JPH09239852A - Manufacture of resin vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin vessel having excellent heat resistance without irregular shrinkage at a port cylindrical part in the case of crystallization by preheating and stress relaxing the cylindrical part at the glass transition point to crystallizing point of the resin, and then heating it at the temperature exceeding the crystallizing point to blush it. SOLUTION: A port cylindrical part 2 is preheated to the glass transition point to crystallizing point of resin. When the resin is polyethylene terephthalate, the temperature is preferably 115 to 125 deg.C. In the stress relaxing step, the part 2 is held at the glass transition point to crystallizing point of the resin. In the case of the polyethylene terephthalate, the conditions of about 120 deg.C for about 1 to 3min can be adopted. In the blushing step, the part 2 is heated to the temperature exceeding the crystallizing point of the resin. As the heating means 3, a near infrared heater is preferable in view of shortening the tie of the step. The heating time is normally 90 to 150sec at 180 to 220 deg.C in the case of the polyethylene terephthalate.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing a resin container. More specifically, the present invention relates to a method for producing a resin container in which a mouth tube portion having excellent heat resistance can be obtained, and the mouth tube portion does not shrink unevenly when the mouth tube portion is crystallized.

[0002]

2. Description of the Related Art Resin bottles are widely used because of their advantages such as light weight and no breakage when dropped.
A blow molding method is generally used for manufacturing such a resin bottle.

In the blow molding method, a preform is first prepared by an extrusion molding machine or an injection molding machine, and this is put in a mold,
This is a method in which compressed gas is blown into the mold to inflate it, and it is brought into close contact with the inner surface of the mold to be shaped and solidified.

When a heat-resistant container is manufactured by this method, the body portion of the container is stretched and sufficiently subjected to heat treatment, but the mouth tube portion of the container is not subjected to such treatment, and thus exposed to high temperatures. May contract when given. Therefore, it is necessary to separately perform heat treatment to crystallize.

[0005]

If the mouth tube portion contracts when it is heated to a high temperature, it may cause a slow leak, a liquid leak or the like after the cap, and it is particularly desired to suppress the change of the inner and outer diameters of the mouth tube portion. There is.

Further, when the mouth tube portion is crystallized, contraction of the mouth tube portion occurs, but this contraction may become uneven. In particular, on the neck ring provided around the lower part of the mouth tube part, in order to improve the tamper evidence of the cap, that is, the mouth tube with a ratchet having a ratchet that is a protrusion for easily cutting the tamper-proof band It is remarkable in the case of a part. For example, FIG. 4 is a diagram showing an example of a state after crystallizing the mouthpiece portion with a ratchet, but the portion B near the neck ring is not vertical due to uneven contraction. Therefore, there is a need for a means to prevent uneven shrinkage.

[0007]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors have found that a mouthpiece having excellent heat resistance can be obtained by adopting a crystallization method consisting of specific steps. The present invention has been completed based on the finding that it can be obtained, and further that uneven shrinkage can be prevented.

That is, the first gist of the present invention is to use a resin preform consisting of a mouth cylinder and a bottomed body,
In a method of manufacturing a resin container including a step of forming the body portion by blow molding and a step of crystallizing the mouth tube portion, crystallization of the mouth tube portion is performed by a method comprising the following steps. The above method exists. (A) The mouth part is preheated to a temperature above the glass transition point of the resin and below the crystallization point. (B) The mouth tube is kept at a temperature not lower than the glass transition point of the resin and not higher than the crystallization point to relax the stress. (C) The stress-relaxed mouth tube is heated to a temperature exceeding the crystallization point of the resin to be whitened. (D) After whitening, the resin is cooled to a temperature below the glass transition point of the resin.

According to the present manufacturing method, since stress on the mouth tube portion is relaxed before whitening, uneven shrinkage can be prevented. In particular, the present manufacturing method is suitable for manufacturing a resin container having a ratchet-equipped mouth tube portion, which was difficult to obtain uniform shrinkage by the conventional method. Further, it is possible to prevent uneven shrinkage during whitening.

