JP3907494B2 - Blow molding method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a blow molding method and apparatus and a final molded product, and more particularly, to a blow molding method and apparatus for performing secondary blow molding after heating in primary blow molding and a final molded product molded thereby.
[0002]
[Background Art and Problems to be Solved by the Invention]
Generally, a container made of synthetic resin such as polyethylene terephthalate (PET) is known as a packaging container.
[0003]
In such a container, a preform such as a preform heated to a predetermined temperature is usually biaxially stretched in the vertical axis and the horizontal axis direction by a stretching rod and high-pressure blow air in a blow mold into a product shape. Molded.
[0004]
By the way, the above-mentioned PET container has a heat resistance problem that the container is deformed when the inside is filled with a high-temperature content such as a heat-sterilized fruit juice drink.
[0005]
Therefore, various molding methods for imparting heat resistance to PET containers have been proposed.
[0006]
As this forming method, for example, the methods shown in Japanese Patent Publication No. 61-29858, Japanese Patent Publication No. 1-56891, Japanese Patent Publication No. 2-33566, Japanese Patent Publication No. 3-51568, and the like are known. Yes.
[0007]
In these molding methods, a preform heated to an appropriate stretching temperature is blown in a primary molding mold and expanded to form an intermediate molded product, and after the intermediate molded product is heated, the intermediate molded product is heated. Is taken out from the primary molding die, and the intermediate molded product which is contracted and softened is secondarily blown in the secondary molding die to be re-expanded.
[0008]
However, a molding apparatus using such a molding method has not been put into practical use.
[0009]
The cause is primarily due to the following points.
[0010]
The intermediate molded product blow-molded by the primary molding die is in a state where its outer surface is in close contact with the cavity surface of the primary molding die by high-pressure blow air, and the body part shrinks at the same time as the blow air is exhausted after blow molding. It becomes.
[0011]
During the shrinkage, if a part of the outer surface of the intermediate molded product is stuck to the cavity surface without being released from the cavity surface, the intermediate molded product is deformed, resulting in a molding defect.
[0012]
In particular, when a bottom mold having a shape corresponding to the bottom of the container is used for the primary molding die, the bottom mold and the bottom are in close contact with each other, and it is difficult to release, and when the bottom is in close contact with the bottom mold, Deformation or inversion of the bottom shape will occur.
[0013]
Such deformation of the intermediate molded product is likely to occur when the bottom mold is heated in order to improve the heat resistance of the container bottom.
[0014]
In addition, since the intermediate molded product is in a state where the neck portion is held and fixed, if the bottom portion is stuck to the bottom mold, the neck portion and the bottom portion of the intermediate molded product are fixed. The body portion contracts from the point where it is peeled off from the cavity surface, and the shape becomes unstable and vertical stripes are formed on the body portion.
[0015]
In particular, if the shape becomes unstable, misalignment occurs and secondary blow molding becomes difficult, or the intermediate molded product is sandwiched between secondary molding dies during secondary blow molding, or the intermediate molded product becomes uneven. As a result, uneven thickness occurs in the final molded product, and further, when vertical stripes occur, the vertical stripes remain in the final molded product and the commercial value is lost.
[0016]
Second, there is the following point.
[0017]
After the intermediate molded product obtained by expanding the preform in the primary molding die is brought into close contact with the primary molding die and heated and then deaerated, the intermediate molded product starts to shrink.
[0018]
At this time, when the intermediate molded product is stuck to the primary molding die and is forcibly separated by shrinkage, the outer surface of the intermediate molded product becomes rough and rough.
[0019]
Even if this is secondarily blown with a secondary mold, the roughness of the outer surface cannot be removed and the state becomes rough and low in transparency, resulting in loss of commercial value.
[0020]
The object of the present invention is that even when an intermediate molded product is heated by a primary molding die, the bottom surface is not deformed, the body shape is not unstable, vertical stripes are not included, and the outer surface is roughened. It is an object of the present invention to provide a blow-molding method and apparatus without any problem.
[0021]
Another object of the present invention is to provide a final molded article having a good quality without causing vertical stripes on the outer surface or roughening even when the intermediate molded article is heated by the primary molding die. .
