ratio (R ₂ ) of the secondary bottle surface area / heat treatment primary bottle surface area is 0.7 to 0.9.
[0009]
According to the method for producing a heat-resistant bottle of the present invention,
( 1 ) The primary blow bottom mold is heated to a temperature (T ₂ ) of 20 ° C. to 80 ° C.,
The heat treatment in (2) type out, carried out at a temperature where the surface temperature of the bottle body portion _{(T 3)} is _T 1 + 0 ° C. to _{T 1 + 120 ℃ (T 3} ), and is a relation of _T 3> _{T 1} thing,
(3) the type out heat treatment at, it bottle bottom surface temperature _{(T 4)} is carried out at _T 2 + 40 ° C. to _T 2 + 160 ° C. and becomes a temperature _{(T 4),} a and relationship _T 4> _{T 2} ,
( 4 ) As the primary blow mold, the ratio of the primary blow mold surface area / preform outer surface area (R ₀₁ ) is 8 to 14, and the primary blow mold surface area / preform surface area ratio (R ₀₂ ) is 12. Use what becomes thirty,
( 5 ) As the secondary blow mold, use a secondary blow mold surface area / secondary bottle surface area ratio (R ₃ ) of 1.0 to 1.3,
( 6 ) The primary blow mold has a waist forming part with a reduced diameter at the body forming part of the cavity mold,
( 7 ) The ratio (D ₁ / D ₂ ) of the diameter (D ₁ ) of the waist forming portion and the diameter (D ₂ ) of the trunk forming portion at the base of the waist forming portion is in the range of 0.65 to 0.90. There is,
( 8 ) Performing primary stretch blow molding so that the thickness at the bottom center is less than 1.5 mm, and the thickness is reduced.
( 9 ) Using a preform whose bottom is thinner than the thickness of the trunk as a preform, and performing primary stretch blow molding so that the longitudinal stretch ratio is 2.5 times or more,
Is preferred.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In general, in the two-stage blow molding method, the thin film is thinned into a highly stretched state in the primary blow molding process, and the thinned primary bottle is heated and shrunk to relieve residual stress due to stretching and to improve heat resistance by heat fixing. Further, it is possible to obtain a bottom shape capable of ensuring heat resistance by further reducing the amount of secondary blow molding stretching.
In the heat-resistant bottle manufacturing method of the present invention, the heat treatment of the primary bottle in this two-stage blow molding is (1) the ratio of heat-treated primary bottle surface area / primary mold surface area using a heated primary blow mold ( Performing in-mold shrinkage such that R ₁ ) is 0.6 to 0.8;
(2) Performing out-of-mold heat treatment so that the ratio (R ₂ ) of the secondary bottle surface area / heat treatment primary bottle surface area is 0.7 to 0.9,
It is an important feature to perform in two stages.
[0011]
In the present invention, it is possible to uniformly heat the entire primary bottle by heating the primary bottle with the heated mold surface without taking out the primary bottle from the primary blow mold after the primary blow is completed. The residual stress caused by stretching can be effectively relaxed and the oriented crystal can be advanced. In addition, a heat-treated primary bottle of a certain size can be obtained by heat shrinkage performed in the primary blow mold, so that the heating time and shrinkage amount by the subsequent heat treatment outside the mold can be reduced, and stable shrinkage is possible. Become. Moreover, it is possible to obtain a secondary bottle having a shape close to that of the final molded product, and to stably obtain a final molded product whose bottom is uniformly thinned.
[0012]
In the present invention, the in-mold heat treatment performed in the primary blow mold has a ratio of heat-treated primary bottle surface area / primary mold surface area (R ₁ ) of 0.6 to 0.8, particularly 0.65 to 0.75. It is important to shrink the primary bottle so that When the ratio of the heat-treated primary bottle surface area / primary mold surface area than the above range (R ₁₎ is small, it is difficult to uniformly heat shrinking the primary bottle due to rapid contraction, whereas than the above range the ratio (R ₁ ) Is large, the amount of shrinkage in the subsequent heat treatment outside the mold increases, and it becomes difficult to ensure stable shrinkage.
