JPH0586903B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention has excellent gas barrier properties and a large capacity.
Concerning plastic containers with a large capacity of 3.5 or more. (Prior art and its problems) Conventionally, resin compositions made of polyolefin and ethylene/vinyl alcohol copolymer or linear polyamide have excellent processability and gas barrier properties, and containers have been made using such resin compositions. It is known that molding is possible (JP-A No. 48-7038;
--No. 41657). However, even if the high gas barrier properties of the resin composition as described above are effectively exhibited in the case of small-capacity containers such as general food containers, the capacity is 3.5%.
When used in large containers such as those mentioned above, there is a problem that sufficient gas barrier properties cannot be obtained. That is, the container to which the above-mentioned prior art is directed has a small capacity, and the thickness of the container is extremely thin, about 0.5 mm at most. On the other hand, in the case of the aforementioned large-capacity containers, the thickness of the container wall is usually in the range of 0.7 mm or more, which is significantly thicker than that of small-capacity containers. The conditions are significantly different from those for small-capacity containers, and it is thought that these differences in manufacturing conditions are responsible for the deterioration of gas barrier properties in large-capacity containers. (Means for Solving the Problems) As a result of intensive studies by the present inventors on a method for manufacturing large-capacity containers using a resin composition consisting of polyolefin and ethylene-vinyl alcohol copolymer or linear polyamide, After melting and kneading the composition, an amount of parison corresponding to the basis weight of the container is stored, and then the melt is discharged in the shape of a parison through a die slit at a discharge amount within a certain range, and then a hollow is formed in the shape of the container. Molding (blow molding)
It has been found that a large-capacity container with excellent gas barrier properties can be obtained when this is carried out. That is, according to the present invention, (A) a composition containing a polyolefin and an ethylene-vinyl alcohol copolymer or a linear polyamide in a weight ratio of 99:1 to 75:25, or (B) the above composition 100 0.5 to 20 per part by weight
After melt-kneading a composition containing parts by weight of carbonyl-modified olefin resin, it is supplied to a die equipped with a storage mechanism to store an amount of parison corresponding to the container basis weight, and the stored melt is discharged through the die slit. Provided is a method for manufacturing a high-gas barrier large-capacity container, which is characterized by discharging into a parison under conditions such that the amount is 2 to 3000 g/sec, and blow-molding the discharged parison into the shape of a container. (Function) In the present invention, by temporarily storing the kneaded melt of the resin composition in the storage mechanism provided in the die, it is possible to maintain the discharge pressure from the die slit within a constant range at all times. Become. That is, when manufacturing a large-capacity container, if the liquid is discharged directly from the die slit without using such a storage mechanism, the discharge pressure tends to fluctuate, and the tip of the discharged parison is cooled.
As a result, blowing failures often occur for reasons described below, and even if blow molding into the shape of a container can be achieved, it is recognized that high gas barrier properties cannot be obtained in the container. Further, a large extruder is required to continuously discharge the resin, but if a storage mechanism is provided, there is no need to use a particularly large extruder. In addition, in the present invention, the discharge amount of the melt from the die slit is set at 2 to 3000 g/ec, particularly 5 to 3000 g/ec.
It is also important to set the range to 2700 g/sec. That is, when a container is molded using a resin composition consisting of polyolefin and an ethylene-vinyl alcohol copolymer (sometimes called EVOH) or linear polyamide, a layer in which polyolefin is preferentially distributed and a layer in which EVOH or linear polyamide is preferentially distributed are formed. It is known that when such a layered distribution structure is formed, excellent high gas barrier properties are exhibited (Japanese Patent Publication No. 51-30104).
issue). However, according to the present invention, for example, the kneaded melt of the resin composition supplied from an extruder is once stored, and then discharged from a die slit at a discharge rate within the above range to be formed into a parison shape. It is recognized that a layered distribution structure as described above is formed. For example, if the melted and kneaded material is discharged from a die slit without going through a storage mechanism, the discharge pressure will fluctuate, so that the layered distribution structure as described above will not be formed. When the discharge amount from the die slit is made larger than the above range, the flow of the melt-kneaded material becomes turbulent and homogeneous mixing of the polyolefin and EVOH or linear polyamide occurs, resulting in a layered distribution structure. is not formed. Furthermore, if the discharge amount is made smaller than the above range, not only will the discharge time become longer and the molding cycle will take a longer time, but also problems such as blowing defects may occur during hollow molding of the parison. Become. Thus, according to the manufacturing method of the present invention, even in large-capacity containers, a layered distribution structure is formed on the container wall, and high gas barrier properties can be obtained. (Preferred Embodiment of the Invention) Resin Composition As the polyolefin used in the present invention, any polyolefin that has conventionally been widely used for molding films, containers, etc. can be used.