[0022]
[Means for Solving the Problems]
In order to achieve the above object, the blow molding method of the present invention includes a primary blow molding step of producing a primary molded product by biaxial stretching blow molding in a heated primary blow mold, and a final process using the primary molded product. In a blow molding method including a final blow molding step of producing a final molded product by biaxial stretching blow molding in a blow mold,
In the primary blow molding step, after the primary molded product is biaxially stretch blow molded, the body portion and the bottom portion of the heated primary molded product are released from the primary blow mold almost simultaneously and contracted. And
[0023]
According to the present invention, after the primary molded product is biaxially stretch blow-molded, the bottom portion of the primary molded product in the heated state is released from the primary blow mold almost simultaneously and contracted, so that the bottom portion is blown into the primary blow. The primary molded product shrinks and deforms while sticking to the mold, and misalignment and uneven thickness occur, resulting in molding defects and vertical stripes on the body. A stable primary molded product having a similar shape can be obtained. As a result, reliable blow molding can be performed in the final blow molding process, and a final molded product of good quality can be obtained.
[0024]
In addition, the body part can be in a good release state, and the surface can be prevented from becoming rough and rough, and as a result, a final product with high transparency and good quality can be obtained.
[0025]
In the present invention, the primary molded product is formed in a substantially circular cross section of the body portion,
In the primary molded product after shrinkage, the ratio of the length of the short diameter portion to the long diameter portion in the cross section of the barrel predetermined position can be 80% or more.
[0026]
In addition, the primary molded product after shrinkage is in the cross section of the barrel predetermined position,
The ratio of the largest shrinkage to the smallest shrinkage can be 80% or more.
[0027]
By adopting such a configuration, in the cross section at a predetermined position of the body portion, the ratio of the length of the short diameter portion to the long diameter portion, or the ratio of the largest shrinkage rate to the smallest shrinkage rate is 80% or more after shrinkage. By using the molded product and performing the final blow molding in the final blow molding process, a final molded product of good quality can be obtained.
[0028]
In the present invention, the primary molded product after the shrinkage can have a turbidity of the body portion of 10% or less.
[0029]
By adopting such a configuration, a final molded product with high transparency and good quality can be obtained by performing final blow molding in the final blow molding process using the primary molded product after shrinkage with a turbidity of 10% or less. Can be obtained.
[0030]
In the present invention, the primary blow mold is incorporated in the blow cavity mold corresponding to the shape of the body part of the primary molded product, the bottom mold corresponding to the shape of the bottom part of the primary molded product, and the bottom mold. A protruding member,
After the completion of the primary blow molding, the projecting member is caused to project at a preset distance from the bottom mold toward the bottom of the primary molded product at the same time as or after the start of blow air exhaust in the primary molded product. The mold can be forcibly released from the bottom of the primary molded product and the bottom mold.
[0031]
By adopting such a configuration, the projecting member is projected from the bottom mold simultaneously with the start of blow air exhaust or after a lapse of a short time, so that it can be forcibly released at least earlier than the mold release from the bottom mold due to contraction. Therefore, it is possible to prevent deformation due to the bottom part of the primary molded product sticking to the bottom mold and the release from the body part being delayed.
[0032]
In addition, by setting the protrusion distance of the protrusion member in advance, it is possible to prevent the protrusion distance from being too long and deforming, or from being too short and eccentric.
[0033]
Furthermore, the control of the protrusion of the protrusion member can be controlled by the control unit so as to drive the protrusion member after the set time of the timer has elapsed by setting a timer that starts from a blow air exhaust start command.
[0034]
In this case, in the primary blow molding step, a primary molded product that is larger in the height direction than the final molded product is molded,
The blow cavity mold of the primary blow mold is heated to at least 160 ° C. or higher,
The protruding distance of the protruding member can be set to a contraction distance in the height direction of the primary molded product.
[0035]
By adopting such a configuration, the primary molded product heat-treated with the heated primary blow mold rapidly contracts in accordance with the internal stress as soon as the blow air is exhausted. By pressing the bottom portion, the bottom portion can be reliably released from the bottom die without deformation due to delay of contraction due to the adhesion force with the bottom die.
[0036]
In addition, the heat-treated primary molded product is greatly shrunk in the height direction of the primary molded product after exhausting blow air, so by setting this shrinkage distance to a distance measured in advance by test molding or calculated from experience values, Eccentricity can be prevented, and molding defects due to eccentricity of the bottom can be prevented during final blow molding.
[0037]
In this case, the shrinkage distance of the primary molded product can be set to a value that is the same or shorter than the difference between the height position of the bottom mold of the primary blow mold and the height position of the bottom mold of the final blow mold.
[0038]
By adopting such a configuration, when blow molding in two stages, the height of the primary molded product after shrinkage is preferably the same as or higher than the height of the final molded product. By setting, a desired final molded product can be obtained.
