JPS63302017A - Manufacture of multi-layer container - Google Patents

Abstract

PURPOSE:To manufacture a multi-layer container without deterioration of barrier properties which may be generated by water absorbing properties by injection molding a parison constituted of a thermoplastic resin layer and an ethylene- vinyl alcohol copolymer layer containing drying agent particles. CONSTITUTION:A composition constituted of an ethylene-vinyl alcohol copolymer, in which drying agent particles (phosphoric acid-sodium fine powder) are mixed, is injection molded between the inner and outer layers of a polypropylene resin by a multi-layer injection molding machine. A parison constituted of three layers of polypropylene/ethylene-vinyl alcohol copolymer composition containing drying agent particles/polypropylene is molded. A multi-layer container thus manufactured is free from the deterioration of barrier properties of an intermediate layer of an ethylene-vinyl alcohol copolymer which may be generated by water absorbing properties, and the content can be preserved for a long time even with the thin intermediate layer.

Description

Detailed Description of the Invention A. Technical Field of the Invention The present invention relates to a method for manufacturing a multilayer container suitable for packaging foods, pharmaceuticals, cosmetics, and other comfortable goods, and more specifically, a multilayer container exhibiting high gas barrier properties. This relates to a manufacturing method.

B. Prior art ethylene-vinyl alcohol copolymer mn& (hereinafter referred to as EV
It is widely used as a packaging material for foods, cosmetics, pharmaceuticals, etc. because it has excellent barrier properties against gases such as oxygen and carbon dioxide, is thermoplastic, and can be easily molded. However, since EVOH has a hydrophilic hydroxyl group, it has insufficient water resistance and moisture proofing properties when used alone, and is often used as a multilayer product by laminating it with other resins that are hydrophobic or water resistant. As for hollow containers, a method has been proposed or put into practical use in which resins such as polyethylene, polypropylene, polyethylene terephthalate, etc. are used for the inner and outer layers, and EVO) I is used for the intermediate layer. For example, JP-A-55-1392
No. 28 discloses a method of simultaneously injecting unsaturated carboxylic acid graft-modified polypropylene and EVOL (i) to form a parison of two layers and three layers, and then stretch-blow molding the parison to obtain a multi-stretch hollow container. Also, If, opening/closing 56-1
No. 67442 proposes a multi-stretch bottle in which the inner and outer layers are made of polyethylene terephthalate and the middle layer is made of EVOH. However, especially in applications that require full gas barrier properties and are used at high temperatures, such as containers for carbonated beverages, beer, wine, and mineral water, humidity can cause a decrease in the gas barrier properties of E V Of. was the problem.U.S. Patent No. 4425
No. 410 describes a method of preventing the deterioration of the barrier properties of EVt)El due to water absorption during retorting by incorporating all the desiccant into one layer of EVO), and furthermore, European Publication No. 0059274 , U.S. Patent No. 44078
No. 97, JP-A No. 5.7-170748 has EVO)
A method is disclosed in which a desiccant is added to the fallen fat layer adjacent to the EVOI to prevent the barrier properties of the EVOI from deteriorating due to water absorption during retorting.

C0 Problems to be Solved by the Present Invention However, when a multilayer container is manufactured by adding a desiccant to the EVOH layer by the method disclosed in the above patent or patent publication, and this is applied to the storage of all beverages, EVOH = i use. If compared with the above case, the same gas permeability resistance can be seen, but
The degree of this was still low, and to make matters worse, the adhesion between the layers was significantly reduced due to the desiccant particles, and delamination was likely to occur, making it impractical for practical use. On the other hand, EVU) Method 1-1 of adding a desiccant to the resin layer adjacent to I: In order to exhibit an effective effect, adhesive resin If containing a desiccant must be used.
fe It is necessary to use it thickly, and the diameter is 8! There is a problem with sexuality.

Means for Solving Problem D1 4- Under these circumstances, the present inventors have developed I-E, which has good indirect lubricity, is economical, and has good gas barrier properties under sieve humidity.
As a result of intensive studies on multi-liter containers using VOH, we found that the intermediate layer is a composition in which desiccant particles are dispersed in the form of fine particles in the matrix of EVU, H, and the inner and outer layers are hydrophobic or water-resistant thermoplastic resins. It has been found that this problem can be solved by manufacturing a multilayer container by injection molding.

E1 More detailed description of the invention EVOH as used in the present invention is obtained by hydrolyzing the vinyl acetate unit in the typical form of ethylene and vinyl acetate, and it can be any arbitrary substance, but it is suitable for the purpose of the present invention. In particular, those having an ethylene unit content of 25 to 60 mole and a saponification degree of vinyl acetate units of 96% or more, especially 99% or more are mentioned. As for 0.2~60
A range of f/10 minutes is exemplified. In addition, E as referred to in the present invention
VO)L is 5 mol% and may be modified with copolymerizable monomers in the following range, such modifying monomers include propylene, 1-puane, 1-hexene, 4-methyl-
1-pentene, acrylic acid ester, methacrylic acid ester, maleic acid, fumaric acid, itaconic acid, higher fatty acid vinyl ester, alkyl vinyl ether, N-(2-
)) f-aminoethyl) methacrylamide, or its quaternized product, N-vinylimidazole, or its quaternized product, N-vinylpyrrolidone, N-n-butoxymethylacrylamide, vinyltrimethoxysilane, vinylmethyldimethoxysilane , vinyldimethylmethoxy7silane, etc. can all be mentioned.

As the E v OH matrix, EVs with different compositions are used.
It is also possible to mix and use two or more OH resins. In addition, to the extent that the effects of the present invention are not impaired, other resins may be blended into L/Lux, color agents such as pigments and dyes, antistatic agents, ultraviolet absorbers, plasticizers, heat stabilizers, lubricants, etc. Additives may also be added.

In addition, the desiccant used in the present invention includes salts that form water 'A11 products, that is, salts that absorb all of the water as crystalline water, especially sodium phosphorus, disodium phosphate,
Although phosphates such as tris-lithium phosphate, trilithium phosphate, and sodium pyrophosphate, especially their anhydrides, are most suitable for the present invention due to their effectiveness, other hydrate-forming salts, such as Salts such as sodium borate and sodium sulfate, especially their anhydrides, are also suitable for the present invention, and other hygroscopic compounds such as sodium chloride and the like can also be used. Two or more of these buildings can be used at the same time.

In the present invention, it is necessary for the desiccant to be dispersed as fine particles in the EV OH matrix, and the desiccant particles have a long diameter of 10 μ'' and the average diameter of the upper particles is 30 μm. /1 or less, and only when such a finely dispersed state is completely formed can the conventionally achieved 7'1
．． It is possible to obtain a multilayer container with unprecedented high degassing gas permeability. Compositions with such a finely dispersed state can only be achieved by carefully combining special processing methods tailored to the purpose. First, the desiccant is precipitated by spray-drying an aqueous salt solution. Special care should be taken to obtain as fine a grain size as possible during deposition. The thickness is 30μ or less, preferably 10
Although it can be used by dividing it into smaller than 100 μm, it is generally used in dry salt whole jet crushers, impact crushers, ball mino [
-Alternatively, perform ultrafine pulverization using a vibrating ball mill, etc.

Use a classifier such as a wind classifier to reduce the pulverized material to 30μ.
In the following, all ultrafinely pulverized products, preferably 10 microns or less, will be separated.

Here, the term 30μ or less means that the number of particles having a diameter of 30μ is at least 999.

When performing this particle size measurement, if necessary, in order to completely concentrate the small amount of coarse particles, it is necessary to pass the coarse particles through a 10 to 75 μm sieve in advance and analyze the coarse particles in each sieve using a coulter counter. All coarse particles can be analyzed with high accuracy.

Next, the desiccant ultrafine powder and avoH described above are completely mixed. The method of mixing is to mix ultrafine desiccant powder and EVOH powder,
The pellet-like material can be mixed in a conventional mixer such as a Henschel mixer, a super mixer, or a tumbler. powder,
There are many methods of mixing granules and pellets into the melt. Next, this mixture -q is kneaded at a temperature higher than the melting point of EVOH to make a composition! ! ! do. EVO)i and desiccant particles may be mixed in advance as described above, or EVOH and desiccant particles may be directly introduced into a mixer and kneaded.

During this kneading operation, desiccant fine particles tend to aggregate with each other, and even if ultrafine powder of 10μ or less is used, if they aggregate to form aggregates exceeding the volume average diameter specified in the present invention, the present invention No significant effect can be obtained. Therefore, crosstalk operation is extremely important in the present invention. Continuous intensive mixers, kneading type twin screw extruders (
Continuous mixer such as same direction or different direction is most suitable, but Banbury Mikya, intensive mixer,
A batch type kneader such as a pressure kneader can also be used. Another type of continuous kneading device is one that conveniently uses a rotating disk with a rock mill-like structure, such as (K)
A KCK kneading extruder manufactured by CK may also be used. Some of the commonly used kneading machines include those that have a single-screw extruder with a complete mixing section (Dulmage, CTM, etc.), and simple mixers such as Prabender mixers. It is quite difficult to obtain an excellent composition for use in non-inventive applications using kumquats.

Among these, continuous intensive mixers are most preferred for the purpose of the present invention. Models on the market include Fa, 1" CM made by SE1, CIM made by Nippon Steel Works, and KC made by Nippon Steel Works.
There are M, CLVII-, LCM, ACM, etc.

In fact, it is preferable to employ an apparatus that has one extruder below these mixers and performs mixing and extrusion into pellets at the same time.

A twin-screw kneading extruder with a kneading disc or a cross-rotating rotor, such as ■Japan Steel Works t7) T
ZSK manufactured by EX % Werner & Pfleiderer, TEM manufactured by Toshiba Machine ■, PCM manufactured by Ikegai Iron Works ■, etc. can also be used for the purpose of kneading in the present invention.

When using these continuous twin-screw kneaders, the shapes of the rotor and disk play an important role. In particular, the gap (tip clearance) between the mixing chamber and the rotor tip or disk tip is important; if it is too narrow or too wide, the composition of the present invention having good dispersibility cannot be obtained. The optimal tip clearance is 1 to 5 square meters. In addition, in order to obtain the composition *-+ having good dispersibility of the present invention, the specific energy of the crosstalk machine is Q, l KWh.
It has been found that it is necessary to knead at a rate of 0.2 to 0.8 Kwh/kf, preferably 0.2 to 0.8 Kwh/kf.

Specific energy is obtained by dividing the energy used for kneading (power consumption; core 0 by the amount of crosstalk per hour (ky), and its unit is shield, -.Specific energy is usually In order to obtain the composition of the present invention, it is necessary to knead at a higher value than that adopted for kneading.
In order to make the specific energy Q, lywhAg or higher, it is insufficient to simply increase the rotational speed of the kneader; the composition being kneaded must be cooled (using a jacket, etc.) to increase the temperature.
It is preferable to lower k and increase the viscosity completely. If the viscosity is kneaded in a low viscosity state, it is difficult to obtain the composition targeted by the present invention. Therefore, it is effective that the crosstalk temperature is within the range of the melting point of EVOH to the melting point +60°C, more preferably within the range of the melting point to the melting point +40°C, based on the temperature of the discharged resin at the exit of the crosswire section. The rotation speed is 100 to 1200 rpm, preferably 200 to 120 rpm.
Orpm, more preferably a range of 400 to 1200 rpm. Mixer units 4 to 10 are suitable. Further, the number of crosstalk devices may be one, or two or more may be used in conjunction.

The longer the crosstalk time, the better the milled rice will be, but from the viewpoint of thermal deterioration and alteration of EVOH, and economic efficiency, it is 10 to 600 seconds,
Suitably the range is 20 to 200, most preferably 20 to 200.
It is 100 seconds.

There is no particular restriction on the usage ratio of EVUH and desiccant, but the weight ratio is 97=3 to 50:50, especially 95:5 to 70:
A ratio in the range of 30 is preferred.

The particle size of the desiccant particles in the composition is determined by microscopy, usually by visual inspection of a photograph taken, or by an image analysis device. In the present invention, it is necessary that among the dispersed particles, particles having a major diameter of 10 μm or more have a body area average diameter of 30 μm or less. Here, the major axis is the projection il! of each particle. It means the distance between two parallel lines that gives the maximum distance when sandwiched between them. For particles with a major diameter of 10 μm or more, it is necessary to determine the average particle diameter. Various methods are known for determining the average particle diameter, but a method suitable for the purpose of the present invention is a method in which the average value of the diameter B in the direction perpendicular to the long axis and the length is determined as the average diameter. is convenient. This method is one of the methods often adopted by those skilled in the art. In this way, within the appropriate measurement range 200μ x 200μ
When the average diameter DN of each particle is determined, body area average diameter -13=DAv is defined by DAv=ΣDN3/ΣDN2.

As clarified in the present invention, among the desiccant particles in the present composition, the body area average diameter of particles with a major axis of 10 μ or more is large in the gas permeation resistance of the multi-F-container containing this composition as a layer. The reason for this is not necessarily clear, but particles with larger diameters have a moisture absorption effect or I! ;V 01(
It is presumed that this has a particularly disadvantageous effect on the gas permeability of .

The composition thus obtained is used by injecting it into a multilayer structure using other thermoplastic resins for the inner and outer layers.

Thermoplastic resins used for the inner and outer layers include polyolefin resins, saturated polyester resins, polyamide resins,
Examples include polyesteramide resin, polystyrene resin, polyvinyl chloride resin, acrylic resin, polyvinylidene chloride resin, polyurethane resin, polyvinyl acetate thread resin, polyacetal resin, polycarbonate resin, etc. Of these, polyolefin resins are particularly important to the present invention in terms of their effectiveness and performance, followed by saturated polyester resins and polyamides, polyvinyl chloride resins, and polystyrene yarns. The fact is also important.

Examples of polyolefin resins include medium-density or low-density polyethylene, vinyl acetate, acrylic ester, or α-olefin gold co-typing polyethylene such as butene, hexene, and 4-methyl-1-pentene; Ionomer resin, polypropylene homopolymer,
Polypropylene graft copolymerized with ethylene, or polypropylene copolymerized with α-olefins such as ethylene, butene, hexene, and 4-methyl-1-pentene, poly-1-butene, poly4-methyl-1-pentene, Alternatively, it includes a modified polyolefin obtained by fully reacting the above-mentioned polyolefin with maleic anhydride.

Saturated polyester resins include poly(ethylene terephthalate), poly(butylene terephthalate), poly(ethylene terephthalate/isophthalate), poly(ethylene glycol/cyclohexane dimetatool/
Typical examples of these polymers include ethylene glycol, butylene glycol, cyclohexane dimetatool, neopentyl glycol, bentane diol diols, isophthalic acid, and benzophenonedicarboxylic acid as copolymerization components. , diphenylsulfone dicarboxylic acid, diphenylmethane dicarboxylic acid, propylene bis(phenylcarboxylic acid), diphenyl oxide dicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, himelic acid, speric acid, azelaic acid, sepacic acid, Also included are those containing dicarboxylic acids such as diethylsuccinic acid. These polyester threads may be mixed with fine powders of carbon black, graphite, lubrication, gypsum, silica, calcium carbonate, etc. as a nucleating agent, or the above-mentioned polyolefin as a crystallization accelerator.

Examples of polyamide resins include polycapramide (nylon-6) and poly-ω-amine hebutanoic acid (nylon-7).
, poly-ω-aminononanoic acid (nylon-9), polyunate amide (nylon 7-11), polylaurin lactam (nylon-12), polyethylenediamine adipamide (nylon-2,6), polytetramethylene adipamide Mido (nylon-4,6), polyhexamenaleneazibamide (nylon-6,6), polyhexamethylene sebamide (nylon-6,10), polyhexamethylene dodecamide (nylon-6,12) ).

Polyoctamethylene adipamide (nylon-8°6),
bolitecamethyleneazibamide (nylon-10,6),
Polydobyl methylene sebaamide (nylon-10,8)
, or caprolactam/laurin lactam copolymer, caprolactam/hexamethylene diammonium adipate copolymer, laurin lactam/hexamethylene diammonium adipate copolymer, hexamethylene diammonium acylate/hexamethylene diammonium sehagut copolymer , ethylene diammony 17 = wamadibate/hexamethylene diammonium adipate copolymer, caprolactam/hexamethylene diammonium adipate/hexamethylene diammonium sebacate copolymer, and the like.

Polyvinyl chloride resins include homopolymers of vinyl chloride, as well as copolymers with vinyl acetate, maleic acid derivatives, higher alkyl vinyl ethers, etc.
Ru.

Examples of the polystyrene resin include styrene homopolymer, polystyrene graft-copolymerized with butadiene, a mixture of styrene-butadiene rubber, and a styrene-maleic anhydride copolymer. The thermoplastic resin used in the present invention can also be used in combination of two or more Sakaki resins.

In the process of forming a container by combining the +fl composition used in the present invention = "f plastic resin, the dispersion shape and eaves of the desiccant fine particles in the composition change unfavorably. From experience, it is true that AF does not.

Next, we will discuss the multilayer injection molding force setting employed in the present invention.

Here, the multilayer injection molding method refers to a method in which multiple injection cylinders are used to perform multilayer injection in one mold clamping operation, or a method in which blow molding is performed after injection. Specifically, for example, (1) These include multilayer injection molding, (2) multilayer injection direct blow molding, and (8) multilayer injection stretch blow molding. In the case of (1), the plasticized resin is formed into a concentric multilayer body by direct injection molding into a container mold and then cooled under pressure.
The number itself is publicly known. (2) and (8) are first formed by multilayer injection molding in a parison (sometimes called preform) mold to form a concentric multilayer bottomed parison.
(2) and (2) are transferred into a blow mold and blow molded using a pressure fluid such as compressed air or compressed nitrogen.
The difference in (8) is that in (2), the entire core with a pressure fluid inlet is transferred into a blow mold and blown while the Varisin is in a substantially molten state without being completely cooled, whereas in (8)
Normally, Harrison is cooled once, separated from the core, reheated to a temperature above the glass transition temperature (generally the softening temperature) and below the melting point (or plasticization temperature K), and then heated in a blow mold. The blowing core equipped with a new stretching rod is fully inserted, and the bottomed parison is stretched in the axial direction in the blow mold.
They are different in that blow molding is performed by injecting pressure fluid at the same time or after that, and in physical terms (2) there is almost no orientation of the resin, whereas in 8) there is no orientation of the resin. There is a difference that is occurring. These n et al.
2, JP-A-60-34819, etc., and (8) is also known in JP-A-57-128520, JP-A-60-240409, and JP-A-61-152411.
No., JP-A-61-152412, JP-A-61-173
No. 924, JP-A-61-203332, JP-A-61-
219644, JP-A No. 61-235126, etc., which are known per se. To explain in more detail the meaning of the multilayer injection method of the present invention, it means a method of molding in one mold clamping operation using a plurality of injection cylinders. On the other hand, using a conventionally known method, mold cavities that are successively larger than the number of layers are used, and injection molding is first performed in the mold cavity for the first layer, then the mold cavity for the first layer is opened, and the mold cavity for the first layer is opened. The primary molded product is placed in a larger mold cavity for the second layer, and the resin for the second layer is injected into the gap between the 2g2/- mold cavity and the primary molded product. The molded product and the second layer resin are thermally fused to obtain a two-layer perforated secondary molded product, and then injection molded using a mold cavity larger than the second molded product to form a three-layered product. Such multi-stage injection molding requires a large number of molds, processes, and cycle time, and has serious drawbacks in practical use. Next, to simplify the explanation, an EV with thermoplastic resin A used in the inner and outer layers and a desiccant dispersed in the middle layer.
The multilayer injection method will be explained by taking as an example how to make a two-food, three-layer container using OH (hereinafter referred to as gvoa composition). As a multilayer injection system, an S system with two injection cylinders is used. First, one part of resin A is primary injected into the mold through the hot runner block and the mold gate from the nozzle opening. During the first injection, resin A is filled, and during or after the first injection, the EVOH composition and resin A that will form the intermediate layer are simultaneously or sequentially injected concentrically to form the intermediate layer.
After injection of u composition, resin AQ alone injection (secondary injection)
As a result, the EVOH composition layer is completely encapsulated. There are various methods (for example, Japanese Patent Application Publication No. 56-501082, Japanese Patent Application Laid-open No. 189407-1982) depending on the structure of the hot runner block, the order of injection such as sequential injection, simultaneous injection, etc., and the combination of injection timing. The invention is not limited to the above examples. EVOf (composition is injected (usually at this time, resin A is also injected in parallel to make the EVOH composition fully ejected), and finally the resins forming the inner and outer layers are injected to completely inject the EVUH composition. An important point of the multilayer injection method adopted in the present invention is to contain the multilayer injection molding method.In addition to multilayer injection molding, there are also coextrusion molding methods and the above-mentioned multistage injection molding method. In some cases, it is difficult to completely confine the intermediate layer inside.Especially: voHg1
If the product cannot be completely contained inside and the end surface is exposed, water will be absorbed from there, resulting in defects in appearance such as whitening. If so, such poor appearance will not occur.

The injection container obtained in this way may be further subjected to direct blowing or stretch blowing, but generally the direct blowing method has a low degree of orientation of the resin molecules, so it does not have high mechanical strength, but it is dimensional stable at high temperatures. Because of its good properties, it is suitable for applications that require high-temperature sterilization, while the stretch blow method is suitable for applications that require pressure resistance and creep resistance, such as carbonated beverage containers. Note that in the case of direct blowing, a polypropylene resin is suitable as the thermoplastic resin, and in the case of stretch blowing, a saturated polyester resin is suitable.

As a method for stretch blow molding, particularly biaxial stretch blow molding, this injection container (parison), known methods such as sequential stretch blow molding or simultaneous stretch blow molding can be employed. For example, in the case of sequential stretch blow molding, an extrusion rod is inserted inside the parison, and the parison is stretched in the axial direction while blowing fluid at a relatively low pressure. There is a method of completely stretching in the direction. In the case of simultaneous stretch blow molding, stretching in both the circumferential direction and the axial direction is simultaneously performed while blowing fluid under high pressure. Air, nitrogen, heated air, steam, etc. can be used as the fluid to be blown during blow molding.For upward stretching in the axial direction, for example, the mouth of the parison is held between a mold and a mandrel, and the parison is stretched inward at the bottom of the parison. This can be easily done by applying a rod and stretching the stretching rod.

In the longitudinal direction, it is best to stretch at least 1.5 times the length of the parison, and in the circumferential direction, at least 2.5 times the diameter of the parison. Insufficient stretching tends to cause uneven stretching, which not only completely ruins the appearance of the bottle, but also has insufficient strength.
If there is no local thickness unevenness abnormality in the gvoH layer in the pipe, uniform stretching will be possible, and the generation of streaks that will worsen the external ffA and lower the product i+ti will be eliminated. The preferred range of the transverse stretching ratio is 2.5 to 5 times. Further, the preferred range of the longitudinal stretch ratio is 1.5 to 5 times, and the overall stretch ratio (horizontal stretch ratio x longitudinal stretch ratio) is 5 to 20 times, preferably 5 to 1
It is 5 times more.