Such polyolefin has the formula

[Formula] In the formula, R is a hydrogen atom or an alkyl group having 4 or less carbon atoms. An olefin polymer or copolymer represented by the following can be used. It is important that these olefin polymers or copolymers be crystalline in order to have sufficient mechanical strength when formed into a molded structure. Examples of such polyolefins include low, medium, or high density polyethylene, isotactic polypropylene, and crystalline ethylene.
Propylene copolymers, polybutene-1, and polypentene-1 can be mentioned. Of course, the polyolefin used in the present invention is not limited to a homopolymer of olefins or a copolymer of two or more types of olefins, and may contain a small amount of other copolymers as long as the properties of the polyolefin are not essentially impaired. A copolymer containing other ethylenically unsaturated monomers, such as vinyl chloride, vinyl acetate, acrylic acid or its esters, methacrylic acid or its esters, in a polymerization component, for example, up to 5 mol%. Good too. The molecular weight of the polyolefin used generally needs to be within the molecular weight range that allows film formation, for example, the average molecular weight is 5,000 to 400,000 [melt index (ASTM-1238) MI = 0.05 to 5.0 g/10 min].
are generally preferably used. Particularly suitable polyolefins for the present invention, in order of importance, are (1) high-density polyethylene with a density of 0.940 g/cc or more, (2) isotactic polypropylene, and (3) polyolefin with a density of 0.930 to 0.939 g/cc. (4) low density polyethylene with a density of 0.917 to 0.929 g/cc or less, and blends thereof. In the present invention, when the above-mentioned low-density polyethylene is used, it is possible to noticeably develop a layered structure with mutually different resin compositions, and it is also possible to improve properties such as transparency, flexibility, and impact resistance. On the other hand, when high density polyethylene or isotactic polypropylene is used, mechanical properties such as stiffness tensile strength and tear strength can be improved. In the present invention, the above-mentioned polyolefin (a)
and EVOH or linear polyamide (b) in a weight ratio of a:b=99:1 to 75:25, particularly 99:5 to 80:20. By adopting such a blending ratio, the polymer composition differs in the thickness direction, but the polymer composition is substantially constant in the plane direction of the container wall, and the layer is continuous in that plane direction. This results in a container with a shaped layered structure. The ethylene-vinyl alcohol copolymer used is usually obtained by saponifying an ethylene-vinyl acetate copolymer having an ethylene content of 25 to 50 mol% to a degree of saponification of 96% or more. The ethylene content in this saponified copolymer is
If it exceeds 50 mol%, the saponified copolymer loses its permeability to gases such as oxygen (gas barrier properties), and the container wall adopts a layered distribution structure in which the polymer composition differs in the thickness direction. This makes it difficult to do so, and is not suitable for the purpose of the present invention. On the other hand, if the ethylene content of the saponified copolymer is lower than 25 mol %, the hydrophilicity increases, the water vapor permeability increases, and the melt moldability decreases, so that it is not suitable for the purpose of the present invention. Further, the degree of saponification of the ethylene-vinyl acetate copolymer is required to be 96% or more in order to improve the gas permeation resistance of the container. EVOH particularly preferably used in the present invention
has an ethylene content of 25 to 45% and a saponification degree of 99% or more. The molecular weight of EVOH used in the present invention is not particularly limited as long as it is within a molecular weight range that can generally form a film. The viscosity of EVOH is generally 85% by weight of phenol.
