JPH01275041A - Plastic container - Google Patents

Abstract

PURPOSE:To impart superior characteristics in terms of gas barrier, drop strength and resilliency by adding a specific wt.% of amorphous ethylene/ propylene copolymer with specific Mooney viscosity and the specified polymerization rate of propylene at least in one reground layer. CONSTITUTION:A multi-layer plastic container for packing is formed using a laminated product which is obtained by sandwiching a gas barrier layer 1 containing an etylene vinyl alcohol copolymer with external and internal surface layer 4, 4' of thermoplastic resin consisting mainly of a propylene copolymer through an adhesive. In this container, reground layers 3, 3' containing thermoplastic resin of a propylene polymer as a main component and a vinyl alcohol copolymer are provided between adhesive layers 2, 2 and the internal surface layer 4 and/or the external surface layer 4'. Then at least in one of the reground layers, 5.0-40 pts.wt. of amorphous ethylene, propylene polymer with Mooney viscosity (ML1+4, 100 deg.C) of 20-100 and copolymerization rate of 20-60weight% are added to 100 pts.wt. of regrind.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plastic container useful for food. More particularly, the present invention relates to a plastic container comprising a gas barrier layer containing an ethylene-vinyl alcohol copolymer as a main component as an intermediate layer, and inner and outer surface layers containing a propylene polymer as a main component.

[Prior art]

Traditionally, each material has been given q advantages,
In order to compensate for the shortcomings of each material, laminates made by laminating different materials have been developed and are widely used as containers and thin products (sheets, films).

The materials for this laminate include thermoplastic resins such as polyethylene resin, polypropylene resin, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer (saponified ethylene-vinyl acetate copolymer), and polyvinyl chloride. Commonly used resins include polyvinylidene chloride resin, polyethylene terephthalate resin, polyamide resin, polycarbonate resin, polystyrene resin, high-impact polystyrene resin, and acrylonitrile-butadiene-styrene terpolymer resin (ABS resin).

Among these thermoplastic resins, polypropylene resin is
It not only has excellent heat resistance and mechanical properties, but also good moldability, and is inexpensive, so it is widely used for containers and thin-walled products. However, its gas barrier properties are extremely poor. Therefore, sheets or parisons are formed by laminating ethylene-vinyl alcohol copolymer and polypropylene resin, which have excellent gas barrier properties, and containers such as bottles and cups are made by vacuum forming, pressure forming, blow molding, and injection blowing. It is well known that they can be manufactured by molding methods such as molding. When manufacturing containers using such a process, there is a problem with the reuse of regrind (scrap). That is, when manufacturing containers from this laminated sheet or blow molding bottles etc., a large amount of regrind (generally 20 to 40 weight 96) occurs due to pinch-off and the like. In addition, in the case of sheet molding, edge loss and punching loss during thermoforming occur by 30 to 50% of the total sheet. Therefore, the first specification of Utility Model Application Publication No. 62-104929
As shown in the figure, it is common practice to provide regrind (scrap) layers on both ethylene-vinyl alcohol copolymer layers.

[Problem to be solved by the invention]

However, if the regrind is simply reused as in the above-mentioned idea, the strength of the container, especially the drop strength, will be extremely reduced, which is not preferable. This phenomenon is particularly noticeable when a polypropylene resin composition containing a filler added to improve the flexural modulus (rigidity) and reduce the number of calories burned is used as the inner and outer layers.

If an amorphous ethylene-propylene copolymer is blended into at least one of the inner and outer surface layers instead of the regrind layer, the drop strength will be improved. On the other hand, when the resulting container is used as a microwave oven container, it not only has poor heat resistance, but also has poor elasticity, and even at room temperature.

Therefore, an object of the present invention is to obtain a container that has good gas barrier properties, excellent drop strength, and is strong.

[Means and effects for solving the problems] According to the present invention, these problems are solved by sandwiching the gas barrier layer with a gas barrier layer containing an ethylene-vinyl alcohol copolymer via an adhesive. A multilayer plastic container for packaging formed of a laminate of inner and outer surface layers of a thermoplastic resin mainly composed of a propylene-based polymer provided on the adhesive layer and the inner and/or outer surface layers. A regrind layer containing a thermoplastic resin mainly composed of a propylene polymer and an ethylene-vinyl alcohol copolymer is provided between the regrind layer and at least one of the regrind layers. 100
Mooney viscosity (ML, 100°C) to parts by weight
is 20 to 100, and contains 5.0 to 40 parts by weight of an amorphous ethylene-propylene copolymer having a copolymerization ratio of Kabu 1+40 pyrene of 20 to 60% by weight. plastic container, can be solved by. The present invention will be explained in detail below.

(A) Ethylene-vinyl alcohol copolymer The ethylene-vinyl alcohol copolymer used to produce the gas barrier layer and the regrind layer in the present invention generally has an ethylene copolymerization ratio of 20 to 60 moles9.
6 (preferably 25 to 60 mol%, preferably 25 to 5
It is a saponified product of ethylene and vinyl acetate copolymer with 0 mol 96). The saponification rate of this saponified product is usually 95% or more, preferably 9696 or more, and particularly preferably 99% or more.

If a saponified product having a saponification rate of less than 95 mol 96 is used, the barrier properties will be poor.

The ethylene-vinyl alcohol copolymer should have a molecular weight sufficient to form a film, and the weight ratio of phenol to water should be 85.
: Measured in a mixed solvent of 15 at a temperature of 30℃, O
, OLdΩ/g or more, particularly those having a viscosity of 0.05dΩ/g or more are preferred.

(B) Propylene polymer In the present invention, the propylene polymer used for producing the inner and outer surface layers and the regrind layer is a propylene homopolymer or propylene containing at least 70% of propylene.
Random copolymers with ethylene or other α-olefins or random or block copolymers with α-olefins containing 1.0 to 50% by weight can be mentioned. % of ethylene-based polymer is mixed with propylene-based polymer, a good product is obtained. Melt flow index of these propylene polymers (according to JIS K-7210,
Conditions are 14, (III constant, hereinafter referred to as rMFR(1)J) is 0.005 to 80 g/10 min, and 0.
0.01 to 60 g/10 min is desirable, especially 0.01 to 60 g/10 min.
01-40 g/10 min of propylene polymer is preferred. If a propylene polymer with an MFR (1) of less than 0.005 g/10 minutes is used, the molding processability to obtain a container will be poor, making it impossible to obtain a good container; If used, the impact resistance of the container will be weak and the container will not be suitable for practical use.

As the propylene polymer in the present invention, one to which an inorganic filler described later may be added may be used.

In this case, when forming a container and filling the container with food, from the viewpoint of food hygiene, a propylene polymer that does not contain an inorganic filler is added inside the inner layer of the propylene polymer that contains an inorganic filler. It is preferable to provide a layer of.

The inorganic filler is generally one widely used in the fields of synthetic resins and rubber.

These inorganic fillers are preferably inorganic compounds that do not react with oxygen and water and do not decompose during kneading and molding.

Examples of the inorganic filler include oxides of metals such as aluminum, copper, iron, lead, nickel, magnesium, calcium, barium, zinc, zirconium, molybdenum, silicon, antimony, and titanium, and hydrates (hydroxides) thereof; It is broadly classified into compounds such as sulfates, carbonates, and silicates, their double salts, and mixtures thereof. Representative examples of the inorganic filler are described in Japanese Patent Application No. 124481/1981.

Among these inorganic fillers, those in powder form have a diameter of 3
The thickness is preferably 0 μm or less (preferably 10 μm or less).

In addition, in the case of a fibrous material, the diameter is 1 to 500 ta (preferably 1 to 300 parts), and the length is 0.1 to 6.0 ta.
mm (preferably 0.1 to 5.0 mm). Further, the flat plate-like material is preferably 30 μm or less (preferably 10 μm or less). Among these inorganic fillers, those in the form of flat plates (flake) and those in the form of powder are particularly suitable.

The composition ratio (content ratio) of the inorganic filler in the inorganic filler-containing propylene polymer is at most 70% by weight, preferably 5 to 65% by weight, particularly 5 to 60% by weight. suitable.

If the composition ratio of the inorganic filler in the inorganic filler-containing propylene polymer exceeds 700, the impact resistance of the resulting container will be significantly reduced, resulting in a container that is not suitable for practical use.

(C) Adhesive In the present invention, adhesiveness between the ethylene-vinyl alcohol copolymer constituting the gas barrier layer and the propylene polymer or the mixture of the propylene polymer and an inorganic filler constituting the inner and outer surface layers is determined. The adhesive used for the improvement is obtained by graft polymerizing the above-mentioned propylene resin or the below-mentioned ethylene resin with the below-mentioned unsaturated carboxylic acid or its derivative. This graft polymerization is generally carried out in the presence of a radical initiator (generally an organic peroxide) as described below.

As the ethylene resin, ethylene homopolymer, ethylene and carbon number at most 12 (preferably 3 to 8)
A copolymer with α-olefin (the copolymerization ratio of α-olefin is usually 20% by weight or less, preferably 15% by weight or less, preferably 122% by weight or less) and ethylene as the main component (generally 65% by weight or less). % or more, preferably 70% or more by weight) with a monomer having a polar group (for example, vinyl acetate, (meth)acrylic acid, or an alkyl ester thereof).

In producing the graft polymer, the melt flow index (JIS K72
10, the condition is 4 and l deviation, below [FR(2)
J) and propylene resin MFR(L)
are generally 0.01 to 100 g/IO min, preferably 0.02 to 50 g/10 min, and particularly preferably 0.05 to 50 g/I [1 min].

When a propylene polymer or an ethylene polymer having M F R (1) or M F R (3) below the lower limit is used, it is difficult to uniformly carry out the graft reaction. On the other hand, if the amount exceeding the upper limit is used, the strength of the resulting adhesive resin will be poor, and the adhesive strength will also be poor.

In producing the graft polymer, among these ethylene resins and propylene resins, low density and high density ethylene homopolymers, propylene homopolymers,
Copolymers of ethylene and propylene as well as copolymers of ethylene or propylene with other α-olefins are preferred.

(D) Amorphous ethylene-propylene copolymer Mooney viscosity (M L
(100°C)) The weight is 0 to 10 degrees and 1+4 degrees, preferably 20 to 8 G, and particularly preferably 30 to 75. Amorphous ethylene with a Mooney viscosity of less than 20
If a propylene copolymer is used, the moldability will be improved, but the resulting container will not have good drop strength. On the other hand, 100
If it exceeds the above range, the dispersibility will be extremely poor when kneading with regrind, and the drop strength of the container will also be poor. Further, the propylene content of this copolymer is generally 20 to 60% by weight, preferably 25 to 50% by weight, and particularly preferably 25 to 45% by weight. This amorphous ethylene-propylene copolymer has rubber-like properties and is industrially produced and used in a wide variety of fields, and its manufacturing method is also widely known.

The amorphous ethylene-propylene copolymer is a copolymer rubber obtained by copolymerizing ethylene and propylene, and contains ethylene and propylene as main components, and contains 1, 4-pentadiene, 2, 5-hexadiene, and 3. .3-dimethyl-1,5-hexadiene, linear or branched diolefins containing two double bonds at the ends, 1,4-hexadiene and 6-methyl-1
, 5-hebutadiene or cyclic diene hydrocarbons such as bicyclo[2,2,13-hebutene-2 (norbornene) and its derivatives (e.g. ethylidene norbornene). Rubbers are broadly classified into multicomponent copolymer rubbers obtained by copolymerizing monomers having a double bond with a small amount of ff1 (generally 10% by weight or less).

(E) Regrind layer The regrind layer used in the present invention consists of at least the ethylene-vinyl alcohol copolymer and a propylene polymer. The composition ratio of the propylene polymer in the total amount is usually 70 to 99% by weight,
It is preferably 70 to 98% by weight, particularly preferably 75 to 98% by weight. If the composition ratio of the propylene polymer in the total amount is less than 70 weight -5, the amount of the ethylene-vinyl alcohol copolymer increases, resulting in a significant drop in drop strength, and is also unfavorable in terms of cost. On the other hand, if it exceeds 99% by weight, the ethylene-vinyl alcohol copolymer layer becomes very thin and cannot maintain barrier properties.

In the present invention, at least one of the regrind layers contains the amorphous ethylene-propylene copolymer (the amorphous ethylene-propylene copolymer may be blended in both layers). The composition ratio of the amorphous ethylene-propylene copolymer to 100 parts by weight of regrind is 3.0 to 100 parts by weight, with 5.0 to 100 parts by weight being heavy, especially 5.0 to 9.0 parts by weight. part is preferred. If the composition ratio of the amorphous ethylene-propylene copolymer to 100 parts by weight of regrind is less than 3.0 parts by weight, the resulting container will have poor impact resistance (particularly drop strength).
is not good. On the other hand, if it exceeds 100 parts by weight, the amount of resin that must be regrind becomes extremely large, which is not preferable.

For example, a layer of ethylene-vinyl alcohol copolymer with a thickness of 40 mm is interposed as an intermediate layer, and a layer of the adhesive resin with a thickness of 15 mm is interposed on both sides, and a layer with a thickness of 0.5 mm is formed as an inner layer and an outer layer. When regrinding three types of five layers consisting of the propylene polymer layer and the propylene polymer layer, even if the inner and outer layers are propylene polymer layers, the drop strength of the container will be significantly improved after reuse. do not have. This is because the compatibility between the propylene polymer and the ethylene-vinyl alcohol copolymer during regrinding is very low, so when the container is dropped, a layer of fine particles of the ethylene-vinyl alcohol copolymer and the propylene polymer will form. It is thought that stress concentrates at the interface between the container and the container, resulting in a decrease in the container's drop strength.

In contrast, according to the present invention, since at least one layer of the regrind layer contains the amorphous ethylene-propylene copolymer, the impact strength of the regrind layer is improved, and therefore the drop strength of the container is improved. The decline can be prevented.

(P) Container and method for manufacturing the same A partially enlarged end view of a representative example of the plastic container of the present invention is shown in FIGS. 1 and 2. In these drawings, 1
is an ethylene-vinyl alcohol copolymer layer (gas barrier layer), and 2 and 2' are adhesive layers. Also,
3 and 3' are regrind layers, and 4 and 4' are propylene polymer layers. By providing this regrind layer, regrind (scrap) generated during container manufacturing can be effectively reused.

In the container of the present invention, the thickness of each layer can vary widely depending on its use and the amount of regrind, but the gas barrier
The ratio of the inner layer and the outer layer (propylene polymer layer) to 1 layer (ethylene-vinyl alcohol copolymer layer) is usually 2 to 100 (preferably 3 to 80). Also, there are 20 to 80 players in the regrind group.

^ Also, the thickness of the adhesive layer is usually 3 to 100 urns, particularly preferably 5 to 50 urns. The thickness of the adhesive layer is 3-
If the thickness is less than that, it will be difficult to form the material to a uniform thickness, and uneven coupling will occur after retort processing or the like. on the other hand,
If it exceeds 100 ufn, not only is there an economical problem, but the container may turn yellow.

Further, the thickness of the inner layer and the outer layer is generally 500 mm or less, and the gas barrier layer has a thickness of 10 tln or more.

Furthermore, the regrind layer has a thickness of 50 um or more.

The containers of the present invention can be manufactured by methods commonly practiced in the field of containers of this type.

In the case of manufacturing by multilayer coextrusion, the resin of each layer is melt-kneaded using an extruder corresponding to the resin, and then extruded into a predetermined shape through a multilayer die such as a T-die or a circinilla die. It can also be manufactured by lamination methods such as dry lamination, sandwich lamination, and extrusion coating.

The molded article may take the form of a film, sheet, bottle or tube forming preform, etc.

Forming a container from a parison or preform can be easily accomplished by pinching off the extrudate with a pair of split dies and blowing fluid into the interior thereof. Furthermore, after cooling the preform, it is heated to a stretching temperature, stretched in the axial direction, and blow-stretched in the circumferential direction using fluid pressure, thereby obtaining a stretched-blown container or the like. Also,
By subjecting the film or sheet to vacuum forming, pressure forming, plug-assist forming, etc., cup-shaped,
Containers such as tray-shaped containers can be manufactured.

[Examples and comparative examples]

Hereinafter, the present invention will be explained in more detail with reference to Examples.

In the examples and comparative examples, four types of upper layer multilayer sheet forming machines (manufactured by Toshiba Machine Co., Ltd., 65 mm diameter, 2 units, 40 ra
Each multilayer sheet was molded at a die temperature of 230° C. using two machines with a diameter of 11 mm and a die width of 800 mm+. Each sheet was formed using a vacuum forming machine (manufactured by Asano Research Institute, model F L V44).
1) was used to mold a container with a diameter of 81.2 m+s, a depth of 70 mm, and a diameter of 230 cc. Each container obtained in this way was filled with water so that 596 of the total internal capacity was a space, and a propylene-based heavy-duty container with a thickness of 60 μs on both sides was placed between 20 μs-thick aluminum foil. The temperature of the lid manufactured by combining is 200℃ and the pressure is 2.5kg.
Ring sealing was performed for 3 seconds under the conditions of /c- to obtain a container filled with water.

The container filled with water in this way is treated for 24 hours at a temperature of 20°C and a relative humidity of 65%,
The condition of the container was examined by dropping the container from a height of 40 cm so that the bottom surface was directly below. The results are shown in Table 1 using the display method shown below.

O: No abnormality △: There is no liquid leakage, but there is a possibility of liquid leakage due to deformation of the container, etc. There was no such thing.

