KR101034638B1 - Preparation method of polyethyleneterephthalate bottle for hot filling - Google Patents

Abstract

The present invention relates to a novel method for producing a high-temperature filling polyethylene terephthalate bottle (PET bottle), a polyester yarn piece or a PET bottle piece heat-treated at high temperature with a polyester resin blended and injection molded to prepare a preform and Blow molding the preform at a mold temperature of 120-180 ° C. can improve the crystallization rate of the material in the bottleneck crystallization process and improve the crystallinity of the walls of the PET bottle and the heat resistance of the PET bottle after the blow process.

Polyethylene terephthalate bottle, degree of crystallinity, polyester yarn

Description

Preparation method of polyethyleneterephthalate bottle for hot filling

The present invention is to prepare a preform by blending a polyester yarn piece or PET bottle piece heat-treated at a high temperature with a polyester resin and injection molding to prepare a preform and blow molding the preform at a mold temperature of 120-180 ℃ material in the bottleneck crystallization process It is related with the manufacturing method of the high temperature filling polyethylene terephthalate bottle (henceforth abbreviation "PET bottle") which improved the crystallization rate of and improved the crystallinity of the wall surface of PET bottle and the heat resistance of PET bottle after a blow process.

Polyethylene terephthalate (hereinafter abbreviated as "PET") is a polyester-based polymer material that is used for various purposes such as fibers, bottles, sheets, films, or tire cords. There is a slight difference in the method of producing PET according to various uses. For example, in order to be used in textile applications, a polyester material having a polymerization degree of intrinsic viscosity of about 0.5 to 0.7 dl / g is produced by a melt polymerization method in which a polymerization reaction proceeds in a molten state, and then a spinning process of making the material into a yarn. Will go through. In addition, in order to be used for bottles, films, tire cords, etc., higher physical strength is required than conventional fiber materials, and a polyester material having a higher degree of polymerization is required for this purpose, so that the intrinsic viscosity is 0.2 to 0.7 dl by melt polymerization. / g of PET in the form of pellets, which are further polymerized in the solid state (solid phase polymerization) to produce a polyester material having the required molecular weight. In particular, polyester materials having an intrinsic viscosity of 0.7 to 0.9 dl / g are used for PET bottles, and most commonly a polyester material having an intrinsic viscosity of 0.80 dl / g is used.

Using PET material produced through fusion polymerization or solid state polymerization as described above, an intermediate product called 'preform' is produced through an injection process, and the 'preform' is heated to a temperature of 90-110 ° C. and blown into a bottle. PET bottles are produced through the blow process. The manufacturing process of these PET bottles also differs little by little depending on the type of bottle produced. For example, a beverage such as water, cola, cider, etc. is a PET bottle is sufficient to exhibit a stable structure and strength at the filling temperature, since the temperature of filling the beverage in the PET bottle is room temperature or less. However, when filling contents such as juice, sports drinks or jams, the filling process of the contents is often performed at a relatively high temperature, for example, 70-100 ° C., for the purpose of sterilization. It must be structurally stable.

However, although general PET bottles are thermally and structurally stable at low temperature and room temperature filling, when the filling temperature of the contents rises above 70 ° C, they cannot be applied as containers because deformation of the bottleneck and shrinkage of the bottle volume are shown. There is this.

This technical problem is solved through heat setting process by thermally crystallizing the bottleneck and keeping the mold temperature at 120 to 180 ° C during the blow. This uses the phenomenon that even if the same PET is subjected to heat treatment, the thermal structural stability of the material is improved. In amorphous polyethylene terephthalate materials, the glass transition temperature determines the applicable upper heat resistance temperature at which thermal structural stability is maintained.However, when a crystal phase is formed by heat, the material is no longer affected by the glass transition temperature, and the melting point of the crystal To the vicinity, the material has thermal structural stability. As a result, the PET bottle for high temperature filling improves the heat resistance of the bottle through a heat setting process using a high temperature mold during the separate bottleneck crystallization process and the blow process, unlike the general bottle production process. At this time, the heat resistance of the bottle is improved as the degree of crystallinity of the bottle is increased. Therefore, the crystallization rate of the polyester material used to improve the heat resistance of the heat bottle and the productivity of the heat bottle manufacturing process is increased. It needs to be higher than that of the ester material. For this reason, co-polyester materials containing copolymers are used for the production of general bottles, while homo-polyesters without copolymers are used for the production of PET bottles for high temperature filling. polyester) material is used.

