JPH0541421B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF INDUSTRIAL APPLICATION This invention relates to the manufacture of partially crystalline biaxially oriented heat-set hollow plastic articles, particularly articles made of polyethylene terephthalate. [Prior Art and Problems to be Solved by the Invention] It has been known for some time that the thermal stability and barrier properties of polyethylene terephthalate stretch blow molded containers are significantly increased by heat setting. A typical heat setting method is described in U.S. Patent No. 4,476,170.
No. 4512948 and No. 4522779. U.S. Pat. Nos. 4,476,170 and 4,512,948 disclose polyethylene terephthalate stretch heatset blow molded containers and methods of making the same.
In this method, a preform preheated to a temperature suitable for stretching is biaxially stretched in a blow mold, and then while the hollow container is still in contact with the walls of the blow mold. (but excluding nets) should be set at a higher heat set temperature, preferably
The container is heat set to a temperature in the range of 200 to 250°C and is at a temperature at which the container maintains its shape without being pressurized while the container is still under anti-shrinkage pressure above atmospheric pressure. and cooled in the mold to a temperature not lower than 100°C.
It is also disclosed that this cooling step can be performed in air outside the mold while maintaining internal pressure. According to these patents, higher shrinkage onset temperatures are obtained when the heat set temperature of the hot mold is in the range of 220-250°C and the quench temperature is not lower than 100°C. U.S. Pat. No. 4,522,779 discloses an improved plastic container and method of making the same.
According to a first embodiment thereof, the container is blow molded in a first hot blow mold and then resized to a larger size in a second cold mold having a larger volume than the first hot mold. Blow molded. Such containers are described as having improved mechanical properties, in particular very high hoop yield stress. however,
The use of larger volume cold molds substantially reduces thermal stability. In a second embodiment, the container is blow molded in a hot blow mold and then reblown to a larger size in a second hot blow mold, i.e. , the container is blown to the molding surface of its second mold, the container is then removed from the second mold, transferred to a third cold mold, and cooled to ambient temperature while maintaining internal pressure. . In yet another embodiment, the container is blow molded in a first hot mold, re-blow molded in a second hot mold, and then the second mold is cooled to cool the container. . US Patent No. 4385089 (UK Patent Specification No.
No. 1,604,203) relates to heat-set biaxially stretched hollow articles, in which the preform or parison is heated to at least the biaxially stretched temperature and is placed in close contact with a hot mold at a temperature up to 40°C above the lowest stretching temperature. It is stated that it must be maintained in a safe condition. In one embodiment thereof, the resulting formed hollow article is gradually cooled by introducing cooling steam or spray into the hollow article, and after the temperature has decreased by 10 to 30 °C, the cooling steam is shut off. and the mold is opened. In other embodiments, the heat-set article is allowed to shrink freely and then re-blow molded in the same hot mold or in a separate cooled mold. This patent requires a heat set temperature 40°C higher than the stretching temperature, which places limits on thermal stability and barrier properties. According to this patent, the temperature of the hot mold must be maintained at 30-50°C above the minimum stretching temperature of the plastic material. Otherwise, there will be a reduction in the production rate, there will be a visual risk of large deformation and shrinkage during demolding, there will be an inherent disadvantage of heating the mold to a very high temperature and keeping it at that temperature, there will be a loss of transparency. It is stated that many disadvantages occur, such as the risk of crystallization. Furthermore, according to this prior patent, excessive shrinkage must be avoided and typically only temperature drops of 10-30°C are allowed. As noted above, such methods do not provide the degree of heat setting that provides thermal stability at higher temperatures as is required when filling containers with various products. Furthermore, such methods do not allow for the high degree of crystallinity and resulting high barrier properties required for certain product applications. U.S. Patent Application No. filed October 27, 1986
No. 923503 discloses an improved plastic container and method for making the same. in this way,
The container is blow molded in a first hot mold maintained at 130-250°C, and the container is heated for a short time (1-10
seconds) and is brought into contact with the molding surface of the mold. The container is then maintained at a lower internal pressure to prevent significant shrinkage, and the container is quickly transferred to a cold mold having a volume substantially the same as or smaller than the hot mold. The temperature of the cold mold is maintained at 1-100°C. The container is rapidly cooled in a cold mold. This method is required when applied to high temperature fillers.
