JPH02189B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a multilayer plastic container, and more particularly to a multilayer plastic container made of an olefin resin layer and an ethylene-layer plastic container.
This invention relates to a multilayer plastic container comprising a laminate of a vinyl alcohol copolymer and an oxygen barrier layer, in which the adhesive strength between the two resin layers is significantly improved. Olefin resin such as polypropylene or polyethylene with excellent moisture resistance and ethylene-vinyl alcohol copolymer with excellent oxygen barrier properties are laminated via an adhesive resin layer made of acid or acid anhydride modified olefin resin. BACKGROUND OF THE INVENTION Laminated bodies are widely used in various fields as containers with excellent content preservation properties in the form of bottles, cups, pouches, etc. It is desirable for these multilayer plastics to have increased adhesion strength between each layer to improve impact resistance. However, conventional laminates using the above-mentioned acid- or acid-anhydride-modified olefin resin as an adhesive layer are not necessarily satisfactory because the adhesive strength between the layers decreases depending on the contents. An object of the present invention is to bond a layer made of an olefin resin and a layer made of an ethylene-vinyl alcohol copolymer via an acid- or acid anhydride-modified linear low-density polyethylene-containing layer, and to have excellent delamination resistance. To provide multilayer plastic containers. Another object of the present invention is to provide a multilayer blow-molded container in which each resin layer exhibits excellent delamination resistance regardless of the type of contents. According to the present invention, at least one layer based on olefin resin; ethylene content is 25 to 60
at least one oxygen barrier layer based on mol% ethylene-vinyl alcohol copolymer;
There is also provided a multilayer plastic container comprising a laminate of adhesive resin layers containing acid- or acid anhydride-modified linear low-density polyethylene interposed between both resin layers. The present invention is characterized in that, among various acid- or acid-anhydride-modified olefin resins, an acid- or acid anhydride-modified resin based on linear low-density polyethylene is selected and used as the adhesive resin layer. It is something. Linear low-density polyethylene, which is the base of the acid- or acid anhydride-modified resin, has several characteristics that are not found in commonly used high-pressure low-density polyethylene and low-pressure high-density polyethylene. That is, high-pressure low-density polyethylene has a molecular structure with long chain branches and is a single polymer of ethylene, whereas linear low-density polyethylene has a substantially straight-chain molecular structure and consists of ethylene and carbon. It consists of a copolymer with α-olefins of numbers 4 to 8. On the other hand, low-pressure high-density polyethylene has a density (25
℃) is in the range of 0.940 to 0.965 g/ ^cm3 , and its molecular structure has almost no short branched chains, whereas linear low-density polyethylene has a density of
It is in the range of 0.915 to 0.935g/ ^cm3 , and the α
- They differ in that they have short branched chains derived from olefins. Comonomers in this linear low density polyethylene include butene-1, pentene-1, 4-methylpentene-1, hexene-1, 2-methyl-
Examples include α-olefins having 4 to 8 carbon atoms such as butene-1 and octene-1.
The olefins are incorporated into the polymer chain in a total amount of 1 to 20% by weight, in particular 3 to 15% by weight. This linear low density polyethylene (L-LDPE)
Also related to the chemical structure mentioned above, other olefin resins, such as high-pressure low density polyethylene (Hp
-LDPE), high-density polyethylene (HDPH), crystalline propylene ethylene copolymer (PPE), etc., it has different physical properties as shown in Table A below.

[Table] From Table A above, it is clear that the linear low-density polyethylene, which is the base of the modified resin, has the characteristics of having a low melting point while having high elongation and strength. The modified resin used in the present invention can be easily obtained by graft-modifying the above-mentioned linear low-density polyethylene with an ethylenically unsaturated carboxylic acid or its anhydride. Ethylenically unsaturated carboxylic acids or their anhydrides include maleic anhydride, maleic acid, fumaric acid, acrylic acid, methacrylic acid,
Examples include crotonic acid, itaconic acid, citraconic acid, hexahydrophthalic anhydride, etc., and carbonyl groups based on acids and acid anhydrides.