An object of the present invention is to improve the thermal and structural instability of PET bottles with increasing filling temperature.

Accordingly, the present inventors blended the polyester yarn pieces or PET bottle pieces heat-treated at high temperature with polyester resin and injection molded to prepare a preform and blow-molded the preform at a mold temperature of 120-180 ° C. in the bottleneck crystallization process. The present invention was completed by finding that the crystallization rate of the material can be improved and that the crystallinity of the wall surface of the PET bottle and the heat resistance of the PET bottle can be improved after the blow process.

In order to achieve the above object,

The present invention comprises the steps of blending 1 to 20 parts by weight of polyester yarn pieces with respect to 100 parts by weight of polyester resin and injection molding to prepare a preform, and blow molding the preform at a mold temperature of 120-180 ℃ Provided is a method for preparing a polyethylene terephthalate bottle for high temperature filling.

The polyester yarn piece is heat-treated at a temperature of 100-200 ℃, uniaxially stretched to a length of 1-50 mm in the longitudinal direction is used.

If the polyester yarn piece is less than 1 part by weight with respect to 100 parts by weight of polyester resin, the effect of improving heat resistance according to the present invention is insignificant, and if it exceeds 20 parts by weight, there is a problem of causing a change in molding conditions during injection molding.

In addition, the present invention is to prepare a preform by blending and injection molding 1 to 20 parts by weight of polyethylene terephthalate bottle pieces with respect to 100 parts by weight of polyester resin and blow molding the preform at a mold temperature of 120-180 ℃ It provides a method for producing a polyethylene terephthalate bottle for high temperature filling comprising.

The polyethylene terephthalate bottle pieces are heat-treated at a temperature of 100 to 200 ° C., and biaxially stretched pieces having a length × length of 1 mm × 1 mm to 10 mm × 10 mm are used.                     

When the polyethylene terephthalate bottle piece is less than 1 part by weight with respect to 100 parts by weight of polyester resin, the effect of improving heat resistance according to the present invention is insignificant, and when it exceeds 20 parts by weight, there is a problem of causing a change in injection molding conditions.

The polyester yarn is already crystallized through uniaxial stretching and heat setting process, and this crystallization structure is mostly broken during the injection molding process and molded in a molten state, but crystals remain in this molding process without being completely destroyed. This affects the crystallization behavior of injection molded parts.

Also, in the case of PET bottles, the polyester is already crystallized, which is no different from that of polyester yarn.

The crystal structure of the polyester yarn or PET bottle remaining in the injection molded product acts as a nucleus of the crystal during the crystallization of the injection molded product, thereby improving the crystallization rate of the molded product during the bottleneck crystallization process or the heat setting process of the heat-resistant bottle molding process. The degree of crystallinity of the final molded article is increased.

Hereinafter, to demonstrate the effect of the present invention in more detail through the comparative examples and examples. However, the scope of the present invention is not limited by the following example.

Comparative Example

3 kg of SK Chemical's SKYPET BB8055, a polyester resin having an intrinsic viscosity of 0.80 dl / g, was dried in a vacuum oven set at 160 ° C. for 10 hours, and then injection molded to produce a preform. The injection conditions were a cylinder temperature of 280 ° C, a coolant temperature of 15 ° C, and a cycle time of 20 seconds. The crystallization peak temperature was measured using a differential scanning calorimeter by taking 10 mg at the bottleneck of the produced preform. The peak temperature of the crystallization curve was measured at 153 ° C. by scanning at a rate of 10 ° C./min from 40 ° C. to 300 ° C.

