JP5428863B2 - High gloss multi-layer plastic container - Google Patents

Description

  The present invention relates to a multilayer plastic container having an excellent appearance and a deep high surface gloss.

Conventionally, multilayer plastic containers have been widely used as packaging containers for storing various contents such as cosmetics, toiletries, various beverages, seasonings and foods.
In this multi-layer container, various plastic materials are used in combination in order to satisfy various characteristics required for moldability, manufacturing cost, and storage of contents. As the resin constituting the outer layer of the multilayer plastic container, polyester resins such as polyethylene terephthalate (PET), polyamide resins, polyolefin resins such as polyethylene and polypropylene are generally used. On the other hand, a linear olefin resin such as polyethylene or polypropylene is often used for the inner layer of the container from the viewpoint of moldability, hygienic characteristics, and cost.

  It has also been known for a long time to provide an oxygen barrier resin layer in a multilayer plastic container in order to prevent permeation of oxygen through the container wall. As such a gas barrier resin, for example, ethylene vinyl alcohol copolymer (saponified ethylene-vinyl acetate copolymer), polyamide, polyvinylidene chloride resin, polyvinyl alcohol, fluororesin and the like are used.

Various layer configurations of multilayer plastic containers combining these resins have also been proposed. For example, a multilayer plastic container having a layer structure in which (1) a polyester-based resin, (2) an adhesive resin, and (3) a polyolefin-based resin are laminated in order from the outer surface side of the container is known. (For example, see Patent Documents 1 and 2)
Further, a multilayer plastic having a layer structure in which (1) polypropylene resin, (2) adhesive resin, (3) gas barrier resin, (4) adhesive resin, and (5) polypropylene resin are laminated in order from the outer surface side of the container. Containers are also known. (For example, see Patent Documents 3 and 4)
Japanese Patent Laid-Open No. 6-79842 JP-A-6-106606 JP-A-5-8355 Japanese Patent Laid-Open No. 5-42641

However, in the multilayer plastic container having such a layer structure, the resin constituting each layer of the container has a difference in molding characteristics such as a molten resin viscosity. Therefore, for example, when a hollow container is manufactured by blow molding after forming a multi-layer parison, an appearance defect such as a ripple pattern may occur between the resin outer layer on the container surface and between each layer. In addition, hue defects such as non-uniform hues and streak patterns may occur. Accordingly, it has not been possible to realize a multilayer plastic container having an excellent appearance, such as a container having a high gloss and a deep uniform metallic color.
In order to finish the container surface smoothly, if the roughness of the inner surface of the mold is reduced, an air trap (transfers the mold shape by entraining air between the mold and the surface of the molded product when molding the container. The phenomenon that the part which is not done remains) occurs. As a result, there is a problem that molding defects such as partial unevenness occur on the surface of the container.

  Accordingly, the present invention provides a multilayer plastic container that has a uniform and smooth surface, a high gloss and deep color tone, and has an excellent appearance, eliminating the problems inherent to such a multilayer plastic container. For the purpose.

  The inventors reduced the surface roughness of the plastic resin outer layer, set the unevenness of the interface between the resin outer layer and the inner adhesive resin layer to 15 μm or less, and the interface between the adhesive resin layer and the inner colored polyolefin resin layer interface. It has been found that the above-mentioned problems can be solved by making the irregularities 15 μm or less, and the present invention has been completed.

