JPH0333499B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for strengthening the mouth part of a polyethylene terephthalate resin molded body mainly used for containing various fluids and the like.

[Prior Art] A polyethylene terephthalate resin molded product having a biaxially stretched bottle body exhibits excellent effects in various mechanical and chemical properties, and is therefore used in a wide range of applications. However, some types of polyethylene terephthalate resin molded bodies with biaxially stretched bottle bodies exhibit excellent performance only when the molded bodies undergo biaxial stretching. , it is something that is demonstrated.

[Problems to be Solved by the Invention] For example, when obtaining a polyethylene terephthalate resin molded body having a biaxially stretched bottle body, the mouth part that is hardly subjected to the stretching action is Crazing resistance is poor when compared to the body of the bottle, which is well resistant to crazing, and when a high concentration of alcohol comes into contact with the neck, this alcohol component permeates into the wall of the neck and causes crazing in that area. It has the disadvantage that whitening occurs due to

In addition, by subjecting the mouth tube portion of the polyethylene terephthalate resin molded body having the biaxially stretched bottle body portion to whitening by subjecting it to heat treatment, that is, the density of the polyethylene terephthalate resin in the mouth tube portion is reduced. By increasing , Due to the heating to cause whitening and the heating that the mouth part receives during slow cooling, thermal contraction always occurs in the mouth part, and in some cases, irregular deformation occurs due to the heat shrinkage. It has disadvantages such as the occurrence of

For this reason, when reinforcing the mouth part by whitening treatment, a hold is inserted into the mouth part of the polyethylene terephthalate resin molded article to be heat-treated, and the mouth part in which the hold is inserted is inserted into the mouth part. ``Unexamined Japanese Patent Publication No. 55-12031'' proposes a method of applying heat treatment for whitening to the mouthpiece. Because of the hold that exists in the mouth part, it is difficult to heat uniformly between the inner circumferential surface side and the outer circumferential surface side of the mouth part. Because it is difficult to heat the entire area uniformly, the shrinkage and deformation of the mouth barrel part during heat treatment is not uniform, and the roundness of the mouth barrel part is lost, or the flatness of the upper end surface of the mouth barrel part is lost. Not only does the shape of the resulting mouth barrel easily become unstable, but also the amount of heat required to whiten the inner circumferential surface of the mouth barrel is large. It also has drawbacks such as the process takes a long time and the cost increases due to the amount of heat required.

On the other hand, in the method for strengthening the mouth part of a polyethylene terephthalate resin molded article of the present invention, when the mouth part is whitened and strengthened by heating and slow cooling treatment, the mouth part is subjected to improper shrinkage. The purpose of this invention is to provide a strengthening method that prevents deformation from occurring and provides a well-ordered mouth barrel.

[Means for Solving the Problems] The method for reinforcing the mouth part of a polyethylene terephthalate resin molded article of the present invention is a method for strengthening the mouth part of the resin molded article, and the first invention includes the following steps:
Strengthening of the mouth tube part of a polyethylene terephthalate resin molded article, which comprises heating the mouth tube part of the polyethylene terephthalate resin molded article and then slowly cooling it to whiten the mouth tube part of the polyethylene terephthalate resin molded article. In the method,
Following the step of heating the mouth part of the polyethylene terephthalate resin molded article, a cylinder having an outer diameter slightly smaller than the inner diameter of the mouth part is placed inside the mouth part of the heated polyethylene terephthalate resin molded article. A step of inserting a mold pin made of a shaped body is provided.

Further, the second invention provides a polyethylene terephthalate resin molded article, which whitens the mouth tube portion of the polyethylene terephthalate resin molded article by heating the mouth tube portion of the polyethylene terephthalate resin molded article and then slowly cooling it. In the method for strengthening the mouth tube of a terephthalate resin molded article, following the step of heating the mouth tube of the polyethylene terephthalate resin molded article, the mouth tube of the polyethylene terephthalate resin molded article is added into the mouth tube of the heated polyethylene terephthalate resin molded article. A step of inserting a mold pin, which is a cylindrical body having an outer diameter slightly smaller than the inner diameter and has a cooling function, is provided, and the cooling function of the mold pin is utilized in the subsequent slow cooling step. It is something.