[0013]
In the next out-of-mold heat treatment, it is important to perform the out-of-mold heat treatment so that the ratio (R ₂ ) of the secondary bottle surface area / heat treated primary bottle surface area is 0.7 to 0.9 . If the ratio of the heat-treated primary bottle surface area / primary bottle surface area (R ₂ ) is smaller than the above range, the amount of stretch processing in the subsequent secondary blow molding becomes large, so that it becomes difficult to achieve uniform thinning at the bottom, When the ratio (R ₂ ) is larger than the above range, it is difficult to obtain satisfactory heat resistance due to insufficient heat treatment.
[0014]
Hereafter, the manufacturing process of the heat resistant bottle of this invention is demonstrated based on an accompanying drawing.
FIG. 1 is a diagram showing a manufacturing process of a heat-resistant bottle of the present invention, where (A) is a primary blow molding process, (B) is an in-mold heat treatment process, (C) is an out-of-mold heat treatment process, and (D). Indicates the secondary blow molding step, and (E) indicates the final molded product.
FIG. 2 shows an example of a preform (a) used in the production of the heat-resistant bottle of the present invention and a molded product obtained in each production process of the present invention, (b) is a primary bottle after primary blow molding, ( (c) is a side view showing an example of a heat treated primary bottle heat-treated in a primary blow mold, (d) a secondary bottle heat-treated outside the mold, and (e) an example of a final molded product.
[0015]
(preform)
As shown in FIG. 2A, the preform used in the present invention includes a neck 1, a body 2, and a closed bottom 3. The neck 1 has a lid fastening mechanism 4 such as a screw and a container for holding the container. The support ring 5 is provided.
In the present invention, it is particularly preferable to use a preform whose bottom is thinner than the thickness of the body as a preform. By thinning the bottom of the preform compared to the body, the bottom, which tends to be thick, can be made thinner by fixing the bottom with a stretch rod and press rod in the primary blow molding process. Is possible. The degree of thinning of the preform bottom is preferably 0.55 to 0.85 times the barrel thickness.
[0016]
In the present invention, the preform whose bottom is made thinner than the body is used as described above, and further, the primary stretch blow molding is performed so that the longitudinal stretch ratio is 2.5 times or more as will be described later. Thus, it becomes possible to orient substantially evenly in the circumferential direction and the height direction, and it becomes possible to provide a final molded product having excellent mechanical strength. In addition, the bottom of the final molded product is sufficiently thinned and highly oriented and crystallized, and a final molded product excellent in transparency and heat resistance can be obtained.
As the preform used in the present invention, any plastic material that can be stretch blow molded and thermally crystallized can be used, but thermoplastic polyesters, particularly ethylene terephthalate thermoplastic polyesters are advantageous. used. Details of the thermoplastic polyester will be described later. Further, the thermoplastic polyester is molded into a preform by a conventionally known method such as injection molding.
[0017]
(Primary blow molding process)
In the present invention, in the primary blow molding step, the preform is first heated to a stretching temperature of about 85 to 135 ° C. and inserted into a blow mold. The preform is heated by a publicly known means such as infrared heating or induction heating.
As shown in FIG. 1 (A), the preform installed in the blow mold composed of the mold 10, the mold 11 and the bottom mold 12 is supported by the core mold 10 at the neck and disposed inside the mold. The bottom portion is sandwiched between the movable extending rod 13 and the press rod 14 pressurized at a predetermined pressure installed outside thereof. Next, the stretching rod 13 is raised and a high-pressure gas is introduced into the preform in synchronism with the movement of the stretching rod 13, whereby the preform is stretched and swelled into a shape along the blow mold. Once formed, the primary bottle is molded.
[0018]
In general, the draw ratio in primary blow molding is desirably about 4.0 to 5.5 times in the circumferential direction and about 2.5 to 3.5 times in the longitudinal direction. By being sufficiently stretched, it can be oriented substantially evenly in the circumferential direction and longitudinal (height) direction, and the mechanical strength can be improved by the biaxial stretching effect.
In primary blow molding, the fluid pressure is preferably 15 to 30 kg / cm ² and the blow time is preferably about 2 to 5 seconds.
