Patent Application
20070063391
The present invention relates to a preform neck crystallization heating method, more particularly to a method for speeding up the crystallization of the polyester bottle mouth that requires crystallization and provides an easy way to be departed from the tools after the manufacturing process is completed.
The traditional polyester container is made of a PET material, and PET refers to the polyethylene terephthalate which is a saturated polyester made by polymerizing the terephthalate and the terephthalatic acid having excellent transparency, glossiness and gas barrier, in compliance with food safety standard, and can be recycled and reused. The glass transition temperature Tg of the PET falls in the range of 75˜85° C., and the injection formation temperature is approximately 270˜310° C., and the mold temperature is approximately 9˜15° C.
Polyester containers have been used extensively for the packaging containers of various different products such as water bottles, juice bottles, soft drink bottles, edible oil bottles, cosmetic bottles, drug bottles, beer bottles, wide-mouth bottles and detergent bottles, etc. Particularly, the growth rate of the market of heat-resisting polyester bottles is much faster than that of the traditional polyester bottles, i.e. carbonatd drink bottles, because the technology for CSD bottles is mature. Therefore, manufacturers turn to develop the heat-resisting polyester bottle market. The heat-resisting polyester bottles can be used in three main areas; the pasteurization bottle can withstand the pasteurized temperature of 65° C. for 20˜30 minutes; the hot-filling temperature bottle can withstand a temperature of 85° C.; and the high temperature hot-filling bottle can withstand a temperature of 120° C.
To achieve the desired quality (particularly, the heat resistance) and the quantity (the maximum production rate) of bottles, two prerequisites are needed: mature manufacturing technology and excellent mechanical equipment. The heat-resisting bottle must go through special processes and keep balance among bottle specification, bottle design, preform design, material properties and technical requirements.
To achieve the high heat resistance and high pressure resistance for the polyester bottles, a crystallization process is conducted at the bottle mouth to improve the physical and mechanical properties such as the heat resistance and pressure resistance, and such crystallization process is generally used in present hot-filling productions.
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The primary objective of the present invention is to overcome the shortcomings of the prior-art single heating source with a slow effect of crystallizing a bottle mouth and provide a method for conducting heat energy to a bottle mouth internal side by thermal conduction, so that heat energy can be dispersed quickly and evenly to the bottle mouth as to expedite the bottle mouth crystallization and increase the hardness.
Another objective of the present invention is to heat the bottle mouth on both internal and external sides during the crystallization, so that the manufacturing method of the invention has much lower contracting radial pressure as produced in the prior art, which can separate the preform and the plug finger easier after the crystallization process.
The present invention discloses a bottle mouth crystallization heating method, which makes use of external heat energies. When a preform is mounted onto a plug finger of a base by a bottle mouth, a first heating source directly heats the external side of the bottle mouth to crystallize the bottle mouth, and a second heating source heats a carrier base which is exposed from the bottom of the plug finger, so that after the carrier base absorbs the heat, the carrier base conducts heat energy to the plug finger. The plug finger with heat energy heats the internal side of the bottle mouth at the same time together with external side of the bottle mouth, so that heat energy can be dispersed evenly and rapidly to the bottle mouth for crystallization.
By means of simultaneously heating the internal and external sides of the bottle mouth, the crystallization of the bottle mouth is expedited. After the preform is separated from the heating area and enters into a wind-cooling zone, the external side of the bottle mouth is cooled faster than the internal side; the external side will stop crystallizing while the internal side continues crystallizing. Since the polyester material becomes denser during the crystallization and the density is inversely proportional to the volume, therefore the internal side contracts towards the formed external side and the manufacturing process in accordance with the present invention no longer has a contraction radial pressure produced at the internal side of the bottle mouth and the plug finger according to the prior art. As a result, the preform and the plug finger used for the crystallization according to the present invention can be separated much easier than the prior art.
To make it easier for our examiner to understand the objective of the invention, its structure, innovative features, and its performance, we use a preferred embodiment together with the attached drawings for the detailed description of the invention.
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The present invention is characterized in that a second heating source 42 is used in addition to the first heating source 41. The second heating source 42 heats a heat absorber 52 underneath the preform 10 that is exposed from the bottom of a plug finger 51, so that after the heat absorber 52 absorbs the heat, the heat absorber 52 conducts heat energy to the plug finger 51, wherein the heat absorber 52 and the plug finger 51 are made of excellent heat conductive materials with a high coefficient of expansion, such as aluminum or copper, and the heat absorber 52 disposed on a lateral side could be a concave surface for increasing the heat absorbability. Therefore, by adding the plug finger 51 with heat energy could be heated both of the internal and external sides of the bottle mouth 11 simultaneously and keep the temperature in a range of 120˜170+ C. for the crystallization, and heat energy can be dispersed evenly and rapidly to the internal and external sides of the bottle mouth 11 required for the crystallization. As a result, the crystallization of the bottle mouth 11 is expedited and the degree of crystallization and hardness of the internal and external sides are higher than those of the middle section inside the bottle mouth since both of the internal and external sides are heated at the same time.
After the preform 10 is passing the heating zone of the single heating source 20 thereafter enters a wind-cooling zone having a wind cooling equipment for fast cooling. Since the external side of the bottle mouth 11 is cooled faster than the internal side by the cooling wind. In other words, the external side will stop crystallizing and form into a fixed shape, but the internal side of the bottle mouth 11 will continue crystallizing because the temperature of the plug finger drops slowly. Since the density of the crystallized polyester material becomes larger, and the density is inversely proportional to the volume, therefore, the internal side is contracted towards the foregoing external side. Then, the volumes of the heat absorber 52 and the plug finger 51 made of good heat conductive materials with a high coefficient of expansion reduce due to the drop of temperature, so that the internal diameter of the plug finger 51 is smaller than that of the bottle mouth 11. Therefore, the manufacturing process according to the present invention will not produce a radial contractive pressure like the prior art and the preform 10 could be separated from the plug finger 51 after the crystallization process much easier than the prior art.
The first heating source 41 and the second heating source 42 could be one of the heating sources selected from a near infrared light source, a far infrared source or an electric-heated hot wind.
To enhance the physical properties of the entire bottle mouth 11, it is necessary to expand the scope of the crystallization. Please refer to
While the invention has been described by way of example and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.