The intrinsic viscosity [η] measured using this mixed solvent at a temperature of 30°C is preferably in the range of 0.07 to 0.17/g. It is. If [η] is lower than 0.07/g, the mechanical strength when used as a container is unsatisfactory, while if [η] is higher than 0.17/g, the moldability of the resin composition tends to decrease. be. In addition, polyamides that can be used instead of the ethylene-vinyl alcohol copolymer have the following formula:

[ka] or

embedded image In the formula, n is a number from 3 to 13, and m is a number from 4 to 11. Examples of the polyamides are as follows. Poly-ω-aminocaproic acid, poly-ω-aminoheptanoic acid, poly-ω-aminocaprylic acid, poly-ω-aminopelagoic acid, poly-ω-aminodecanoic acid, poly-ω-aminoundecanoic acid, poly-ω-amino Dodecanoic acid, poly-ω-aminotridecanoic acid, polyhexamethylene adipamide, polyhexamethylene sebacamide, polyhexamethylene decamide, polyhexamethylene tridecamide, polydecamethylene adipamide, polydecamethylene sebacamide Bacamide, polydecamethylene dodecamide, polydecamethylene tridecamide, polydodecamethylene adipamide, polydodecamethylene sebacamide, polydodecamethylene dodecamide, polydodecamethylene tridecamide, polytridecamethylene adipamide , polytridecamethylene sebamide, polytridecamethylene dodecamide, polytridecamethylene tridecamide, polyhexamethylene azeramide,
Homopolyamides such as polydecamethylene azeramide, polydodecamethylene azeramide, and polytridecamethylene azeramide. caprolactam/laurinlactam copolymer,
Caprolactam/hexamethylene diammonium adipate copolymer, laurin lactam/hexamethylene diammonium adipate copolymer, hexamethylene diammonium adipate/hexamethylene diammonium sebacate copolymer, ethylene diammonium adipate/hexamethylene diammonium adipate copolymer Mention may be made of polymers, copolyamides such as caprolactam/hexamethylene diammonium adipate/hexamethylene diammonium sebacate copolymers. These homopolyamides and copolyamides are
It can also be used in the form of a so-called blend, such as a blend of polycaprolactam and polyhexamethylene adipamide, a blend of polycarolactam and a caprolactam/hexamethylene diammonium adipate copolymer, etc., all of which are suitable for the purpose of the present invention. It can be used for These polyamides are substantially linear;
Also, the melt molding temperature of the final resin composition, e.g. 170
It must melt at temperatures between 300°C and 300°C. In the present invention, those that are easily available and particularly desirable for the purpose of the present invention are poly-ω-aminocaproic acid, poly-ω-aminoundecanoic acid, poly-
These are aliphatic polyamides such as ω-aminododecanoic acid, polyhexamethylene adipamide, polyhexamethylene sebamide, and caprolactam/hexamethylene diammonium adipate copolymer. The molecular weight of these polyamides may generally be a molecular weight sufficient to form a film. This molecular weight range has a relative viscosity of 1.5 to 6.0, particularly preferably 1.8 to 6.0, measured at a concentration of 10 g of polyamide in 1 part of 98% sulfuric acid at a temperature of 20°C. It can be expressed as a range of 4.0. In the present invention, the above-mentioned resin composition used for molding the container includes the composition in order to improve the smoothness, uniformity, etc. of the surface of the container, and to improve processability or workability during molding. It is desirable to blend 0.5 to 20 parts by weight of carbonyl-modified olefin resin per 100 parts by weight of the material. Such modified olefin resins have a carboxylic acid, carboxylic anhydride, carboxylate, carboxylic acid amide, or carboxylic ester group bonded to a polymer chain, and an ethylenically unsaturated monomer containing these groups. It can be obtained by copolymerizing the polymer with olefins, or by modifying polyolefins by means such as graft polymerization or block copolymerization. Suitable examples of the carboxylic acid derivative group-containing ethylenically unsaturated monomers mentioned above are as follows. Carboxylic acid or carboxylic acid anhydride; acrylic acid, methacrylic acid, fumaric acid, maleic acid, maleic anhydride, itaconic anhydride, crotonic acid, tetrahydrophthalic anhydride. Carboxylic acid amides; acrylamide, methacrylamide, maleimide. Carboxylic acid ester; Vinyl esters such as vinyl acetate and vinyl propionate. and (meth)acrylates such as ethyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 3-hydroxypropyl (meth)acrylate, and N-ethylaminoethyl (meth)acrylate. Suitable examples of carbonyl-modified olefin copolymers are as follows. Ethylene-vinyl acetate copolymer, for example, ethylene or propylene and acrylic acid or methacrylic acid, are copolymerized with these ester monomers if necessary, and alkali metal ions such as sodium and potassium, alkaline earths such as magnesium, etc. Copolymers formed by ionic crosslinking with similar metal ions, zinc ions, organic cations, etc., such as ionomers (Himilan manufactured by DuPont Mitsui Polychemicals). Backbone polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene-1 copolymer, ethylene-vinyl acetate copolymer, etc., maleic acid, maleic anhydride, acrylic acid, methacrylic acid, (meth)acrylate A copolymer obtained by grafting , (meth)acrylamide, etc. These carbonyl-modified