Examples 1-4. Comparative Examples 1 to 4 As the inner and outer layers, ethylene-propylene block copolymer (hereinafter referred to as "PP (^
), propylene homopolymer 10 as adhesive layer.
Modified propylene resin (hereinafter referred to as rER (1) J), an amorphous ethylene-propylene copolymer (hereinafter referred to as rEPR(a)J) with a propylene copolymerization ratio of 27% by weight and a Mooney viscosity (ML1+4.100°C) of 35. ), and as an ethylene-vinyl alcohol copolymer layer, an ethylene-vinyl alcohol copolymer layer with an ethylene copolymerization ratio of 38 mol%
Multilayer sheets of each resin are manufactured using a saponified product obtained by saponifying vinyl acetate copolymer (MFR'(2) 4.0 g/10 min, saponification degree 99%, hereinafter referred to as rEVOH(I)J). Equipment (manufactured by Toshiba Machine Co., Ltd., feed block type, screw diameter 401. 4 extruders.

The original fabric sheets whose configurations are shown in Table 1 were each molded using a four-type upper layer sheet molding machine (the thickness of the adhesive layer was 20 mm in each case). Each raw sheet is processed using a vacuum forming machine (
The above-mentioned container was formed using a container (manufactured by Asano Research Institute, model: FLV441).

The resin for the regrind layer is a propylene polymer (hereinafter referred to as rPPJ) whose type and composition ratio are shown in Table 2, an adhesive resin (ER(
1) L ethylene-vinyl alcohol copolymer (EVOH
(I)) and amorphous ethylene-propylene copolymer (
Hereinafter referred to as rEPRJ) was pelletized using an extruder (L/D-26) at a resin temperature of 22.0° C. while kneading a composition whose composition ratio is shown in Table 2. Further, in Table 1, the thickness of each layer is the thickness of each layer of the multilayer sheet.

Example 5. Comparative Example 6.7 P P (A) used as the inner and outer layers in Example 1
Instead, MFR (1) is 0.5 g/10 minutes,
and 60% by weight of an ethylene-propylene block copolymer in which the copolymerization ratio of ethylene is 18% by weight, M F R
(3) is 0.2g/10min, and the density is 0.95
Table 1 shows the same procedure as in Example 1 except that an inorganic filler consisting of 10% by weight of ethylene homopolymer (96% by weight) and 30% by weight of talc having an average particle size of 3.0 g/cJ was used. The raw sheets having the configurations shown were each molded, and each raw sheet was molded into a container in the same manner as in Example 1.

Comparative Example 8.9 Instead of EPR(a) used in Example 1, an amorphous ethylene-propylene copolymer having a Mooney viscosity of 300 (hereinafter referred to as rEPR(b)J) (Comparative Example 8) , and amorphous ethylene with a Mooney viscosity of 15.
Propylene copolymer (hereinafter referred to as rEPR(C)) (
Each raw sheet was produced in the same manner as in Example 1, except that Comparative Example 9) was used.

Each container was manufactured in the same manner as in Example 1 using each obtained original fabric sheet.

A drop test was conducted on each container obtained as described above.

The results are shown in Table 2.

〔Effect of the invention〕

As described above, the plastic container of the present invention allows regrind (scrap) to be reused without reducing the drop strength. Typical uses are shown below.

(1) Various processed seasoning food containers (2) Various liquid seasoning food containers (3) Other various food containers

[Brief explanation of the drawing]

1 and 2 are partially enlarged sectional views of representative examples of the plastic container of the present invention. 1... Ethylene-vinyl alcohol copolymer layer (gas barrier layer) ・2.2'... Adhesive layer 3.3'... Regrind layer 4.4'... Propylene polymer layer Patent applicant Showa Denko Co., Ltd.

Claims (1)

[Claims] Lamination of a gas barrier layer containing an ethylene-vinyl alcohol copolymer and inner and outer surface layers of a thermoplastic resin mainly composed of a propylene polymer, which are sandwiched between the gas barrier layer and an adhesive. A multilayer plastic container for packaging made of a plastic material, and between the adhesive layer and the inner surface layer and/or the outer surface layer, a thermoplastic resin mainly composed of a propylene polymer and ethylene-vinyl alcohol are used. A regrind layer containing a copolymer is provided, and at least one of the regrind layers has a Mooney viscosity (ML_l_+_4, 100°C) of 20 to 100 with respect to 100 parts by weight of regrind, and propylene An amorphous ethylene-propylene copolymer with a copolymerization ratio of 20 to 60% by weight is 5.0 to 60% by weight.
A plastic container characterized by containing 40 parts by weight.