[Formula] can be present in a concentration of 1 to 600 millivalent/100 g polymer, based on the final resin. The adhesive layer used in the present invention can be made of acid-modified linear low-density polyethylene alone, or can be made of a blend of acid-modified linear low-density polyethylene and unmodified linear low-density polyethylene. In the latter case, the blending ratio of both can be freely changed as long as the overall carbonyl group concentration is within the above range. Furthermore, this adhesive layer has a linear low density polyethylene content of 50
Other olefin resins, such as acid-modified or unmodified crystalline polypropylene, high-density polyethylene, high-pressure low-density polyethylene, crystalline ethylene, as long as the total carbonyl group concentration is within the above-mentioned range. -Propylene copolymers etc. may be included in the form of blends. According to the present invention, the peel strength of the polyolefin/ethylene vinyl alcohol copolymer laminate, especially the contents, can be preserved by using an adhesive layer mainly composed of acid or acid anhydride-modified linear low-density polyethylene. The subsequent peel strength can be significantly improved compared to conventional acid- or acid anhydride-modified olefin resins. Generally, in this type of laminated structure, there is almost no peeling between the olefin resin layer and the adhesive resin layer, and peeling occurs between the adhesive resin layer and the ethylene-vinyl alcohol copolymer layer. is recognized. Table B below shows carbonyl group concentration of 30meq/
The peel strength (Kg/15 mm width) of a laminated sheet of 100 g of polymeric maleic anhydride-modified olefin resin and ethylene-vinyl alcohol copolymer with an ethylene content of 40 mol% is shown.

[Table] The above results show that compared to conventional acid- or acid anhydride-modified olefin resins such as modified low-density polyethylene, modified high-density polyethylene, and modified polypropylene,
It can be seen that the acid- or acid anhydride-modified linear low-density polyethylene according to the present invention has excellent delamination resistance. In the present invention, by using acid or acid anhydride-modified linear low-density polyethylene as the adhesive resin layer, it is possible to obtain superior interlayer adhesive strength and impact resistance compared to conventional modified olefin resins. This is thought to be due to the fact that modified linear low-density polyethylene has the property of being able to stretch well under relatively low tension. The above results demonstrate that the resin based on linear low-density polyethylene has the property of being able to stretch well under relatively low tension, and due to this property, in the laminated container of the present invention, the adhesive interface may be damaged or the adhesive interface may be It is recognized that residual strain is prevented and excellent adhesive strength is maintained. Furthermore, it is believed that the fact that the adhesive resin itself has excellent mechanical strength under normal conditions is also helpful in increasing adhesive strength. It should be understood that acid modification within the range described above causes almost no change in the physical properties of the resin. In addition to the acidic or acid-modified base resins mentioned above, such as low-density polyethylene, high-density polyethylene, polypropylene, ethylene-propylene copolymer, and linear low-density polyethylene, the layer mainly composed of olefin resin may be made of ethylene-vinyl acetate. It is also possible to use a material containing a copolymer or the like as a main component, and a resin that constitutes an oxygen barrier layer or an adhesive layer as a minor component. Thus,