Reheat time 30 seconds, Equilibration time 5 seconds, mold temperature 120 ° C, blow time 3 seconds, blow low pressure 7 kg / cm ² , blow high pressure 15 kg / cm ² in Krupp Corpoplast LB01E blow molding machine with the preform set to constant conditions Heat-resistant bottles were molded under the conditions of. Filling the molded heat-resistant bottle with water to measure the volume was confirmed to be 1650 ml. The same heat-resistant bottle was placed in a convection oven set at 80 ° C., stored for 1 hour, taken out, and poured again into water to measure the volume, which was 1400 ml. Therefore, it was confirmed that the produced heat-resistant bottle showed a volume shrinkage of 15% for 1 hour at 80 ℃.

≪ Example 1 >

100% of the yarn fragment obtained by cutting the polyester yarn produced by HUVIS, Superbright product at intervals of 2 cm in the length direction, and 3 Kg of SK Chemical's SKYPET BB8055 product, the polyester resin used in the comparative example, were evenly mixed. Preforms were produced by drying and injection molding in the same conditions, machines and methods. Differential scanning calorimetry was measured in the same manner as in Comparative Example 10 bottleneck region of the produced preform, it was confirmed that the crystallization temperature was 145 ℃.

Also, the PET bottle was produced by blow molding under the same method, machine, and condition as in the comparative example, and the initial volume of the PET bottle was 1653 ml, and the bottle was measured again after the convention oven treatment under the same conditions (80 ° C., 1 hour). The volume of was 1560 ml. Thus, the produced heat-resistant bottle was confirmed to exhibit a volume shrinkage of 5.6% for 1 hour at 80 ℃.

<Example 2>

After crushing the reused waste PET bottles, 100 g of PET bottle scraps of approximately 1.5 × 2 cm in width and 3 Kg of SK Chemical's SKYPET BB8055, a polyester resin used in Comparative Example, were mixed and compared. Preforms were produced by drying and injection molding using the same conditions, machines and methods as in the examples. Differential scanning calorimetry was measured in the same manner as in Comparative Example 10 bottleneck region of the produced preform, it was confirmed that the crystallization temperature was 148 ℃.

Also, the PET bottle was produced by blow molding in the same method, machine, and conditions as in the comparative example, and the initial volume of the PET bottle was 1652 ml, and the bottle was measured again after the convention oven treatment under the same conditions (80 ° C., 1 hour). The volume of was 1505 ml. Therefore, the produced heat-resistant bottle was confirmed to exhibit a volume shrinkage of 8.9% for 1 hour at 80 ℃.

As described above, according to the method for producing a PET bottle according to the present invention, the dimensional stability is excellent at 80 ° C., thereby making it possible to manufacture a PET bottle for high temperature filling with improved crystallization rate and heat resistance.

Claims (6)

Blending 1 to 20 parts by weight of polyester yarn pieces with respect to 100 parts by weight of polyester resin and injection molding to prepare a preform, and Method for producing a high-temperature filling polyethylene terephthalate bottle comprising the step of blow molding the preform at a mold temperature of 120-180 ℃. The method of claim 1, wherein the polyester yarn pieces are heat-treated at a temperature of 100-200 ℃. The method of claim 1, wherein the polyester yarn piece is a uniaxially stretched polyester yarn piece cut to a size of 1-50 mm in the longitudinal direction of the polyethylene terephthalate bottle for hot filling. Preparing a preform by blending and injection molding 1-20 parts by weight of a polyethylene terephthalate bottle piece with respect to 100 parts by weight of polyester resin; and Method for producing a high-temperature filling polyethylene terephthalate bottle comprising the step of blow molding the preform at a mold temperature of 120-180 ℃. The method of claim 4, wherein the polyethylene terephthalate bottle pieces are heat-treated at a temperature of 100-200 ℃. The polyethylene terephthalate bottle filling according to claim 4, wherein the polyethylene terephthalate bottle piece is a biaxially stretched polyethylene terephthalate bottle piece having a width x length of 1 mm x 1 mm to 10 mm x 10 mm. Method for producing terephthalate bottle.