A second gist of the present invention is to use a resin preform comprising a mouth cylinder and a bottomed body, and to form the body by blow molding and the mouth cylinder. In the method for producing a resin container, which comprises a step of crystallizing, the crystallization of the mouth tube portion is performed by a method comprising the following steps. (A) The mouth part is preheated to a temperature above the glass transition point of the resin and below the crystallization point. (B ') Insert a nozzle having a diameter 1 to 2.5% larger than the inner diameter of the mouthpiece of the preform into the mouthpiece. (C) The mouth tube is heated to a temperature exceeding the crystallization point of the resin to be whitened. (D) After whitening, the resin is cooled to a temperature below the glass transition point of the resin.

According to the present manufacturing method, the use of the nozzle can prevent the shrinkage of the inner and outer diameters of the mouth when the mouth tube is exposed to a high temperature.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The resin used as the material of the container manufactured by the manufacturing method of the present invention is usually a thermoplastic resin, preferably polyethylene terephthalate.

The resin preform consisting of the mouth tube and the bottomed body is the same as that for ordinary blow molding and can be obtained by a known method such as injection molding. The size of the preform is usually 20 mm
-40 mm, outer diameter of mouth tube part is 25-46 mm, diameter of neck ring (outer diameter) is 33-53 mm, inner diameter of body part is 27
.About.45 mm, and the outer diameter of the body is 12 to 40 mm.

The order of the step of blow-molding the body and the step of crystallizing the mouthpiece is not particularly limited, and either step may be performed first or simultaneously. Alternatively, a method in which blow molding is performed in two steps, that is, an intermediate container is created in the first blow molding process, the mouth cylinder is crystallized in the crystallization process, and the final container is manufactured in the second blow molding process, is also possible. Good.

The blow molding can be carried out under the conditions usually adopted. For example, when polyethylene terephthalate is used as the resin, the temperature is 9
Conditions of 0 to 110 ° C. and a draw ratio of 7 to 11 can be usually adopted.

The manufacturing method of the present invention is characterized by the crystallization of the mouth tube portion which comprises a specific process. Hereinafter, first,
Each step for this crystallization in the manufacturing method of the first aspect, the outline of which is shown in FIG. 1, will be described.

First, the preheating step (a) will be described. In this step, the mouthpiece is heated to a temperature above the glass transition point of the resin and below the crystallization point. This temperature is appropriately selected depending on the type of resin, but when the resin is polyethylene terephthalate, it is preferably 115 to 125 ° C.
As a heating means, a near-infrared heater or heating with warm air can be adopted, but a near-infrared heater is preferable from the viewpoint of shortening the time until the target temperature is obtained.

In the stress relaxation step (b), the mouthpiece is kept at a temperature not lower than the glass transition point and not higher than the crystallization point of the resin. This time is appropriately selected depending on conditions such as the type of resin and temperature. For example, in the case of polyethylene terephthalate,
A condition of about 1 to 3 minutes at around 120 ° C can be adopted.
When it is shorter than 1 minute, the stress relaxation is insufficient, while when it is longer than 3 minutes, the improvement of the stress relaxation effect becomes small, which is uneconomical.

After relaxing the stress, cooling may be performed before the next whitening step. Not cooling is preferable because it is economical in heating in the whitening step. Whether or not the stress relaxation is sufficient can be determined by inspecting the contraction of the mouth tube portion in the next step (c).

In the whitening step (c), the mouth tube is heated to a temperature exceeding the crystallization point of the resin. As a heating means, a near infrared heater or heating with warm air can be adopted,
From the viewpoint of shortening the time of the whitening process, a near infrared heater is preferable. The heating time is appropriately selected depending on the type of resin, temperature and the like. In the case of polyethylene terephthalate, conditions of 180 to 220 ° C. and 90 to 150 seconds are usually adopted. The crystallinity obtained is usually 35-4.
5%.

In the present specification, the term "whitening" means that the mouth tube portion is heated above the crystallization temperature of the resin to be crystallized and turned cloudy. This whitening step is preferably performed by inserting a nozzle into the mouth tube portion. The nozzle may be inserted before starting heating for whitening or after heating to a predetermined temperature, but from the viewpoint of making the dimension of the inner diameter of the mouth cylinder more stable, insert the nozzle before starting heating. Preferably.

The size of the nozzle is preferably 1 to 2.5% larger than the inner diameter of the mouth tube portion of the preform (FIG. 7). By doing so, the nozzle uniformly contacts the inner surface of the mouth tube portion in response to the expansion of the resin when heated above the glass transition point, so that the whitening is more uniform and the surface wave is generated. Is less likely to occur.