That is, in the present invention, the following configurations 1 to 8 are adopted.
1. In a multilayer plastic container having (1) a transparent ethylene-vinyl alcohol copolymer resin outer layer , (2) a transparent adhesive resin layer, and (3) a colored polyolefin resin layer in order from the outer surface side, a transparent ethylene-vinyl alcohol copolymer resin surface roughness of the outer layer is Ra ≦ 0.2 [mu] m, by the resin constituting the multilayer plastic container layers is adjusted so as to satisfy the following formula (a) and (b) simultaneously, wherein (1) a transparent ethylene -Unevenness at the interface between the vinyl alcohol copolymer resin outer layer and the (2) transparent adhesive resin layer is 15 µm or less, and the unevenness at the interface between the (2) transparent adhesive resin layer and the (3) colored polyolefin resin layer is 15 µm. High gloss multi-layer plastic container characterized by being configured as follows:
(A) The shear stress (unit: KPa) of the resin constituting each layer is “(3) colored polyolefin resin−55 ≦ (2) transparent adhesive resin ≦ (1) transparent ethylene-vinyl alcohol copolymer resin + 70”. Satisfying;
[Here, the shear stress of the resin is based on JIS K7199, the pellet before the resin used is melted at a temperature of 210 ° C. and a shear rate of 50 / sec, the orifice of the resin extrusion part is L = 10 mm, D = It is a value measured under the condition of a diameter of 1 mm. ]
(B) The melt flow rate (MFR) (g / 10 min) of the resin constituting the transparent adhesive resin layer satisfies “1.0 ≦ MFR ≦ 2.5”.
[Here, the melt flow rate of the resin is a value obtained by measuring pellets of the resin to be used before melting at a temperature of 190 ° C. and a load of 2.16 kg in accordance with JIS K7210. ]
2. (3) The high gloss multilayer plastic container according to 1, wherein the colored polyolefin resin layer contains a luster pigment .
3. (3) The high gloss multilayer plastic container according to 1 or 2, wherein the colored polyolefin resin layer is composed of a block polypropylene resin .
4). (3) The highly glossy multilayer plastic container according to 1 or 2 , wherein the colored polyolefin resin layer is composed of a high density polyethylene resin .
5. The multilayer plastic container has the following layer structure in order from the outer surface side: (1) a transparent ethylene-vinyl alcohol copolymer resin outer layer, (2) a transparent polypropylene adhesive resin layer, (3) a colored polypropylene resin layer containing a bright pigment, ( 4) The high-gloss multilayer plastic container according to any one of 1 to 3, which has a polypropylene resin layer not containing a luster pigment .
6). The multilayer plastic container has the following layer structure in order from the outer surface side: (1) a transparent ethylene-vinyl alcohol copolymer resin outer layer, (2) a transparent polyethylene adhesive resin layer, (3) a colored polyethylene resin layer containing a bright pigment, ( 4) The high-gloss multilayer plastic container according to any one of 1, 2 and 4, which has a polyethylene resin layer not containing a luster pigment.
7). 7. The high gloss multilayer plastic container according to any one of 1 to 6, wherein the multilayer plastic container further has a polyolefin resin inner layer .
8). The high gloss according to any one of 1 to 7, wherein the total thickness of the (1) transparent ethylene-vinyl alcohol copolymer resin outer layer and the (2) transparent adhesive resin layer is 30 to 200 µm. Multi-layer plastic container.

  According to the present invention, it is possible to efficiently obtain a multi-layer plastic container having a smooth surface without appearance defects such as a ripple pattern and foaming and a uniform metallic color tone with high gloss and depth without causing molding defects.

It is a cross-sectional schematic diagram which shows an example of the layer structure of the high gloss multilayer plastic container of this invention.

Explanation of symbols

A Transparent ethylene-vinyl alcohol copolymer resin outer layer B Transparent adhesive resin layer C Colored polyolefin resin layer containing bright pigment D Polyolefin resin layer not containing bright pigment

In the present invention, the layer structure of the multilayer plastic container is (1) a transparent ethylene-vinyl alcohol copolymer resin outer layer (hereinafter sometimes simply referred to as “transparent plastic resin outer layer” ) in order from the outer surface side . It shall have a transparent adhesive resin layer and (3) a colored polyolefin-based resin layer, and the surface roughness of the transparent plastic resin outer layer should be Ra ≦ 0.2 μm, and the shear stress of each resin constituting the container By adopting means such as adjustment, the unevenness at the interface between (1) the transparent plastic resin outer layer and (2) the transparent adhesive resin layer is 15 μm or less, and (2) the transparent adhesive resin layer and (3) the colored polyolefin resin. The unevenness of the layer interface is 15 μm or less.