Resulting in a thermally stable container with a higher shrinkage onset temperature and higher mechanical properties. This method also results in shorter cycle times. If the bottom of the container has a complex shape, for example if the bottom of the container has an axially projecting part so that the container stands without support, i.e. the container has an inwardly recessed bottom. , transfer from a hot mold to a cold mold with the interior of the container under pressure tends to deform the bottom and cause it to revert to a hemispherical bottom. This tends to occur both when the blow molded container is at rest and when the container is transferred from a hot mold to a cold mold. To overcome these problems, in U.S. patent application Ser. The method comprises: engaging the open end of a plastic parison at a temperature within the stretching temperature of the molecules; positioning a mold base in axial alignment with the engaged hot parison; A hot mold surrounds the mold base, the hot mold is at a heat set temperature, and the plastic parison in the hot mold and mold base is expanded by internal pressure to cause the second part of the plastic parison to expand. Applying the internal pressure for a sufficient time to cause axial stretching, forcing the plastic parison into intimate contact with and conforming to the hot mold, and causing partial crystallization in the biaxially stretched container. Thus maintaining contact between the hot mold and the biaxially oriented container, reducing internal pressurization within the blow molded container and preventing engagement of the open end and the mold base and blow molding. Opening the hot mold while maintaining engagement with the molded hollow container, maintaining reduced internal pressurization of the container to prevent significant shrinkage, and engaging the open end and opening the mold. A method of engaging the container with a mold base and cooling the container while maintaining at least sufficient pressure within the container to prevent shrinkage is disclosed. US Pat. No. 4,233,022 discloses a method and apparatus in which a parison is blow molded and heat treated in a single hot mold. After blow molding, the blow pressure is preferably maintained within the blow molded article so that the material resists heat shrinkage and remains in the hollow walls during heat treatment. Selected portions of the biaxially stretched hollow bottle are heated while other portions are cooled. More specifically, the body is heat treated while the finish or less stretched portions, such as the heel, are cooled or heat treated.
According to this patent, the main body of the bottle is 150℃~220℃
The material is heat treated by being heated to a temperature within the range of . According to this patent, the bottom of the bottle can be cooled if little molecular stretching takes place, or the bottom of the bottle can be cooled within a range of 100°C to 200°C if heat treatment is appropriate. heated to a temperature of The remaining parts, such as the bottom, which are less stretched, are cooled or heat treated. As described, heat treatment cycles range from 10 seconds to about 10 minutes. After heat treatment, a cooling fluid is circulated through ducts within the mold, allowing the article to cool and stand free. After heat treatment, additional cycle time is required to cool the mold from the heat treatment temperature to the cooling temperature. This method therefore requires a long process due to the time for heat setting and the time required to cool the mold before removing the container from the mold and then allowing the container to stand without support. Requires full cycle time. SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for heatsetting containers that stand up without support and which has short cycle times. In the method of the invention, the hot mold in which the container is blown and heat set is immediately molded without deformation of the bottom which can occur due to the internal pressure used to handle the container without shrinkage. It can be opened. This method allows containers to be moved more quickly between hot and cold molds. This method does not require maintaining contact between the mold base and the bottom of the container during the transfer from hot to cold molds. [Means for Solving the Problems] According to the present invention, there is provided a method for manufacturing a partially crystalline biaxially stretched heat-set hollow polyethylene terephthalate container that stands without support from a hollow parison having an open end and a closed end, the method comprising: engaging the open end of a plastic parison at a temperature within a stretching temperature of and locating a mold base in axial alignment with the engaged hot parison;
surrounding the mold base with a hot mold, the hot mold being at a heat set temperature and the mold base being preferably at a significantly lower temperature than the hot mold;
expanding the plastic parison within the hot mold and mold base by internal pressure to cause biaxial stretching of the plastic parison, forcing the plastic parison into intimate contact with the hot mold; partial crystallization on the side walls and bottom of the container, which is aligned and biaxially stretched, and the mold is opened;
and when the mold base is moved axially away from engagement with the heated hollow container, the bottom of the base, which stands unsupported, deforms or deteriorates under the internal pressure. on a base that stands without the support of said container sufficiently to prevent it from returning;
The internal pressure maintains contact between the hot mold and the biaxially stretched container for a sufficient time to cause less heat set and crystallization within the blown container. Opening the hot mold while reducing the internal pressure and maintaining engagement with the open end of the blow molded hollow hot container, the heated mold base is inserted into the hot blow molded hollow container. moving away from the engagement in the axial direction,
When the cold mold is closed around the hot container,
maintaining a low internal pressurization of the hot container sufficient to prevent expansion of the container and sufficient to prevent significant deflation as the container is blown;
by relatively moving the container adjacent to a cold mold that is at a temperature substantially lower than the temperature of the hot mold while maintaining engagement with the open end of the hot container; , and transferring the biaxially stretched container while maintaining the reduced internal pressurization;
3. The heated mold base temperature is 100℃ and 160℃
℃, so that the temperature also ensures that the base of the container does not deform due to the pressure within the blow-molded container during transfer to the cold mold and the temperature is sufficiently high to prevent reversion to the hemispherical shape, and the base of the blow-molded container does not stick to the mold base during transfer of the blow-molded container to the cold mold. , and the temperature of the mold base is low enough so that it does not return to its hemispherical shape, and the cold mold base engages the bottom of the container, and the cold mold base
The container is enclosed within the cold mold by surrounding the cold mold base with the cold mold, and the cold mold is heated to a temperature not higher than 100°C.