In the method of the present invention comprising the above-mentioned steps, in the first step, the mouth tube portion of the polyethylene terephthalate resin molded article is heated to a concentration that can whiten the mouth tube portion, usually about 140 to 170 ° C. , the mouth barrel portion is heated to an accurate heating temperature that is preset based on the wall thickness of the mouth barrel portion.

In addition, the mold pin used in the process following the heating process has slightly thermally shrunk due to being heated in the previous stage process, but it is smaller than the inner diameter of the mouth tube part which is still in the heated state. It is made of a cylindrical body having a slightly small outer diameter, and in particular, in the invention of subject 2, a mold pin made of a cylindrical body having a cooling function is used. Note that the outer diameter of the mold pin made of the cylindrical body is such that the mold pin is not inserted into the mouth cylinder part of the polyethylene terephthalate resin molded body after the mouth cylinder part is heated in the previous step. When subjected to cooling treatment, it is larger than the inner diameter of the mouth barrel part in a contracted and fixed state, and moreover, it is larger than the inner diameter of the mouth barrel part that has been slightly heat-shrinked due to heating in the previous step. It is small, that is, it has slightly thermally shrunk due to the heating in the previous step, but is set to be slightly smaller than the inner diameter of the mouth tube part that is still in the heated state. In other words, the shape of the inner peripheral surface of the mouth tube part of the polyethylene terephthalate resin molded product obtained by each of the methods of the present invention corresponds to the shape of the outer peripheral surface of the mold pin made of the cylindrical body. be.

Moreover, the cooling function of the mold pin used in the second invention is sufficient if cooling fluid is circulated and supplied inside.

Note that when the mouth tube portion with the mold pin inserted therein is slowly cooled, the mouth tube portion shrinks and deforms in a state that tightens the outer peripheral surface of the mold pin. In order to facilitate removal of the mold pin in subsequent steps, a mold pin having a tapered peripheral surface whose outer diameter is slightly narrowed toward the tip is preferred.

[Example] Hereinafter, one embodiment of the method for reinforcing the mouth part of a polyethylene terephthalate resin molded article of the present invention will be described based on the drawings.

The figure shows a case in which a bottle 1 obtained by biaxial stretch blow molding is used as a polyethylene terephthalate resin molded body to be strengthened. After inserting only the bottle (thickness: approximately 3.0 mm) into the heating furnace 3 in which the heater 4 is built into the frame wall 5 and positioning it, the bottle 1 is rotated at a constant speed and placed inside the heating furnace 3. By moving the mouth part 2
Heating H was applied by the heater 4 from the outer periphery of the bottle 1 to uniformly heat the entire area of the neck part 2 of the bottle 1 to about 170°C.

In the subsequent step, the inside of the mouth tube part 2 that has been heated in the previous step, that is, the inside of the mouth tube part 2 that has slightly thermally contracted due to the heating but is still in a heated state. Then, a mold pin 6 was inserted, which was made of a cylindrical body having an outer diameter slightly smaller than the inner diameter of the mouth tube part 2, and had a cooling function in which cooling fluid was circulated and supplied.

Further, by activating the cooling function of the mold pin 6 inserted into the mouth tube part 2, that is, cooling water is supplied into the cooling fluid passage formed in the mold pin for about 25 seconds. By passing it through, the mouth tube part 2 was actively cooled from the inner peripheral surface side, and the mouth tube part 2 of the bottle body 1 made of the biaxially stretched blow-molded product was whitened.

In addition, after the slow cooling process, the mouth tube part 2 becomes white, and the inner peripheral surface of the mouth tube part 2 matches the outer peripheral surface of the mold pin 6, which is a cylindrical body having a perfect circular cross section. The neck part 2 of the bottle 1 obtained by removing the mold pin 6 from the inside of the mouth part 2 following the slow cooling process has a cross section of It had a perfectly circular cylindrical shape, and had a flat top surface.

[Operations and Effects of the Invention] The method for strengthening the mouth part of a polyethylene terephthalate resin molded article according to each of the present inventions includes heating the mouth part of a polyethylene terephthalate resin molded article and then slowly cooling it. This method consists of whitening the mouth part of the terephthalate resin molded article, and in the first invention, following the step of heating the mouth part of the polyethylene terephthalate resin molded article, the heated mouth part is whitened. A step of inserting a mold pin made of a cylindrical body having an outer diameter slightly smaller than the inner diameter of the mouth tube into the tube is provided, and then the mouth tube into which the mold pin is inserted is slowly cooled. Shrinkage molding of the mouth part is performed by whitening the mouth part and solidifying the mouth part with the inner circumferential surface of the mouth part in close contact with the outer circumferential surface of the mold pin.