The material of the nozzle is preferably a material having good thermal conductivity (eg BeCu). Poor heat conduction,
Materials such as engineered plastic are not preferable because whitening may proceed too much.

In the case of polyethylene terephthalate, the nozzle temperature is usually 100 ° C. after the whitening of the mouth tube.
Since it is cooled to the vicinity, it is preferably 90 to 130 ° C.

In the cooling step (d), the mouth tube is cooled to a temperature below the glass transition point of the resin. As cooling means, cooling by blowing air or natural cooling can be adopted. Usually, 10 to 30 seconds after the end of heating for whitening, the cooling nozzle is inserted into the mouth tube. Taking the case of using polyethylene terephthalate as an example, the temperature of the mouth tube portion at this time is 100 to 140 ° C., and it is rapidly cooled to a temperature below the glass transition point by inserting the nozzle.

When the nozzle is inserted in the step (c), it is possible to cool the nozzle with the nozzle still inserted. In this case, after completion of heating for whitening, quenching (100 ° C. in the case of polyethylene terephthalate),
The nozzle is removed from the mouth tube, and gradually cooled to a temperature below the glass transition point over 20 to 30 seconds.

The change in the shape of the mouth tube portion in the above process will be described with reference to FIGS. FIG. 2 shows the shape of the mouth tube before stress relaxation, and FIG. 3 shows the shape after stress relaxation. Due to the stress relaxation, as shown in FIG.
However, when whitening is performed after that, the thick neck ring portion shrinks less, so that the shrinkage occurs in a well-balanced manner, and the inner surface of the mouth tube portion becomes straight as shown in FIG.

In particular, in the case of a ratchet-equipped mouth tube portion, in the conventional method, the contraction may become uneven like the portion B shown in FIG. 5, but according to the method of the present invention, Uniform contraction can be achieved even with a mouthpiece with a large ratchet.

Next, the crystallization step in the manufacturing method of the second aspect will be described. The crystallization in the manufacturing method of the second gist is based on the crystallization in the first manufacturing method (b).
The process is omitted, and the insertion of the nozzle at the time of whitening ((b ′) step) is essential. Preheating of (a) in this crystallization, whitening of (c), and
The cooling steps (d) are basically the same as those in the manufacturing method of the first aspect.

In step (b '), a nozzle is inserted into the mouth tube portion before the whitening step (c). The size of the nozzle is preferably 1 to 2.5% larger than the inner diameter of the mouth tube portion of the preform (FIG. 7). In this way, the nozzle uniformly contacts the inner surface of the mouth tube portion in response to the expansion of the resin when heated to the glass transition point or higher,
Whitening becomes more uniform, and surface waves are less likely to occur.

The material of the nozzle is preferably a material having good thermal conductivity (eg BeCu). Poor heat conduction,
Materials such as engineered plastic are not preferable because whitening may proceed too much.

In the case of polyethylene terephthalate, the nozzle temperature is usually 100 ° C. after the whitening of the mouth tube.
Since it is cooled to the vicinity, it is preferably 90 to 130 ° C.

The nozzle before whitening may be inserted before the start of heating for whitening or after heating to a predetermined temperature. However, from the viewpoint of stabilizing the inner diameter of the mouth cylinder, It is preferable to insert the nozzle before the start.

The manufacturing method according to the second aspect can be applied to a container having a small nonuniform contraction, such as a container having a ratchet portion without a ratchet. There is an advantage that it is quick because the time for stress relaxation can be omitted.

The glass transition point of the resin is measured by differential scanning calorimetry (DSC). The crystallization point of the resin is measured by thermomechanical analysis (TMA).

[0036]

The present invention will be described in more detail with reference to examples. In the examples, a preform made of polyethylene terephthalate was used, and the dimensions of its mouthpiece were as follows. Inner diameter: 20.6 mm Outer diameter: 24.94 mm Screw thread diameter 1 (first thread): 27.56 mm Screw thread diameter 2 (second thread): 27.56 mm Turnip diameter: 27.97 mm Neck ring diameter: 33 mm Turnip height : 14.1 mm Neck height: 22.43 mm FIG. 8 shows the mouth tube portion represented by the above dimensions.