It is possible to use burrs and the like produced by-product during blow molding as the olefin resin layer or a part thereof. In addition, from the viewpoint of oxygen barrier properties, the ethylene-vinyl alcohol copolymer constituting the multilayer container should be an ethylene-vinyl acetate copolymer with an ethylene content of 25 to 60 mol%, and a saponification degree of 96% or more. In particular, a copolymer obtained by saponification to a concentration of 99% or more can be suitably used. Of course, this oxygen barrier layer may contain other thermoplastic resins as long as the essence of the ethylene-vinyl alcohol copolymer is not impaired. In the present invention, the above-mentioned olefin resin layer
(B), the oxygen barrier layer (A) and the adhesive layer (C) are
Any layer arrangement can be used as long as (C) is interposed between layer (A) and layer (B), such as (i) three-layer structure of A/C/B, (ii) ) Four-layer structure of C/A/C/B, (iii) B/C/A/C/B, B/C/A/C/B',
(B+A+C)/C/A/C/(B+A+C) five-layer structure, (iv) six-layer structure B/B'/C/A/C/B (7) B/(B+A+C)/C/A/C /B (8) (v) Seven-layer configuration B/(B+A+C)/C/A/C/(B+A+
C)/B (9) B/B'/C/A/C/B'/B (10) Any layer configuration can be taken. The thickness of each layer is also not particularly limited, and it is generally preferable to provide each layer with a thickness ratio of B:A=1:1 to 500:1 and B:C=1:1 to 500:1. According to the present invention, a parison or sheet having a multilayer structure as described above is formed by simultaneous melt extrusion, and then this parison or sheet is formed into a bottle-shaped, cup-shaped, can-shaped container, etc. by a plastic processing method known per se. . The multilayer parison is manufactured by simultaneous melt extrusion or simultaneous injection molding of the resin layers described above into multiple layers, and a blow-molded container is obtained by expanding the parison in a molten state with a fluid. The molded container according to the present invention differs depending on its use, but generally 0.01 to 5 dl/g, particularly 0.05 dl/g.
Area weight of 2 dl/g (volume per gram of resin)
and the thickness of the container wall is 0.02 to 1 mm,
In particular, it can be in the range of 0.08 to 0.8 mm, and within these ranges a desired combination of gas barrier properties, stiffness, and transparency can be achieved. The container according to the present invention is useful as a container for preserving the contents as is, such as liquid or base foods and beverages, such as low-malt beer such as beer, fruit liquor such as alcohol, whisky, shochu, and grape wine. Alcoholic beverages including various cocktails such as Ginfuise; Various carbonated drinks including cola, cider, plain soda, etc.; Including processed fruit juice drinks such as straight, juice, and nectar such as lemon juice, orange juice, plum juice, budoji youth, and iogoji youth. Fruit juice drink; tomato juice,
Vegetable juice drinks containing various vegetable juices; Synthetic drinks and vitamin-fortified drinks containing synthetic fruit juices made with sugars such as sugar or fructose, citric acid, coloring agents, flavorings, etc., or with vitamins added as necessary; Lactic acid bacteria Beverages: cooked curry, cooked hash,
Stews such as borscht and beef stew; Gravy such as meat sauce; Sweet and sour pork, sukiyaki,
Boiled vegetables, fish, and meat such as Happo-na, Chinese-style boiled vegetables, boiled asparagus, beans, and cream-stewed tuna; Soups such as consommé soup, potage soup, miso soup, pork soup, and kenchin soup; rice, sekihan, Rice foods such as fried rice, gomokumeshi, pilaf, and kayu; Noodles such as spaghetti, soba, udon, Chinese soba, and macaroni; Compound seasonings for fried rice soup or Chinese soba soup; Yude azuki beans, Zenzai, shiruko, and ammitsu , honey beans, pudding, jelly, water yokan, etc.; processed seafood and livestock products such as meatballs, hamburgers, corned beef, ham, sausages, grilled fish, kunsei, bacon, kamaboko; mandarin oranges, peaches, pineapple pulls, cherries, olives, etc. fruit products; seasonings such as mustard oil, sauces, vinegar, mirin, dressings, mayonnaise, ketchup, edible oil, miso, lard, ketchup; luxury goods such as tofu, jam, butter, margarine; and liquids such as Ringer's liquid Pharmaceuticals, pesticides, cosmetics, cosmetics, detergents; Ketones such as acetone and methyl ethyl ketone; Aliphatic hydrocarbons such as n-hexane and n-butane; Alicyclic hydrocarbons such as cyclohexane; Aromatics such as benzene, toluene, and xylene. chlorine-containing compounds such as group hydrocarbons, ethane tetrachloride, and ethylene tetrachloride; or various higher fatty acids; gasoline, kerosene, petroleum, benzene, heavy oil, thinner, grease, silicone oil, light oil, machine oil; Dupont Co., Ltd.'s product name), etc., there is little deterioration or weight loss, and it is useful as a container for preserving each of the above-mentioned contents. The invention is illustrated by the following example. Example 1 Melt index is 0.5g/10min, density is
