JP2792544B2 - Method and apparatus for producing stretch blow molded bottle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and an apparatus for producing a stretch blow-molded bottle.

[Conventional technology]

The biaxially stretched blow-molded container made of a saturated polyester resin represented by polyethylene terephthalate has extremely excellent transparency and surface gloss, is beautiful, has excellent gas barrier properties and moisture impermeability, and has excellent content resistance. It has many advantages such as excellent storage stability, no generation of toxic gas in additives such as plasticizers and stabilizers, and low heat generation during combustion and no damage to the furnace. Therefore, it is widely used for various drinking water, seasonings, alcoholic beverages and other food containers. Such bottles usually have a mouth coaxial with it at the upper end of the body.

Recently, a bottle having a mouth provided at a slightly inclined position instead of the upper end has been used. The bottle is housed in a paper container having a slope, and the mouth protrudes from the slope. Conventionally, such bottles have been disclosed in Japanese Utility Model Laid-Open Nos. 56-15076, 62-29375 and 62-29376.
Is disclosed in US Pat. Each of these bottles is provided with a coaxial opening at the upper end of the biaxially stretched blow-molded main body. The mouth can be inclined when it is accommodated in a paper container.

However, in the above-mentioned conventional bottle, the mouth is inclined by deforming means such as a bellows provided at the upper part of the main body,
Extra irregularities will be present in the bottle body. The contents easily remain in these bellows and the like, and the smooth outflow of the contents is prevented. Further, since the surface area of the container is increased, characteristics such as gas barrier properties are reduced. In addition, by providing a deformed portion having a complicated shape such as a bellows portion, the manufacturing cost of the entire bottle increases.

Therefore, the present inventor has conducted various studies on a method of manufacturing a synthetic resin bottle body in which the plug portion is inclined, and as a result,
Along the circumference of the radius R that is in contact with the center axis of the parison near the plug section, a stretch rod having the same radius of curvature as the circumference is inserted into the plug section of the parison, and biaxially stretch blow-molded. It was discovered that a bottle having an inclined plug and a uniform wall thickness could be obtained, and a patent application was filed earlier.

However, in the above-described biaxial stretch blow molding method using a curved stretch rod, there is a problem that the apparatus is complicated because a stretch rod having a curvature has to be used in advance.

[Problems to be solved by the invention]

Due to the above circumstances, when manufacturing a bottle with an inclined plug by blow molding, without using a complicated mechanism,
There is a need for a method and apparatus capable of obtaining a bottle having a uniform thickness and a thick portion corresponding to the parison tip located at the center of the bottom. Further, even in the case of a bottle having an oblique plug, a method and apparatus for easily uniforming the thickness of the bottle and positioning the bottom thick portion are desired.

Accordingly, an object of the present invention is to provide a method for easily producing a bottle by stretch blow molding without using a device having a complicated mechanism, particularly in the case of a bottle having an inclined plug portion. is there.

Another object of the present invention is to provide an apparatus for producing such a stretch blow-molded bottle.

[Means for solving the problem]

As a result of intensive research in view of the above object, the present inventor uniaxially stretched the body of the parison before stretch blow molding and fixed the tip of the parison to the bottom of the mold cavity,
The present inventors have discovered that a bottle can be easily manufactured by stretch blow molding, and have completed the present invention.

That is, the method of the present invention for producing a stretch blow-molded bottle from a parison having a plug portion and a bottomed cylindrical shape comprises a stretch blow-molding mold having a recess at the bottom of the cavity for holding the tip of the parison. Using a stretching rod at a temperature equal to or higher than the softening point, the body of the parison is uniaxially stretched in the longitudinal direction to a length that reaches the bottom of the cavity of the stretch blow molding die. The parison is installed in the mold so as to be held in the concave portion, and the parison is stretch blow-molded by blowing air.

