JPH0825220B2 - Multi-layer container - Google Patents

Description

TECHNICAL FIELD The present invention relates to a multilayer container, and more particularly to a multilayer container excellent in transparency, interlayer adhesion strength, gas barrier property and mechanical strength.

[Conventional technology]

Conventionally, glass has been widely used as a container for soft drinks such as carbonated drinks, beer, liquors such as sake, seasonings, edible oils, cosmetics, detergents, etc.However, glass containers are easy to handle and safe. It has the disadvantage of.

In order to eliminate these drawbacks, conversion from glass containers to various plastic containers is in progress. In particular, biaxially stretched and oriented containers made of a resin mainly composed of polyethylene terephthalate are widely used in the fields of seasonings, soft drinks, detergents, cosmetics, etc., which require transparency.

However, a biaxially stretched and orientated container made of a thermoplastic polyester resin mainly composed of polyethylene terephthalate does not necessarily have perfect performance, and the content to be filled is a beverage product which particularly requires a high gas barrier property. In some cases, their gas barrier properties to oxygen and carbon dioxide are insufficient.

Heretofore, the following methods have been known for producing a multi-layer container having a gas barrier property.

In order to produce a multi-layer container having gas barrier properties,
A single mold using an injection molding machine having an injection cylinder for a thermoplastic polyester resin and an injection cylinder for a polyamide resin containing a metaxylylene group (hereinafter abbreviated as "MX nylon") which is a thermoplastic gas barrier resin. In a single mold clamping operation, molten thermoplastic polyester resin and MX nylon are continuously and sequentially injected in the order of thermoplastic polyester resin and MX nylon, and the thermoplastic polyester resin is applied to the inner and outer surface layers and MX nylon. An attempt to make a three-layer structure in which is a core layer has already been disclosed. (JP Sho
57-128516, JP-A-57-128520) In this case, when the layer of MX nylon is made thin, that is, when the injection amount of MX nylon is reduced, there is a drawback that the layer of MX nylon is not formed on the entire body of the container. is there.

Also, first inject the thermoplastic polyester resin, then MX
By injecting the thermoplastic polyester resin again after injecting nylon, the thermoplastic polyester resin is surrounded by two inner and outer surface layers and one central layer, and MX nylon is surrounded by the inner and outer surface layers and the central layer. A five-layer structure with two intermediate layers, resulting in a two-layer MX nylon layer, which can be made extremely thin, and a method of making the injection amount of MX nylon less than the above method is also disclosed. There is. (JP-A-60-240409, JP-A-61-108542) Further, JP-B-60-16326 is also disclosed as a method for reducing the injection amount of the gas barrier resin.

In this method, first, a part of the thermoplastic polyester resin is injected, and then the thermoplastic polyester resin and the gas barrier resin are simultaneously injected.

In this case, the gas barrier layer is located outside the center 3
A layer cross-section structure is obtained.

[Problems to be solved by the invention]

However, gas barrier resins, including MX nylon, generally have poor affinity with thermoplastic polyester resins and the like, so the interlayer adhesion strength in the multilayer container obtained by the above method is low, and as a result, the force that deforms the container from the outside However, when internal pressure is applied like a container filled with impact force and a liquid in which carbon dioxide gas is dissolved, there is a drawback that delamination is likely to occur in a multilayer container.

The delaminated container looks somewhat white and its appearance is unfavorable because its part separates into two films.

As a measure for preventing delamination, it can be considered that the gas barrier layer is a mixed resin layer of resin A and resin B.

However, in this case, when the ratio of the resin B in the mixed resin is increased, the container becomes cloudy or pearly and the adhesive strength is not improved.

On the other hand, when the proportion of the resin A is increased, the interlayer adhesion strength is improved, but in this case, there is a problem that haze is generated in a milky white or pearl shape which is a general drawback of resin mixing. It is an object of the present invention to improve such conventional problems and obtain a multi-layer container having improved interlayer adhesion without lowering gas barrier properties, mechanical properties, and transparency.

[Means for solving problems]

As a result of intensive studies by the present inventors, when a mixed resin layer is formed as a gas barrier layer, such a problem occurs due to the mixed state of the resin. It was found that this problem can be solved by the above, and the present invention was reached.

