JPS6089326A - Manufacture of multi-layered container - Google Patents

Abstract

PURPOSE:To obtain a PET container excellent in gas permeation resistance and impact resistance, by biaxially stretching and blow molding a preform that has been prepared by laminating a polyethylene terephthalate (PET) and a polyester in a melted state under specified conditions that has been prepared using isophthalic acid as a major raw material. CONSTITUTION:A melted PET at 230-300 deg.C and a melted polyester at 180- 260 deg.C that consists of a dicarboxylic acid constituent containing at least more than 20mol% of isophthalic acid and ethylene glycol as major constituent are laminated under a molding pressure (gauge pressure) of 20kg/cm<2> or more. The laminate is cooled and solidified at a cooling temperature of -10-30 deg.C to provide a preform made up of a PET layer and a polyester layer. Thereafter, the preform is biaxially stretched and blow molded at a stretching temperature of 80-130 deg.C with the degree of the stretching at least 1.5 times longitudinally and at least 2 times laterally to obtain a multi-layer container mainly made of PET excellent in gas permeation resistance and impact resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a multilayer container mainly made of polyethylene terephthalate. More specifically, the present invention relates to a method for producing a multilayer container with excellent gas permeability and impact resistance.

Biaxially stretched molded products of polyethylene terephthalate (hereinafter sometimes referred to as PET) take advantage of their excellent properties such as mechanical strength, rigidity, heat resistance, chemical resistance, oil resistance, and transparency to produce films, sheets, and containers. Widely used as packaging material.

However, biaxially stretched blow-molded containers mainly made of PET are not without drawbacks, such as inability to achieve sufficient heat fixation and insufficient gas permeability. Among these, the insufficient gas permeability is due to the original material of PET, and it has been difficult to solve it by molding.

As a method to improve the gas permeability of PET containers, P
Resins with superior gas permeation resistance compared to ET, such as polyvinylidene chloride, saponified ethylene/vinyl acetate copolymer,
A method of laminating it with polyester, etc. is considered, but in any case, such resin has poor adhesion with PET, so even if the three-layer structure is sandwiched between PET, parts of the resin may peel off during stretch molding or use. There was a risk that gas permeability resistance would decrease.

Therefore, the present inventors conducted various studies in order to develop a method for manufacturing PET containers with excellent gas permeability and impact resistance. As a result, the present inventors added polyester containing isophthalic acid as a main raw material to PET under specific conditions. It has been found that the above object can be achieved by biaxially stretching blow molding a preformed product obtained by laminating layers, and the present invention has been completed.

That is, the present invention provides molten polyethylene terephthalate (A) at 230 to 300°C and molten polyethylene terephthalate (A) at 180 to 260°C.
A molten polyester (B) consisting of a dicarboxylic acid component containing at least 20 mol% of isophthalic acid and a glycol whose main component is ethylene glycol is laminated at a molding pressure (gauge pressure) of 20 kg/cnt or more, and the cooling temperature - Cool and solidify at 10 to 30°C to form at least a polyethylene terephthalate (A) layer and a polyester (B) layer.
) polyethylene terephthalate, characterized in that after the preform consisting of the layers is removed, it is biaxially stretched by blow molding at a stretching temperature of 80 to 130° C. at least 1.5 times in the machine direction and at least twice in the transverse direction. The present invention provides a method for producing a multilayer container with excellent gas permeability and impact resistance.

Polyethylene terephthalate (A) in the present invention usually has a dicarboxylic acid component of 80 mol% or more, preferably 90 mol% or more of terephthalic acid, and a glycol component of 80 mol% or more, preferably 90 mol% or more of ethylene glycol. Crystalline l: () is a plastic polyester resin. In addition, the remaining dicarboxylic acids are as follows:
Specifically, for example, isophthalic acid, diphenyl ether-
Aromatic dicarboxylic acids such as 4,4'-dicarboxylic acid, naphthalene-1,4- or 2,6-dicarboxylic acid, aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, undecadicarboxylic acid, etc. , alicyclic dicarboxylic acids such as hexahydroterephthalic acid, and other glycol components include propylene glycol, 1,4-
Examples include aliphatic glycols such as butanediol and neopentyl glycol, alicyclic glycols such as cyclohexane dimetatool, and aromatic dihydroxy compounds such as bisphenol A. As long as terephthalic acid and ethylene glycol are within the above range, a copolymer or a mixture of PET and other polyester may be used.

