JPH0460830B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a plastic multilayer container having a novel multilayer laminate structure and having a combination of excellent transparency, surface gloss and gas barrier properties.

(Prior art) Olefin-vinyl alcohol copolymers, especially saponified ethylene-vinyl acetate copolymers (ethylene-vinyl alcohol copolymers), are among the various thermoplastic resins that contain various gases such as oxygen and aromas. It is one of the resins with the best barrier properties (permeation resistance) against components, but even if this resin shows excellent gas barrier properties under low humidity conditions, it becomes extremely permeable to gases under high humidity conditions. The disadvantage is that it increases.

In order to improve this drawback, a moisture-resistant thermoplastic resin such as polyolefin or polyester is laminated on the olefin-vinyl alcohol copolymer layer, and the laminate is used as a cup, bottle, tube, or film-like container. is widely practiced.

(Problems to be Solved by the Invention) Among moisture-resistant thermoplastic resins used in multilayer containers, polypropylene has excellent transparency, mechanical strength, rigidity, and heat resistance compared to other olefin resins. Furthermore, although it has excellent hygienic properties and extraction resistance, it tends to crystallize easily during thermoforming. In addition, thermoplastic polyesters such as polyethylene terephthalate (PET) have higher transparency, surface gloss, and
Although it has excellent rigidity and impact resistance, it also tends to crystallize easily during thermoforming.

For this reason, bottles made by blow-molding the above multilayered structure in a molten state have a problem in that they become cloudy due to crystallization of polypropylene or polyester and lose transparency and surface gloss. For this reason, in the production of conventional multilayer containers, a preformed product having the above multilayered structure is produced in a supercooled state (amorphous state), and after this preformed product is reheated to a temperature that allows stretching, stretch blow molding is performed. We are adopting a method of doing so.

This type of stretch blow molding method requires a large number of steps and a large amount of equipment cost.
It would be desirable to produce plastic multilayer containers with a combination of excellent transparency, surface gloss and gas barrier properties by simple means.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a plastic multilayer container having a novel multilayer laminate structure and having an excellent combination of transparency, surface gloss and gas barrier properties.

(Means for Solving the Problems) According to the present invention, the outer layer is made of a copolyester of cyclohexylene dimethylene terephthalate/ethylene terephthalate (COPET), the inner layer is made of a propylene copolymer resin (CPP), and the copolymer of ethylene-vinyl alcohol is used as the outer layer. A multilayer container having a basic structure of a multilayer coextruded laminate with a polymer (EVOH) as an intermediate layer and an adhesive resin as an intervening layer between the inner and outer layers and the intermediate layer is provided.

The copolymerized polyester preferably contains 2 to 50 mol%, particularly 5 to 30 mol%, of cyclohexylene dimethylene units, and the propylene copolymer resin preferably contains 1 to 20 olefin units other than propylene. A propylene copolymer containing mol%, particularly 3 to 15 mol% is preferable.

(Function) In the present invention, an ethylene-vinyl alcohol copolymer is used as the intermediate layer as a resin with the best barrier properties (permeation resistance) against gases such as oxygen and aroma components, and a moisture-resistant thermoplastic resin is sandwiched. The moisture-resistant thermoplastic resin is characterized by the use of a combination of a cyclohexylene dimethylene terephthalate/ethylene terephthalate copolyester for the outer layer and a propylene copolymer resin for the inner layer.

In the present invention, by using a polyester obtained by copolymerizing cyclohexylene dimethylene terephthalate with ethylene terephthalate, the crystallization rate is slower than that of polyethylene terephthalate, which is a polymer of ethylene terephthalate alone, and the achieved crystallinity is also lower. This makes it possible to carry out blow molding in the molten state.

Another important feature of the present invention is that a propylene copolymer resin is used as the inner layer. That is,
By using a propylene copolymer resin, while maintaining the excellent hygienic properties and heat resistance of polypropylene, the crystallization rate is slower than that of polypropylene, and the achieved crystallinity is also lower. It is.

According to the present invention, excellent melt moldability is achieved by using a cyclohexylene dimethylene terephthalate/ethylene terephthalate copolymer polyester and a propylene copolymer resin as the moisture-resistant thermoplastic resin for sandwiching the ethylene-vinyl alcohol copolymer layer. Although excellent transparency can be obtained by preventing crystallization, it is also important to use the copolymerized polyester as the outer layer and the propylene copolymer resin as the inner layer. In other words, by using copolyester as the outer layer, excellent surface gloss, scratch resistance, and rigidity can be obtained as a container, and since the outer layer has a greater cooling effect after molding, it is possible to further suppress crystallization. , resulting in even greater transparency. On the other hand, polypropylene resin has excellent hygienic properties such as extraction resistance and flavor retention, so by using it as the inner layer, these advantages are brought to the multilayer container.