That is, according to the present invention, at least the mouth opening end portion has a single structure made of a thermoplastic resin (resin A), and at least the body thin portion has a resin A and a thermoplastic gas barrier resin other than the resin A ( A container having a multilayer structure in which one or more mixed resin layers made of a resin mixture mixed with resin B) and more resin A layers than the mixed resin layers are alternately laminated and biaxially stretched and oriented. In the above-mentioned mixed resin layer, the ratio of the resin A particles and the resin B particles having a major axis of 10 μm or less in total is 10% or less in total.

When the present inventors produce a container by biaxially stretch-blow molding a parison having a mixed resin layer composed of the resin A and the resin B, the mixed resin layer is sufficiently mixed with the resins A and B. The inventors have conducted further studies and found that a multilayer container having less haze and improved interlaminar adhesive strength can be obtained in the absence (hereinafter referred to as "coarse mixed state").

Generally, when molding a multi-layer parison that is a precursor of a container, the mixing is sufficiently performed in melt mixing in which two kinds of resins are mixed by using an ordinary mixing screw, and the mixed layer of the parison after molding is sufficient. In the above, the resin with a small amount is present in a state of being scattered in an island shape with a fine particle diameter with respect to the resin with a large amount.

It was found that when this parison was stretched by blow molding to have an area ratio of 5 to 15 times, the island-shaped particle diameter became a fine particle diameter of 10 μm or less in major axis, which was a cause of haze.

When molding the above-mentioned multilayer parison, if the mixing of the resins is in a roughly mixed state, there is almost no resin having such a fine particle diameter in the mixed resin layer of the container after blow molding, and therefore the haze is very high. It turned out to be less.

As a result, the haze (JIS
In order to reduce the measured value based on K6714) to 15% or less, the resin A particles and the resin B particles in the mixed resin layer of the container have a major axis of 10
It has been found that the proportion of particles present in the range of μm or less needs to be 10% or less in total.

In order to achieve such a rough mixed state, it is important not to knead the two resins and to make them complicated.
Examples of the method include a method of mixing with a static mixer and a method of mixing with a cylinder having a screw with a low kneading effect and by adding a lubricant such as stearic acid or a stearate. explain.

FIG. 1 is a schematic view showing an example of a molding apparatus for a parison which is a precursor of a multilayer container of the present invention.

This device has a cylinder 1 for resin A and a cylinder 2 for resin B, like a normal device, and the resin A and the resin B melted in each cylinder pass through a gate 13 and a cavity in the mold 8 is passed through. Injecting resin A alone or a mixed resin composed of resin A and resin B into 14
In order to form a mixed resin layer composed of resin A and resin B, a switching valve 15, a connecting pipe 7 and a static mixer are further added.
Have 11.

In this device, the switching valve 15 has the resin A nozzle 5
When the resin A and the in-mold flow path 9 are connected to each other, the resin A can be injected into the cavity 14 as in the conventional method.

On the other hand, by switching the switching valve 15, the resin A nozzle 5
And the connecting pipe 7 are in communication with each other, by applying back pressure from the resin A cylinder 1 and the resin B cylinder 2 at the same time, the resin A nozzle 5 and the molten resin A3 flowing through the connecting pipe 7 Molten resin B4 passing through the resin B nozzle 6
After being roughly mixed in the static mixer 11, they can be injected into the cavity 14 through the mixed resin in-mold channel 10 and the gate 13.

When the resin A, then the mixed resin, and finally the resin A are injected in this order using the apparatus shown in FIG. 1, a parison having a five-layer cross-sectional structure is obtained as shown in the schematic view of FIG.

FIG. 2 is a schematic view of another injection molding device. The apparatus shown in FIG. 2 has a cylinder 1 for resin A and a cylinder 16 for mixed resin in which resin A and resin B are roughly mixed. Using this apparatus, resin A3 is first injected and then mixed. resin
When 17 and resin A3 are simultaneously injected, a three-layer structure parison as shown in the schematic view of FIG. 4 is obtained.

The content weight ratio of the resin A and the resin B in the crude mixed resin layer which is the gas barrier layer can be set in a wide range, but from the adhesiveness with the resin A layer, 1: 9 to 9: 1 is suitable.