[0019]
Further, in the primary blow molding, the obtained primary bottle needs to be stretch-molded so as to satisfy the above-described conditions, but in order to make the bottom center of the final molded product 2 mm or less thin, It is preferable to carry out stretching and thinning so that the thickness at the bottom center is less than 1.5 mm.
[0020]
FIG. 3 shows examples of primary blow bottles created using various primary blow molds that can be used in the present invention. In the present invention, as shown in FIG. 3 (A), it is of course possible to create a bottle in which the waist portion is not formed, but it is preferable that the bottle has a waist portion formed in the body portion. By having the waist part in the final molded product, it is possible to reinforce the strength by forming the central part of the bottle body part without making it thinner than necessary, and the orientation of the body part of the bottle It becomes possible to adjust the balance as a boundary.
In this case, as shown in FIG. 1 (A) and FIG. 3 (C), a waist forming portion 15 with a reduced diameter is formed on the body forming portion of the cavity mold of the primary blow mold, and the waist forming portion It is particularly preferable that the ratio (D ₁ / D ₂ ) between the diameter (D ₁ ) and the diameter (D ₂ ) of the body forming portion at the base of the waist forming portion is in the range of 0.65 to 0.90.
[0021]
(In-mold heat treatment process)
In the present invention, the primary bottle formed by the primary blow molding is not immediately taken out from the mold, but is subjected to heat treatment in the primary blow mold (FIG. 1 (B)).
For this reason, the primary blow cavity mold has a temperature (T ₁ ) of Tg + 30 ° C. to Tg + 80 ° C. with respect to the glass transition point (Tg) of the polyester, and the primary blow bottom mold has a temperature of 20 ° C. to 80 ° C. ₂ ) It is desirable to be heated. Although the heating time depends on the temperature of the mold, it is generally preferably 2 to 5 seconds.
[0022]
Further, in the present invention, it is important to cause in-mold shrinkage in the primary blow mold so that the ratio (R ₁ ) of the heat treated primary bottle surface area / primary blow mold surface area is 0.6 to 0.8. Therefore, as a primary blow mold, the ratio of the primary blow mold surface area / preform outer surface area ( _R01 ) is 8 to 14 and the ratio of the primary blow mold surface area / preform inner surface area (R _02). ) Is preferably 12 to 20.
The heat-treated primary bottle thus obtained has a shape as shown in FIG.
[0023]
(External mold heat treatment process)
In the present invention, as described above, the heat-treated primary bottle obtained by primary stretch blow molding and heat shrinking in the primary blow mold is taken out from the primary blow mold, and this is further subjected to heat treatment outside the mold. Perform (FIG. 1C).
The heat-treated primary bottle rotates while being held by the core mold 21, and is heated by the infrared radiator 22 installed at a position corresponding to the trunk and the bottom to contract the trunk and the bottom. In addition, the heat shielding board 23 is provided in the part corresponding to a neck part.
[0024]
In the present invention, the heat-treated primary bottle taken out from the primary blow mold is heat-shrinked so that the ratio (R ₁ ) of heat-treated primary bottle surface area / primary mold surface area is 0.6 to 0.8. However, in the present invention, by further heat-treating this heat-treated primary bottle, residual strain is alleviated and oriented crystals are advanced, and heat resistance is improved by heat setting, and further shrinks to a shape close to the final molded product. Thus, it is possible to improve the stretch workability by reducing the stretch processing amount in the secondary blow molding process.
[0025]
Generally, the heat treatment of the primary bottle is performed by preferentially shrinking the bottom and then shrinking the entire bottle. In the present invention, the bottle can be shrunk after the bottom is preferentially shrunk. In the out-of-mold heat treatment process of the present invention, since the in-mold heat treatment is performed in advance, the entire heat treated primary bottle can be heat-treated without first shrinking the bottom. As a result, the heat treatment process outside the mold is simplified and the workability is improved.
In the mold outside the heat treatment, the surface temperature of the bottle body portion _{(T 3)} is _T 1 + 0 ° C. to _T 1 + 120 ° C. and becomes a temperature _{(T 3),} and _T 3> It is the relationship _{T 1,} and / or It is preferable that the temperature is at a temperature (T ₄ ) at which the bottle bottom surface temperature (T ₄ ) is T ₂ + 40 ° C. to T ₂ + 160 ° C., and T ₄ > T ₂ .
