KR20020009244A - An aging method of preform - Google Patents

Abstract

The present invention relates to a method for aging preforms, and more particularly, in an aging method for passing an injected preform to a space maintained at a constant temperature and humidity for a predetermined time, wherein the injected preform is subjected to a temperature of 40 to 65 ° C. and a humidity of 55. By aging for 30 minutes to 4 hours in a space designed to be adjusted to ˜80%, the time is shortened as compared to the conventional aging method to increase the space utilization according to the storage of the preform, and the aged preform has a certain range of moisture content. The present invention relates to a preform aging method that can be used for high-temperature beverages with excellent heat resistance due to high crystallinity when applied to beverage bottles, minimizing residual stress, minimizing residual stress, and applying to beverage bottles.

Description

Aging method of preform

The present invention relates to a method for aging preforms, and more particularly, in an aging method for passing an injected preform to a space maintained at a constant temperature and humidity for a predetermined time, wherein the injected preform is subjected to a temperature of 40 to 65 ° C. and a humidity of 55. By aging for 30 minutes to 4 hours in a space designed to be adjusted to ˜80%, the time is shortened as compared to the conventional aging method to increase the space utilization according to the storage of the preform, and the aged preform has a certain range of moisture content. The present invention relates to a preform aging method that can be used for high-temperature beverages with excellent heat resistance due to high crystallinity when applied to beverage bottles, minimizing residual stress, minimizing residual stress, and applying to beverage bottles.

Currently, the beverage bottle (bottle) that is in use is mainly made of PET, the beverage bottle is divided into four types according to the characteristics of the beverage composition is injected. First, the normal pressure bottle containing bottled water and shochu; Pressure-resistant bottles used for carbonated drinks such as cola and cider; Heat-resistant bottles used for 100% fruit juices such as juice and Thomas; And heat-resistant diseases used in less than 10% fruit juices and ionic drinks; Divided into the back. Among them, heat-resistant bottles and heat-resistant bottles are required to have heat resistance as a high-temperature beverage is injected, and absorbs moisture sufficiently through an aging step of standing in the air for 3 to 5 days without blowing immediately after injection according to a conventional method. It is manufactured by crystallizing and then blowing to minimize the stress remaining in the preform.

Therefore, the beverage bottle accompanying the aging process is complicated compared to other beverage bottles, the manufacturing method is very expensive, and the equipment and containers are very expensive, and the injection preform must be stored separately for aging, there are various problems such as securing space. have. In addition, when the crystallization immediately after injection of the preform, the size of the bottle inlet portion is out of the standard, so that it is difficult to seal the stopper after injecting the beverage and there is a problem that the beverage leaks even after sealing.

As a result, many studies are being carried out to shorten the aging time, secure space and reduce costs, and establish aging conditions for obtaining high crystallinity. U.S. Patent No. 4,379,099 proposed a patent to improve the heat resistance by heating the inlet portion of the preform for at least 30 minutes or more above the glass transition temperature to produce spherulite crystals. However, in the above patent, there is no mention of the aging method and the state and condition of the preform to crystallize easily to make the crystal of the spherical form, it is difficult to obtain a product of high crystallinity as well as a high probability of non-uniform product. In US Pat. No. 4,846,656, there was a reference to the method of aging, but it proposed a mechanism for crystallizing the inlet of the preform, but also no reference to the preform to crystallize. In addition, US Pat. No. 4,025,594 proposes an aging method that is baked at a glass transition temperature or lower and cooled to remove internal stress remaining in the preform after injection. However, there is no mention in this patent of the crystallization process for improving the heat resistance of the preform. On the other hand, Korean Patent Application No. 97-46388 suggested conditions for aging, that is, conditions for temperature, humidity, and time during aging. As a result, the crystallinity was 32-35%, but there was no mention of the state of the preform after aging. .

The aging method of the conventional preform is too long, the crystallinity is too long, 2 to 5 days, and there is no mention of the state of the preform after aging.

Accordingly, the present inventors can propose a new aging condition to solve the above problems, establish the conditions of the preform after aging to produce a uniform product having a high crystallinity and to manage the state of the preform can significantly lower the defect rate Efforts have been made for many years to establish the conditions. As a result, after the injection, the preform was aged for 30 minutes to 4 hours at a temperature of 30 to 50 ° C. and a humidity of 50 to 80%. As a result, the time was significantly shortened and remaining compared to the conventional aging method (2 to 5 days). The stress is minimized and the product has a crystallinity of 40% or more. In addition, the preform aged according to the present invention has a water content of 1000 to 2000 ppm, the glass transition temperature is 80 ~ 85 ℃, the crystallization temperature is 137 ~ 142 ℃ to complete the present invention. When the aging method of the present invention is applied to a beverage bottle, the crystallization of the inlet portion is increased, so that the heat resistance and strength are improved, and thus it can be used as a heat-resistant bottle very well.

Accordingly, an object of the present invention is to provide a aging method of a preform that can shorten the time during aging, increase the crystallinity and control the water content, and present the state of the aged preform.