[0039]
Further, in the present invention, the primary blow mold has a blow cavity mold corresponding to the shape of the body part of the primary molded product, and a bottom mold corresponding to the shape of the bottom part of the primary molded product,
At least the blow cavity mold is subjected to a surface coating treatment for mold release on the cavity surface,
The bottom mold is provided with a forced release means for forcibly releasing the bottom,
The surface coating can promote the release of the body portion, and the forced release means can perform the forced release of the bottom portion with respect to the bottom die.
[0040]
By adopting such a configuration, the release of the body part is promoted by the surface coating of the cavity surface, and the bottom part is forcedly released from the bottom mold by the forced release means, so that the cavity part of the bottom part and the body part is removed from the cavity surface. It is possible to obtain a stable primary molded product that has almost the same shape as the final molded product while preventing sticking, and the body part can have high transparency, so that reliable blow molding is possible in the final blow molding process. And a final molded product of good quality can be obtained.
[0041]
The final molded product of the present invention is a container-shaped final molded product molded by the blow molding method, and the turbidity of the body portion can be 10% or less.
[0042]
According to the present invention, the turbidity of the body portion can be made high with a transparency of 10% or less.
[0043]
The blow molding apparatus of the present invention comprises a primary blow molding part for producing a primary molded product by performing biaxial stretch blow molding in a heated primary blow mold,
In a blow molding apparatus having a final blow molding section for producing a final molded product by performing biaxial stretching blow molding in a final blow mold using a primary molded product,
The primary blow mold has a blow cavity mold corresponding to the shape of the body part of the primary molded product, and a bottom mold corresponding to the shape of the bottom part of the primary molded product,
The bottom mold includes a projecting member incorporated in the bottom mold and having a tip portion constituting the cavity surface of the bottom mold, drive means for projecting the projecting member from the cavity surface of the bottom mold, and at the time of blow molding An elastic member that constantly urges the protruding member in the backward direction is provided.
[0044]
According to the present invention, when a bottom mold is used as a primary blow mold, a protruding member is incorporated into the bottom mold, and at the time of blow molding, the protruding member is retracted by an elastic member so that the tip portion is a bottom mold cavity. The bottom part and the bottom mold are separated by projecting the projecting member from the bottom mold to the bottom part by the driving means when the primary molded part is contracted by blow air exhaust in the primary molded part after the molding is finished as a part of the surface. Forcibly, it is possible to reliably prevent the bottom portion from being deformed or inverted when contracted.
[0045]
Another blow molding apparatus of the present invention includes a primary blow molding section for producing a primary molded product by performing biaxial stretch blow molding in a heated primary blow mold,
In a blow molding apparatus having a final blow molding part for producing a final molded product by performing biaxial stretching blow molding in a final blow mold using the primary molded product,
The primary blow mold has a blow cavity mold corresponding to the shape of the body part of the primary molded product, and a bottom mold corresponding to the shape of the bottom part of the primary molded product,
At least the blow cavity mold is subjected to a surface coating treatment for mold release on the cavity surface,
The bottom mold is provided with a forced mold release means for forcibly releasing the bottom part.
[0046]
According to the present invention, it is possible to forcibly release the bottom portion from the bottom portion by the forced releasing means, and to reliably prevent the bottom portion from being deformed or inverted when contracted, and to blow. The release surface coating on the cavity surface of the cavity mold can promote the release of the body part from the cavity surface, making the primary molded product stable and almost transparent with the same size as the final molded product. As a result, a final molded product with good quality can be obtained.
[0047]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0048]
1-4 is a figure which shows the blow molding apparatus which concerns on one embodiment of this invention.
[0049]
FIG. 1 is a plan view showing the overall configuration of the blow molding apparatus.
[0050]
The blow molding apparatus 100 manufactures a heat-resistant container as a final molded product, and a supply unit 102, a heating station 104, a transfer unit 106, and a blow molding station 108 convey preforms (not shown). It is arranged on a straight line along the direction A.
[0051]
The supply unit 102 supplies the preform to the heating station 104, and includes a supply rail 110, an alignment mechanism 112, and a reverse delivery mechanism 114.
[0052]
The supply rail 110 supports the lower portion of the neck portion of the preform, and in the inverted state, the preform is continuously conveyed to the alignment mechanism 112 along the conveyance direction A by its own weight, and the preform continuously conveyed by the alignment mechanism 112 is supported. A predetermined number of reforms are received and aligned at a predetermined pitch in a direction orthogonal to the conveyance direction A, and the preforms of a predetermined pitch aligned by the alignment mechanism 112 are gripped by the gripping member 116 by the reversing delivery mechanism 114 and reversed. Then, it is transferred to the heating station 104 in an inverted state.