The polyester (B) mainly composed of isophthalic acid used in lamination with the PET (A) fit contains isophthalic acid in an amount exceeding at least 20 mol%, preferably 30 mol% or more, and more preferably 40 mol% or more. It is an amorphous or low-crystalline polyester consisting of a dicarboxylic acid component and a glycol whose main component is ethylene glycol. If the amount of isophthalic acid is less than 20 mol %, the effect of improving gas permeability resistance will be small, and the object of the present invention will not be met. Examples of dicarboxylic acids other than isophthalic acid include terephthalic acid, diphenyl-4,4'-dicarboxylic acid, diphenyl ether-4,4'-dicarboxylic acid, and naphthalene-1,4- or 2,6-dicarboxylic acid. Examples include aromatic dicarboxylic acids such as oxalic acid, succinic acid, aliphatic dicarboxylic acids such as succinic acid, sebacic acid, and undecadicarboxylic acid, and alicyclic dicarboxylic acids such as hexahydroterephthalic acid. In addition, glycol whose main component is ethylene glycol means that it contains 80 mol% or more, preferably 90 mol% or more of the glycol component, and other glycol components include propylene glycol, 1,4-butanediol,
Aliphatic glycol (such as neopentyl glycol) IMP
, alicyclic glycols such as cyclohexane dimetatool, aromatic dihydroxy compounds such as bisphenol A, and the like.

Specific examples of the polyester (B) include polyethylene isophthalate and polyethylene isophthalate/terephthalate copolymers in which the content of isophthalic acid in the dicarboxylic acid component is 20 mol% or more.

Also, the molecular weight is usually phenol/tetrachloroethane-1
Intrinsic viscosity [η] measured at 25°C in 1% by weight solvent
ranges from 0.6 to 1 to 1.3 d//g. Further, the polyester (B) is an amorphous or low-crystalline polyester, and although not particularly limited, it is preferable that the glass transition temperature (Tg) is 55 to 90°C.

Those with a Tg of less than 55°C have poor heat resistance, and those with a Tg of over 90°C may not be sufficiently stretched at a stretching temperature suitable for PET when laminated with the above-mentioned PET and biaxially stretched. . Note that the above Tg is measured using a differential scanning calorimeter (DS
C) at a temperature increase rate of 10° C./min.

PET (A) and polyester (B) used in the present invention
Heat-resistant stabilizers, weather-resistant stabilizers, lubricants, nucleating agents, pigments, dyes, and inorganic or organic fillers may be added to the composition without impairing the purpose of the present invention.

The method for manufacturing a multilayer container of the present invention includes
C1 Molten polyethylene terephthalate (A) preferably at 240 to 260°C and molten polyester (B) at 180 to 260°C, preferably 190 to 210°C
are laminated at a molding pressure (gauge pressure) of 20 kg/cJ or more, preferably 50 kg/ct& or more, and cooled and solidified at a cooling temperature of -10 to 30°C, preferably O to 10°C, to form at least polyethylene terephthalate (A
) layer and polyester (B)N, the stretching temperature is 80 to 130° C., preferably 90 to 110° C., at least 1.5 times, preferably 2 to 2.5 times and This is a method of biaxially stretching blow molding in the transverse direction at least 2 times, preferably 3 to 4 times.

Polyethylene terephthalate (A) and polyester (
When the melting temperature of B) is outside the above range, the melt viscosity is either too high or too low, resulting in poor moldability. If the forming pressure is less than 20 kg/c+a', the strength of polyethylene terephthalate (A) and polyester (B) will be low and the impact resistance will be poor. If the stretching temperature is less than 80°C, it will be cold stretched and the transparency will be significantly reduced. On the other hand, if the temperature exceeds 130°C, the uneven thickness of the container will become significant.The stretching ratio is 1.5.
If it is less than double (in the longitudinal direction) or less than twice (in the transverse direction), the gas permeability and impact resistance will be poor.

As a method for obtaining a preform, for example, polyethylene terephthalate (A) and polyester (B) are each melted using a plurality of extruders, and the polyethylene terephthalate (A) and polyester (B) are fed to a coextrusion multilayer die at the above melting temperature to form a coextrusion in a goo. Molding pressure 20 kg
/cJ or more, extrude the multilayer pipe, cool it at the cooling temperature, and then process the bottom and mouth parts, or use multiple injection devices to melt polyethylene terephthalate (A) and polyester (B), respectively. , a method of multi-layer injection molding in a single mold at the above-mentioned melting temperature, but in the case of injection molding, if the first injection molded material is cooled and solidified and then injection molded, the interlayer adhesion may be inferior. There is.

The multilayer container obtained by the method of the present invention is made of PET (A)
/As long as polyester (B) is a constituent element, the inner layer is P.
Either ET (A) or polyester (B) may be used, or polyester (B)/PET (A)/polyester (B), PET (A)/polyester with PET (A) or polyester (B) as an intermediate layer. (B)
/PET (A) The container may have a three-layer structure or more.

Furthermore, the thickness of the PET (A) layer and the polyester (B) layer is not particularly limited;
) The thickness of # is usually 100 to 600μ, preferably 2
00 to 500μ, and the thickness of the polyester (B) layer is usually 10 to 350μ, preferably 60 to 2
It is 00μ.