The thickness of the mixed resin layer in the container after blow molding can be set in a wide range, but 20 to 100 μm is suitable.

The resin A used in the present invention includes thermoplastic polyester resin, polyolefin resin, polycarbonate,
Among them, polyacrylonitrile, polyvinyl chloride, polystyrene and the like can be mentioned, and among them, the thermoplastic polyester resin is preferable.

Examples of the resin B used in the present invention, that is, the thermoplastic gas barrier resin include MX nylon, saponified ethylene / vinyl acetate copolymer resin, polyacrylonitrile copolymer resin, polyvinylidene chloride resin, and the like. Is preferred. A thermoplastic polyester resin, especially a combination of polyethylene terephthalate and MX nylon is most preferable, because the transparency of the resin is
This is because they are all excellent in mechanical strength, injection moldability, and stretch blow moldability.

The thermoplastic polyester resin is usually an acid component of 80
A polyester in which terephthalic acid is terephthalic acid in an amount of not less than 90% by mole, preferably 80% by mole or more, and preferably not less than 90% by mole of a glycol component is ethylene glycol is used. Acid, diphenyl ether-4,4-dicarboxylic acid, naphthalene-1,4
Alternatively, 2,6-dicarboxylic acid, adipic acid, sebacic acid, decane-1,10-dicarboxylic acid, hexahydroterephthalic acid, and other glycol components include propylene glycol, 1,4-butanediol and neopentyl. Examples thereof include glycol, diethylene glycol, cyclohexanedimethanol, and 2,2-bis (4-hydroxyethoxyphenyl) propane.

Further, a polyester resin containing P-oxybenzoic acid or the like as the oxyacid can be exemplified.

The intrinsic viscosity of these thermoplastic polyester resins is 0.
A value of 55 or more is suitable, and preferably 0.65 to 1.4.

When the intrinsic viscosity is less than 0.55, it is difficult to obtain the multilayer parison in a transparent amorphous state, and the mechanical strength of the obtained container is insufficient.

On the other hand, MX nylon is metaxylylenediamine alone or mixed xylylenediamine containing metaxylylenediamine and paraxylylenediamine of 30% or less of the total amount and α, ω-linear aliphatic having 6 to 10 carbon atoms. It means a polymer containing at least 70 mol% or more of a constitutional unit obtained from dicarboxylic acid.

Examples of these polymers include homopolymers such as polymeta-xylylene adipamide (hereinafter abbreviated as "N-MXD6"), poly-meta-xylylene sebacamide, poly-meta-xylylene speramide, meta-xylylene / para. Examples thereof include copolymers such as xylylene adipamide copolymer and metaxylylene / paraxylylene speramide copolymer, and homopolymers or copolymers thereof.

Furthermore, a part of the raw material of the above homopolymer or copolymer,
Aliphatic diamines such as hexamethylenediamine, cycloaliphatic diamines such as piperazine, aromatic diamines such as para-bis- (2-aminoethyl) benzene, aromatic dicarboxylic acids such as terephthalic acid, ε-caprolactam. Lactams like, ω-aminoheptanoic acid like ω
-Substituted with an aromatic aminocarboxylic acid such as -aminocarboxylic acid or para-amibenzoic acid can also be exemplified.

In addition, for example, nylon 6, nylon
Polymers such as 66, nylon 610 and nylon 11 may be contained.

The above MX nylon has a relative viscosity of 1.5 or more, preferably 2.0 to 4.0.

On the other hand, examples of the thermoplastic resin other than these gas barrier thermoplastic resins include thermoplastic polyester resins, polyolefin resins, polycarbonate, polyacrylonitrile, polyvinyl chloride, polystyrene, and the like. Resins are preferred.

In the present invention, one or both of the resin A and the resin B may contain a colorant, an ultraviolet absorber, an antistatic agent, if necessary.
Antioxidants, lubricants, nucleating agents and the like can be added within a range that does not impair the object of the present invention.