[0053]
The heating station 104 heats the preform supplied from the supply unit 102, and two heating paths 104 are arranged in parallel along the conveyance direction A, and two are arranged on each conveyance path 118. Heating box 120.
[0054]
Each conveyance path 118 has a plurality of conveyance members 122 that support the preform delivered from the supply unit 102 in an inverted state, and the plurality of conveyance members 122 intermittently convey the preform along the conveyance direction A. The preform is heated when it passes through the heating box 120, and the preform is heated to an appropriate temperature for stretching.
[0055]
Although not shown, a rotation mechanism is disposed in the conveyance path 118, and the preform temperature can be made uniform in the circumferential direction by conveying the preform while rotating.
[0056]
Further, each heating box 120 is provided with a shielding plate 124 along the preform conveying direction A in a state of shielding the preforms arranged in parallel.
[0057]
The transfer unit 106 transfers a predetermined number of preforms heated by the heating station 104 to the blow molding station 108 in an inverted state.
[0058]
Further, the transfer unit 106 has a pitch changing mechanism 126 to convert the pitch between the preforms into a blow molding pitch at the blow molding station 108.
[0059]
The blow molding station 108 has a substantially rectangular conveyance path 134 in which a conveyance chain 130 to which a plurality of conveyance members 128 are fixed is stretched over four sprockets 132.
[0060]
Further, one side of the rectangular conveyance path 134 is opposed to the transfer unit 106 to be a preform receiving unit 136, and a container which is a final molded product is taken out from the apparatus on one side opposed to the receiving unit 136. A portion 138 is provided.
[0061]
Further, a preform is biaxially stretched and blow-molded in a primary blow mold 142 on one side between the receiving portion 16 and the take-out portion 138 to form a primary molded product and heat-treated on the inner surface of the primary blow mold 142. The primary blow molding part 140 and the final blow molding part 146 that biaxially stretch blow-molds the primary molded product that has passed through the primary blow molding part 140 into the shape of the final molded product in the final blow mold 144 are arranged. ing.
[0062]
The receiving unit 136 receives the inverted preform transferred from the transfer unit 106 as it is on the conveying member 128, and the takeout unit 138 reverses the inverted blown container that has been finally blow-molded. It is reversed and is taken out in an upright state.
[0063]
The primary blow molding unit 140 and the final blow molding unit 146 are provided with a mold clamping mechanism 150 for opening / closing and clamping the primary blow mold 142 and the final blow mold 144, respectively.
[0064]
The primary blow mold 142 and the final blow mold 144 are such that the cavity of the primary blow mold 142 is larger than the cavity of the final blow mold 144, whereas the primary blow mold 142 is heated. The final blow mold 144 is not heated, and the primary blow mold has a surface coating on the cavity surface of the blow cavity mold and a forced mold release means is provided on the bottom mold, whereas the final blow mold is Is different only in that there is no surface coating and no forced release means. Therefore, only the primary blow mold 142 will be described below, and description of the final blow mold 144 will be omitted.
[0065]
FIG. 2 shows the state of the primary blow molding part 140 among the above-mentioned parts.
[0066]
The primary blow molding unit 140 is provided with a conveyance path 134 at the bottom, and a blow cavity mold 14 formed of a split mold as a primary blow mold 142 and a bottom mold 16 are disposed above the conveyance path 134. .
[0067]
In the transport path 134, a transport member 128 is engaged with the transport rail 18 disposed along the transport direction via the cam follower 20, and a transport chain 130 fixed to the transport member 128 is disposed along the transport direction. Further, the conveying member 128 is intermittently conveyed by driving the conveying chain 130 by a driving means (not shown).
[0068]
The conveying member 128 includes an inner cylindrical mounting member 28 and an outer cylindrical fixing member 30 that penetrates the mounting member 28, and a preform (not shown) is formed on the upper end portion of the mounting member 28. ) And a placing portion 32 for placing the preform in an inverted state.
[0069]
In addition, with the preform placed on the transport member 128 and transported to the primary blow molding unit 140 and stopped, the stretching rod 34 is inserted into the preform from below the transport member 128 and inserted into the preform. In addition to stretching in the vertical axis direction, blow air is supplied into the preform through the mounting member 28 and stretched in the horizontal axis direction, so that biaxial stretch blow molding is performed.