Here, terms used in the present invention are defined as follows.
(Surface roughness Ra of the container)
In the present invention, (1) the surface roughness Ra of the transparent plastic resin outer layer is in accordance with JIS B0601, and the flat portion of the container wall other than the nozzle portion is measured per 4 mm in length using a stylus type roughness measuring instrument. It means the surface roughness (Ra) measured and obtained as an arithmetic average.
(Roughness of the resin layer interface)
Container wall other than the nozzle part is used to measure (1) the outer layer of the transparent plastic resin, (2) the irregularities at the interface of the transparent adhesive resin layer, and (2) the irregularities at the interface of the transparent adhesive resin layer and (3) the colored polyolefin resin layer A portion having a large interfacial irregularity is sampled from the flat portion. Subsequently, the container cross section of the sample obtained using the rotary microtome is cut to obtain an observation surface. Further, the sample is cut in a direction perpendicular to the observation surface to a thickness of 30 μm in parallel with the observation surface to obtain a sample.
(Outer layer + thickness of transparent adhesive resin layer)
(1) For the measurement of the combined thickness of the transparent plastic resin outer layer and (2) the transparent adhesive resin layer, the container side wall obtained from the container wall flat part other than the nozzle part is used similarly to the unevenness of the resin layer interface. On the other hand, a sample having a cross section in the vertical direction as an observation surface is prepared. And an observation surface is observed with an optical microscope, and the thickness of (1) transparent plastic resin outer layer and (2) transparent adhesive resin layer is measured.

The ethylene-vinyl alcohol copolymer resin (EVOH) constituting the outer layer of the multilayer plastic container is not particularly limited as long as it has transparency necessary for constituting the outer layer of the container. Preferable ethylene-vinyl alcohol copolymer resins include saponified ethylene-vinyl acetate copolymers having an ethylene content of 20 to 60 mol%, particularly 25 to 50 mol%.

As long as the (1) plastic resin outer layer of the multilayer plastic container is transparent, it may be uncolored or colored. However, it is preferable to avoid adding pigments or the like that increase the surface roughness of the plastic resin.
Moreover, you may add a well-known additive to the plastic resin outer layer to such an extent that transparency is not impaired. For example, thermoplastic elastomers, other thermoplastic resins, rubber resins, inorganic fillers, pigments, plasticizers, antioxidants, antistatic agents, light stabilizers, antiblocking agents, lubricants, dyes, and the like can be added.

Hereinafter, the multilayer plastic container of the present invention will be further described.
(1) To make the surface roughness of the outer layer of the transparent plastic resin to be Ra ≦ 0.2 μm, a blow mold having a surface roughness of the inner surface of the blow mold of about 0.2 μm ≦ Ra ≦ 0.8 μm is used. use. By using such a treated mold, a container with Ra ≦ 0.2 μm can be obtained even when the surface roughness of the outer layer of the container is maximum. When the surface roughness Ra of the container exceeds 0.2 μm, the reflected light on the surface of the container is disturbed, and the gloss is reduced in appearance.

If the surface roughness of the inner surface of the blow mold is reduced, an air trap is generated during molding of the plastic container, and molding defects such as partial surface irregularities may occur. Further, (1) the unevenness of the transparent EVOH outer layer and the inner side (2) the interface of the transparent adhesive resin layer; or (2) the unevenness of the transparent adhesive resin layer and the inner side of (3) the colored polyolefin resin layer interface, Hue defects such as a non-uniform hue and a streak pattern may occur.
In the present invention, the water content of the transparent EVOH is adjusted to 5000 ppm or less, preferably about 500 to 2,500 ppm, and by adopting means such as adjusting the shear stress of each resin constituting the container, each of the above resins The maximum unevenness of the layer interface is set to 15 μm or less to prevent such molding defects. When the water content of the transparent EVOH exceeds 5000 ppm, foaming occurs during the molding of the container.

EVOH and polyolefin resin have low adhesion, and there is a difference in molding characteristics such as melt viscosity. Therefore, when a multilayer plastic container is molded using EVOH as an outer layer and a polyolefin resin as an inner layer, an appearance defect such as a ripple pattern may occur on the EVOH outer layer on the container surface or at each layer interface.
The ripple pattern is unevenness generated at (1) the interface between the transparent EVOH outer layer and the inner (2) transparent adhesive resin layer, and (2) the transparent adhesive resin layer and (3) the colored polyolefin resin layer. Means a pattern. The irregularities appear as ripples connected in the circumferential direction of the container when viewed from the surface of the container side wall. When the cross section of the side wall of the multilayer plastic container is observed, the resin on the inner surface side layer has a wave-like convex shape in the outer surface side layer resin at the uneven surface. The unevenness can be observed well from the height direction cross section of the side wall of the container, and many of them have a width of several hundred μm and a convex thickness of 15 to 50 μm. The cause of the unevenness is unknown, but it is considered that the unevenness occurred due to the non-uniform resin flow in the molten resin joining portion when the multilayer parison was manufactured.
In the present invention, by adjusting the shear stress of each layer resin constituting the multilayer plastic container and the melt flow rate (MFR) of the resin constituting the transparent adhesive resin layer, the difference in molding characteristics between the EVOH outer layer and the polyolefin resin layer is reduced. Complement. As a result, (1) the outer surface of the transparent EVOH and the inner side thereof (2) the unevenness of the transparent adhesive resin layer interface; and (2) the unevenness of the transparent adhesive resin layer and the inner side of (3) the colored polyolefin resin layer interface are reduced. Thus, it is possible to obtain a multilayer plastic container that has excellent appearance, prevents peeling between resin layers, and has excellent properties such as impact resistance.

  As the transparent adhesive resin, a known resin having adhesiveness to both EVOH and polyolefin resin can be used. For example, ethylene / α-olefin copolymer resins and acid-modified resins thereof, olefin / acid copolymer resins, glycidyl group-containing resins, and the like can be used. Moreover, in order to improve adhesiveness, you may add a well-known tackifier to those resin.

  As the copolymer, those produced by any bonding mode such as random, block, graft and the like can be used. Examples of the acid-modified resin include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and crotonic acid; or resins that are graft-modified with these anhydrides. When an acid-modified resin is used as the adhesive resin, it is preferable because the hydroxyl group of EVOH and the acid group of the acid-modified resin are chemically bonded to increase the adhesion between the outer layer and the adhesive resin layer. These resins can be used alone or as a blend resin of two or more; or as a blend resin with other resins. Examples of the tackifier include rosin resin, terpene resin, and petroleum resin. These resins can be used alone or in admixture of two or more. As the adhesive resin, an acid-modified polyolefin resin is particularly preferable.

Moreover, you may add a well-known additive to a transparent adhesive resin layer. For example, thermoplastic elastomers, other thermoplastic resins, rubber resins, inorganic fillers, pigments, plasticizers, antioxidants, antistatic agents, light stabilizers, antiblocking agents, and the like can be added.
The transparent adhesive layer resin may be uncolored or colored as long as it is transparent, and may contain a bright pigment. When the adhesive resin layer is colored, for example, by adding a bright pigment to the colored polyolefin layer, the reflected light from the bright pigment is transmitted through the transparent colored adhesive layer, giving a deep and unique metallic feeling. This is preferable. In addition, a special hue effect may be obtained by changing the color tone of the transparent adhesive layer and the polyolefin layer. The colorant used in the transparent adhesive resin layer is not particularly limited as long as the transparency is not impaired. As such a colorant, for example, an organic pigment such as an azo pigment, a phthalocyanine pigment, a condensed polycyclic pigment, or a dyed lake pigment can be used.

(1) Unevenness of the transparent EVOH outer layer and the inner side thereof (2) Unevenness of the transparent adhesive resin layer interface; and (2) Unevenness of the interface of the transparent adhesive resin layer and the inner (3) colored polyolefin-based resin layer is a multilayer plastic container It can be made small by adjusting so that resin which comprises each layer may satisfy the following (a) and (b) simultaneously.
(A) The shear stress (unit: KPa) of the resin constituting each layer satisfies “(3) Colored polyolefin resin−55 ≦ (2) Transparent adhesive resin ≦ (1) Transparent EVOH + 70”.
Here, the shear stress of the resin is based on JIS K7199, the pellet before the resin used is melted at a temperature of 210 ° C. and a shear rate of 50 / sec, the orifice of the resin extrusion part is L = 10 mm, D = diameter It is a value measured under the condition of 1 mm.
When the shear stress of the transparent adhesive layer resin is lower than “(3) Colored polyolefin resin-55”, a ripple pattern is generated which is unevenness at the interface between the transparent adhesive resin layer and the colored polyolefin resin layer. On the other hand, when the shear stress of the transparent adhesive layer resin exceeds “(1) Transparent EVOH + 70”, a ripple pattern that is unevenness at the interface between the transparent plastic resin layer and the transparent adhesive resin layer is generated.

(B) The melt flow rate (MFR) (g / 10 min) of the resin constituting the transparent adhesive resin layer satisfies “1.0 ≦ MFR ≦ 2.5”.
Here, the melt flow rate of the resin is a value obtained by measuring pellets before melting of the resin to be used at a temperature of 190 ° C. and a load of 2.16 kg in accordance with JIS K7210.
When the MFR of the transparent adhesive layer resin is less than 1.0 (g / 10 min), a ripple pattern that is unevenness at the interface between the transparent EVOH layer and the transparent adhesive resin layer is generated. On the other hand, when the MFR of the transparent adhesive layer resin exceeds 2.5, a ripple pattern which is unevenness at the interface between the transparent adhesive resin layer and the colored polyolefin resin layer is generated.