by maintaining pressure within the container for a time sufficient to cool the container and prevent shrinkage. holding the container, releasing the pressure in the container, opening the cold mold, and removing the container;
the sidewall heat set temperature is in the range of about 120 to 250°C, the heat set time is in the range of about 1 to 30 seconds, and the transfer time is in the range of about 0.8 to 15 seconds; A method is provided. (Example) In FIGS. 1 to 6, an apparatus for carrying out the present invention is equipped with a stationary thermal mold 20, and this thermal mold 2
0 includes mold parts 21 that are movable toward and away from each other. Hot mold 20
is heated, and as a result,
When the parison is blown to the molding surface of the mold cavity, the resulting article is heat set. The device further includes a cold mold 22, and the cold mold 22
includes mold portions 23 movable toward and away from each other to form a cavity substantially the same size as the cavity of thermal mold 20. The mold bases 24, 25 are associated with each of the molds 20, 22, and
The cylinders 26 and 27 are respectively provided to move the molds 25 toward and away from the respective molds 20 and 22. The device is equipped with a conditioning station A;
The parison or preform P supported on the mandrel 28 is then placed in position to heat and equilibrate it to the drawing temperature. The apparatus further includes a blow molding and heat setting station B at the hot mold 20 location and a quenching station C at the cold mold 22 location. The mandrel 28 supporting the parison P has a track 30 defined by spaced rods.
It is attached to a block 29 which is movable above.
Block 29 is connected to piston rod 31 of cylinder 32 which is mounted on a bracket 33 which has a clamping and blow pin assembly 34 mounted thereon. A bracket 33 is also mounted movably on the track 30. Clamping and blow pin assembly 34 consists of a two-part clamp ring 34a and blow pin assembly 34b. Cylinder 40 at station A is adapted to rotate pinion 41, which engages gear 42 of mandrel 28 to rotate mandrel 28 at station A. Clamping and blow pin assembly 34 is moved longitudinally on track 30 by rotating cylinder 47. That is, the rotating cylinder 47 imparts an oscillating motion to the arm 46, and the arm 46 is inserted into the slot 4 of the link 45 fixed to the bracket 33.
4, so that the bracket 33 and the clamping and blowing pin assembly 34 are moved along the track 30 between stations B and C. First, at position A, a parison P is placed on a mandrel 28, heated in a heating channel H to the drawing temperature, and held at that temperature for a predetermined time to equilibrate the temperature inside and outside the parison. maintained. Next, the cylinder 32
It is activated to move the parison P to the blow molding and heat setting station B. next,
Mold base cylinder 26 is actuated to place mold base 24 in position within mold section 21, and hot mold 20 closes around mold base 24 and neck clamp ring 34a. The parison is expanded by fluid pressure through blow pin assembly 34b to the forming surface of hot mold 20 to produce a biaxially oriented container. The injected fluid is first at a low pressure, e.g. 4.9-14Kg/cm ² (70-200p.s.