The secondary bottle obtained in this way has a shape as shown in FIG.
[0026]
(Secondary blow molding process)
The secondary bottle shrunk to a size close to the final molded product by the above-mentioned heat treatment outside the mold is stretched and blown in the secondary blow mold as shown in FIG.
The neck of the secondary bottle 31 is supported by a core mold 32 and is held in a closed secondary blow molding split mold (cavity) 33. A bottom mold 34 that defines the bottom shape of the final container is also disposed on the opposite side of the core mold. In the secondary blow molding step, a fluid is blown into the secondary bottle held in the secondary blow molding die to produce a final molded product as shown in FIG.
In the secondary blow molding process, the secondary blow mold to be used is naturally larger than the secondary bottle and must match the size and shape of the final molded product, including the self-supporting bottom shape. In the present invention, it is particularly preferable to use a secondary mold surface area / secondary bottle surface area ratio (R ₃ ) of 1.0 to 1.3.
[0027]
In secondary blow molding, since the elastic modulus is increased by crystallization by heat treatment, it is preferable to use a high fluid pressure, and it is generally preferable to use a pressure of 15 to 45 kg / cm ² .
Furthermore, the mold temperature of the secondary blow mold may be maintained at a cavity mold temperature of 140 ° C. to 170 ° C. and a bottom mold temperature of 30 ° C. to 120 ° C., and cooling may be performed immediately after molding. Cooling may be performed by flowing cool air or the like in the final molded product.
The formed final molded product is taken out from the opened secondary blow mold by a publicly known take-out mechanism (not shown).
In addition, when forming a waist part in a final molded product, it is desirable that the waist formation part 35 in a secondary blow mold is formed in the position which corresponds with the waist part 36 currently formed in the secondary molded product. Thereby, it is possible to prevent the waist portion formed in the final molded product (FIG. 1E) from becoming thinner than necessary, and to reinforce the bottle body portion.
[0028]
(Thermoplastic polyester)
As the thermoplastic polyester resin used in the present invention, a polyester resin conventionally used in polyester bottles can be used.
Preferably, ethylene terephthalate units occupy most of the ester repeating units, generally 70 mol% or more, have a glass transition point of 50 to 90 ° C, particularly 55 to 80 ° C, and a melting point (Tm) of 200 to 275. Thermoplastic polyesters at a temperature of 220 ° C., in particular 220 to 270 ° C. are preferred.
[0029]
Examples of dibasic acids other than terephthalic acid include aromatic dicarboxylic acids such as isophthalic acid and naphthalenedicarboxylic acid; aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and dodecanedioic acid; 1,4-cyclohexanedicarboxylic acid, Examples thereof include one or a combination of two or more polycarboxylic acid components such as 1,3-cyclohexanedicarboxylic acid and alicyclic dicarboxylic acid such as 1,2-cyclohexanedicarboxylic acid. Glycol, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 1,4-cyclohexane Ol or one or two polyalcohol component such as p- xylylene glycol.
[0030]
The thermoplastic polyester resin used should have at least a molecular weight sufficient to form a film, and an injection grade or an extrusion grade is used depending on the application. The intrinsic viscosity (IV) is generally in the range of 0.6 to 1.4 dl / g, particularly 0.63 to 1.3 dl / g.
[0031]
(Heat resistant bottle)
The heat-resistant bottle formed by the manufacturing method of the present invention described above is measured by X-ray diffraction using a curved PSPC micro diffractometer, particularly in the bottle body, and the following formula (1)
Ih / Ic ≧ 0.55 (1)
In the equation, Ih is the X-ray incident perpendicularly to the barrel wall and the diffraction intensity near Bragg angle (2θ) = 16 ° in the direction perpendicular to the bottle height, and Ic is the barrel wall. It is characterized by having an orientation crystallized part that satisfies the X-ray incidence and the diffraction intensity at around the Bragg angle (2θ) = 16 ° in the bottle height direction.