The first apparatus of the present invention for producing a stretch blow-molded bottle from a parison having a plug portion and a bottomed cylindrical body portion,
A blow mold for forming a cavity with a pair of body molds and a bottom mold, and a recess for holding the tip of the parison at the bottom of the cavity, wherein the recess is one of the body molds; And the notch formed in the bottom mold, and the tip of the parison is clamped in the recess by mold clamping.

Further, a second apparatus of the present invention for producing a stretch blow-molded bottle from a parison having a plug portion and a bottomed cylindrical body portion includes a pair of body molds that open in a lateral direction and a mold opening downward. A blow mold for forming a cavity with a bottom mold to be formed, a concave portion for holding a tip of the parison is provided at an upper portion of the bottom mold, and the tip of the parison is closed by mold clamping. It is characterized by being fixed by a concave portion.

(Operation)

Using a mold having a concave part holding the tip of the parison at the center of the bottom of the cavity, the barrel of the parison is uniaxially stretched before stretch blow molding, and the tip of the parison is uniaxially stretched at the center of the bottom of the mold cavity. , A stretch blow-molded product having a uniform thickness can be easily manufactured by free blow molding. This is because the parison tip is held at the bottom of the cavity, which prevents the parison from being easily displaced during free blow molding.The parison's body is located almost in the center of the cavity, so the stretching ratio of the parison's body is Is substantially uniform.

Also, even in the case of a bottle where the plug is inclined with respect to the trunk,
By deforming the body of the uniaxially stretched parison into a predetermined curved shape before stretch blow molding, the thickness of the bottle can be made substantially uniform by free blow without the need for complicated mechanisms. it can. This is considered to be because the curved parison body is located substantially at the center of the cavity body of the stretch blow molding die, so that each part of the parison body is stretched at a substantially uniform magnification. .

〔Example〕

The stretch blow molding method of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view of a mold for stretch blow molding according to one embodiment of the present invention. This mold is formed from body molds 1 and 2, mouth mold 3, and bottom mold 4.

The shape of the cavity 5 formed by the mold of this embodiment is as follows.
A rectangular parallelepiped torso 5a whose corners and ridges are curved
, A cylindrical plug portion 5b, the body portion 5a and the plug portion 5b
And a concave portion 5e provided at the center of the bottom portion 5d. The shape is suitable for producing bottles that are inclined with respect to the body. Central axis of l ₂ and plugging portions 5b of the body portion 5a
As l ₁ and intersect at an angle theta, barrel 5a is inclined with respect to plugging portion 5b.

Further, as shown in this embodiment, in order to stabilize the sitting of the bottle to be molded and increase the strength, the bottom 5d of the cavity is raised so that the bottom of the bottle is raised. When the product is provided, the angle of raising the bottom should be equal to or larger than the angle ψ (formed by the central axis of the body 5a and the horizontal line) so that an undercut portion is not formed when the product is released after the stretch blow molding. Must be set to

The reason why the bottom mold 4 is used in this embodiment is to prevent the protrusion formed in the recess 5e by stretch blow molding from becoming an undercut when the mold is opened. Therefore recess
5e is formed by the cutout of the body mold 1 and the cutout of the bottom mold 4.

Further, by making the concave portion 5e of this embodiment shallower than the height of the bottom portion 5d raised, the protrusion formed by the concave portion 5e in the stretch blow-molded bottle does not interfere.

Next, the parting surface of the mold of this embodiment will be described with reference to FIG.

From the viewpoint of facilitating the release of the bottle after blow molding, in the embodiment shown in FIG. ₁ , the parting surfaces of the body dies 1 and 2 are along the lines l ₁ , l ₂ and l _3. (Perpendicular to the plane of FIG. 1).

First, in mouth part 5b, parting plane extends substantially along the central axis l _1. Since in the central axis l ₁ of the plugging portion 5b in this embodiment is a vertical, it is convenient to carry out the mold clamping by moving the body part mold 1,2 laterally.