olefin resins preferably contain a carbonyl group (>C=0) based on a carboxylic acid or a derivative thereof at a concentration of 10 to 400 mmol per 100 g of the resin. The modified olefin resin should have a molecular weight sufficient to form a film, and preferably has a melting point in the range of 50 to 200°C, particularly 70 to 160°C. The resin composition used in the present invention may contain well-known compounding agents such as ultraviolet absorbers, stabilizers, lubricants, antioxidants, pigments, dyes, antistatic agents, etc., depending on the purpose of the container. It can be blended according to the prescription. In addition, other polymers such as olefin copolymers and diolefin copolymers may be added to the extent that they do not substantially affect properties such as gas barrier properties and impact resistance.
It can be blended in amounts up to parts by weight. Molding Method In the present invention, a large-capacity container is molded using the above-mentioned resin composition, and FIG. 1 shows the overall configuration of an extrusion molding apparatus for suitably carrying out this molding. In this device, a cylinder 2 is provided in the lower half of the accumulator head 1;
A ring piston 3 that slides up and down along the inner circumferential surface of the piston 3 is provided. In addition, in the center of the accumulator head 1,
A core 4 is provided that passes through the ring piston 3 and is fixed to the cylinder 2. Furthermore, the inside of the cylinder 2 is partitioned by a ring piston 3, and the cylinder 2 and a core 4 are separated from each other by a ring piston 3.
A resin storage chamber (resin reservoir) 5 is formed surrounded by. This resin storage chamber 5 contains a molten resin composition continuously extruded from an extruder 6.
It is designed to be supplied through an annular communication path 7 connected to an extruder 6. Further, the cylinder 2 is provided with a temperature adjustment mechanism (not shown) consisting of a heater, etc., and the temperature of the resin composition stored in the resin storage chamber 5 is adjusted to be within a certain range. An annular die 8 is provided at the lower end of the cylinder 2.
are fixed concentrically, and an annular core support 9 is fixed to the lower end of the core 4, and a core 10 concentric with the die 8 is fixed to the center of the core support 9. are fitted to be slidable in the direction. The inner circumferential surface of the lower end of the die 8 and the circumferential surface of the lower end of the core 10 are each formed into a conical shape, and an annular die slit 11 is formed therebetween.
The die slit 11 communicates with the resin storage chamber 5 through an annular resin passage 12 formed between the core 4 and the core support 9. Further, the core 10 is moved up and down by a hydraulic cylinder (not shown) via a rod 13, thereby adjusting the width of the die slit 11 formed between it and the die 8, that is, the thickness in the radial direction. It's getting old. The ring piston 3 is lowered by a single-acting hydraulic cylinder 15 via a rod 14, and the hydraulic cylinder 15 and the ring piston 3 move the resin composition in the resin storage chamber 5 into the resin passage 12. Also, an accumulator 16 is configured to force-feed to the die slit 11. According to the method of the present invention, the above-described resin composition is melt-extruded using an extruder 6. In this case, the premixing of the polyolefin, ethylene-vinyl alcohol copolymer, linear polyamide, carbonyl-modified olefin resin, etc. can be carried out by any method known per se, and is not particularly limited. For example, these polymers are in powder or granular form, and prior to melt extrusion, they can be simply dry blended (room temperature mixing) using a mixer or the like at room temperature, and there is no particular need for mixing them in a molten state. Also, like burrs that occur during molding,
It is possible to use what has been melted and mixed once. Further, as the extruder 6 used, any well-known melt extruder can be used, but care must be taken so that the molten resin flow becomes a laminar flow, that is, mixing of each resin flow does not substantially occur. For this reason, it is desirable to use an extruder equipped with a full-flight screw such as a metering screw. The resin composition melted and extruded from the extruder 6 is supplied to the resin storage chamber 5 through an annular communication path 7. In this case, the rod 13 is raised by the operation of the hydraulic cylinder, and the die slit 11 is thereby closed. Therefore, as the melt of the resin composition is supplied to the resin storage chamber 5, the ring piston 3 rises, and thus a parison amount of the melt corresponding to the basis weight of the container is stored in the resin storage chamber 5. Then, by the operation of the hydraulic cylinder, rod 1
3 is lowered, the die 10 is also lowered, and a predetermined gap is maintained in the die slit 11. In this state, the accumulator 16 operates, the ring piston 3 descends, and the molten resin composition is discharged through the resin passage 12 and the die slit 11. In the present invention, the amount of the melt discharged from the die slit 11 is 2 to 2, as described in detail above.