i). and then the insufflation fluid is applied at a higher pressure, e.g. 10.5-24.5 Kg/ ^cm2 (150-350 p.si). is applied to maintain contact between the container and the molding surface of the hot mold. Contact with the molding surface of the hot mold is maintained for a predetermined period of time by maintaining internal pressure;
The container is heat set. The blowing pressure is then reduced to a lower transfer pressure, the hot mold 20 is opened, the cylinder 26 is actuated to move the mold base 24 away from the hot mold 20, and the clamping and Blow pin assembly 34 is moved to quench station C. During transfer of the blow molded article to the cold mold, the article is maintained under pressure inside the container, thereby preventing significant shrinkage of the container. Since the complex-shaped bottom of the container is partially heat-set and therefore partially crystallized, the reduced internal pressure will cause the bottom of the container to deform, or to form a hemispherical bottom. There's no going back. At the quench station, the cylinder 27 is actuated to place the mold base 25 into position inside the mold section 23, the cold mold 22 is closed, and the container is reblown to the forming surface of the cold mold 22. and then quenched while maintaining the pressure inside the container. The pressure is returned to atmospheric pressure. Cold mold 22 is then opened, cylinder 27 is actuated to move mold base 25 away from cold mold 22, and clamping and blow pin assembly 34 is returned to position B. , the mandrel 28 is returned to position A with the container. The container is then removed. In the apparatus for carrying out the modified method shown in FIGS. 7-12, the clamping and blow pin assembly remains stationary while the hot mold 20 and the cold mold 22 and their associated mold bases 24, 25 and cylinders 26, 27 are moved longitudinally;
The now blow-molded container is moved relative to hot mold 20 and cold mold 22. In this form, the mold parts 21 and 23 are attached to the slider 50
The slider 50 is mounted on a surface plate 51. The surface plate 51 is moved by a cylinder (not shown) on its shaft 52 in the transverse direction to a mold opening position and a mold closing position. The movement of each slider along the surface plate 51 is controlled by the bracket 5.
This is done by a cylinder 53 with a piston rod 54 which is connected to a slider 50 via a cylinder 53. In all other respects, the methods are substantially similar and provide the same cycles. A particular hot mold 20 and cold mold 22 may have a structure as shown in FIGS. 13 and 14, respectively. In FIG. 13, the hot mold 20 is
It includes a mold part 21, a shoulder forming part 60, a clamp ring 34a which is divided into two parts, and a mold base 24.
The mold portion 21 is provided with electric heaters 61 that are circumferentially spaced apart and extend longitudinally.
The shoulder forming part 60 has an inlet 6 in each mold part.
3 and an outlet 64 are provided. The mold base 24 has an annular ring 65 that engages in a semicircular groove 66 fixed in the upper part of the mold part 21 . An insulator 68 in the form of a layer of Teflon® is provided between the mold part 21 and the mold base 24. The mold base 24 includes a fluid passage for controlling the temperature of the mold base 24.
A passageway 69 having an inlet 70 and an outlet 71 is provided. Each half of the finish clamp or clamp ring 34a is provided with a passage 77 having an inlet 78 and an outlet 79 for passage of fluid for controlling the temperature of the clamp ring. An insulating layer 80, such as glass-filled Teflon®, is provided between the shoulder formation 60 and the mold portion 21. Air gap 81 connects each mold part 21
and the insulating layer 80. The cold mold 22 shown in FIG.
The lower end of 2 engages with the clamp ring 34a, and the upper end surrounds the mold base 25. In this form, the ring 65a of the mold base 25 is attached to the mold part 2.