0.918g/cc, DTA method (heating rate, 10℃/min)
The inner and outer layers are low-density polyethylene with a peak melting point of 110℃, and the oxygen barrier resin layer (middle layer)
As, the ethylene content is 30 mol%, the vinyl alcohol content is 70 mol%, and the melting point according to the above method is
It is made of ethylene-vinyl alcohol copolymer at 182℃, and as adhesive layer resin, (i) Melt index (MI) is 0.4g/10min,
Modified linear low-density polyethylene with a density of 0.93 g/cc, a melting point of 122°C, and a carbonyl group concentration of 30 mmol/100 g polymer. (ii) The mixing ratio of the modified linear low density polyethylene and unmodified linear low density polyethylene is 90:10.
(weight ratio) mixture. Outer layer / adhesive layer / middle layer /
The diameter of the bottle is made up of 5 layers consisting of an adhesive layer and an inner layer.
40mm, effective length 880mm, 1 melt channel
Channel (for middle layer), diameter 40mm, effective length 880
mm, extruder group with 2 melt channels (for adhesive layer) and dimensions of 65 mm in diameter, effective length of 1430 mm, and 2 melt channels (for inner and outer layers), 5-layer die for coextrusion using 5
A multilayer parison with a layered structure was molded. The composition ratio of each layer of these parisons is 1:1/200:1/5:1/200:1 of outer layer:adhesive layer:intermediate layer:adhesive layer:inner layer, and the total thickness is about 5 mm.
, the inner diameter was 30 mm and the length was 30 mm. Below, as the resin for the adhesive layer, (i) the parison used is A and the same
The parison using (ii) is designated as B. This multilayer parison is sandwiched between molten blow molds, air is blown from one end to expand the parison, and the parison is blow molded to form a five-layer blow bottle.
I got AB and BB. The inner diameter of the resulting bottle is 100
mm, height 150mm, average bottle wall thickness 0.6
mm, the internal volume was about 1000 c.c., the basis weight was about 0.31 dl/g, and it was a cylindrical bottle. The oxygen permeability (Qo ₂ ) of these bottles is
It was measured by the method described in Publication No. 52-11263, and 1000 c.c. was added to each of 20 bottles AB and BB.
Filled with water, the bottle was dropped from a height of 120 cm onto a concrete floor at room temperature, and 5 people examined the presence or absence of delamination in various parts of the bottle, including the bottom, bottom corners, body, shoulders, and mouth. The delamination resistance was examined by visual judgment using a panel. For comparison, a bottle CB similar to the above-mentioned bottle was molded using low-density polyethylene having a carbonyl group concentration of 30 mmol/100 g polymer and a melting point of 110° C. as an adhesive resin. Table 1 shows the evaluation results for these bottles. It can be seen that the oxygen permeability is the same among bottles AB, BB, and CB, but in terms of resistance to delamination, bottles AB and BB are significantly superior to bottle CB.

【table】

Claims (1)

[Claims] 1 At least one layer mainly composed of an olefin resin; at least one oxygen barrier layer mainly composed of an ethylene-vinyl alcohol copolymer having an ethylene content of 25 to 60 mol%; and between these resin layers. A laminate of adhesive resin layers containing acid- or anhydride-modified linear low-density polyethylene with a density of 0.915 to 0.935 g/cm ³ and a concentration of 1 to 600 mm equivalent/100 g polymer. A multilayer plastic container comprising: