KR100671666B1 - The method of manufacturing a preform for multi-layered plastic bottle - Google Patents

Abstract

The present invention relates to a method for producing a preform for a multi-layer container, and to a method of manufacturing a preform for a multi-layer container by injection molding a barrier resin containing MXD6 or Aegis (AEGIS-OX, Honeywell, USA) to a polyethylene terephthalate resin for manufacturing a multi-layer container. In the step, the barrier resin is dried for 4 to 5 hours in the 80 ~ 90 ℃ dryer before injection, wherein the moisture content is maintained at 50 ~ 400ppm; In the multi-layer preform manufacturing process, the polyester injection barrel melts each resin under the conditions of 290 to 295 ° C. and the barrier material injection barrel is 270 to 285 ° C., and the injection pressure of the polyester is 1300 psi to 1900 psi and the barrier material. The injection pressure of 1000 ~ 1200psi at the same time by injection molding the multilayer preform; characterized in that it comprises a. The preform for a multilayer container according to the present invention is improved in peeling compared to the multilayer container produced by the existing method, and has excellent durability and excellent shape stability. This has the effect that can be usefully used as a carbonated beer container or hot fill coffee, tea container.

Preform Barrier, Crystalline, Haze, Injection, Multilayer Container, MXD6, Aegis

Description

Method for manufacturing preforms for multi-layer containers {THE METHOD OF MANUFACTURING A PREFORM FOR MULTI-LAYERED PLASTIC BOTTLE}             

1 is a block diagram of a Kortec 48Cavity multi-layer injection machine according to the present invention.

2 is a cross-sectional view of the multilayer preform according to the present invention.

3 is a block diagram of a preform heating apparatus according to the present invention.

The present invention relates to a multilayer container comprising a thermoplastic polyester resin and a barrier material, and more particularly, to a multilayer container having excellent durability, transparency, oxygen and carbon dioxide barrier properties by including a barrier material as an intermediate layer in the thermoplastic polyester resin layer. It relates to a method of manufacturing.

Conventionally, PET-based resin containers have been widely used in foodstuffs, beverages and medicines because of their excellent moldability, transparency, chemical resistance, heat resistance, and mechanical strength. However, due to poor gas barrier properties, they are sensitive to oxygen such as beer, tea, and coffee. Beverage containers have been limited in their use.

In order to improve the gas barrier property of a PET blow molding container, several methods have been proposed in which a multilayer preform having a gas barrier resin layer disposed on an intermediate layer is formed by a blow molding method.

Japanese Laid-Open Patent Publication No. 56-64839 discloses a multi-layer container which forms a preform having a multi-layer structure consisting of a polyamide resin containing an outer layer and an inner layer with a PET layer, and an intermediate layer made of a methacrylic group-containing polyamide resin. A method is proposed.

Since MXD6 nylon has a melting point close to that of PET, it shows very good moldability in combination with polyester. In addition, since the glass temperatures of the two resins are similar, it is easy to set an appropriate molding temperature at the time of blow blow molding.

However, in general, the affinity between gas barrier resins (MXD6, Aegis) and the polyester resin is not excellent, and the peeling resistance is weak. Therefore, when the preform is manufactured by the method described in the above publication, the adhesion between the polyester layer and the polyamide layer is poor, the preform configuration is poor, and the durability of the final molded multi-layer container is poor. Layer separation of layers and multilayer container formability may be poor.

The present invention has been made to solve the above problems, an object of the present invention is to adjust the pre-treatment conditions and processing conditions of the barrier material to optimize the adhesion state of the polyester layer and the barrier layer, the blow process after the preform molding process It is to proceed smoothly, to provide a multi-layered container excellent in gas barrier properties and durability.

The object of the present invention as described above, MXD6 or Aegis (AEGIS-OX, Tg = 80 ± 5 ℃, melting point = 265 ± 5 ℃, hereinafter referred to as Aegis only) in polyethylene terephthalate resin for manufacturing a multi-layer container A method of manufacturing a multilayer container preform by injection molding a barrier resin, comprising: drying the barrier resin in an 80 to 90 ° C. dryer for 4 to 5 hours before injection, and maintaining a moisture content at 50 to 400 ppm; In the multi-layer preform manufacturing process, the polyester injection barrel melts each resin under the conditions of 290 to 295 ° C. and the barrier material injection barrel is 270 to 285 ° C., and the injection pressure of the polyester is 1300 psi to 1900 psi and the barrier material. The injection pressure of is achieved by the method of manufacturing a preform for a multi-layered container comprising a; injection molding the multilayer preform by simultaneously injecting at 1000 ~ 1200psi.

In the present invention, by optimizing the drying conditions of the barrier material to optimize the peeling of the multi-layer container after the blow molding of the multi-layer preform by controlling the crystallinity and haze of the preform barrier layer to provide a container having excellent gas barrier properties and shape stability Can be.

Other objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description of the invention and the preferred embodiments.

Hereinafter, the structure of the manufacturing method of the preform for multilayer containers which concerns on this invention is demonstrated.

Iii) drying the barrier material at 80-90 ° C. for 4-5 hours, wherein the moisture content is dried at 50-400 ppm; And ii) injecting the polyester and the barrier material into the polyester injection barrel at a temperature of 290 to 295 ° C. and the barrier material injection barrel at a temperature of 270 to 285 ° C. for injection molding the multilayer preform. By stretching and blow molding the preform, a multilayer container having excellent durability (less peeling) and gas barrier properties is produced.

 Hereinafter, the present invention will be described in more detail.

The present invention is a method for producing a preform for a multi-layer container by the following two steps.

Iii) Steps:

The barrier resin is dried for 4 to 5 hours in an 80 to 90 ° C. dryer before injection, at which time the moisture content is maintained at 50 to 400 ppm, more preferably at 50 to 200 ppm.

Ii) step:

In the multilayer preform manufacturing process, the temperature of the polyester injection barrel is 290 to 295 ° C., and the barrier material injection barrel is injection molded to the multilayer preform at a temperature of 270 to 285 ° C.

The resin from which moisture is removed is transferred from the dryer to the injection machine hopper, and is continuously supplied to the reciprocating screw injection molding machine by a predetermined amount and injected into the mold through melt plasticization. Since a predetermined time is required until the injection process is completely completed, a considerable amount of resin remains in the injection machine hopper and is maintained at 100 ° C. or more and more preferably 160 ° C. in order to prevent moisture reabsorption. In addition, the temperature in the barrier injector hopper is controlled at 50 ° C or higher.

 Examples of the barrier resins include MXD6 and Aegis, which are polyamide resins containing a metha xylene group. Moreover, polyester resin is a well-known resin manufactured by esterification (or transesterification), liquid polycondensation, and a solid state polymerization reaction using terephthalic acid as a dicarboxylic acid component and ethylene glycol as a dihydroxy component.

If the moisture content of the barrier material is less than 50 ppm, barrier materials such as MXD6 and Aegis may deteriorate, or the barrier layer may not be properly cooled after injection of the preform, resulting in increased crystallinity of the barrier layer. Occurs. In addition, when the moisture content is more than 400ppm, the moisture in the barrier resin acts as a crystal nucleating agent, and the crystallinity of the injection molded preform is excessive, causing peeling during blow molding.

If the temperature of the array is too high during injection molding, the preform may not be cooled properly after injection, which increases the crystallinity of the preform and causes the problem of peeling after blow molding.

In the present invention, a Kostec 48 cavity (cavity) multi-injection molding machine (see FIG. 1) was used, and a preform preform was manufactured using injection molding conditions under the conditions shown in Table 1 below. Silver has a structure including a barrier material as an inner layer between the polyester outer layer. The injection molding conditions of the injection molding machine are summarized in Table 1.                     