(Preferred Embodiment of the Invention) In FIG. 1 showing an example of a multilayer container of the present invention, this container has the shape of a bottle 1, a body 2,
It consists of a closed bottom part 3, a shoulder part 4 and a mouth part 5.
In FIG. 2 showing the cross-sectional structure of this vessel wall, the vessel wall includes the copolyester outer layer 6, the propylene resin inner layer 7, the ethylene-vinyl alcohol copolymer intermediate layer 8, and the inner and outer layers interposed between the inner and outer layers and the intermediate layer. It consists of adhesive resin layers 9 and 10.

The copolymerized polyester forming the outer layer is a cyclohexylene dimethylene terephthalate/ethylene terephthalate copolymer containing 2 to 50 mol%, preferably 5 to 30 mol% of cyclohexylene dimethylene terephthalate, which improves transparency and surface gloss. This is important from the viewpoint of impact resistance, etc. That is, if the amount of cyclohexylene dimethylene terephthalate is greater than the above range, the advantages of polyethylene terephthalate, such as excellent impact resistance and rigidity, will be lost, and the properties of polyester will not be fully maintained. On the other hand, if the amount is less than the above range, the above-mentioned advantages obtained by copolymerizing cyclohexylene dimethylene terephthalate with ethylene terephthalate, that is, transparency and surface gloss cannot be expected. The intrinsic viscosity [η] of this cyclohexylene dimethylene terephthalate/ethylene terephthalate copolyester is:
0.05 when measured at a temperature of 30°C in a mixed solvent of phenol and tetrachloroethane in a weight ratio of 60:40.
It is preferably 0.18/g to 0.18/g. If the intrinsic viscosity is greater than this range, the extrudability of the resin will be reduced, resulting in poor moldability; if it is smaller than the above range, the physical properties of the container will be poor.

The propylene copolymer resin contains olefin units other than propylene in an amount of 1 to 20 mol%, especially 3 to 20 mol%.
The content is preferably 15 mol%. When the amount exceeds this range, the transparency, mechanical strength, rigidity, heat resistance, etc. that polypropylene originally has will be impaired, and when it is less than the above range, the effects obtained by containing other olefin units will not be achieved.
This propylene copolymer resin is a random copolymer,
Any form of block copolymer may be used, but a random copolymer is more preferable. Examples of olefin units other than propylene include, but are not limited to, ethylene, butene-1, pentene-1,
1,4-methyl-pentene-1, hexene-1,
2-methyl-butene-1, octene-1, etc. can be used alone or in combination.

In the present invention, the ethylene-vinyl alcohol copolymer used for the intermediate layer has an ethylene content of 40 to 85 mol%, particularly from the viewpoint of gas barrier properties.
A copolymer obtained by saponifying 50 to 80 mol % of an ethylene-vinyl acetate copolymer to a degree of saponification of 90% or more, particularly 96% or more can be preferably used.

Since ethylene vinyl alcohol copolymer and propylene copolymer resin or cyclohexylene dimethylene terephthalate/ethylene terephthalate copolymer do not have adhesive properties, it is necessary to provide adhesive properties between them during coextrusion. Adhesive resins that can be used for this purpose include copolyesters, copolyamides, modified polyolefins, and the like, and are specifically as shown below.

As the copolyester, a copolyester containing ester units mainly composed of ethylene terephthalate units and in which at least one of the acidic component and the alcohol component is an acid component other than terephthalic acid or an alcohol component other than ethylene glycol is used.

In this copolyester, acid components other than terephthalic acid include isophthalic acid, naphthalene dicarboxylic acid, diphenylcarboxylic acid, 2,2-
Bis(4-carboxyphenyl)propane, bis(4-carboxyphenyl)methane, cyclohexanedicarboxylic acid (hexahydroterephthalic acid,
Examples of alcohol components other than ethylene glycol include propylene glycol, butanediol, neopentyl glycol, hexanediol, glycerol, and diethylene glycol. , triethylene glycol, tetraethylene glycol, dibutylene glycol, tributylene glycol, and the like. Of course, these acid components and/or alcohol components can be used alone or in combination of two or more.

Copolyamides include caprolactam/laurin lactam copolymer, caprolactam/hexamethylene diammonium adipate copolymer, laurin lactam/hexamethylene diammonium adipate copolymer, and hexamethylene diammonium adipate/hexamethylene diammonium sebacate copolymer. Examples include ethylene diammonium adipate/hexamethylene diammonium adipate copolymer, caprolactam/hexamethylene diammonium adipate/hexamethylene diammonium sebacate copolymer, and the like.

As the acid-modified olefin resin, any olefin resin graft-modified with an ethylenically unsaturated carboxylic acid or its acid anhydride can be used. Examples of the above-mentioned acids or acid anhydrides include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid,
Examples include maleic anhydride, itaconic anhydride, citraconic anhydride, and tetrahydrophthalic anhydride, among which maleic anhydride is particularly preferred.