The multi-layer container of the present invention is produced by biaxially stretching a parison at a temperature of 70 to 130 ° C in an axial direction of 1 to 4 times, in a circumferential direction of 2 to 7 times, and an area stretching ratio of 5 to 15 times. However, since the resin B, which is a thermoplastic gas barrier resin, absorbs moisture in the content and whitens in the unstretched state, or the gas barrier property deteriorates, at least the unstretched portion of the mouth opening end portion. Must be formed from a single layer of resin A.

The amount of the resin B used in the entire container can be selected in the range of 1 to 10% by volume, but since the gas barrier resin is generally expensive, it may be at least the minimum amount that can provide the required gas barrier performance. . The number of mixed resin layers is not limited, but 1-3 layers are suitable in view of productivity.

The wall thickness of the multi-layer container is 200 to 500 μm, preferably 250 to 4
It is 50 μm.

[Operation and effect of the invention]

According to the present invention, the presence of the crude mixed resin layer in the specified state between the resin A as the inner and outer surface layers makes it possible to obtain a multilayer container having excellent interlayer adhesive strength and less haze.

The multi-layer container of the present invention is excellent in interlayer adhesion strength, transparency, gas barrier property, and mechanical strength, and is an epoch-making thing that has never been seen before.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to examples. The method of measuring the characteristics and the like adopted is as follows.

(1) Polyester resin intrinsic viscosity [η]: Phenol / tetrachloroethane = 6/4 (weight ratio) mixed solvent used, measurement temperature 30 ° C. (2) Polyamide resin relative viscosity [ηrel.]: Resin 1 g, 96 sulfuric acid 100 ml (3) Haze: [diffuse transmittance (light quantity) / total transmittance (light quantity)] × 100 JIS K-6714 or ASTM D883-62T.

Digital Density Meter NDH-2D manufactured by Nippon Denshoku Industries Co., Ltd. (4) Interlayer adhesion strength: peeling direction: 180 degrees Peeling speed: 300mm / min Specimen size: 25mm width x 170mm length (5) Oxygen permeability: Oxygen permeability Was measured in accordance with ASTM D3985 using OXTRAN100 manufactured by Modern Control.

Measurement temperature 20 ℃, inner relative humidity 100%, outer relative humidity 65
% (6) Content ratio of particles having a major axis of 10 μm or less in the mixed resin layer: A dye that dyes only N-MXD6 in the mixed resin layer (manufactured by Nippon Kayaku Co., Ltd., trade name: Kyanol Red NB No Q02
705) and the size and surface area of the resin particles were measured with a microscope, and the ratio of the layer area to the total area was shown as a percentage.

Examples 1 and 2 Resin A is polyethylene terephthalate (hereinafter abbreviated as "PET") having an intrinsic viscosity of 0.75, and mixed resin is N-MXD6 having a relative viscosity of 2.1 as the resin A (PET) and the resin B described above. The equipment shown in Fig. 2 is used (the injection molding machine is manufactured by Meiki Co., Ltd., model: M200P).
The parison was molded using (DM-MJ was used).

As the mixed resin cylinder 16, a screw having a bad kneading effect described below was used.

Specifications of screw used Outer diameter: 40 mmφ, Pitch: 40 mm Number of threads: 19, Compression ratio: 2.3 As a mixed resin, the mixing ratio (weight ratio) of PET and N-MXD6 is 7: 3 (Example 1) or 3: 7 (Example 2).

In order to improve the operability of the mixed resin cylinder in FIG. 2, 0.1% by weight of calcium stearate was added to the mixed resin.

The order of injection was such that only the resin A was injected first, and then the mixed resin and the resin A were simultaneously injected.

The injection amount of each is shown as a ratio to the cavity volume as follows.

First injection amount Resin A: 70% Second injection amount Mixed resin: 15% Resin A: 15% The temperature conditions at the time of injection are as follows.

Injection cylinder for resin A: 270 ℃ Injection cylinder for mixed resin: 260 ℃ Resin flow path in mold: 270 ℃ Mold cooling water: 15 ℃ With the above injection, the wall thickness of about 4.5 mm shown in the schematic diagram of Fig. 4
As a result, a parison having a three-layer body and weighing about 59 g was obtained.

This parison was heated by a quartz heater using a biaxial stretch blow molding machine until the surface temperature of the parison reached 95 ° C, and then transferred into a blow mold, and the transfer speed of the draw rod was 20.
Biaxial stretch blow molding under conditions of cm / sec, stretching blow pressure 20 kg / cm ² G, total length 300 mm, outer diameter 90 mmφ, inner volume 1500 ml,
A bottle-shaped hollow multi-layer container having a body thickness of 400μ was obtained.

The thickness ratio of each layer in the 3 layer part of the body is
Side: mixed resin layer: outer PET layer = 2: 2: 6.

The oxygen transmission rate of the obtained multilayer container was measured, and a test piece was cut out from the body to measure the content ratio of particles having a major axis of 10 μm or less in the mixed resin layer, haze and interlayer adhesion strength. The obtained results are shown in Table 1.

Comparative Examples 1 and 2 For comparison, the following mixed resin cylinder was used, which has a better kneading effect than the screw of the crude mixed resin cylinder used in Examples 1 and 2.

Specifications of screw used Outer diameter: 40 mmφ, Pitch: 30 mm Number of ridges: 25, Compression ratio: 3.03 Calcium theearate was not added.

The resins used were all the same as those used in Examples 1 and 2, and as a mixed resin, the compounding ratio (weight ratio) of PET and N-MXD6 was 7: 3 (Comparative Example 1) or 3: 7 ( It was set as Comparative Example 2).

Other conditions were the same as in Examples 1 and 2. The results obtained are summarized in Table 1.

Comparative Examples 3 to 4 For comparison, a screw described below, which has a better kneading effect than Examples 1 and 2 and a poorer kneading effect than Comparative Examples 1 and 2, was used.

Specifications of screw used Outer diameter: 40 mmφ, pitch: 35 mm, number of ridges: 22, compression ratio: 3.03 Calcium theearate was reduced to 0.01% by weight to improve the kneading effect from Examples 1 and 2.

The resins used were all the same as those used in Examples 1 and 2, and as the mixed resin, the mixing ratio (weight ratio) of PET and N-MXD6 was 7: 3 (Comparative Example 3) or 3 :. 7 (Comparative Example 4).

 Other conditions are the same as in Examples 1 and 2.

 The results are summarized in Table 1.

Comparative Example 5 For comparison, the same N-MXD6 as that used in Examples 1-2 was used instead of the mixed resin, and the other conditions were the same as those in Examples 1-2, and a three-layer structure parison was obtained. It was The ratio of the thickness of each layer in the three-layered body part after stretch blow is
PET layer: N-MXD6 layer: outer PET layer = 6: 2: 2.

 The test results obtained are shown in Table 1.

However: Mixed state means that the major axis in the mixed resin layer is 10μ
It means the content ratio of particles of m or less.

The adhesive strength means the adhesive strength between the inside and the outside of the resin A layer located with the mixed resin layer interposed therebetween.

[Brief description of drawings]

1 and 2 are schematic views showing an example of an apparatus for molding a parison which is a precursor of a multi-layer container according to the present invention, and FIGS. 3 and 4 are precursors of the multi-layer container according to the present invention. It is a schematic diagram of the cross section of the parison which is a body.

 ─────────────────────────────────────────────────── --Continued from the front page (56) Reference JP-A-57-128516 (JP, A) JP-A-57-128520 (JP, A) JP-A-60-240409 (JP, A) JP-A 61- 108542 (JP, A) JP 62-52021 (JP, A) JP 51-68373 (JP, A) JP 60-16326 (JP, B2)

Claims (2)

[Claims] 1. At least an opening end portion of a mouth portion has a single structure made of a thermoplastic resin (resin A), and at least a thin portion of a body portion has a resin A and a thermoplastic gas barrier resin other than the resin A ( A container having a multilayer structure in which one or more mixed resin layers made of a resin mixture mixed with resin B) and more resin A layers than the mixed resin layers are alternately laminated and biaxially stretched and oriented. In the above multi-layer container, the ratio of the resin A particles and the resin B particles present in the mixed resin layer in the form of particles having a major axis of 10 μm or less is 10% or less. 2. A multilayer container according to claim 1, wherein the resin A is a thermoplastic polyester resin and the resin B is a metaxylylene group-containing polyamide resin.