3 and is not provided with an insulating layer. Each half of the cold mold 22 includes
For fluid passage to control cold mold temperature,
A passage 74 having an inlet 75 and an outlet 76 is provided. The mold base 25 is provided with a passage 69a having an inlet 70a and an outlet 71a for the passage of a cooling fluid to control its temperature. The methods and products of the invention particularly relate to polymers of polyethylene terephthalate having an internal viscosity of at least 0.6. The polyethylene terephthalate polymers useful in the present invention contain repeating units of ethylene terephthalate and the remainder consisting of minor amounts of ester-forming components and copolymers of ethylene terephthalate, where up to about 10 mole percent copolymer The polymer is butane-1,4-diol, diethylene glycol, propane-1,3-diol,
Polytetramethylene glycol, polyethylene glycol, polypropylene glycol, 1,4-
Monomer units selected from hydroxymethylcyclohexane etc. which are substituted with glycol moieties during the preparation of the copolymer, or isophthalic acid, naphthalene-1,4-dicarboxylic acid,
Monomer units selected from naphthalene-2,6-dicarboxylic acid, adipic acid, sebacic acid, decane-1,10-dicarboxylic acid, etc., in which up to 10 mole percent of acid moieties ( terephthalic acid). Of course, the polyethylene terephthalate polymer can contain various additives that do not adversely affect it. For example, such additives may include stabilizers such as antioxidants or UV screeners, extrusion aids, additives to make the polymer more degradable or flammable, dyes or pigments, etc. It will be done. Additionally, small amounts of crosslinking or branching agents such as those disclosed in US Pat. No. 4,188,357 may be included to increase the melt strength of the polyethylene phthalate. The method of the present invention provides a multilayer parison comprising an extensible heat-settable polymer and another polymer providing suitable barrier properties, wherein the extensible heat-settable polymer constitutes a major portion of the total weight. , preferably at least 70% of the total weight. Typical examples include multilayer parisons made of polyethylene terephthalate and copolyester, polyethylene terephthalate,
Mention may be made of multilayer parisons made of nylon and copolyesters, as well as multilayer parisons made of polyethylene terephthalate, adhesives, nylon, glue and polyethylene terephthalate. The method of the invention also provides a blend of polyethylene terephthalate with another polymer providing suitable barrier properties, wherein the polyethylene terephthalate is a major portion of the total weight, preferably at least 70% of the total weight.
% can also be applied. Accordingly, the term "polyethylene terephthalate" as used herein is intended to include polyethylene terephthalate-containing materials as described above. According to the invention, the following parameters yield optimal results. Table 1 Heatset parameters 1 Heatset mold temperature 120~250℃ 2 Heatset time 1~30 seconds 3 Hot mold base temperature 100~160℃ 4 Transfer molding pressure 0.07~2.1Kg/cm ² (1~30p.si) 5 Transfer time 0.8~15 seconds 6 Quenching temperature - cold mold 1~100℃ 7 Quenching temperature - cold mold base 1~100℃ 8 Quenching time 0.5~10 seconds If the bottom heat set temperature is lower than 100℃, move During this period, it was found that the displacement pressure caused the bottom of the container standing without support to deform or return to its semi-spherical shape. Also, if the heat set temperature at the bottom of the container standing without support is 160
It has been found that above 0.degree. C., the material at the bottom of the container, which stands unsupported, tends to stick to the mold base and to revert to its hemispherical shape during movement. When the heat set temperature of the bottom is in the range between 100℃ and 160℃, the bottom of the container that stands without support will not deform during movement or return to the semi-spherical shape, and the bottom The material does not stick to the mold and the container has high drop impact resistance. EXAMPLE A 4 liter freestanding container was successfully manufactured in accordance with the present invention using polyethylene terephthalate having an IV of 0.8. The container is the first
6 and 13-14, in which the clamping and blow pin assemblies are reciprocated and the mold is stationary. maintained in condition. The finish and the shoulder adjacent to the finish were water cooled to room temperature, and the sidewalls were heat set at 230°C. The bottom was maintained at 105°C during blow molding and heat setting. The container is then placed in a cold mold of the same size maintained at 22°C at a density of 0.35Kg/ ^cm2.
(5 p.si) and quenched. Oxygen Permeability Non-heat set containers and heat set containers were tested for overall oxygen permeability at 22.8°C (73〓) using a PA-3 analyzer.
Tested under atmospheric pressure and 100% RH. The results are shown in Table 2.

[Table] Average bottle heat set 131.0 0.243 34.3%
Yes - Average of 2 Bottles It can be seen that the heat-set containers have over 34% better oxygen barrier properties than the non-heat-set containers. Mechanical Properties Mechanical properties and crystallinity for heat-set and non-heat-set containers are summarized in Table 3.

[Table] It can be seen that satisfactory mechanical properties and density were obtained. Elastic modulus, yield stress, yield strain, ultimate strength and ultimate elongation were measured in accordance with ASTM standard D-638. Density was measured according to ASTM1505. Drop Test Drop impact tests were conducted on heat-set and non-heat-set containers. In this test, one set of containers was filled with room temperature water;
He was then dropped onto the concrete floor.
The other set of containers is filled with water at room temperature and 4.4°C.
(40〓) for 24 hours and then tested. The results of the drop tests are summarized in Table 4.