[0070]
The blow cavity mold 14 includes a split mold, and each split mold is attached to a mold clamping plate (not shown) via a heating plate 36, a heat insulating plate 38, and a mounting plate 40.
[0071]
Further, a release surface coating 152 is formed on the cavity surface 80 of the blow cavity mold 14 to prevent the body portion 45 of the primary molded product 43 from sticking to the cavity surface 80, thereby promoting the release. The rough and rough state or deformation of the surface of the body 45 or the occurrence of vertical stripes is prevented.
[0072]
As the material of this surface coating 152, organic materials having characteristics such as lubrication, mold release, anticorrosion, insulation, etc., such as fluororesin and siloxane resin, are combined with high-hardness inorganic materials such as metals, ceramics, and chemical conversion films. Can be used.
[0073]
By using such a material, even if the blow cavity mold 14 is made of a material having high thermal conductivity such as aluminum, it can follow the thermal expansion and contraction.
[0074]
The mold clamping plate is driven by a mold clamping driving means constituting a mold clamping mechanism so that the mold opening / closing and mold clamping of the blow cavity mold 14 are performed.
[0075]
The heating plate 36 has a cast heater 42 therein. By heating the cast heater 42, the blow cavity mold 14 is heated to 160 ° C. to 200 ° C., and is subjected to primary blow molding to blow blow cavity. The primary molded product 43 in contact with the mold 14 is heat treated.
[0076]
The heat insulating plate 38 prevents the heat of the heating plate 36 from being transmitted to the mounting plate 40.
[0077]
A cooling path 44 is formed in the mounting plate 40, and a cooling medium is supplied into the cooling path 44, thereby preventing transmission of heat to the mold clamping plate.
[0078]
Further, at the lower part of the mold clamping plate, the neck portion holding member 46 can be moved forward and backward in the opposing direction, and the neck portion holding member 46 holds the neck portion of the preform with the blow cavity mold 14 closed. To get.
[0079]
The bottom mold 16 is mounted above the blow cavity mold 14 via a bottom mold mounting plate 50, and can be moved up and down and clamped with respect to the blow cavity mold 14 by driving a bottom mold drive means (not shown). ing.
[0080]
Further, the cavity surface 52 of the bottom mold 16 protrudes inward of the cavity and is formed with a plurality of annular steps, and the inner side of the primary molded product 43 is formed on the bottom 54 of the primary molded product 43. A concave portion (raised bottom) 76 with an annular stepped portion is formed.
[0081]
In addition, a heating path 56 is formed in the bottom mold 16, and a heating medium is supplied into the heating path 56, so that the bottom mold 16 has a glass transition point of molding material (about 70 ° C. in the case of PET) or more, Preferably, the heat resistance of the bottom portion 54 is improved by heating to about 80 ° C. to 100 ° C. and heating the bottom portion 54 of the primary molded product 43.
[0082]
Further, the bottom mold 16 is formed with a cylinder 58 at the center position in the vertical direction, and a projecting member 62 as a forced mold release means formed integrally with the piston 60 is disposed in the cylinder 58. .
[0083]
In addition, a spring 64 is disposed around the piston 60 so as to constantly urge the piston 60 upward, so that the round bar-like tip of the protruding member 62 always has the cavity surface 52 of the bottom mold 16. It is in the state which forms a part of.
[0084]
In FIG. 2, the left side shows a blow-molded state, and the right side shows a state after shrinkage.
[0085]
Then, by supplying air from the air flow path 66 into the cylinder 58, the piston 60 descends against the urging force of the spring 64, and the protruding member 62 moves from the cavity surface 52 to the bottom 54 of the primary molded product 43. It protrudes toward the center.
[0086]
The projecting of the projecting member 62 is performed at the same time as or after a short time from the start of exhausting the blow air in the primary molded product 43 after the biaxial stretch blow molding is completed, and the bottom 54 of the primary molded product 43 is separated from the bottom mold 16 by contraction. The mold can be forcibly released by protruding earlier than the mold.
[0087]
This protrusion can be controlled by setting a timer that starts from a blow air exhaust start command, and is controlled by the control unit so as to open the air supply valve to the cylinder 58 of the protruding member 62 after the set time of the timer has elapsed.
[0088]
Here, if the timer setting is set to 0, the air will protrude at the same time as the blow air exhaust.
[0089]
In the present embodiment, a final molded product of 500 ml was molded. However, until the timer setting was 0 to 0.3 seconds, molding could be performed without deformation at the bottom.