In the multilayer plastic container of the present invention, the total thickness of (1) the transparent plastic resin outer layer and (2) the transparent adhesive resin layer is preferably about 30 to 200 μm, particularly about 60 to 150 μm.
If this thickness is less than 30 μm, problems such as roughening of the container surface due to molding and inferior surface gloss or cutting of the plastic resin outer layer during molding occur. Moreover, when this thickness exceeds 200 micrometers, a transparent layer may become thick too much and may become cloudy and transparency may fall.
And by making the total thickness of the transparent plastic resin outer layer and the transparent adhesive resin layer within this range, the reflected light from the colored polyolefin resin layer on the inner layer side is slightly refracted, so the hue and gloss Depth comes out. Further, when a bright pigment is blended in a colored polyolefin resin layer to form a metallic color container, in order to obtain a desired surface roughness, (1) a transparent plastic resin outer layer and (2) a transparent adhesive resin layer It is preferable to make the combined thickness larger than the major axis of the pigment.

  (2) There is no restriction | limiting in particular as resin which comprises the colored polyolefin-type resin layer used as the inner layer of a transparent adhesive resin layer (3). For example, known low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, polypropylene, propylene-ethylene copolymer, ethylene-vinyl acetate copolymer, ethylenically unsaturated carboxylic acid or its anhydride. Any polyolefin-based resins such as graft-modified polyolefin resins can be used. Particularly preferred polyolefin resins include propylene-ethylene block copolymers. These polyolefin resins can be used alone or in admixture of two or more. Moreover, you may mix and use the repro (collection material) generated at the time of shaping | molding of a container.

  The colored polyolefin resin layer may be either a transparent colored layer or an opaque colored layer. Moreover, you may comprise not only one colored layer but 2 or more colored layers. Further, an intermediate layer made of another resin or the like, or an inner surface resin layer made of, for example, a polyolefin resin constituting the inner surface of the container can be provided on the inner side of the colored polyolefin resin layer.

  (3) The colorant blended in the colored polyolefin resin layer is not particularly limited, and organic pigments such as azo pigments, phthalocyanine pigments, condensed polycyclic pigments and dyed lake pigments, and aluminum such as polarized pearl pigments. Bright pigments such as a bright pigment, a mica bright pigment, and a glass bright pigment can be used. These colorants can be used alone or in combination of two or more. These colorants and extender pigments may be used in combination.

(3) When a bright pigment is blended in the colored polyolefin resin layer, the reflected light of the bright pigment passes through a layer combining (1) the outer layer of the transparent plastic resin and (2) the transparent adhesive resin layer. Thus, it is possible to obtain a multi-layer plastic container with a metallic color tone having a deep gloss.
In particular, when (3) the colored polyolefin resin layer has a multilayer structure comprising (2) a transparent colored resin layer adjacent to the transparent adhesive resin layer and a colored resin layer containing a bright pigment provided on the inner layer side thereof, It is preferable because a deep and distinctive metallic feeling as if a transparent ink is printed on a metal ground is obtained.

Next, although the high gloss multilayer plastic container of this invention is further demonstrated by an Example, the following specific examples do not limit this invention.
FIG. 1 is a schematic cross-sectional view showing an example of the layer structure of the multilayer plastic container of the present invention. This container is composed of (1) a transparent plastic resin (EVOH) outer layer A, (2) a transparent adhesive resin layer B, (3) a colored polyolefin-based resin layer C containing a bright pigment, and (4) a bright pigment in order from the outer surface side. A polyolefin resin layer D not included is included. (2) The transparent adhesive resin layer B may be formed as a transparent colored adhesive resin layer by adding a color pigment or the like within a range not impairing transparency.

  In the following example, a container having the layer configuration shown in FIG. 1 was manufactured as follows. Four extruders (hereinafter, the resin extruders constituting the resin layers A, B, C, and D are referred to as extruders A, B, C, and D, respectively) were filled with the resin. Each resin is plasticized and kneaded while being heated and extruded, and from the outer surface side, (1) transparent EVOH outer layer A, (2) transparent colored adhesive resin layer B, and (3) coloring including a bright pigment, using a multilayer head. A multilayer parison composed of a polyolefin resin layer C and (4) a polyolefin resin layer D not containing a bright pigment was formed. Next, the parison was sandwiched between molds having cavities, and compressed air was blown into the parison to produce a rectangular tube-shaped hollow container with a capacity of 500 mL. The inner surface roughness of the mold used was Ra = 0.6 μm.

In the following examples, each physical property value was measured by the method described above. The moisture content of the transparent EVOH was measured by the Karl Fischer method for the pellets before melting. In measuring each physical property value, “Surfcom 1400A-3DF-12 manufactured by Tokyo Seiki Kogyo Co., Ltd.” was used as the stylus roughness profile measuring instrument. The rotary microtome used “Leica inspection RM2125RT”, the optical microscope used “Olympus measuring microscope STM5-321”, and the resin shear stress measuring instrument “Tokyo Seiki Seisakusho Capillograph 1D”.
In addition, the surface roughness Ra of the multilayer plastic container was used by measuring a portion having a large surface roughness directly or directly with a size of 15 mm × 15 mm from a flat portion other than the nozzle portion of the container. The “outer layer + transparent adhesive resin layer thickness” was measured at 8 points at 45 ° intervals in the circumferential direction at the upper, middle and lower portions of the container body, and the average value was adopted. Further, the gloss evaluation of the container was visually observed on the entire flat part of the container other than the nozzle part.

Example 1
An extruder A having a diameter of 40 mm was filled with a transparent ethylene-vinyl alcohol copolymer resin (EVOH) having a shear stress of 100 (KPa) and a water content of 1500 ppm. Extruder B having a diameter of 40 mm was filled with MFR 1.6 (g / 10 min), a transparent and colorless acid-modified polypropylene resin having a shear stress of 110 (KPa), and 0.3% by weight of an azo red pigment as a coloring pigment. . Extruder C having a diameter of 50 mm was charged with transparent colorless ethylene / propylene block copolymer resin having an MFR of 0.8 (g / 10 min) and a shear stress of 120 (KPa), and 1.0% by weight of pearl red (average particle size) as a bright pigment. A mica pigment having a diameter of 21 μm) and 0.3% by weight of an azo red pigment as a coloring pigment were filled. An extruder D having a diameter of 40 mm was filled with the transparent colorless ethylene / propylene block copolymer resin. The resin filled in each extruder was plasticized and kneaded while being heated, and extruded from a multilayer head to form a multilayer parison. Subsequently, the parison was sandwiched between molds having cavities, and compressed air was blown into the parison to obtain a square-tube hollow bottle having a capacity of 500 mL.
The thickness of each layer of this bottle was outer layer A 50 μm, transparent colored adhesive resin layer B 70 μm, brightly colored polyolefin resin layer C 710 μm, and transparent polyolefin resin layer D 170 μm. The surface roughness Ra of the bottle is 0.11 μm, the surface unevenness between the transparent EVOH outer layer A and the transparent colored adhesive resin layer B is 6 μm, and the surface unevenness between the transparent colored adhesive resin layer B and the brightly colored polyolefin resin layer C is The surface gloss of the bottle was good.

(Example 2)
A similar hollow bottle was obtained in the same manner as in Example 1 except that EVOH having a shear stress of 60 (KPa) and a water content of 1200 ppm was used as the outer layer resin A.
The thickness of each layer of this bottle was outer layer A 50 μm, transparent colored adhesive resin layer B 70 μm, brightly colored polyolefin resin layer C 710 μm, and transparent polyolefin resin layer D 170 μm. Moreover, the surface roughness Ra of the bottle is 0.18 μm, the interface unevenness between the transparent EVOH outer layer A and the transparent colored adhesive resin layer B is 15 μm, and the interface unevenness between the transparent colored adhesive resin layer B and the brightly colored polyolefin resin layer C is The surface gloss of the bottle was good.

(Example 3)
In Example 2, the same procedure as in Example 2 was used, except that a transparent colorless acid-modified polypropylene resin with MFR 2.5 (g / 10 min) and shear stress 65 (KPa) was used as the transparent colored adhesive resin B. A hollow bottle was obtained.
The thickness of each layer of this bottle was outer layer A 50 μm, transparent colored adhesive resin layer B 70 μm, brightly colored polyolefin resin layer C 710 μm, and transparent polyolefin resin layer D 170 μm. Further, the surface roughness Ra of the bottle is 0.12 μm, the interface irregularity between the transparent EVOH outer layer A and the transparent colored adhesive resin layer B is 7 μm, and the interface irregularity between the transparent colored adhesive resin layer B and the brightly colored polyolefin resin layer C is The surface gloss of the bottle was good.