By the method of the present invention, the multilayer container obtained can be made of conventional PE.
Compared to a biaxially stretched container made of T alone, it has superior gas permeability, and the original rigidity, transparency, and mechanical strength of PET are not impaired at all, and it is also compatible with polyvinylidene chloride and saponified ethylene/vinyl acetate copolymers. It has superior interlayer adhesive strength compared to multilayer containers made of PET (A) and
Since the material and polyester (B) are laminated under pressure, it has excellent impact resistance and is suitable for beer containers, soft drink containers, alcoholic beverage containers, fruit juice beverage containers, and the like.

Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these examples in any way unless it goes beyond the gist thereof.

Example 1 PET-4 (trade name, three-layer PET J 055) dried at 150°C for 3 hours was melted at a molding temperature of 280°C using a 90mmφ extruder, and separately dried at 50°C for 24 hours. polyethylene isophthalate (Tg: 6
2°C, [η): 0.8dl/g, hereinafter abbreviated as PEl-2) was molded at a molding temperature of 230°C using a 40+nmφ extruder.
Melt at
0°C) and molding pressure (gauge pressure) 80
PET-1/PEl-2/PET- in kg/cnl
1 (thickness 1.2/1.2/1.2 mm) was extruded, cooled with water at 10℃, and the outer diameter was 2 mm.
A three-layer pipe with a diameter of 4.8 mm and a thickness of 3.6 mm was obtained. Next, the pipe was cut, one end was heated and melted to form a bottom part, and the other end was similarly heated and melted to form a plug part, thereby obtaining a preform having a total length of 16.5 cm and a weight of 50 g.

Next, a biaxial stretch blow molding machine (CORP
Using LB 01) manufactured by OPLAST, the blowing pressure was 2.
A multilayer container (PET-1/ P.E.
T-2/PF, T-1= 120/ 120/ 120
μ) was obtained. Next, the oxygen gas permeability of this multilayer container was measured using Oxide-3/7 (OX
When measured using a device (TRAN), it was 0.14 m1/day-bottle・aim, and carbon dioxide gas permeability was measured using a Permatran (Pl'! RMATRAN') C-IV device manufactured by MOCON. When measured, it was 2.0ml/day, bottle-
It was an ATM. Next, when the multilayer container was filled with O''c of water to determine the minimum height at which the multilayer container would break, it was found that the multilayer container did not break at a height of 2 m or less.

Further, delamination of each layer was not observed.

Comparative Example 1 The oxygen gas permeability of a multilayer container obtained under the conditions of a molding pressure of 10 kg/c+a instead of the molding pressure of 80 kg/cJA in Example 1 was 0.16 m1/day,
Bottle, ATM, carbon dioxide permeability is 2.1ml
/ Day-Bottle-ATM was good, but
In a drop strength test, delamination occurred at a drop of 0.2 m or less, and destruction occurred at a drop of 0.5 m.

Example 2 Using a two-layer injection molding machine, one injection molding machine produced 15
PET-3 (trade name, three-layer PE) dried at 0°C for 3 hours
TJ 135) was melted at a molding temperature of 280°C and separately dried at 50°C for 24 hours. Molding pressure 200 kg in preform mold
/CD two-layer injection molding, inner layer PET-3/PEI
-2 (thickness 1.6/1.6 mm), a two-layer preform with an outer diameter of 24 mm, 8 mmφ, and a thickness of 3.2 mm was obtained. Next, using a biaxial stretch blow molding machine (LB 01 manufactured by CORPOPLAST), it was lengthwise 2.5 cm under the conditions of a blowing pressure of 25 kg/cn+, a preform heating time of 15 seconds, and a stretching temperature of 115°C. A multilayer container (biaxially stretched 5 times and 4 times horizontally, with an internal volume of about 1.0 l)
PET-3/PEI-2=150/150μ
) was obtained. The oxygen gas permeability of this container is 0.09m1
/day-bottle-atm, and the carbon dioxide gas permeability was 0.8 ml/day-bottle-atm. In a drop strength test, it broke at 1.4 meters, but no delamination was observed.

Comparative example 2

Claims (1)

[Claims] (No 11230) Molten polyethylene terephthalate (A) at 300°C and molten polyester (B) consisting of glycol whose main component is ethylene glycol and a dicarboxylic acid component containing at least 20 mol% of isophthalic acid at 180 to 260°C. Molding pressure (gauge pressure)
After laminating at 20 kg/cd1 or more and cooling and solidifying at a cooling temperature of -10 to 30°C to obtain a preformed product consisting of at least polyethylene terephthalate (A) Fit and polyester (B) layers, the stretching temperature is 80 to 130°C. at least 1.5 times vertically and at least 2 times horizontally
A method for manufacturing a multilayer container characterized by double biaxial stretch blow molding.