Figure 1 shows the change in glass transition temperature according to the water content in the preform.

Figure 2 shows the change in crystallization temperature according to the water content in the preform.

Figure 3 shows the change in the water content of the preform with the aging time.

Figure 4a shows the residual stress distribution of the beverage bottle immediately after injection.

Figure 4b shows the residual stress distribution when aging according to the aging conditions of the present invention.

The present invention relates to a method of aging the injected preform,

It characterized in that the preform aging method for aging the injected preform for 30 minutes to 4 hours the space designed to adjust the temperature to 30 to 50 ℃, humidity 50 to 80%.

In another aspect, the present invention is characterized by an aged preform having a water content of 1000 to 2000 ppm, a glass transition temperature of 80 to 85 ℃, and a crystallization temperature of 137 to 142 ℃.

Referring to the present invention in more detail as follows.

The present invention relates to a method of aging preforms by aging the injected preform, which can shorten the time compared to the conventional method and can be effectively applied to a beverage bottle with excellent heat resistance as the degree of crystallinity is increased.

In general, in injection blow molding, such as a beverage bottle, a material is injected and melted during injection molding to prepare a preform, followed by an "aging" process, which is left at a constant temperature and pressure for a predetermined time without blowing. After the injection into the molding machine to complete the product is followed.

Immediately after injection, preforms typically have a water content of 80 to 120 ppm, a glass transition temperature of 86 ° C, a crystallization temperature of 168 ° C and a crystallinity of about 25 to 29%. When the preform is crystallized immediately after injection, the water content and crystallinity are low, and the crystallization temperature and the glass transition temperature are high. When the crystallinity is low, the inlet dimension of the preform is larger than the standard value, so the defect rate is high and the contents of the container leak out when used as a product. As a result, in order to control the moisture content of the preform, the aging is performed to leave the preform in a space where a certain time and humidity are maintained, thereby increasing the water content and crystallinity in the preform, minimizing the residual stress in the preform, and at the same time, the glass transition temperature. And the crystallization temperature can be adjusted to improve the physical properties of the finished product.

In the present invention, the injected preform is aged at a temperature of 30 to 50 ° C. and a humidity of 50 to 80% at a factory designed for 30 minutes to 4 hours.

At this time, if the temperature during aging is less than the above range, residual stress in the preform is present, so that the occurrence rate of defects during blow molding becomes high, and when the temperature exceeds the above range, the glass transition temperature of the PET is approached, causing pressing or scratching by the blow nozzle. It becomes undesirable. In addition, if the humidity is less than the range during aging, the crystallization rate is slow and the aging takes a long time. If the humidity exceeds the range, hydrolysis of the material occurs during molding, resulting in poor transparency and undesirable effects. When the temperature and humidity range is maintained and less than the above range in aging time, the removal rate of the residual stress and the crystallization rate are slowed to increase the incidence of defects, and when the range is exceeded, problems such as scratching, crushing and transparency during molding may occur. It is not desirable.

As a result, the aging method of the present invention aims to control the water content of the preform after aging. Thus, the preform subjected to the aging process as described above has a water content of 1000 to 2000 ppm, a glass transition temperature of 80 to 85 ℃, a crystallization temperature of 137 to 142 ℃, especially high crystallinity of 40% or more Indicates.

The water content of the preform affects the glass transition temperature, crystallization temperature and crystallinity, which will be described in more detail as follows.

In general, the moisture contained in the preforms causes hydrolysis during crystallization, which breaks the molecular chain of PET and reduces the glass transition temperature to facilitate the movement of the molecular chain. According to the accompanying drawings, it can be seen that the glass transition temperature decreases as the moisture content increases, but the degree is not large. The reason is that the water contained in the preform penetrates between the PET molecular chains and acts as a plasticizer to reduce the glass transition temperature, but it does not cause a sudden decrease in the glass transition temperature due to the small amount of water penetrated.

In addition, the moisture contained in the preform also acts as a crystal nucleus to increase the crystallinity, where the crystallinity is affected by the crystallization temperature and the crystallization rate. According to Figure 2, the change in the crystallization temperature according to the water content of the preform, it can be seen that the crystallization temperature is lowered as the water content is increased and does not affect much above a certain amount. The crystallization temperature is a measure of the maximum crystallization rate when the resin is crystallized. When the water content is small, the crystallization temperature is high at 168 ° C., but the water content is 1000 ppm, and there is a decrease of 25 ° C. or more from 143 to 140 ° C. have. That is, it can be seen that the crystallization at a high crystallization rate even at a low temperature of 140 ℃ when containing about 1000 ppm water.

If the moisture content is too high, hydrolysis occurs mainly, and when the preform is blown, turbidity occurs due to overstretching of the body. Aging passes the closed space for a certain time to maintain a constant temperature and humidity. It is necessary to contain water of 1000 to 2000 ppm, to reduce the crystallization temperature to about 140 ℃ and to reduce the glass transition temperature. In addition, if the water content in the preform increases, the role of hydrolysis that breaks the molecular chain rather than the role of crystal nucleus may lead to physical property deterioration. Therefore, an appropriate amount of water may increase crystallinity and speed up crystallization without deteriorating physical properties. have.