Example 4
In Example 1, a transparent and colorless acid-modified polyethylene resin having an MFR of 1.4 (g / 10 min) and a shear stress of 110 (KPa) was used as the transparent colored adhesive resin B. In addition, a high-density polyethylene resin having an MFR of 0.36 (g / 10 min) and a shear stress of 120 (KPa) was used as the transparent colorless resin of the brightly colored polyolefin resin C and the transparent polyolefin resin D. Other conditions were the same as in Example 1, and a similar hollow bottle was obtained.
The thickness of each layer of this bottle was outer layer A 50 μm, transparent colored adhesive resin layer B 70 μm, brightly colored polyolefin resin layer C 710 μm, and transparent polyolefin resin layer D 170 μm. Further, the surface roughness Ra of the bottle is 0.12 μm, the interface unevenness between the transparent EVOH outer layer A and the transparent colored adhesive resin layer B is 6 μm, and the interface unevenness between the transparent colored adhesive resin layer B and the brightly colored polyolefin resin layer C is The surface gloss of the bottle was good.

(Example 5)
In Example 1, EVOH having a shear stress of 70 (KPa) and a water content of 1500 ppm was used as the outer layer resin A, and transparent colorless adhesive resin B was MFR1.0 (g / 10 min), shear stress of 120 (KPa), and transparent and colorless. A similar hollow bottle was obtained in the same manner as in Example 1 except that the acid-modified polypropylene resin was used.
The thickness of each layer of this bottle was outer layer A 50 μm, transparent colored adhesive resin layer B 70 μm, brightly colored polyolefin resin layer C 710 μm, and transparent polyolefin resin layer D 170 μm. Further, the surface roughness Ra of the bottle is 0.20 μm, the interface irregularity between the transparent EVOH outer layer A and the transparent colored adhesive resin layer B is 15 μm, and the interface irregularity between the transparent colored adhesive resin layer B and the brightly colored polyolefin resin layer C is The surface gloss of the bottle was good.

(Example 6)
In Example 1, a similar hollow bottle was obtained in the same manner as in Example 1 except that the discharge amounts of the extruders A and B were changed.
The thickness of each layer of the bottle was an outer layer A of 13 μm, a transparent colored adhesive resin layer B of 17 μm, a brightly colored polyolefin resin layer C of 710 μm, and a transparent polyolefin resin layer of D 170 μm. Further, the surface roughness Ra of the bottle is 0.12 μm, the interface irregularity between the transparent EVOH outer layer A and the transparent colored adhesive resin layer B is 7 μm, and the interface irregularity between the transparent colored adhesive resin layer B and the brightly colored polyolefin resin layer C is The surface gloss of the bottle was good.

(Example 7)
In Example 1, a similar hollow bottle was obtained in the same manner as in Example 1 except that the discharge amounts of the extruders A and B were changed.
The thickness of each layer of this bottle was outer layer A85 μm, transparent colored adhesive resin layer B115 μm, brightly colored polyolefin resin layer C710 μm, and transparent polyolefin resin layer D170 μm. The surface roughness Ra of the bottle is 0.11 μm, the surface unevenness between the transparent EVOH outer layer A and the transparent colored adhesive resin layer B is 5 μm, and the surface unevenness between the transparent colored adhesive resin layer B and the brightly colored polyolefin resin layer C is The surface gloss of the bottle was good.

(Comparative Example 1)
A similar hollow bottle was obtained in the same manner as in Example 1, except that EVOH having a shearing stress of 30 (KPa) and a water content of 1600 ppm was used as the outer layer resin A.
The thickness of each layer of this bottle was outer layer A 50 μm, transparent colored adhesive resin layer B 70 μm, brightly colored polyolefin resin layer C 710 μm, and transparent polyolefin resin layer D 170 μm. Further, the surface roughness Ra of the bottle is 0.22 μm, the interface unevenness between the transparent EVOH outer layer A and the transparent colored adhesive resin layer B is 18 μm, and the interface unevenness between the transparent colored adhesive resin layer B and the brightly colored polyolefin resin layer C is The ripple pattern was generated between the EVOH outer layer A and the transparent colored adhesive resin layer B.