[Table] Tests at room temperature and lower temperatures passed the drop test. No breakage was observed even when the bottle was dropped from a height of 9 feet. Thus, it can be seen that satisfactory drop impact properties were obtained by controlling the degree of crystallization at the bottom. This was accomplished by limiting the bottom heatset temperature range to between 100°C and 160°C. The method of the present invention is useful for hot and cold molds in which the cold mold is larger than the hot mold, such as described in the aforementioned U.S. Pat. No. 4,522,779, or as described in the aforementioned U.S. Patent Application No. It can also be used for hot and cold molds, where the cold mold has the same volume as the hot mold or a smaller volume than the hot mold. If the method of US Pat. No. 4,522,779 is used, the resulting container will exhibit improved mechanical properties, while having a lower shrinkage onset temperature and reduced hot-fill capacity. This container can be used when the filling is pressurized. When the method of U.S. Patent Application No. 923,503 is used, the resulting container has a higher shrinkage onset temperature;
The container can therefore be hot-filled at higher temperatures. If desired, axial stretching using a stretching rod may be applied to the parison before or simultaneously with the expansion of the parison, as is well known. Although the method has been described as using a parison that is heated, blow molded, and heat set, it is possible to use a previously blow molded container and heat set it at station B. Heat setting of a mold that is placed between the mold parts of the mold and moved to the cold mold at station G while maintaining the net engagement may also provide several advantages. SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a method of manufacturing a biaxially oriented heat-set polyethylene terephthalate container that stands free of supports, which method has a shorter cycle time, and in which the container is blow molded. and the hot mold being heat set can be opened faster without bottom deformation that can occur due to the internal pressure used to handle the container without shrinkage; this method allows for faster transfers to and from cold molds, and this method eliminates the need to maintain contact between the mold base and the bottom of the container during transfer from hot to cold molds. It can be understood that there is no The resulting containers have satisfactory mechanical properties, density, drop impact properties and barrier properties.

[Brief explanation of the drawing]

1 to 4 are partial schematic views of an apparatus for carrying out the method of the present invention, FIG. 5 is a partial vertical sectional view of the apparatus of FIGS. 1 to 4, and FIG. 7 to 11 are partial schematic diagrams of an apparatus for carrying out a modified embodiment of the method of the invention;
2 is a longitudinal cross-sectional view of the apparatus shown in FIGS. 7 to 11, FIG. 13 is a cross-sectional view of a hot mold that can be used in carrying out the method of the present invention, and FIG. 14 is a cross-sectional view of the apparatus shown in FIGS. 1 is a cross-sectional view of a cold mold that may be used in carrying out the method; FIG. 20... Hot mold, 21... Mold part, 22...
cold mold, 23...mold part, 24...mold base, 25...mold base, 28...mandrel,
34...clamping and blowing pin assembly, 34
a...Clamp ring, 34b...Blow pin assembly.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a partially crystalline biaxially stretched heat-set hollow polyethylene terephthalate container that stands unsupported from a hollow parison having an open end and a closed end, the method comprising: a temperature within the stretching temperature of its molecules; engaging the open end of a polyethylene terephthalate parison in the container and positioning a heated mold base in axial alignment with the engaged hot parison, the heated mold base forming an unsupported standing base of the container; wherein the heated mold base is surrounded by a hot mold, the hot mold is at a heat set temperature, and the heated mold base is shaped to form a hot mold. the plastic parison in the hot mold and mold base is expanded by internal pressurization through the open end to effect biaxial stretching of the plastic parison; and forcing the parison into close contact and conformity with the hot mold, causing partial crystallization in a biaxially stretched container, and the mold being opened and the mold base Sufficiently so that the bottom of the base, standing free of support, does not deform or return to a bad condition under said internal pressure when moved axially away from engagement with said heated hollow container. , contact between the hot mold and the biaxially stretched container is maintained by the internal pressurization for a sufficient time to cause less heat-setting and crystallization in a standing base without the support of the container. reducing the internal pressure within the blow molded container, opening the hot mold while maintaining engagement with the open end of the blow molded hollow hot container, and opening the heated mold base. , moving the blow molded hollow hollow axially away from engagement with the hot container to cause expansion of the container so that the container is notched when a cold mold is closed around the hot container. maintaining a low internal pressurization of the hot container sufficient to prevent and preventing significant shrinkage; and increasing the temperature of the hot mold by relatively moving the container. The container is biaxially stretched adjacent to a cold mold at a temperature substantially lower than The temperature of the heated mold base is 100℃.
