KR20010084816A - Low crystalline PET resin manufacturing method for large packaging and big bottle - Google Patents

Abstract

PURPOSE: Provided is a process for producing low crystalline polyester resin, having high transparency, a high viscosity, and a low melting point, for producing large containers. CONSTITUTION: The low crystalline polyester resin having an intrinsic viscosity of 0.5-1.0dl/g is produced by reacting terephthalic acid(PTA), ethylene glycol, and 0.5-23mol%/PTA of a modifier such as isophthalic acid, 1,4-cyclohexane dimethanol, naphthalene dicarboxylate, phthalic acid, bisphenol and alkylester derivatives thereof. The low crystalline polyester is used for producing large bottles having a capacity of 1-10 gallon and a thickness of 300 micrometer to 2mm.

Description

Low crystalline PET resin manufacturing method for large packaging and big bottle}

Polyethylene terephthalate (PET) has a degree of polymerization through polycondensation reaction through esterification or transesterification using high purity telephthalic acid (PTA) or dimethyl terephthalate (DMT) and ethylene glycol (EG) as main ingredients. Polymerization) is made of about 100 polymer.

Ethylene glycol (EG), which is produced as a by-product in addition to the PET main product, is recovered and reused as a raw material, and the reaction water (H ₂ O) is treated by a wastewater treatment facility.

PET is used as a raw material resin for long fibers, short fibers, films, sheets, bottles, and engineering plastics.The important physical properties of resins are intrinsic viscosity (IV), color, melting point, Residual Carboxyl End Group, diethylene glycol (DEG content) and the like. In particular, according to the intrinsic viscosity, it is used for general clothing, living clothes, film, bottles, engineering plastics, etc.

PET contains polar molecules and is easy to crystallize. Therefore, in order to form highly transparent containers or sheets, it is necessary to change the polymer chain structure by adding an appropriate modifier or to control molding temperature and cooling conditions for each application. .

PET has properties such as gloss, gas barrier, hygiene, chemical resistance, strength, and recyclability, so that bottled water, carbonated beverage bottles, fruit juice containers for heat, and other foods by injection molding and blow molding The demand for replacement of conventional PC, PVC, PP, PE containers, etc. for the use of containers, cosmetic containers, pharmaceutical containers, etc. is increasing at a very rapid rate. In particular, PET is a resin that can be recycled and pelletized and recycled, and can be called an environmentally friendly and economical resin in terms of recycling resources.

Existing PET bottle resins are made of high purity terephthalic acid (PTA) and ethylene glycol (EG) as the main raw materials, and are made of polymer without transparent matting agent (TiO ₂ ). Isophthalic acid (PIA), diethylene glycol (DEG), 1,4-cyclohexanedimethanol (CHDM), etc. are used to prepare a low melting point modified resin.

Copolymer modifiers are also used in addition to isophthalic acid, 1,4-cyclohexanedimethanol, naphthalenedicarboxylic acid, phthalic acid, bisphenols and their alkylester derivatives.

The prepolymers are usually obtained by melt polymerization as polymers having an intrinsic viscosity of 0.57 to 0.67 dℓ / g, which are produced in pellet sizes ranging from 1.0 to 3.0 g / 100 degree of correction so that crystallization steps and solid phase polymerization ( SSP (Solid State Polymerization) process to produce a high viscosity polymer of intrinsic viscosity of 0.70 to 1.0 dL / g. Compared to general textiles, physical strength, moisture and gas barrier properties are particularly required for use in food preservation containers and thick plate sheets. Therefore, the viscosity and molecular weight should be increased rather than using the base polymer. .

The pellet size is preferably prepared as small and uniform as possible from the prepolymer preparation step in order to homogenize crystallinity and viscosity, and usually 100 pellets are prepared in a size of 1.0 to 3.0 g. In order to increase the specific surface area of the pellets, even in the form of an excessively small powder form, the unevenness and loss of physical properties may occur in the solid phase polymerization process, and the process may become unstable.

The present invention is to provide a low crystalline polyester resin manufacturing method for the application of a large vessel through the control of the selection and control of additives in the melt polymerization step in the production of high transparency, high viscosity, low melting point copolymer PET resin.

The present invention will be described in detail with reference to Examples.

The present invention is to prepare a high-transparency low-melting copolymer to have the uniformity of blow moldability and burst resistance, high transparency in the production of large transparent containers before and after 5 gallons (gallons) and to enable low-temperature molding and energy of the post-processing process It is a manufacturing technology related to the modification of PET polymer that has achieved the reduction and minimization of acetaldehyde, which is a decomposition gas.

As the polymerization catalyst, antimony trioxide and antimontrea acetate are used, and the mixing ratio is applied in a mixing ratio of 0.100 to 50:50 by weight, and an insoluble impurity of Sb _n O _m (n = 2, m = 3 to 5) And a catalyst of high purity (purity of 99.8% or more) almost free of impurities such as Pb, Ni, and other metallic components. This is because insoluble components contained in the catalyst act as crystal nuclei and appear as defects in the post-processing process even if a precise filter is used immediately after the polymerization reaction.

As the cocatalyst, metal complexes are used, and germanium dioxide catalysts can be used by mixing 5% to 50% with the main catalyst. Phosphorus compounds are prepared together with ethylene glycol to be supplied at the beginning of base polymer production in order to impart thermal stability during post-molding process after polymer production.

Catalysts, promoters, and heat stabilizers are completely dissolved and dispersed in ethylene glycol (EG) and diethylene glycol (DEG) just before esterification or just before condensation polymerization. In order to suppress crystallization and increase moldability in post-processing molding processes, high purity isophthalic acid, cyclohexanedimethanol (CHDM), diethylene glycol (DEG), and the like are used. In particular, uniform mixing and stable quantitative feeding of these sub-materials are very important for uniform melting point and stabilization of molecular structure.

In the ester reaction step, an oligomer is formed by reacting within a range of 245 to 260 ° C. under pressurization conditions of about 1.0 kg / cm ² at normal pressure, and in a condensation polymerization step, at a high vacuum condition of 1 Torr or less at 275 to 285 ° C. The prepolymer is made of a melt polymer having an intrinsic viscosity of 0.57 to 0.67 dL / g and pelletized to a specification of 1.0 to 3.0 g / 100 or less. The prepolymer in a completely transparent state is made of a high viscosity resin having an intrinsic viscosity of 0.70 to 1.0 dL / g having a degree of crystallinity of 45% to 60% through the steps of precrystallization, crystallization and solid phase polymerization.

It can be used at the melting point of 240 to 255 ° C for the manufacture of general atmospheric pressure and pressure resistant bottles, but it requires uniform blow elongation and high transparency to form large containers of 1 gallon or more (especially 5 gallon capacity for cold and hot water). Must be given from the manufacturing stage. That is, when the crystallization is suppressed and the melting point is lowered to 210 to 240 ° C., post-processing formability is increased, and 1 gallon to 10 gallons (3.75 L to 37.5 L) can be manufactured in a high transparent quality state. The low crystalline polymer developed for the production of large-sized containers is expected to contribute to energy saving as it shows the optimum molding conditions at 260 to 280 ℃, which is about 20 ℃ lower than the 280 to 290 ℃ for general bottled water or heat-resistant bottles. do.

The low crystalline resin thus obtained has not only sufficient strength in a large container but also lowers acetaldehyde, which is one of decomposition products due to low temperature molding, to 3 ppm or less, and suppresses crystallization and transparency of molten resin during molding. Can be guaranteed together.

In the case of solid phase polymerization, if the conditions of precrystallization and water removal are not sufficient, the physical properties of the resin may decrease due to fusion between pellets, degradation due to hydrolysis, and increased generation of acetaldehyde. Consideration of stable operating conditions is important. In the post-processing molding of the solid-phase polymerized resin, it is preferable to dry the water of the pellet to 50 ppm or less by using a hopper dryer to remove moisture sucked in the air and then injection molding.

<Example>

High-purity terephthalic acid and ethylene glycol 3 to 17.5 mole of high-purity isophthalic acid by adding 500 to 700 ppm / PET of antimontria acetate, 100 to 150 ppm / PET of cobalt acetate, 150 to 200 ppm of phosphorus thermal stabilizer and 10 to 50 ppm of tin compound A base copolymer melt-polymerized in a batch comprehensive facility by adding% / PTA and 0.2-3.74 wt% / PET of dimethylene glycol was prepared at an intrinsic viscosity (IV) of 0.640 dℓ / g, followed by an intrinsic viscosity of 0.756 dℓ / Solid phase polymerization with g forms a large capacity container.

Table 1. Base Polymer and Solid Polymer Properties

division Intrinsic Viscosity (IV) Color CEG (eq / ton) DEG (wt%) Acetaldehyde (ppm) Melting Point (℃) 100 (weight g) L b Prepolymer 0.640 50.0 0.50 24.5 1.21 56.0 238.0 2.35 Solid polymer 0.756 82.0 0.40 22.4 1.21 0.40 236.2 2.30

Table 2. Molding Conditions for Large Containers

Item Exam conditions Remarks Resin drying 160 ° C × 4 hours 50 ppm or less Injection Machine Barrel Temperature Neck Front Middle Rear One-Step 2 Cavities Facility 260 ℃ 260 ℃ 260 ℃ 265 ℃ Blowing pressure Primary pressure 16kg / cm ^{2 2} primary pressure 30kg / cm ² cooling water 9 degrees Celsius * 26 second Vessel 5 Gal Bottled Water Bottle Thickness 500μ Weight 700g / piece 1) Haze 0.3% or less (transparency is very good) 2) Drop burst test at height of 1.5m after filling with bottled water (10 pieces): Normal

According to the low crystalline polyester resin manufacturing method of the present invention, a large container of 5 gallons of bottled water and other 2 to 5 gallons of bottled water or food containers made of expensive raw materials such as polycarbonate (PC) to date Increased economic value and scrapping of household goods by replacing polyethylene terephthalate (PET), which is inexpensive and free of environmental hormones, and expands to small bottles of less than 1 mm in thickness and thick sheets of 2 to 10 mm. It has the effect of producing an environmentally friendly resin that can be recycled.

Claims (4)

In polyester polymerization of terephthalic acid and ethylene glycol, Branched copolymer (Branch Copolymer) modifier for terephthalic acid to prepare a copolyester resin with a content of 0.5 to 23 mole% / PTA low-crystalline polyester resin for the production of large containers, such as large pressure of 1 gallon to 10 gallon and pressure-resistant bottles Manufacturing method. The method of claim 1, The copolymer modifier is a polyester resin prepared using isophthalic acid, 1,4-cyclohexanedimethanol, naphthalenedicarboxylic acid, phthalic acid, bisphenol and alkyl ester derivatives thereof. The method of claim 1, Intrinsic viscosity (IV) of the low crystalline resin is a polyester resin production method having a physical property of 0.5 to 1.0 dℓ / g. The method of claim 1, The thickness of the vessel 300 μ 2 mm polyester resin manufacturing method.