Examples of the olefin resin that serves as the backbone polymer of the graft copolymer include low density, medium density, or high density polyethylene, isotactic polypropylene, propylene-ethylene copolymer, propylene-butene-1 copolymer, propylene-ethylene-
A butene-1 copolymer, an ethylene-vinyl acetate copolymer, an ionically crosslinked olefin copolymer (ionomer), or a blend of two or more thereof is used.

In the present invention, in addition to using the acid-modified olefin resin described above alone, at least one of the acid-modified olefin resins is substituted with an unmodified olefin resin so that the concentration of acid groups in the composition is within a certain range. It can be used in combination with at least one of the above, or it can be used in a blend of multiple types with various degrees of acid modification.

Alternatively, a mixture of an ethylene-vinyl alcohol copolymer having a content of vinyl acetate units of 10 to 30 mol % and a tackifier such as chromanindene resin, phenol resin, or xylene resin may also be used.

As the adhesive resin between propylene copolymer resin (CPP) and EVOH, acid-modified olefin resin such as maleic anhydride grafted polypropylene, and copolymer polyester (COPET) can be used.
The adhesive resin provided between EVOH and EVOH is preferably copolyamide.

The container can be manufactured by means known per se, except that the multilayered coextrudate described above is used. For example, to manufacture hollow containers such as bottles, the multilayered preform is coextruded using a multilayer die, and this preform is sandwiched between a pair of split molds.
A fluid is blown into the inside and formed into the shape of a bottle or the like. Alternatively, a multilayer film or sheet is produced by passing it through a multilayer die, and after heating this film or sheet to a melting temperature, vacuum forming,
A cup-shaped or tray-shaped container can be formed by applying a melt sheet forming operation such as air pressure forming, plug assist forming, or male molding.

(Effects of the Invention) According to the present invention, cyclohexylene dimethylene terephthalate/ethylene terephthalate copolyester is used as the outer layer, propylene copolymer resin is used as the inner layer, ethylene-vinyl alcohol copolymer is used as the intermediate layer, and adhesive resin is used as the inner and outer layers. By having a new multilayer laminated structure with an intermediate layer as an intervening layer, blow molding in the molten state is possible, the manufacturing process is reduced, and a multilayer container with high gas barrier properties can be obtained. .

(Example) The invention is illustrated in the following example.

Example Inner layer extruder and outer layer extruder with a built-in full-flight screw with a diameter of 65 mm and effective length of 1430 mm, middle layer extruder with a built-in full-flight screw with a diameter of 50 mm and an effective length of 1100 mm A copolymerized polyester containing an ethylene-propylene copolymer with an inner layer containing 8 mol% of propylene and an outer layer containing cyclohexanedimethanol of about 18 mol% of the alcohol component was prepared using a machine, an extruder for adhesives, and a 5-layer die. , the intermediate layer is an ethylene-vinyl alcohol copolymer containing about 68 mol% of vinyl alcohol, and the adhesive layer interposed between the intermediate layer and the inner and outer layers and the outer layer is an ethylene-vinyl acetate copolymer containing 25 mol% of vinyl acetate. A multilayer bottle of 4 types and 5 layers, which is a composition containing a rosin adhesive, has an average wall thickness of 500μ, inner layer: adhesive layer: middle layer: adhesive layer:
The outer layer was molded so that the thickness ratio was 30:1:2:1:10.

Using the obtained bottle body wall as a test piece, the peel strength by T-peel type peeling was 800 g/15 mm width at the interface between the copolymerized polyester and the adhesive layer, and between the ethylene-vinyl alcohol copolymer layer and the adhesive layer. and the interface between the polypropylene layer and the adhesive layer had a width of 1500 g/15 mm and a width of 1200 g/15 mm, respectively.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a multilayer container according to the present invention;
FIG. 2 is an enlarged sectional view of the body wall of the multilayer container of FIG. 1. 1...bottle, 2...body, 3...bottom, 4...
Mold part, 5... Mouth part, 6... Outer layer, 7... Inner layer, 8...
...Intermediate layer, 9,10...adhesive resin layer.

Claims (1)

[Scope of Claims] 1 Cyclohexylene dimethylene terephthalate/ethylene terephthalate copolymer polyester as an outer layer, a propylene copolymer resin as an inner layer, an ethylene-vinyl alcohol copolymer as an intermediate layer, and an adhesive resin as an inner layer and an intermediate layer. A multilayer container whose basic structure is a multilayer coextruded laminate with an intervening layer. 2. The multilayer container according to claim 1, wherein the copolymerized polyester is a copolymerized polyester containing 2 to 50 mol% of cyclohexylene dimethylene units. 3. The multilayer container according to claim 1, wherein the propylene copolymer resin is a propylene copolymer containing 1 to 20 mol% of olefin units other than propylene. 4. A bottle-shaped multilayer container made by blowing the coextruded laminate of 4 types and 5 layers according to claim 1 in a molten state.