JPH0451423B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a novel multilayer container with excellent gas barrier properties suitable for packaging various foods such as soft drinks, seasonings, and alcoholic beverages.

(Prior art) Linear polyester in general, and polyethylene terephthalate (hereinafter referred to as PET) in particular, has attracted attention as a material for various containers including bottles due to its excellent mechanical and chemical properties. Demand is growing as a new transparent container material to replace polyolefin containers such as polyethylene and polyvinyl chloride, which have been the mainstream of containers.

However, improvements in packaging technology and expansion of packaging applications require the addition of even higher functionality to PET containers.In particular, when considering alternative uses for metal cans and glass containers, it is necessary to use plastics to reduce weight and make them transparent. Although it has many advantages in terms of performance and safety, its lack of performance as a gas barrier has been a hindrance, limiting the expansion of its applications.

As a means for improving the gas barrier properties of such PET containers, bottles in which a gas barrier resin is laminated on PET are known. (JP-A-56-77143, JP-A-56-77144.) Gas barrier resins generally include ethylene vinyl alcohol copolymer, polyvinylidene chloride, and polyacrylonitrile resins.
Although the development of composite technology for these resins and PET is actively underway, technical problems in terms of adhesion and processability have not yet been completely resolved.

On the other hand, polyamide resin also has better gas barrier properties than PET, and is also superior in moldability, so it is thought that multilayer containers with excellent gas barrier properties can be obtained by laminating it with PET, and many attempts have been made. ing.

However, due to the inherent lack of adhesion between PET and polyamide, multilayer containers with good physical properties cannot be obtained without adhesives.
At present, a good adhesive suitable for this has not been found.

(Problems to be solved by the invention) Although it is highly predicted that a highly functional multilayer container with excellent gas barrier properties can be obtained by combining PET and polyamide, its practical application has not yet been achieved. The biggest reason for the delay is the problem of adhesion between these materials. This lack of adhesion can be said to be a fatal problem in terms of production technology, especially in cases such as deep-drawn containers that require sheet forming prior to container forming. Therefore, in order to complete a multilayer container by combining PET and polyamide, there is a strong need for the development of a technology to efficiently bond the two layers.

(Means for Solving the Problems) The present inventors have conducted extensive research in order to solve these problems and develop a multilayer container that has excellent rigidity and gas barrier properties, and can also provide transparency if necessary. As a result, the present invention was achieved.

That is, the present invention is a multilayer container characterized in that an adhesive layer made of a sulfon group-containing polyester is provided between a polyester resin layer containing PET or a polyester resin layer mainly composed of PET and a polyamide resin layer, and further comprising an adhesive layer made of a sulfon group-containing polyester. Sodium sulfoisophthalic acid and/or sodium sulfioterephthalic acid is added to the total acid components.
This is a multilayer container characterized by being made of polyethylene terephthalate copolymerized with 0.5 to 10 mol%.

The PET used in the present invention is a polyester whose main repeating unit is ethylene terephthalate, and the amount of phthalic acid, isophthalic acid, hexahydrophthalic acid, naphthalene dicarboxylic acid, adipic acid, and sebacin is 10 mol% or less of the total acid component. It is possible to use dicarboxylic acids such as acids, polyhydric carboxylic acids such as trimellitic acid and pyromellitic acid, or oxyacids such as P-oxybenzoic acid as the acid component.
1,2-propanediol in an amount of up to mol%;
Dihydric alcohols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, cyclohexanedimethanol, trimethylolpropane,
Polyhydric alcohols such as triethylolpropane and pentaerythritol can be used as the alcohol component. PET like this
is obtained by a conventional melt polycondensation reaction, and if necessary, the degree of polymerization can be further increased by a solid phase polymerization reaction.

Examples of the polyamide used in the present invention include polycapramide, polylaurinlactam, polyhexamethyleneadipamide, poly11-aminoundecanoic acid, poly-methaxylyleneadipamide, poly-paraxylyleneadipamide, etc. For example, these may be used alone, as a copolymer, or as a mixture.

The sulfon group-containing polyester used in the adhesive layer of the present invention is produced by a melt polycondensation reaction using a conventional method using sodium sulfoisophthalic acid or sodium sulfophoterephthalic acid as part of the acid component in the polyester. When a polymer with a higher degree of polymerization is required, a solid phase polymerization reaction can also be used.