As described above, the water content in the preform particularly affects the degree of crystallinity, so that the water content has a range of water content through an aging process. In the present invention, the water content of the aged preform is 1000 to 2000 ppm, and it is very easy to manage the water content of the preform after aging.

As a result, the product manufactured according to the present invention is excellent in heat resistance and can be suitably applied to a heat-resistant beverage bottle, wherein the juicer or other high-temperature sterilized beverage is injected into the container, the cap of the container by the hot beverage By preventing the deformation of the product and preventing the leakage of the beverage after sealing can reduce the defective rate of the product, and can increase the productivity of the space and the use of space according to the storage of the preform.

Hereinafter, the present invention will be described by the following examples, but the present invention is not limited to these examples.

Example 1

Preforms prepared by conventional methods were aged by the aging conditions shown in Table 1 below, wherein the transparency, crystallinity and defective rate of the aged preforms were measured and the results are shown in Table 1 below.

Aging condition transparency(%) Crystallinity (%) Defective rate per 1000 Moisture content (ppm) Temperature (℃) Humidity(%) Hours (hr) 30 60 8 3.4 38.2 2.4 1660 50 30 6 3.3 38.5 2.1 1550 50 60 One 3.5 40.6 0.2 1300 50 90 One 2.6 41.1 11 1210 70 60 0.6 1.9 40.3 123 1810

Transparency was measured with a Haze meter, crystallinity was measured with a density meter (device-B type (Japan)), and defect rate was visually measured.

According to Table 1, when the aging condition (temperature / humidity) is 30/60, the low temperature during aging does not sufficiently remove the stress remaining in the preform. In the case of 50/30 aging condition, the crystallization rate was low due to low humidity during aging, and low crystallization rate was shown. . In addition, the aging condition of 50/60 corresponds to the aging condition of the present invention, and the crystallinity was very high, very transparent, and the defect rate was very low compared to other conditions. In the case of aging conditions of 50/90, due to the high humidity, the water content in the preform is excessive, so that the hydrolysis reaction occurs during molding, and the transparency is very low. Finally, when the aging condition is 70/60, the glass transition temperature is approached at a high temperature, and the blow rate is caused by pressing or scratching by the nozzle during blow molding.

Example 2

Aging time to reach the moisture content of the aged preform of the present invention when aging under the aging conditions of Example 1 is shown in the following Table 2, these results are shown in Figure 3 attached.

Aging condition Hour ^* (hr) Crystallinity (%) Temperature (℃) Humidity(%) 30 60 32 38.1 50 30 10 39.2 50 60 3 41.6 50 90 2 41.9 70 60 2 41.2 * Time when water content is 2000 ppm

According to Table 2, when the aging conditions (temperature / humidity) is 30/60, the water content in the preform is required for about 32 hours to reach 2000 ppm. For other aging conditions, the moisture content was very good, about 2-4 hours, to reach 2000 ppm. However, with the exception of 50/60, the crystallinity is low, which indicates low heat resistance and high defect rate.

On the other hand, according to Figure 3, when continuously aging under the above aging conditions, the water content is much more than 2000 ppm, when the blow molding of the preform occurs a turbidity phenomenon and loses the value as a product.

In addition, as a result of analyzing the decrease of the residual stress in the preform by the polarization photograph immediately after the injection of the preform and with aging conditions and time, FIG. 4 shows the residual stress distribution immediately after the injection, and FIG. 4B shows the residual stress after aging for 2 hours. The distribution is shown. Comparing the two figures it can be seen that the residual stress is almost eliminated in the case of the beverage bottle aged according to the present invention.

As described above, the preform injected according to the present invention is passed through a space designed to control the temperature 40 ~ 65 ℃, humidity 55 ~ 80% for 30 minutes to 4 hours, the moisture content of the preform is 1000 ~ 2000 ppm, glass A preform having a transition temperature of 80 to 85 ° C. and a crystallization temperature of 137 to 142 ° C. was prepared.

The preform aging method of the present invention enables the production of high-quality containers having high heat resistance and high crystallinity, thereby preventing deformation of the cap portion of the container by injection of hot beverage and preventing leakage of the beverage after sealing. In addition, compared with the conventional method, it is possible to shorten the time, increase the use of another space for storing the preform, and reduce the defective rate of the product by checking and managing the state of the preform.

Claims (2)

A method of aging a preform, characterized by aging through the space designed to control the injected preform at a temperature of 40 to 65 ° C. and a humidity of 55 to 80% for 30 minutes to 4 hours. The preform after aging according to claim 1 is characterized in that the water content is 1000 to 2000 ppm, the glass ion degree (Tg) is 80 to 85 ℃, crystallization temperature (Tc) is 137 ~ 142 ℃.