[0090]
This timer setting varies depending on the size of the container to be molded, and the molder can appropriately set the timer setting of the control means by looking at the state of the final molded product.
[0091]
Further, the projecting member 62 has a stroke set in advance within or equal to the shrinkage amount (shrinkage distance) L of the primary molded product 43 after molding.
[0092]
In the two-stage blow molding as in the present embodiment, the height of the primary molded product 43 after shrinkage is adjusted to be the same as or slightly higher than the height of the final molded product. It is desirable to set the stroke to be the same as or slightly shorter than the height of the final molded product.
[0093]
This adjustment of the stroke can be arbitrarily adjusted with a spacer or the like while the molder confirms the state of the bottom of the final molded product.
[0094]
Next, a blow molding method in such a blow molding apparatus 100 will be described.
[0095]
First, the preform continuously supplied to the supply unit 102 in an upright state reaches the alignment mechanism 112 from the supply rail 110, is aligned there, and is inverted by the inversion delivery mechanism 114, and is transferred to the conveyance path 118 of the heating station 104. It is delivered on the provided conveying member 122.
[0096]
In the heating station 104, the conveyance member 122 holding the preform moves along the conveyance path 118, and intermittently conveys the position of the heating box 120 while rotating the preform by the rotation mechanism, thereby heating the preform to an appropriate temperature for stretching. .
[0097]
The preform heated to an appropriate stretching temperature is transported to the transfer unit 106 position, and the transfer unit 106 converts the pitch into a blow molding pitch and remains in an inverted state, and the transport path 134 at the receiving unit 136 position of the blow molding station 108. It is delivered to the upper conveying member 128.
[0098]
The preform delivered to the conveying member 128 is conveyed to the primary blow molding unit 140 by driving the conveying chain 130.
[0099]
In a state where the preform has been conveyed to the primary blow molding section 140, the mold clamping plate is driven by the mold clamping drive means to close the blow cavity mold 14 and the mold is clamped. The mold 16 is lowered, the mold clamping plate is driven by the mold clamping driving means, the blow cavity mold 14 is closed, and the mold is clamped.
[0100]
Next, the inside of the carrying member 128 is inserted into the mounting member 28 and the stretching rod 34 is inserted into the preform. The stretching rod 34 extends the vertical axis until the bottom of the preform reaches the bottom mold 16, and the mounting rod 28 is loaded. Blow air is supplied into the preform through the placement member 28, and the preform is stretched in the horizontal axis to biaxially stretch blow-mold the preform into the shape of the primary molded product 43.
[0101]
Next, after the end of this biaxial stretch blow molding, the blown air in the primary molded product 43 is exhausted and at the same time the primary molded product 43 starts to shrink.
[0102]
Since the release surface coating 152 is applied to the cavity surface 80 of the blow cavity mold 14, it is considered that the mold release starts from the body 45 due to this contraction, and at the same time as the exhaust or for a short time, for example, When air is supplied into the cylinder 58 in 0.2 seconds and the piston 60 is lowered, the tip of the protruding member 62 protrudes from the cavity surface 52 of the bottom mold 16 while pushing the center of the bottom 54 of the primary molded product 43, The bottom 54 is forcibly released from the bottom mold 16 with little delay, and further, the bottom 54 is moved by a predetermined contraction amount (contraction distance) L while the center of the bottom 54 is held by the tip of the protruding member 62.
[0103]
As a result, the bottom 54 of the primary molded product 43 is forcibly released from the cavity surface 52 of the bottom mold 16, and the bottom 54 of the primary molded product 43 is inverted and protrudes outward from the primary molded product 43. It is possible to reliably prevent the deformation.
[0104]
Further, since the amount of movement of the projecting member 62 is within a range that falls within the contraction amount L of the primary molded product 43, the projecting member 62 pushes the bottom portion 54 of the primary molded product 43 more than necessary and deforms it in reverse. Can be prevented.
[0105]
Further, the protruding member 62 presses the center of the bottom 54 of the primary molded product 43, so that the center position can be prevented from being displaced due to the deformation of the primary molded product 43 when the primary molded product 43 is contracted. The final blow molding can be performed easily and reliably by preventing the primary molded product 43 from being squeezed by the final blow mold 140 in the blow molding portion 146, the bottom molding failure, and the like.
[0106]
As described above, the body 45 and the bottom 54 are separated from the blow cavity mold 14 and the bottom mold 16 almost simultaneously, so that deformation of the body 45 and occurrence of vertical stripes during contraction can be prevented.