In barrel 5a, parting plane extends substantially along the central axis l _2. Since the body 5a is inclined by the angle θ with respect to the plug 5b, the parting surface also needs to be inclined at substantially the same angle. In addition, by providing the parting plane along the central axis l _2, barrel cavity is almost symmetrical, the release of the stretch blow molding the bottle is facilitated.

The parting surface l ₃ of the body part mold 2 and bottom mold 4 is required to pass through the almost end of the cavity bottom 5d. This is to prevent undercut, as is apparent from FIG. That is, since the position where the undercut that hinders the release of the bottle can be completely prevented is the end of the bottom 5d, it is necessary to pass therethrough. The clamping moved laterally to the body part mold 1,2 sandwich the bottom mold 4, so to carry out mold opening is usually the party along l ₃ passing through the substantially ends of the bottom portion 5d Preferably, the bearing surface is substantially vertical.

Furthermore parting surface between the body part mold 1 and the bottom mold 4 is made of a plane along the line l _4, l ₅ of FIG. 1 (perpendicular to the paper surface in FIG. 1). Since the recess 5e is a portion for fixing the parison tip is to be provided so as to be positioned at the center of the cavity bottom l ₄ is the central axis of the body portion of the cavity 5
l Set to be on extension of ₂ . The l ₅ from the bottom 4 is being clamping laterally by body part type 1
Preferably is perpendicular in the same manner as l _3.

With such a structure, the installation of the deformed parison and the removal of the stretch blow-molded bottle are performed by opening and closing strokes of the pair of body dies 1 and 2 in the horizontal direction and moving the bottom mold 4 in the vertical direction. Is convenient.

FIG. 2 is a cross-sectional view showing a state in which a deformed parison in which the trunk is uniaxially stretched in the longitudinal direction in advance and which is bent is installed in the blow molding die shown in FIG. At this time, the protruding portion 7a formed at the tip of the deformed parison 7 is clamped and fixed in the center concave portion of the bottom surface of the cavity formed by the cutout of the body die 1 and the cutout of the bottom die 4. The curved state of the deformed parison 7 at this time is substantially along the center axis of the cavity 5 so that the stretching ratio of each part of the parison body is substantially the same.

FIG. 3 is a sectional view of the distal end portion of the stretching rod used in the method of the present invention, and FIG. 4 is a sectional view taken along line AA of FIG. When the parison body is uniaxially stretched in the longitudinal direction by the stretching rod, the tip of the parison is deformed to have a cross section as shown in FIG. As shown in FIG. 6, the projecting portion 9a is sandwiched between the body mold 1 and the projecting mold 4 from the side during mold clamping, and is fixed to the center of the cavity bottom.

The stretch blow molding method of the present invention is not limited to a bottle having a plug portion inclined with respect to a body portion, but also a stretch blow molding method for a bottle body having a plug portion formed coaxially with a body portion. Also applicable to

FIG. 7 is a cross-sectional view showing an example of the apparatus of the present invention for producing a bottle in which the plug is formed coaxially with the body. This apparatus is a mold for stretch blow molding. The mold for stretch blow molding is formed of a pair of body dies 11, 12, a mouth mold 13, and a bottom mold 14.

The shape of the cavity 15 formed by the mold of the present embodiment is
A cylindrical or rectangular parallelepiped body 15a and a cylindrical plug 15b
A shoulder 15c that smoothly connects the body 15a and the plug 15b; a bottom 15d that smoothly connects from the body 15a and is raised toward the center thereof; and a bottom 15d. And a concave portion 15e formed at the center of.

In the mold release after the stretch blow molding of the mold shown in FIG. 7, the body dies 11 and 12 move laterally, and the bottom mold 14 moves downward. The parting plane between the body part mold and the bottom mold is a surface along the line l _11, l ₁₂ of FIG. 7 (perpendicular to the paper surface in FIG. 1)
Is set to Further, since a force is applied to the molds during the stretch blow molding from the lateral direction of the body dies 11, 12, it is preferable that l ₁₁ and l ₁₂ be vertical.