Since the heat-resistant polyester bottle obtained by the production method of the present invention having such characteristics is oriented almost uniformly in the circumferential direction and the height direction, it has excellent mechanical strength as a biaxial stretching effect. At the same time, the center of the bottom is sufficiently thinned and oriented crystallized, so that it is excellent in transparency.
[0032]
【The invention's effect】
According to the heat-resistant bottle manufacturing method of the present invention, in the heat-resistant bottle manufacturing method by two-stage blow molding, the ratio of heat-treated primary bottle surface area / primary blow mold surface area using a heated primary blow mold ( Shrink in the mold so that R ₁ ) is 0.6 to 0.8, and then the ratio (R ₂ ) of the secondary bottle surface area / heat treated primary bottle surface area is 0.7 to 0.9. Provided is a production method capable of stably performing heat shrinkage by heat treatment outside the mold, and capable of producing a heat-resistant bottle that is uniformly oriented in the circumferential direction and the height direction and has excellent mechanical strength. I was able to.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining each step of a method for producing a heat-resistant bottle of the present invention.
FIG. 2 is a view for explaining a molded product obtained in each step of the method for producing a heat-resistant bottle of the present invention.
FIG. 3 is a view for explaining a primary bottle obtained by a primary blow mold used in the present invention.

Claims (10)

A preform of thermoplastic polyester is subjected to primary stretch blow molding using a primary blow mold, and the resulting primary bottle is subjected to in-mold shrinkage using a heated primary blow mold, and then removed from the primary blow mold. In a method for producing a heat-resistant bottle, the heat-treated primary bottle is heat-treated outside the mold under a condition allowing shrinkage, and the secondary bottle is subjected to secondary blow molding with a secondary blow mold.
Using a primary blow mold heated to a temperature (T ₁ ) of Tg + 30 ° C. to Tg + 80 ° C. based on the glass transition point (Tg) of polyester, the ratio of the heat-treated primary bottle surface area / primary blow mold surface area (R ₁ ) To 0.6 to 0.8, and then the mold is adjusted so that the ratio (R ₂ ) of the secondary bottle surface area / heat treated primary bottle surface area is 0.7 to 0.9. A method for producing a heat-resistant bottle, characterized by external heat treatment. The manufacturing method according to claim 1, wherein the primary blow bottom mold is heated to a temperature (T ₂ ) of 20 ° C to 80 ° C. Wherein the heat treatment at the mold outside surface temperature _{(T 3)} of the bottle body portion is performed at _T 1 + 0 ° C. to _T 1 + 120 ° C. and becomes a temperature _{(T 3),} a and relationship _T 3> _{T 1} The manufacturing method according to claim 1. The heat treatment in the mold outside said the bottle bottom surface temperature _{(T 4)} is carried out at _T 2 + 40 ° C. to _T 2 + 160 ° C. and becomes a temperature _{(T 4),} a and relationship _T 4> _{T 2} The manufacturing method according to claim 2. As the primary blow mold, the ratio of the primary blow mold surface area / preform outer surface area (R ₀₁ ) is 8 to 14, and the ratio of the primary blow mold surface area / preform surface area (R ₀₂ ) is 12 to 20. The manufacturing method according to claim 1, wherein: 6. A secondary blow mold having a secondary blow mold surface area / secondary bottle surface area ratio (R ₃ ) of 1.0 to 1.3 is used. The manufacturing method as described in.   The manufacturing method according to claim 1, wherein the primary blow mold has a waist forming portion with a reduced diameter at a body forming portion of the cavity mold. The ratio (D ₁ / D ₂ ) between the diameter (D ₁ ) of the waist forming portion and the diameter (D ₂ ) of the trunk forming portion at the base of the waist forming portion is in the range of 0.65 to 0.90. The manufacturing method according to claim 7, wherein the manufacturing method is characterized.   The production method according to any one of claims 1 to 8, wherein the primary stretch blow molding is performed so that the thickness at the bottom center is reduced to be less than 1.5 mm.   2. A preform having a bottom portion made thinner than a thickness of a body portion as a preform, and performing primary stretch blow molding so that a longitudinal stretch ratio is 2.5 times or more. The manufacturing method in any one of thru | or 9.

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