(Comparative Example 2)
In the same manner as in Example 1, except that a transparent colorless acid-modified polypropylene resin with MFR 3.5 (g / 10 min) and shear stress 48 (KPa) was used as the transparent colored adhesive resin B in Example 1. A hollow bottle was obtained.
The thickness of each layer of this bottle was outer layer A 50 μm, transparent colored adhesive resin layer B 70 μm, brightly colored polyolefin resin layer C 710 μm, and transparent polyolefin resin layer D 170 μm. Further, the surface roughness Ra of the bottle is 0.12 μm, the interface irregularity between the transparent EVOH outer layer A and the transparent colored adhesive resin layer B is 7 μm, and the interface irregularity between the transparent colored adhesive resin layer B and the brightly colored polyolefin resin layer C is The ripple pattern was generated at the interface between the transparent colored adhesive resin layer B and the brightly colored polyolefin-based resin layer C.

This international application claims priority based on Japanese Patent Application No. 2007-325397 filed on Dec. 18, 2007, and the entire contents of Japanese Patent Application No. 2007-325397 are incorporated herein by reference.

Claims (8)

In a multilayer plastic container having (1) a transparent ethylene-vinyl alcohol copolymer resin outer layer , (2) a transparent adhesive resin layer, and (3) a colored polyolefin resin layer in order from the outer surface side, a transparent ethylene-vinyl alcohol copolymer resin surface roughness of the outer layer is Ra ≦ 0.2 [mu] m, by the resin constituting the multilayer plastic container layers is adjusted so as to satisfy the following formula (a) and (b) simultaneously, wherein (1) a transparent ethylene -Unevenness at the interface between the vinyl alcohol copolymer resin outer layer and the (2) transparent adhesive resin layer is 15 µm or less, and the unevenness at the interface between the (2) transparent adhesive resin layer and the (3) colored polyolefin resin layer is 15 µm. High gloss multi-layer plastic container characterized by being configured as follows:
(A) The shear stress (unit: KPa) of the resin constituting each layer is “(3) colored polyolefin resin−55 ≦ (2) transparent adhesive resin ≦ (1) transparent ethylene-vinyl alcohol copolymer resin + 70”. Satisfying;
[Here, the shear stress of the resin is based on JIS K7199, the pellet before the resin used is melted at a temperature of 210 ° C. and a shear rate of 50 / sec, the orifice of the resin extrusion part is L = 10 mm, D = It is a value measured under the condition of a diameter of 1 mm. ]
(B) The melt flow rate (MFR) (g / 10 min) of the resin constituting the transparent adhesive resin layer satisfies “1.0 ≦ MFR ≦ 2.5”.
[Here, the melt flow rate of the resin is a value obtained by measuring pellets of the resin to be used before melting at a temperature of 190 ° C. and a load of 2.16 kg in accordance with JIS K7210. ] 2. The high gloss multilayer plastic container according to claim 1, wherein the (3) colored polyolefin resin layer contains a luster pigment . The high gloss multilayer plastic container according to claim 1 or 2, wherein the (3) colored polyolefin resin layer is composed of a block polypropylene resin . 3. The high gloss multilayer plastic container according to claim 1 or 2 , wherein the (3) colored polyolefin resin layer is composed of a high density polyethylene resin . The multilayer plastic container has the following layer structure in order from the outer surface side: (1) a transparent ethylene-vinyl alcohol copolymer resin outer layer, (2) a transparent polypropylene adhesive resin layer, (3) a colored polypropylene resin layer containing a bright pigment, ( 4) The high gloss multilayer plastic container according to any one of claims 1 to 3, which has a polypropylene resin layer not containing a luster pigment . The multilayer plastic container has the following layer structure in order from the outer surface side: (1) a transparent ethylene-vinyl alcohol copolymer resin outer layer, (2) a transparent polyethylene adhesive resin layer, (3) a colored polyethylene resin layer containing a bright pigment, ( 4) The high-gloss multilayer plastic container according to any one of claims 1, 2, and 4 , wherein the container has a polyethylene-based resin layer not containing a luster pigment. The multi-layer plastic container according to any one of claims 1 to 6, wherein the multi-layer plastic container further has a polyolefin resin inner layer . The total thickness of the (1) transparent ethylene-vinyl alcohol copolymer resin outer layer and the (2) transparent adhesive resin layer is 30 to 200 µm, according to any one of claims 1 to 7. High gloss multilayer plastic container.

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