TABLE 1

EX1 ~ EX6: Barrel Temperature

BHE: Barrel Head Temperature

SP1 to SP2: Shooting port temperature

DIS: Distributor temperature

The preform injection-molded under the above conditions using a preform heating apparatus as shown in Figure 3 is heated by a heater in the temperature range of 100 to 110 ℃, stretched under the conditions of the primary pressure 10bar or less, the secondary pressure 40bar or more Blow molding. At this time, the stretching ratio of the abscissa is two times or more, and the stretching ratio of the ordinate is four times or more.

Hereinafter, the structure and effect of the present invention will be described in more detail with specific examples and comparative examples, but these examples are only intended to more clearly understand the present invention, and are not intended to limit the scope of the present invention.                     

EXAMPLE

The durability (peelability improvement) of the multilayer container manufactured according to the present invention was evaluated as follows. Table 2 shows the process conditions, and Table 3 shows the results of evaluation of the physical properties.

1) Evaluation of Crystallinity of Preform Barrier Layer

The injection molded preform body was cut and specimens of the barrier layer were taken to evaluate crystallinity as the size of the crystal and the distance between molecules using X-ray.

2) DSC measurement of preform barrier layer

In the process of cooling at a temperature-fall rate of 10 ° C / min from the molten state and the melting point Tm defined as the maximum point of the endothermic peak by melting of the crystal detected during the heating at 20 ° C / min using a differential scanning calorimeter. Crystallization is evaluated by the difference of the crystallization temperature Tc2 defined as the maximum point of the exothermic peak by crystallization detected.

3) Haze evaluation of preform barrier layer

After cutting the injection molded preform body, the specimen of the barrier layer is taken and the haze of the specimen is measured.

4) Drop test of bottle                     

After the drop test is carried out at a height of 50 cm, the blow molded multilayer container is examined for peeling of the multilayer container.

Example 1

Polyethylene terephthalate having an intrinsic viscosity of 0.8 dl / g was selected and dried at 160 ° C. for 4 hours and Aegis resin at 90 ° C. for 4 hours. Using the dried resin, the polyester injection temperature is set to 290 ℃, the barrier material is set to a temperature of 285 ℃ conditions and the injection molding of the multi-layer preform to 7% Aegis content. At this time, the surface temperature of the multilayer preform is heated by a heater so as to be 104 ° C, and stretch blow molding is performed under conditions of a primary pressure of 9 bar and a secondary pressure of 40 bar.

Example 2

Polyethylene terephthalate having an intrinsic viscosity of 0.8 dl / g was selected and dried at 160 ° C. for 4 hours and Aegis resin at 80 ° C. for 4 hours. Using the dried resin, the polyester injection temperature is set at 295 ° C., the barrier material is set at 275 ° C., and the multilayer preform is injection molded so that the Aegis content is 7%. At this time, the surface temperature of the multilayer preform is heated by a heater so as to be 104 ° C, and stretch blow molding is performed under conditions of a primary pressure of 9 bar and a secondary pressure of 40 bar.

Example 3

A polyethylene terephthalate having an intrinsic viscosity of 0.8 dl / g was selected and dried at 160 ° C. for 4 hours and Aegis resin at 80 ° C. for 5 hours. Using the dried resin, the polyester injection temperature is set to 290 ℃, the barrier material is set to a temperature of 285 ℃ conditions and the injection molding a multi-layer preform so that the Aegis content is 5%. At this time, the surface temperature of the multilayer preform is heated by a heater so as to be 104 ° C, and stretch blow molding is performed under conditions of a primary pressure of 9 bar and a secondary pressure of 40 bar.

Comparative Example 1

Polyethylene terephthalate having an intrinsic viscosity of 0.8 dl / g was selected and dried at 160 ° C. for 4 hours and Aegis resin at 70 ° C. for 4 hours. Using the dried resin, the polyester injection temperature is set to 290 ℃, the barrier material is set to a temperature of 285 ℃ conditions and the injection molding of the multi-layer preform to 7% Aegis content. At this time, the surface temperature of the multilayer preform is heated by a heater so as to be 104 ° C, and stretch blow molding is performed under conditions of a primary pressure of 9 bar and a secondary pressure of 40 bar.