It is adjusted to 3000 g/sec, particularly in the range of 5 to 2700 g/sec. In addition, in order to maintain the discharge amount within the above range, the die slit 1 is controlled by a single acting hydraulic cylinder 15.
The discharge pressure from the cylinder 1 varies depending on the scale of the cylinder, but is generally 5 to 8000 Kg/cm ² , especially 10
It is set in the range of 5000Kg/cm ² . When this discharge pressure is less than 5Kg/ ^cm2 ,
There is almost no difference between the average flow velocity of the polyolefin resin flow and the average flow velocity of the EVOH or linear polyamide flow, making it difficult to provide the desired layered distribution structure on the container wall. Furthermore, since the speed at which the parison is discharged from the die slit 11 is reduced, the parison becomes cold, which is not preferable. Further, if the discharge pressure exceeds 8000 Kg/cm ² , mixing of the resin melt flow occurs, which tends to make it difficult to provide the desired layered distribution structure. Further, in the present invention, the discharge temperature of the melt, that is, the temperature of the melt stored in the storage chamber 5 is set at 2 to 50°C, particularly 3°C, higher than the melting point of the ethylene-vinyl alcohol copolymer or the linear polyamide. It is desirable to adjust the temperature to 40°C higher. If this temperature is lower than the above range, the molding temperature will be close to the melting point of EVOH or linear polyamide, so the layered structure of the container wall will tend to become discontinuous in the plane direction, and if it is higher than the above range. in case of,
There is a tendency for EVOH or linear polyamide to deteriorate due to oxidation or thermal decomposition, and in either case it becomes difficult to obtain a sufficiently high gas barrier property. According to the invention, the melt is passed through the die slit 1.
1 in the form of a parison, which is formed into a container by blow molding, which is known per se. (Effects of the Invention) According to the present invention, it is possible to maintain sufficiently high gas barrier properties even in large capacity containers of 3.5 or more. In particular, in the case of large-capacity containers, unlike small-capacity containers for general food, etc., it is extremely difficult to construct the container from a multilayered laminate, so it is difficult to obtain the high gas barrier properties described above. It should be understood that the present invention is extremely useful. The invention is illustrated by the following example. (Example) Example 1 50 kg of the following four types of resins were prepared according to the following blending ratio.
The mixture was dry blended using a tumbler-type dry blender. High density polyethylene 45% by weight Density (ASTM D-1505) 0.945g/cm ³ MI 0.33g/10min Melting point 148℃ Low density polyethylene 45% by weight Density (ASTM D-1505) 0.922g/cm ³ MI (ASTM D-1238 )0.50g/10min Melting point 108℃ Ethylene-vinyl alcohol copolymer
5% by weight Ethylene content 30mol% Saponification degree 99% Intrinsic viscosity 0.15/g Melting point 182℃ Ionomer 5% by weight (Ethylene with sodium ion bond)
Methyl methacrylate copolymer) Ethylene content 96 mol% Density (ASTM D-1505) 0.945 g/cm ³ MI (ASTM D-1238) 1.0 g/10 min Melting point 106°C Furthermore, in the apparatus shown in Figure 1, as extruder 6 An extrusion molding device equipped with a built-in full-flight screw (diameter: 60 mm, effective length to diameter ratio: 22) was used. The dry blend was fed into the extruder 6 to perform melt extrusion, and the blended melt having a container basis weight was stored in the storage chamber 5 of the molding device and discharged from the die slit 11 to mold a parison. The molding conditions at this time were as follows. Indicated temperature (extruder screw supply section) 170℃ Indicated temperature (storage chamber) 180℃ Indicated temperature (die slit section) 200℃ Resin temperature (parison temperature) 202℃ Discharge pressure 450Kg/cm ^2Discharge amount 162g/sec This parison The average thickness is 3.93mm, and the filled volume is
A large capacity container with a weight of 23.6 kg and a weight of 1.63 kg was manufactured.