FIG. 8 is a sectional view of the distal end of a stretching rod suitable for use in the second embodiment, and FIG.
It is B sectional drawing. When the body of the bottomed cylindrical parison is uniaxially stretched in the longitudinal direction by the stretching rod 16 shown in FIG. 8, the tip of the parison is deformed to have a cross section as shown in FIG. The tip 17a of the parison 17 obtained in this manner is inserted into the recess 1 at the bottom of the mold cavity shown in FIG.
Insert into 5e and fix (Fig. 11).

As can be seen from FIG. 11, in this embodiment, a parison 17 whose body is uniaxially stretched is located along the central axis of the cavity body, and a projection 17a at the tip of the parison is inserted into the recess 15e of the cavity bottom 15d. Since it is fixed, a bottle having a uniform wall thickness can be manufactured even when free blow molding is performed.

Further, by making the depth of the groove 15e smaller than the height of raising the cavity bottom 15d in advance, the protrusion of the molded bottle (derived from the protrusion 17a of the parison tip) does not become an obstacle. .

In the first embodiment, it is necessary to deform the parison body in a curved shape after uniaxial stretching so that the center axis of the parison body is substantially along the center axis of the mold cavity. The modified parison used in the first embodiment can be manufactured by various methods. For example, first, the stretching rod 32 is placed in the parison 30 shown in FIG. 12, and is uniaxially stretched in the longitudinal direction (FIG. 13). It is preferable that the body portion 31c of the uniaxially stretched parison 31 has a length that reaches the bottom of the cavity of the stretch blow molding die after being deformed into a curved shape after being deformed into a curved shape.

FIG. 14 is a longitudinal sectional view showing an example of an apparatus for deforming the parison body in a curved manner by applying a pressing force from the lateral direction.
The figure is a sectional view taken along the line CC of FIG. This device is a mold 34 in which a groove 35 having a curved and smooth surface is formed, and the groove 35 has a substantially semicircular cross section as shown in FIG. The curved state of the groove 35 can be variously set according to the desired curved state of the modified parison. Generally, when performing stretch blow molding of a bottle with an inclined plug, if the curvature of the parison body is maximized in the vicinity of the stopper, the difference in stretch ratio during stretch blow molding should be minimized as a whole. The groove 35 is curved accordingly.
Is preferably formed. In such a case, the upper part of the groove 35
The curvature of 35a is relatively large, and the curvature of lower portion 35b is relatively small. However, the present invention is not limited to such a shape, and may be in any curved state. For example, the groove 35 may be curved with a constant curvature.

A heater 36 is embedded in the mold 34 inside the groove 35 in order to keep the deformed parison in a softened state.

16 to 19 are schematic sectional views showing a series of steps for manufacturing a deformed parison by deforming a straight parison body into a curved shape using the apparatus of FIG.

As shown in FIG. 16, first, the parison 31 in the softened state
The stopper 31a is fixed on the mold 34 while being held by the holder 37. At this time, the tip of the parison 31 is positioned so as to be in contact with the upper end of the groove 35 of the mold 34.

Next, as shown in FIG. 17, when the mold 34 is slowly lifted, the parison body 31C comes into sliding contact with the groove 35 and deforms into a curved shape according to the shape of the groove 35. Parison trunk 31C and groove 35
The state of sliding contact with is as shown in FIG. Further mold
When the flange 34b rises and the flange 31b of the parison 31 comes into contact with the mold 34, the rise of the mold 34 is stopped, and the deformation of the parison body is completed (FIG. 18). After the deformation, the mold 34 is lowered to take out the deformed parison 31 (FIG. 19).

In the present invention, the length of the uniaxially stretched parison body may be both curved and non-bent, as long as the tip can be fixed to the bottom of the cavity. If the parison is longer than the length that reaches the bottom of the cavity of the mold, the parison can be placed in the mold while compressing the parison in the longitudinal direction in the step of closing the mold.