Comparative Example 2

Polyethylene terephthalate having an intrinsic viscosity of 0.8 dl / g was selected and dried at 160 ° C. for 4 hours and Aegis resin at 80 ° C. for 3 hours. Using the dried resin, the polyester injection temperature is set to 290 ℃, the barrier material is set to a temperature of 285 ℃ conditions and the injection molding of the multi-layer preform to 7% Aegis content. At this time, the surface temperature of the multi-layer preform is heated by a heater so as to be 104 ° C, and stretch blow molding is performed under conditions of a primary pressure of 9 bar and a secondary pressure of 40 bar.

Comparative Example 3

Polyethylene terephthalate having an intrinsic viscosity of 0.8 dl / g was selected and dried at 160 ° C. for 4 hours and Aegis resin at 80 ° C. for 4 hours. Using the dried resin, the polyester injection temperature is set at 295 ° C., the barrier material is set at 290 ° C., and the multilayer preform is injection molded so that the Aegis content is 7%. At this time, the surface temperature of the multi-layer preform is heated by a heater so as to be 104 ° C, and stretch blow molding is performed under conditions of a primary pressure of 9 bar and a secondary pressure of 40 bar.

TABLE 2

TABLE 3

<Note> C.S (Å): The size of the crystal of the barrier layer, the higher the crystallinity is larger

d002 (mm): Distance between molecular chains of the barrier layer, the higher the degree of orientation (crystallinity)

Tm: melting temperature

Tc2: cooling crystallization temperature

Drop Test: (Excellent-> 0/5-1/5, Normal-> 2/5, Poor-> 3/5-5/5)

As shown in the above DSC measurement results, the smaller the temperature difference of (Tm-Tc2), the higher the crystallinity since the crystallization rate is faster due to the faster crystallization rate in the case of blow molding. In other words, the difference in Tm-Tc2 decreases, resulting in poor elongation during blow molding, and poor peelability of the container after blow molding.

Therefore, the haze and peeling of the final bottle may exist within a desired range only if the difference between the melting temperature and the cooling crystallization temperature (Tm-Tc2) is maintained at least 62 ° C. In the present invention, it was confirmed that the durability of the container was improved by improving the peeling occurrence, which is a weak point of the multilayer container, by controlling the drying time, temperature conditions, and injection conditions of the barrier material.

According to the manufacturing method of the multi-layer container preform according to the present invention as described above, the peeling is improved compared to the multi-layer container produced by the existing method is excellent in durability and excellent in shape stability. This has the effect that can be usefully used as a carbonated beer container or hot fill coffee, tea container.

Although the present invention has been described in connection with the above-mentioned preferred embodiments, it is possible to make various modifications or variations without departing from the spirit and scope of the invention. Accordingly, the appended claims include such modifications and variations as fall within the spirit of the invention.

Claims (2)

In the method for manufacturing a multi-layer container preform by injection molding a barrier resin containing MXD6 or Aegis (AEGIS-OX, Honeywell, USA) to a polyethylene terephthalate resin for manufacturing a multi-layer container, Drying the barrier resin in an 80 to 90 ° C. dryer for 4 to 5 hours before injection, wherein the moisture content is maintained at 50 to 400 ppm; And In the multi-layer preform manufacturing process, the polyester injection barrel melts each resin under the conditions of 290 ~ 295 ℃ and barrier material injection barrel is 270 ~ 285 ℃ .The injection pressure of polyester is 1300psi ~ 1900psi, and the barrier material Injection pressure is injection into the 1000 ~ 1200psi at the same time injection molding the multi-layer preform; method of manufacturing a preform for a multi-layer container comprising a. The method of claim 1, A method (Tm-Tc2) between the melting point (Tm) of the surface barrier layer of the preform for multilayer containers and the crystallization temperature (Tc2) is adjusted to 62 ° C or higher.

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