The temperature is also within the range between 160°C and
during transfer to the cold mold, the pressure within the blow-molded container is sufficiently hot so that the base of the container does not deform and return to its hemispherical shape; During the transfer of the blow-molded container to the cold mold, the blow-molded container is placed on the mold base so that the base of the blow-molded container is not stuck to the mold base and does not return to the hemispherical shape. the temperature of the cold mold base is sufficiently low to engage the cold mold base with the bottom of the container, the cold mold base is at a temperature of no more than 100°C, and the surroundings of the cold mold base are enclosing the container within the cold mold by surrounding it with the cold mold, the cold mold being at a temperature not higher than 100°C, to cool the container and prevent shrinkage; holding the container against the confinement of the cold mold by maintaining pressure in the container for a sufficient period of time; relieving the pressure in the container and opening the cold mold; the heat set temperature of the side wall is in the range of about 120 to 250°C, the heat set time is in the range of about 1 to 30 seconds, and the transfer time is in the range of about 0.8 to 15 seconds. ,
The method comprising: 2. Relative movement between the container and the hot mold and the cold mold causes the container to move while the hot mold, the hot mold base, the cold mold, and the cold mold base 2. The method of claim 1, which is accomplished by maintaining the . 3. Relative movement between the container and the hot mold and the cold mold moves the hot mold, the hot mold base, the cold mold and the cold mold base relative to the container. Claim 1 achieved by
The method described in section. 4. The method of claim 1, including the step of moving the cold mold base axially away from the container after opening the cold mold. 5. The method of claim 1, including the steps of heating the hot parison to a molecular stretching temperature and transferring the hot parison to a location adjacent to the hot mold. 6. A method of manufacturing a partially crystalline biaxially stretched heat-set hollow polyethylene terephthalate container that stands up without support from a hollow parison having an open end and a closed end, the method comprising: a heated mold base axially engaged with the bottom of the container, the container being made by expanding a polyethylene terephthalate parison at a temperature within the stretching temperature of its molecules; locating the heated mold base, the heated mold base having a shape mating with the unsupported bottom of the container, surrounding the heated mold base with a hot mold; the mold is at a heat-set temperature, the heated mold base is at a heat-set temperature substantially lower than the temperature of the hot mold, and the heated mold base is at a heat-set temperature substantially lower than the temperature of the hot mold; applying internal pressure within the molded container, keeping the container in close contact and conformity with the hot mold, causing partial crystallization in the walls of the biaxially stretched container, and the mold being opened; and when the mold base is moved axially away from engagement with the hollow hot container, the bottom of the base, which stands free of support, does not deform or return to a bad condition under the internal pressure. Biaxially stretched the container with the mold by means of the internal pressurization for a sufficient period of time to cause less heat-setting and crystallization in the standing base of the container without support. reducing the internal pressure within the container; opening the hot mold while maintaining contact with the open end of the hollow hot container; axially moved away from engagement with the hot container, and sufficient to prevent expansion of the container so that the container is gouged when a cold mold is closed around the container; and maintaining a low internal pressurization of the container sufficient to prevent significant shrinkage, and by moving the container relative to the temperature substantially lower than the temperature of the hot mold. The biaxially stretched container is transferred adjacent to a cold mold while maintaining the reduced internal pressure, and the temperature of the heated mold base is 100°C.
The temperature is also within the range between 160°C and
during transfer to the cold mold, the pressure within the blow-molded container is sufficiently hot so that the base of the container does not deform and return to its hemispherical shape; During the transfer of the container to the cold mold, the temperature of the mold base is sufficiently low so that the base of the container does not stick to the mold base and does not return to its hemispherical shape. , by engaging a cold mold base with the bottom of the container, the cold mold base being at a temperature not higher than 100°C, and surrounding the cold mold base with the cold mold; enclosing the container in the cold mold, the cold mold being at a temperature not higher than 100°C, and maintaining pressure for a sufficient time to cool the container and prevent shrinkage; holding the container against the confinement of the cold mold by opening the cold mold and removing the container, the heat set temperature of the sidewall is in the range of about 120-250°C, and the heat set time is in the range of about 1 to 30 seconds, and the transfer time is in the range of about 0.8 to 15 seconds.