The center part of the body of this container was cut out into a square of about 1.5 m, and the cut surface of the cut test piece was thoroughly polished with sandpaper, and then dyed with a 1 wt % Congo Red aqueous solution at 85°C. When the cut surface and partially peeled surface of this dyed test piece were observed using a stereomicroscope, it was found that the red-stained portion, that is, the ethylene-vinyl alcohol copolymer layer, was continuously distributed in a layered manner in the axial direction of the bottle. It was recognized that there was. The oxygen permeability of this container was measured by gas chromatography (see Japanese Patent Publication No. 57-48459) and found to be 0.33 cc/bottle·day·atm [37°C]. For comparison, the high-density polyethylene from 1) above was discharged and blow-molded under the same conditions as above, and a large-capacity container with the same wall thickness, filled volume, and weight as above was manufactured. When the oxygen permeability was measured in the same way, it was 2.43cc/bottle・day・atm
It was [37℃]. Comparative example 1 For comparison, (1) discharge amount 1.5g/sec and (2) discharge amount
Discharge blow molding was carried out in exactly the same manner as in Example 1 except that the rate was 3200 g/sec. Under condition (1), the discharged parison cooled and could not be formed into a container. Furthermore, under the condition (2), it was possible to mold it into a container. According to the dyeing test for this container, the red dyed portions were distributed almost evenly throughout the container, indicating that the ethylene-vinyl alcohol copolymer was mixed almost homogeneously. The oxygen permeability of this container is 2.36cc/bottle.
day・atm [37℃]. Example 2 A dry blend was prepared in the same manner as in Example 1 except that the following 6-nylon was used instead of the ethylene-vinyl alcohol copolymer. 6-Nylon Melting point: 220°C Relative viscosity: 2.20 Using this dry blend, a parison was molded under the following molding conditions, and a container was manufactured in the same manner as in Example 1. Indicated temperature (extruder screw supply section) 210℃ Indicated temperature (storage chamber) 225℃ Indicated temperature (die slit section) 223℃ Resin temperature (parison temperature) 225℃ Discharge pressure 4300Kg/cm ² Discharge rate 715g/sec Obtained The containers had an average thickness of 17.0 mm, an internal capacity of 104, and a weight of 7.25 kg. When this container was subjected to the same dyeing test as in Example 1, it was found that 6-nylon was continuously distributed in a layered manner. Also, the oxygen permeability of this container is 0.41cc/bottle.
day・atm [37℃].

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the overall configuration of an extrusion molding apparatus for suitably carrying out the method of the present invention. DESCRIPTION OF SYMBOLS 1... Accumulator head, 2... Cylinder, 3... Ring piston, 5... Resin storage chamber, 6... Extruder, 8... Die, 9... Core support, 10... Core, 11... ...Dice List.

Claims (1)

[Claims] 1 (A) Polyolefin and ethylene/vinyl alcohol copolymer or linear polyamide in a ratio of 99:1
After melt-kneading a composition containing a carbonyl-modified olefin resin in a weight ratio of 0.5 to 20 parts by weight per 100 parts by weight of the composition, or (B) a composition comprising a storage mechanism. A parison quantity corresponding to the container basis weight is stored in the die, and the stored melt is discharged into a parison shape through the die slit under conditions such that the discharge rate is 2 to 3000 g/sec. A method for manufacturing a large-capacity container with high gas barrier properties, which is characterized by blow-molding a parison into the shape of a container. 2. The manufacturing method according to claim 1, wherein the melt is discharged at a temperature 2°C to 50°C higher than the melting point of the ethylene-vinyl alcohol copolymer or the linear polyamide.