[0107]
Then, with the bottom 54 of the primary molded product 43 reliably released from the cavity surface 52 of the bottom mold 16, the projecting member 62 is retracted into the bottom mold 16, and the blow cavity mold 14 and the bottom mold 16 are retreated. When the mold is opened, the primary molded product 43 can be transported by the transport member 128. In this state, the primary molded product 43 is transported to the blow molding unit, and the final molded product is molded. The final molded product will be taken out in an upright state.
[0108]
Next, the primary molded product after shrinkage formed when the release cavity surface coating is applied to the cavity surface of the blow cavity mold of the primary blow molding portion used in such a blow molding method, and the mold release on the cavity surface FIG. 3 shows the result of comparison of the shapes of the respective body portions of the primary molded product after shrinkage formed by using the blow cavity mold not coated with the coating.
[0109]
The primary molded product after shrinkage was for molding a 500 ml container, and the height was about 200 mm, and the measurement was performed at three positions of 65 mm, 125 mm, and 170 mm from the top of the neck portion, respectively.
[0110]
The shape was determined by the ratio of the length of the short diameter portion to the long diameter portion at each position.
[0111]
As a result, when the release surface coating is applied, it is 80% or more at each position as shown in the left column, and when the release surface coating is not applied, the right side As shown in the column, it was over 80% at the positions of 65 mm and 170 mm, but it became a large state of deformation that was 80% divided by 63.1% at the position of 125 mm.
[0112]
From this result, when the release surface coating is applied, the primary molded product after shrinkage has a good shape in which the ratio of the length of the minor axis to the major axis is 80% or more at all positions. Turned out to be.
[0113]
In addition, the results of comparing the turbidity of the blow molded mold with the release surface coating and the primary molded product and the final molded product molded using the blow cavity mold without the release surface coating are shown in the figure. 4 (1) and (2).
[0114]
As a turbidity measuring instrument, Nippon Denshoku Industries Co., Ltd. NDH-300A (turbidimeter Turbidimeter) standard JIS K7105 was used.
[0115]
Turbidity was determined by the following equation.
[0116]
Turbidity = (diffuse transmittance / total light transmittance) × 100
The measurement was performed at two locations of the lower body portion and the middle body portion in both the primary molded product and the final molded product.
[0117]
As a result, in the primary molded product, as shown in FIG. 4 (1), when the release coating is applied, the turbidity is 10% or less at all positions as shown in the left column. In contrast, the surface is rough and rough, and no vertical stripes are generated. On the other hand, when the surface coating for release is not applied, the turbidity exceeds 10% at all positions, and the transparency is very high. The surface is rough, rough and has vertical stripes.
[0118]
In the case of the final molded product, as shown in FIG. 4 (2), almost the same result as in the case of the primary molded product was obtained.
[0119]
From these results, it was found that when the release surface coating was applied, a highly transparent product having a turbidity of 10% or more was obtained in both the primary molded product and the final molded product.
[0120]
FIG. 5 is a perspective view showing a tip portion of a protruding member according to another embodiment of the present invention.
[0121]
The projecting member 62 is provided with an abutting portion 70 extending radially in a cross shape from the center at the tip, and an annular shape in which a contact surface 72 of the abutting portion 70 with the bottom 54 of the primary molded product 43 has the shape of the bottom 54. A stepped portion shape corresponding to the shape of the stepped portion 74 is used.
[0122]
As a result, a contact area with the bottom 54 of the projecting member 62 is secured, deformation of the bottom 54 is prevented, and more reliable mold release is possible.
[0123]
Other configurations and operations are the same as those in the above embodiment, and a description thereof will be omitted.
[0124]
The present invention is not limited to the above-described embodiment, and can be modified into various forms within the scope of the gist of the present invention.
[0125]
For example, in the above embodiment, in the primary blow molding process of blow molding the primary molded product, the surface coating for mold release and the projecting member as the forced mold release means for forcibly releasing the bottom from the bottom mold are provided. However, depending on the conditions, it is possible to omit the surface coating for release.
[0126]
Moreover, in the said embodiment, also in a secondary blow molding process, it is also possible to make a protrusion member protrude from a bottom mold | type similarly to a primary blow molding process.
[0127]
Furthermore, although the drive mechanism of the protruding member is an air cylinder, a known drive mechanism such as a hydraulic cylinder can be employed.
[0128]
Further, the forced mold release means is not limited to the protruding member, and it is also possible to release the mold by blowing air from the bottom mold to the bottom.