In addition, in the method for strengthening the mouth tube part of a polyethylene terephthalate resin molded article according to the second invention, after heating the mouth tube part of the polyethylene terephthalate resin molded article, following the heating step, the heated polyethylene terephthalate resin molded article is heated. A step of inserting a mold pin made of a cylindrical body having an outer diameter slightly smaller than the inner diameter of the mouth barrel part and having a cooling function into the mouth barrel part of the resin molded body is provided, and then the process is carried out. In the slow cooling step, the cooling function of the mold pin is utilized, and by this slow cooling step, the mouth tube portion is whitened and the inner circumferential surface of the mouth tube portion is made to match the mold. This method is performed for contraction molding of the mouth barrel part, which consists of solidifying the mouth barrel part in close contact with the outer circumferential surface of the pin.

Therefore, in the method for reinforcing the mouth part of a polyethylene terephthalate resin molded article of the present invention having the above-mentioned configuration, by increasing the density of the resin in the mouth part of the polyethylene terephthalate resin molded article, This is intended to improve various physical properties, and furthermore, the heat shrinkage deformation of the mouth barrel caused by the heat treatment process to increase the density of the resin in the mouth barrel of the polyethylene terephthalate resin molded article causes damage to the interior of the mouth barrel. Since this is done in an orderly manner using mold pins inserted into the mold, the mouth part is not distorted and deformed by heating and slow cooling when increasing the density of the resin in the mouth part. , it is possible to strengthen the mouth part of a polyethylene terephthalate resin molded article of good quality.

Furthermore, in the method of the present invention, after heat treatment is performed to increase the density of the resin in the mouth tube portion of the polyethylene terephthalate resin molded article, the mold pin is inserted into the mouth tube portion. Since the amount of heat generated at the time is not absorbed by the mold pins, it is possible not only to uniformly heat the mouth part, but also to perform heating for whitening extremely efficiently.

Furthermore, in each of the methods of the present invention, the insertion operation of a mold pin is added to the conventional method for strengthening the mouth tube part of a polyethylene terephthalate resin molded article, or the insertion operation of the mold pin and the attachment to the mold pin are added. Since it can be carried out by simply adding the operation of the cooling function described above, the workability is not particularly deteriorated, and the operation characteristics are also excellent.

[Brief explanation of the drawing]

FIG. 1 is a model explanatory drawing showing one embodiment of the method for reinforcing the neck part of a polyethylene terephthalate resin molded article of the present invention. 1: Polyethylene terephthalate resin molded body,
2: Mouth tube part, 6: Mold pin, H: Heating.

Claims (1)

[Scope of Claims] 1. A polyethylene terephthalate resin which whitens the mouth part of the polyethylene terephthalate resin molded article by heating the mouth part of the polyethylene terephthalate resin molded article and then slowly cooling it. In the method for strengthening the mouth part of a molded article, the step of heating the mouth part of the polyethylene terephthalate resin molded article is followed by a step of heating the mouth part of the polyethylene terephthalate resin molded article, and then inserting a resin into the mouth part of the heated polyethylene terephthalate resin molded article from the inner diameter of the mouth part. 1. A method for reinforcing the mouth tube of a polyethylene terephthalate resin molded article, comprising the step of inserting a mold pin made of a cylindrical body having a slightly smaller outer diameter. 2. A mouth tube part of a polyethylene terephthalate resin molded article, which is made by heating the mouth tube part of the polyethylene terephthalate resin molded article and then slowly cooling it to whiten the mouth tube part of the polyethylene terephthalate resin molded article. In the reinforcing method, following the step of heating the mouth part of the polyethylene terephthalate resin molded article, an outer diameter slightly smaller than the inner diameter of the mouth part is placed in the mouth part of the heated polyethylene terephthalate resin molded article. A step of inserting a mold pin which is made of a cylindrical body having a cooling function and has a cooling function is provided,
A method for reinforcing the mouth part of a polyethylene terephthalate resin molded article, characterized in that in the subsequent slow cooling step, the cooling function of the mold pin is utilized.