The thermoplastic resin used for the modified parison of the present invention is preferably a polyester resin comprising a saturated dicarboxylic acid and a saturated dihydric alcohol. As saturated dicarboxylic acids, terephthalic acid, isophthalic acid, phthalic acid, naphthalene-1,4- or 2,6-dicarboxylic acid, diphenylether-4,4'-dicarboxylic acid, diphenyldicarboxylic acids, diphenoxyethanediethanedicarboxylic acids And aromatic dicarboxylic acids such as adipic acid, sebacic acid, azelitic acid, and decane-1,10-dicarboxylic acid, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid. Examples of the saturated dihydric alcohol include aliphatic glycols such as ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, hexamethylene glycol, dodecamethylene glycol, and neopentyl glycol. Glycols, alicyclic glycols such as cyclohexanedimethanol, 2,2-bis (4'-β-hydroxyethoxyphenyl) propane, and other aromatic diols can be used. A preferred polyester is polyethylene terephthalate consisting of terephthalic acid and ethylene glycol.

The polyester resin used in the present invention has an intrinsic viscosity of 0.5
It has a value in the range of 1.51.5, preferably 0.55 to 0.85. Such polyesters are also produced by melt polymerization,
Those subjected to a reduced pressure treatment or a heat treatment in an inert gas atmosphere at a temperature of 0 to 250 ° C., or those obtained by solid phase polymerization to reduce the content of oligomers and acetaldehyde, which are low molecular weight polymers, are preferable.

In the polyester resin used in the present invention, additives such as stabilizers, pigments, antioxidants, heat deterioration inhibitors, ultraviolet light deterioration inhibitors, antistatic agents, antibacterial agents, etc. are used as long as the object of the present invention is not impaired. And other resins can be added in appropriate amounts. Needless to say, a known gas barrier resin, a heat-resistant resin, and a multilayer parison having a multilayered heat-resistant resin can also be used.

The present invention is described in more detail by the following specific examples.

Example 1 First, a parison having a cylindrical shape with a bottom and a straight body was made of polyethylene terephthalate. The thickness of this trunk was 3.2 mm. The parison was heated to 95 to 120 ° C. to be in a softened state, and as shown in FIG. 13, uniaxially stretched in a longitudinal direction by a stretching rod. The wall thickness of the body of the uniaxially stretched parison thus obtained is 2.1 mm.
Met. FIGS. 14 and 15 show the uniaxially stretched parison.
Using the mold shown in the figures, deformation was performed by the steps shown in FIGS. The mold 34 was kept at about 90 ° C.

The body of the modified parison obtained in this way was smoothly curved, and its cross section maintained a substantially circular shape.

Further, the modified parison was set in a stretch blow molding die as shown in FIG. Free stretch blow molding was performed in this state. The mold temperature at this time is about 50 ° C,
Blow air was 20 ° C. and 28 atm.

The body of the bottle thus obtained had a generally uniform wall thickness (0.30-0.45 mm) overall.

Example 2 First, a parison having a cylindrical shape with a bottom and a straight body was made of polyethylene terephthalate. The thickness of this trunk was 3.2 mm. The parison was heated to 95 to 120 ° C. to be in a softened state, and uniaxially stretched in the longitudinal direction by a stretching rod in the same manner as in the method shown in FIG. The thickness of the body of the uniaxially stretched parison thus obtained is
It was 2.1 mm. The uniaxially stretched parison was set in a stretch blow molding die as shown in FIG. 11, and free blow molding was performed in this state. The mold temperature at this time is about
The temperature was 50 ° C. and the blow air was 20 ° C. and 28 atm.

The body of the bottle thus obtained had a generally uniform wall thickness (about 0.35 mm).

〔The invention's effect〕

As described in detail above, the front end of the parison, whose trunk has been uniaxially stretched in advance, is fixed to the center of the bottom of the cavity of the stretch blow molding die, and stretch blow-molded, so that a uniform device can be used without using a complicated apparatus. A thick bottle can be easily manufactured.