The amount of copolymerization of sodium sulfoisophthalic acid and/or sodium sulfioterephthalic acid is 0.5 with respect to the total acid components in the polyester.
If the amount is mol % or more, it can have sufficient adhesion to the adjacent layers of PET and polyamide. In addition, at a copolymerization amount of 10 mol% or more, the adhesive force reaches saturation, and no further effects can be expected, and at the same time, hygroscopic effects due to sulfon groups occur, which also has a negative effect on the gas barrier properties of polyamide. do not have.

The basic properties of sulfonate group-containing polyester are:
It is desirable that the polyester be as close to PET as possible in terms of heat resistance, processability, etc., and this can be solved by using PET containing sulfone groups as the polyester.

The structure of the multilayer container according to the present invention is based on PET/polyester containing a sulfon group/polyamide as a basic unit, and may have a five-layer structure such as PET/polyester containing a sulfon group/polyamide/polyester containing a sulfon group/PET, or more if necessary. It can have a multilayer structure.

Such a multilayer container can be obtained by heating a coextruded multilayer sheet having the above structure and then subjecting it to deep drawing processing such as vacuum forming or pressure forming.

Further, bottle molding such as direct blow molding using coextrusion or biaxial stretch blow molding using a co-injected multilayer preform can also be used.

Furthermore, after cutting the coextruded multilayer pipe to a certain length, the ends of the pipe are heated and compression molded to form the mouth and weld the bottom.The resulting multilayer preform is then biaxially stretched and blow molded into a bottle. This method is also an effective method.

(Function) In the present invention, PET which has no mutual adhesive force at all
By providing an adhesive layer of sulfonated polyester with excellent adhesion to both PET and polyamide, PET and polyamide are integrated.
To obtain a gas barrier multilayer container that can be molded by any molding method without impairing its excellent properties.

Each of its constituent components is selected from materials with excellent secondary processing properties, making it extremely easy to form containers.Furthermore, when considering alternative uses for metal cans and glass containers, It can be said with certainty that this is an epoch-making container that has gas barrier properties that cannot be achieved with PET containers themselves.

(Example) Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

Example 1 An extreme clay having a composition of 98.5 mol% terephthalic acid, 1.5 mol% 5-sodiumsulfoisophthalic acid, and 100 mol% ethylene glycol, measured at 20 °C in a mixed solvent of equal weight of phenol/tetrachloroethane. A polyester containing 0.71 sulfone groups was obtained by a conventional melt polycondensation reaction.

Separately, PET and polymethaxylylene adipamide with an intrinsic viscosity of 1.0 (Mitsubishi Gas Chemical Reny 6001)
After thoroughly drying these materials, they were extruded through a multilayer die using three dedicated extruders for each to form PET (340 μ) / sulfon group-containing polyester (20 μ) / polymethaxylylene adipamide (80 μ). )/Sulfon group-containing polyester (20μ)/PET (340μ), a sheet with a thickness of 800μ was obtained. There was no thickness unevenness between each layer, and the adhesion was so strong that it could not be peeled off.

This sheet was heated at 120° C. for 5 seconds and then vacuum-formed into a cup with a diameter of 100 mm and a depth of 40 mm, resulting in a uniformly stretched transparent product. The carbon dioxide permeability of the film cut out from this container was measured.
Compared to 12.8cc・mm/24hr・m ²・atm of PET alone
It was confirmed that the fuel consumption had been significantly improved to 1.1cc・mm/24hr・m ²・atm.

Example 2 Using each resin used in Example 1, a multilayer blow molding machine produced PET (230 μ) / sulfon group-containing polyester (20 μ) / polymethaxylylene adipamide (40 μ) / sulfon group-containing polyester (20 μ) / 500ml with body wall structure of PET (190μ)
molded into a bottle.

The film cut out from the body of this bottle had strong adhesion between the layers, and the permeation rate of carbon dioxide was good at 1.7 cc·mm/24 hr·m ² ·atm.

(Effect of the invention) As is clear from the above, the requirements of the present invention are satisfied.
A multilayer container with a structure consisting of PET/sulfon group-containing polyester/polyamide as a basic unit has excellent interlayer adhesion and is also provided with excellent gas barrier properties.

Claims (1)

[Scope of Claims] 1. A multilayer container characterized by providing an adhesive layer made of sulfon group-containing polyester between polyethylene terephthalate or a polyester resin layer mainly composed of polyethylene terephthalate and a polyamide resin layer. 2 The sulfon group-containing polyester contains sodium sulfoisophthalic acid and/or sodium sulfioterephthalic acid relative to the total acid components.
The multilayer container according to claim 1, characterized in that it is polyethylene terephthalate copolymerized with 0.5 to 10 mol%.