[0129]
Further, in addition to the cavity surface of the blow cavity mold of the primary blow mold, a mold release surface coating may be applied to the cavity surface of the bottom mold.
[0130]
In this embodiment, the primary blow mold has a cavity with a substantially circular cross section. However, the primary blow mold may have a substantially rectangular or substantially elliptical shape.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a blow molding apparatus according to an embodiment of the present invention.
2 is a cross-sectional view showing a state of a primary blow molding portion in FIG. 1. FIG.
FIG. 3 is a diagram showing the results of measuring the shape of a primary blow-molded product after contraction when a release cavity coating is applied to a blow cavity mold of a primary blow mold and when it is not applied.
FIG. 4 is a diagram showing the results of measuring the turbidity of a primary molded product when a release surface coating is applied to a blow cavity mold of a primary blow mold and when it is not applied. (2) These are figures which show the result of having measured the turbidity of the final molded product in the same case.
FIG. 5 is a perspective view showing a distal end portion of a protruding member according to another embodiment of the present invention.
[Explanation of symbols]
14 Blow cavity mold
16 Bottom mold
34 Stretched rod
43 Primary molded products
45 Torso
52 Cavity surface of bottom mold
54 Bottom
62 Protruding member
70 Contact part
72 Contact surface
140 Primary blow molding part
142 Primary blow mold
144 Final blow mold
146 Final blow molding part
152 Surface coating

Claims (9)

A primary blow molding process for producing a primary molded product by biaxial stretching blow molding in a heated primary blow mold, and a final molded product by biaxial stretching blow molding in the final blow mold using the primary molded product. In a blow molding method including a final blow molding step of manufacturing
The primary blow mold is provided with a blow cavity mold corresponding to the shape of the body part of the primary molded product and a bottom mold corresponding to the shape of the bottom part of the primary molded product, and the bottom mold includes the bottom mold. A projecting member incorporated in the mold and having a tip portion constituting the cavity surface of the bottom mold, drive means for projecting the projecting member from the cavity surface of the bottom mold, and the projecting member always in a backward direction during blow molding An elastic member for biasing,
In the primary blow molding step, after the biaxially stretched blow molding of the primary molded product, at the same time as or after the start of blow air exhaust in the primary molded product, the bottom of the primary molded product from the bottom mold The projecting member is projected by the driving means at a distance set in advance, and the body and bottom of the primary molded product are released from the primary blow mold and contracted by the blow air exhaust and the projecting member. A blow molding method. In claim 1,
The primary molded product is formed with a circular cross section of the body part,
The primary molded product after shrinkage is characterized in that the ratio of the length of the short diameter part to the long diameter part in the cross section at a predetermined position of the body part is 80% or more. In claim 1,
The primary molded product after shrinkage is in the cross section of the barrel predetermined position,
A blow molding method, wherein the ratio of the largest shrinkage to the smallest shrinkage is 80% or more. In any one of Claims 1-3,
The primary molded article after shrinkage has a turbidity of the body part of 10% or less. In any one of Claims 1-4,
In the primary blow molding step, a primary molded product that is larger in the height direction than the final molded product is molded,
The blow cavity mold of the primary blow mold is heated to at least 160 ° C. or higher,
The blow molding method, wherein the protruding distance of the protruding member is set to a contraction distance in the height direction of the primary molded product. In claim 5,
The shrinkage distance of the primary molded product is set to be equal to or shorter than the difference between the height position of the bottom mold of the primary blow mold and the height position of the bottom mold of the final blow mold. Blow molding method characterized. In any one of Claims 1-6,
At least the blow cavity mold is subjected to a surface coating treatment for mold release on the cavity surface,
Blow molding method characterized in that release of said body portion is promoted by said surface coating. A primary blow molding section for producing a primary molded product by performing biaxial stretch blow molding in a heated primary blow mold;
In a blow molding apparatus having a final blow molding section for producing a final molded product by performing biaxial stretching blow molding in a final blow mold using a primary molded product,
The primary blow mold has a blow cavity mold corresponding to the shape of the body part of the primary molded product, and a bottom mold corresponding to the shape of the bottom part of the primary molded product,
The bottom mold includes a projecting member incorporated in the bottom mold and having a tip portion constituting the cavity surface of the bottom mold, driving means for projecting the projecting member from the cavity surface of the bottom mold, and at the time of blow molding A blow molding apparatus, comprising: an elastic member that constantly urges the protruding member in the backward direction. In claim 8,
At least the blow cavity mold is subjected to a surface coating treatment for mold release on the cavity surface.

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