Further, according to the method of the present invention, not only a bottle having a plug portion inclined with respect to a body portion but also a bottle having a plug portion formed coaxially with the body portion can be manufactured by free blow.

[Brief description of the drawings]

1 and 7 each show an apparatus for producing a stretch blow-molded bottle according to one embodiment of the present invention, and FIG. 2 shows that the body is uniaxially stretched in a longitudinal direction in the mold shown in FIG. FIG. 3 is a cross-sectional view showing a state in which a bent and deformed parison is installed. FIG. 3 and FIG. 8 are cross-sectional views each showing an example of an elongated rod used in the method of the present invention. 5 is a cross-sectional view of the tip of the parison drawn by the drawing rod shown in FIG. 3, and FIG. 6 is a drawing showing the tip of the parison shown in FIG. FIG. 9 is a cross-sectional view showing a state of being held and fixed to the bottom of the cavity of the molding die. FIG. 9 is a cross-sectional view taken along line BB of FIG. 8, and FIG. 10 is drawn by a drawing rod shown in FIG. FIG. 11 is a cross-sectional view showing a tip portion of the parison. FIG. 12 is a cross-sectional view illustrating a state where a uniaxially stretched parison is installed. FIG. 12 is a cross-sectional view illustrating a parison before deformation used for stretch blow molding of a bottle. FIG. 13 illustrates a state where the parison is uniaxially stretched. FIG. 14 is a cross-sectional view showing an example of a device for bending the body of the parison, FIG. 15 is a cross-sectional view taken along the line CC of FIG. 14, and FIGS. FIG. 15 is a schematic view showing a step of manufacturing a modified parison using the apparatus of FIG. 1,2,11,12 ... Body type 3,13 ... Mouth type 4,14 ... Bottom type 5,15 ... Cavity 7,6,12 ... Parison 8,16,32 ... Stretched rod

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B29C 49/48 B29C 49/06 B29C 49/08

Claims (5)

(57) [Claims] 1. A method for producing a stretch blow-molded bottle from a parison having a plug portion and a bottomed cylindrical body, wherein a stretch blow-molding metal having a concave portion for holding a tip of the parison at a bottom portion of a cavity. Using a mold, the body of the parison is uniaxially stretched in the longitudinal direction to a length reaching the cavity bottom of the stretch blow molding mold by a stretching rod at a temperature equal to or higher than the softening point, and the tip of the uniaxially stretched parison is The method according to claim 1, wherein the parison is placed in the mold so as to be held in the recess, and the parison is stretch blow-molded by blowing air. 2. The method according to claim 1, wherein the central axis of the plug of the cavity is inclined with respect to the central axis of the body of the cavity, and substantially along the central axis of the body of the cavity. After the uniaxially stretched parison body is bent into a curved shape, stretch blow molding is performed. 3. The method according to claim 1, wherein a projection is formed at a tip of the parison during uniaxial stretching of the parison, and the parison is fixed by holding the projection at the recess. Features method. 4. An apparatus for producing a stretch blow-molded bottle from a parison having a plug portion and a bottomed cylindrical body, wherein a pair of body and bottom molds form a cavity. Having a recess at the bottom of the cavity to hold the tip of the parison, wherein the recess is formed by a notch formed in one of the body molds and the bottom mold, respectively. The apparatus according to claim 1, wherein a tip of the parison is held between the recesses. 5. An apparatus for producing a stretch blow-molded bottle from a parison having a plug portion and a cylindrical body with a bottom, wherein a pair of body dies are opened in a lateral direction and a bottom is opened in a downward direction. It has a blow molding die that forms a cavity by a mold, and a concave portion that holds the front end of the parison is provided on the upper portion of the bottom die, and thus the front end of the parison is closed by the concave portion by mold clamping. An apparatus characterized by being fixed.