JPH0326646B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of heating and crystallizing the spout of a polyester resin blow bottle or preform. In order to impart heat resistance to the spout of a polyester resin blow bottle, the spout is heated and crystallized at the stage of the blow bottle or a preform for molding the blow bottle. However, with conventional heating methods, when heated at a high heating temperature, the internal strain remaining during preform molding recovers, causing the top surface and threaded portion of the spout to become wavy, resulting in incomplete sealing by the cap. It was hot. On the other hand, if the heating temperature is lowered in order to avoid deformation, the time required for crystallization becomes longer and manufacturing efficiency decreases. The object of the present invention is to solve the above-mentioned problems and to efficiently crystallize the spout part without deformation. A method of heating and crystallizing a stopper part is characterized by dividing the heating into multiple stages, gradually heating at a low heating temperature in the first stage, and then increasing the heating temperature in the second stage to perform heating crystallization. This is a method of crystallizing a spout. By dividing heating into multiple stages as described above and gradually heating at a low heating temperature in the first stage,
This has the effect of eliminating internal strain without deforming the plug portion. Then, in the second stage, the heating temperature is raised and the heating is carried out, so combined with the preliminary temperature increase in the first stage, it is possible to quickly crystallize at a sufficient crystallization rate, and the internal strain is reduced even further. Since it is removed in one step, the spout does not deform. The heating temperature in the first stage varies depending on the preform molding conditions, wall thickness, etc., but the polyethylene terephthalate resin spout is heated to 100 to 120°C at the temperature of the spout itself for 15 to 40 seconds. It is preferable that the temperature can be gradually reached at 50° C. since the spout does not deform and is sufficient for preliminary heating. In the second stage, it is preferable to increase the heating temperature following the first stage so that the spout reaches 160 to 180°C in 20 to 40 seconds. Under such heating conditions, usually within 100 seconds from the start of the first stage heating,
The crystallinity of the spout reaches 30%, improving heat resistance. In the present invention, the preform or blow bottle made of polyester resin is a preform formed into a tubular shape by injection molding, extrusion molding, etc. of polyester resin such as polyethylene terephthalate or a copolymer having ethylene terephthalate as a main repeating unit, or a preform made of such a preform. A bottle biaxially stretched and blow-molded at a temperature range of not less than the glass transition temperature and not more than the melting temperature of the polyester resin is preferably used. This bottle may be heat-fixed in advance in parts other than the spout. Next, referring to the accompanying drawings, FIG. 1 is a schematic plan view showing an example of a heating device for carrying out the method of crystallizing a bottle cap of the present invention;
The figure is an enlarged view of the - cross section of FIG. 1. As shown in Figures 1 and 2, the entire heating device is divided into three sections a, b, and c, and a pair of rod-shaped near-infrared heaters 1a, 1b, and 1c are installed in each section facing each other. ing. A mandrel 2 is arranged between these heaters and moves in the direction of arrow A while rotating. Furthermore, a heat shield plate 3 is installed above the heater to prevent heat from being applied to areas other than the spout. Heater 1a, 1
b and 1c are arranged so that the heating temperature can be controlled by adjusting the current independently. As shown in Fig. 2, the mandrel 2 has a diameter that matches the inner diameter of the spout 4 of the preform, etc., and is transported while being inserted into the preform, and prevents deformation of the spout 4 from the inside during heating. It is something to do. If the mandrel 2 is made or coated with a heat-resistant plastic such as poly-4, fluoride, ethylene, polyacetal, polyamide, polycarbonate, or polypropylene, the surface will be smoother than a metal one, making it easier to insert the preform, etc. , pulling out becomes smooth. Further, a support rod 21 may be provided above the mandrel 2 in contact with the inner bottom surface of the preform etc. to support the weight of the preform. The heaters 1a, 1b, and 1c may be rod-shaped heaters such as infrared heaters as shown in the figure, as well as induction heating using high-frequency electrodes, hot air heating, contact heating, or combinations thereof, as long as the heating temperature can be substantially controlled. Any suitable method can be used. As explained above, according to the present invention, the spout of the polyester resin blow bottle or its preform is heated at a low heating temperature in the first step, and then heated and crystallized by increasing the heating temperature. Crystallization can be performed quickly without causing deformation of the plug portion. This will be explained in more detail below using experimental examples. Experimental Example A polyethylene terephthalate preform having a spout 4 having a length of 22.4 mm, a thread diameter of 28 mm, and an inner diameter of 21.6 mm was heated using a heating device arranged as shown in FIG. Heating heaters 1a, 1b, and 1c are all near-infrared heaters (200V, 1K.W., length 35
cm) is used. The time required for each section of the preform to be transported by the mandrel 2 is 30 seconds. In this device, the heating temperature can be adjusted by adjusting the heater current within the ranges of 1.1 amperes to 3.5 amperes in section a, 3.5 amperes in section b, and 4.0 to 2.0 amperes in section c, as shown in Table 1 Nos. 1 to 10. control, insert the preform into mandrel 2 and press 3.
The sample was allowed to pass through the section and crystallized until the spout 4 became sufficiently white in appearance (crystallinity of 30% or more). For the preform that has been crystallized, the irregularities on the top surface 41 of the spout portion 4 were observed using a reading microscope, and those with a difference of 0.1 mm or more between the concave and convex portions were determined to be defective, and No. 1 shown in Table 1 was determined. 200 pieces were tested under each condition from 1 to 10, and the number of defective pieces was displayed.

【table】

[Table] As is clear from Table 1, those heated at a relatively low heating temperature (3.3 amperes or less) in section a, that is, the first stage, as shown in Nos. 1 to 9,
The number of defective pieces ranged from 0 to 36, which resulted in less deformation than those that were heated at high temperatures (3.5 amperes) from the beginning (93 defective pieces). Also, when the heater current in section a is Ia and the heater current in section b is Ib, if the heating capacity P of section a to section b is expressed as Ia ² /Ib ² × 100 (%), then P is 30% to 70 Conditions Nos. 3 to 7, which are between % and 3, are particularly preferable because the number of defective pieces is particularly small, 0 to 3 pieces. The purpose of adjusting the heater current in section c is
In order to prevent the surface of the spout from melting due to overheating, the temperature rise of the spout is suppressed and the temperature is maintained at a substantially constant temperature. Also, if you perform a similar test with the heater current in each section a, b, and c at the same heating capacity of 29 amperes, the number of defective wires is 0, but there is only a slight clouding after passing through section c. Only whitening occurred, and the degree of crystallization was small.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view showing an example of an apparatus for carrying out the method of crystallizing a bottle cap according to the present invention, and FIG. 2 is an enlarged cross-sectional view taken along the line -- in FIG. 1a, 1b, 1c...heater, 2...mandrel, 3...heat shield plate.

Claims (1)

[Claims] 1. A method of heating and crystallizing the spout of a polyester resin blow bottle or a preform for molding the blow bottle, in which heating is divided into multiple stages, and in the first stage, heating is gradually performed at a low heating temperature, A method for crystallizing a spout portion, which is characterized in that the heating temperature is subsequently increased in a second step to perform heating crystallization.