Example 1 [(a), (b), (c) and (d) Steps (No Insertion of Nozzle during Whitening)] The mouthpiece of the preform was preheated to 120 ° C.
After keeping the temperature at 1 ° C for 1 minute, it was immediately heated to 180 ° C for whitening for 1 minute. After whitening, a cooling nozzle was inserted to cool. FIG. 6 shows the relationship between the temperature of the mouth tube portion and time in this crystallization.

The mouth cylinder thus obtained was immersed in warm water at 87 ° C. for 5 minutes and the amount of dimensional change at the mouth was measured (heat resistance test). The results are shown in Table 1 below. The smaller the absolute value of this dimensional change, the better the heat resistance.

Table 2 below shows shrinkage values (amount of dimensional change before and after whitening) of each portion of the mouth tube due to whitening.

Example 2 [Steps (a), (b), (c) and (d) (nozzle insertion during whitening)] In Example 1, after maintaining at 120 ° C. for 1 minute, heating before heating Crystallization was performed in the same manner as in Example 1 except that a nozzle having a diameter of 0.2 mm larger than the inner diameter of the reform was heated to 110 ° C., inserted into the mouthpiece, and then whitened. Parts were subjected to a heat resistance test under the same conditions as in Example 1.
The results are shown in Table 1 below. In addition, Table 2 below shows the shrinkage value of each part of the mouth tube part due to whitening.

Comparative Example 1 Crystallization was performed in the same manner as in Example 1 except that the temperature was not kept at 120 ° C. for 1 minute. Further, the shrinkage values of the respective parts of the mouth tube part are shown in Table 1 below. A heat resistance test was conducted on the obtained mouth tube part under the same conditions as in Example 1. The results are shown in Table 1 below. In addition, Table 2 below shows the shrinkage value of each part of the mouth tube part due to whitening.

[0042]

[Table 1] Dimensional change in the mouth cylinder (normal heat resistance test conditions) after immersion in warm water at 87 ° C for 5 minutes (Unit: mm) ───────────────────── ────────── Example 1 Example 2 Comparative Example 1 Port inner diameter −0.11 0.00 −0.17 Port outer diameter −0.11 −0.02 −0.13 Screw thread diameter 1 -0.06 -0.01 -0.05 Screw thread diameter 2 -0.03 0.00 0.00 Fog diameter -0.01 0.00 +0.02 Neck ring diameter 0.00 -0.02 0. 00 Turnip height 0.00 0.00 0.00 Neck height +0.02 -0.04 +0.06 ──────────────────────────── ───

As is clear from Table 1 above, when stress relaxation is performed, the amount of shrinkage of the inner and outer diameter portions, which is a problem with slow leak after capping, decreases. Also,
Further, it can be seen that when the nozzle is inserted into the mouth tube portion during whitening, the shrinkage amount becomes even and smaller.

[0044]

[Table 2] Shrinkage of each part of the mouth cylinder due to whitening (unit: mm) ────────────────────────────── Example 1 Example 2 Comparative example 1 Inner diameter -0.95 +0.20 -0.99 Outer diameter -1.00 +0.01 -0.96 Thread diameter 1 -0.76 +0.03 -0.73 Screw Mountain diameter 2-0.72 +0.09 -0.64 Turnip diameter -0.57 +0.15 -0.83 Neck ring diameter -0.50 -0.26 -0.77 Turnip height -0.65 -0. 32 -0.40 Neck height -1.18 -0.76 -0.97 ───────────────────────────────

As is clear from Table 2 above, when stress relaxation is performed, the amount of shrinkage of the ratcheted portion (fogger, neck ring diameter portion) is small and uniform. Further, it can be seen that the shrinkage is more uniform and less by inserting the nozzle into the mouth tube portion during whitening.

Example 3 The mouthpiece of the preform was preheated to 120 ° C., the nozzle having a diameter 0.2 mm larger than the inner diameter of the preform before heating was heated to 90 ° C., 110 ° C. and 130 ° C. It was inserted into the heated mouth tube, heated to 180 ° C., and whitened for 1 minute. After the whitening, it was gradually cooled to 100 ° C. for 30 seconds, and the nozzle was removed from the mouth cylinder part.

The mouth cylinder thus obtained was immersed in warm water at 91 ° C. for 5 minutes and the amount of dimensional change at the mouth was measured (heat resistance test). The results are shown in Table 3 below. The smaller the dimensional change, the better the heat resistance.

Comparative Example 2 Preheating and whitening were performed in the same manner as in Example 3 except that the nozzle was not inserted. After whitening, a 100 ° C. nozzle was put in, and the mixture was gradually cooled to 100 ° C. for 30 seconds. Was removed from the mouthpiece. Example 1 of the obtained mouthpiece
A heat resistance test was conducted under the same conditions as above. The results are shown in Table 3 below.

[0049]

[Table 3] Amount of dimensional change in mouth cylinder (high heat resistance test condition) after immersion in hot water at 91 ° C for 5 minutes (unit: mm) ───────────────────── ────────── Example 3 Comparative Example 2 Nozzle temperature (° C) 90 100 130 No nozzle Inner diameter -0.04 -0.08 -0.06 -0.05 Outer diameter -0.05 -0.02 0.00 -0.05 Thread diameter 1- 0.03 -0.03 -0.03 -0.02 Thread diameter 2 0.00 -0.02 0.00 -0.01 Turnip diameter 0.00 0.00 0.00 +0.01 Neck ring diameter -0.03 -0.02 -0.02 -0.06 Turnip height -0.04 +0.01 0.00 0.00 Neck height +0.04 +0.04 +0.03 +0.07 ───────────────────────────────

As is clear from Table 3, when the nozzle is inserted into the mouth tube and whitening is performed, the shrinkage of the outer diameter portion is reduced, and therefore slow leak and liquid leak after the cap are eliminated.

[0051]

As described above, according to the present invention,
Provided is a method for producing a resin container, which is capable of obtaining a mouthpiece having excellent heat resistance and which does not cause uneven shrinkage of the mouthpiece during crystallization. The manufacturing method of the present invention is particularly suitable for manufacturing a heat-resistant resin container in which sufficient crystallization of the mouth tube portion is required.

[Brief description of drawings]

FIG. 1 shows a schematic view of a crystallization process in the present invention.

FIG. 2 shows an example of a shape of a mouth tube portion before a whitening process.

FIG. 3 shows an example of the shape of the mouth tube portion after stress relaxation and before crystallization.

FIG. 4 shows an example of the shape of the mouth cylinder after the whitening process.

FIG. 5 shows an example of the shape of the mouth tube portion that contracts unevenly, which occurs in the case of the mouth tube portion with a ratchet.

FIG. 6 shows the relationship between the temperature of the mouth tube portion and time in Example 1.

FIG. 7 shows the relationship between the inner diameter of the preform mouth tube portion and the outer diameter of the nozzle.

FIG. 8 shows the names of the dimensions of each part of the mouthpiece part.

[Explanation of symbols]

 1 preform 2 mouth tube part 3 heating means 4 nozzle 5 neck ring 6 ratchet

Claims (5)

[Claims] 1. A resin container including a step of molding the body by blow molding, and a step of crystallizing the mouth cylinder, using a resin preform having a mouth cylinder and a bottomed body. In the manufacturing method described above, the crystallization of the mouth cylinder is performed by a method including the following steps. (A) The mouth part is preheated to a temperature above the glass transition point of the resin and below the crystallization point. (B) The mouth tube is kept at a temperature not lower than the glass transition point of the resin and not higher than the crystallization point to relax the stress. (C) The stress-relaxed mouth tube is heated to a temperature exceeding the crystallization point of the resin to be whitened. (D) After whitening, the resin is cooled to a temperature below the glass transition point of the resin. 2. After the step (b), the step (c) is performed by inserting a nozzle having a diameter of 1 to 2.5% larger than the inner diameter of the mouth tube of the preform into the mouth tube. The method described. 3. A resin container comprising a step of molding the body by blow molding, and a step of crystallizing the mouth cylinder, using a resin preform having a mouth cylinder and a bottomed body. In the manufacturing method described above, the crystallization of the mouth cylinder is performed by a method including the following steps. (A) The mouth part is preheated to a temperature above the glass transition point of the resin and below the crystallization point. (B ') Insert a nozzle having a diameter of 1 to 2.5% larger than the inner diameter of the mouthpiece of the preform into the mouthpiece, and (c) heat the mouthpiece to a temperature above the crystallization point of the resin to whiten it. Let (D) After whitening, the resin is cooled to a temperature below the glass transition point of the resin. 4. The method according to claim 1, wherein the resin is polyethylene terephthalate. 5. The heating temperature in step (a) is 16
The method of claim 4, which is 0 to 220 ° C.