The parison heating temperature for biaxial stretch blow molding is 7
The temperature can be selected within the range of 5°C to 130°C, but a temperature range of 80°C to 125°C is preferred to obtain a more refined appearance of the bottle.

In order to obtain the multilayer injection container of the present invention, EVOR
A stress-adhesive resin gold can also be provided between the composition oak and the thermoplastic 81)3Vi layer. The interlaminar shoulder resin is not particularly limited, but includes thermoplastic resins (polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, etc.), all ethylenically unsaturated carboxylic acids, or Typical examples include polyesters modified with anhydrides (maleic anhydride, etc.) (attached, grafted, etc.), and polyesters in which aluminum element and monocarboxylic acid are bonded, as described in JP-A-59-115327. Agera spreads.

25- The multilayer container of the present invention is characterized by having desiccant fine particles in a highly dispersed state in the EV U HO layer, but is there a desiccant in I- (e.g. adhesive resin layer) outside EVtJHVt? It may also contain M.

The polycontainer of the present invention has better gas permeability resistance under high humidity conditions of 4 degrees Celsius, especially when subjected to retort treatment, compared to conventionally known plastic materials. Therefore, they can be easily distinguished. Retort processing is carried out at 120° C. by placing a container filled with food into an autoclave, usually called a retort pot.

Processing time varies depending on the type of food, and for some foods 20 minutes is sufficient, while for others 120 minutes is required. The multilayer container of the present invention is also extremely useful for food containers that undergo so-called boil sterilization, in which food containers are sterilized in boiling water at normal pressure.

Furthermore, it has been confirmed that the multilayer container of the present invention exhibits reasonable gas permeation resistance even in applications where no retort treatment or boiling treatment is performed. In particular, in the case of candy whose inner and outer layers are made of resin with moisture permeability such as polystyrene, polyvinyl chloride, or polyester, or resin with low moisture permeability such as polyethylene or polypropylene, the inside of the multilayer container (
Alternatively, moisture (outside the container) permeates the inner and outer layers and becomes EVO) f
However, the multilayer container containing the composition used in the present invention has a high gas permeation resistance retention effect and can significantly extend the shelf life of food, and its industrial significance is big.

Next, regarding the layer structure of the container in the present invention, if the thermoplastic resin is A%, the gvoH composition layer is B1, and the adhesive resin layer is all C, then (1) A/B/A (2) A/C/B 7C/A (81A/B/A/B/A (4) Layer configurations such as A/C/B/C/A/C/B/C/A are examples, but are not limited to this. .

The present invention will be further explained below with reference to Examples, but the present invention is not limited thereto. Note that parts mean parts by weight.

F. Examples Example 1 and Comparative Example 1 Anhydrous/Haenato 1 Fukum powder was finely pulverized and classified using a jet pulverizer (Mikron Jets manufactured by Honkawa Micron ■ Model ALJ-3) and an air classifier (Micron manufactured by the same company). The test was carried out using all separators).

When the raw powder particles were observed with a magnifying glass using methanol as a dispersion medium, it was confirmed that they contained many particles of 500μ or more, and the average particle diameter (median diameter) was found to be 86μ by Coulter counter. Similarly, the maximum particle size (by Coulter counter) of the fine powder after all milling is 1
3μ, and the median diameter was 6.4μ. (Particle size is 13μ
The volume fraction of particles exceeding 0.1% is less than 0.1%. ) 20 parts of this anhydrous sodium phosphorus powder and EV (JH (
7 units 1/) '@ 'jij: 32 mol%
, 190 °C, load m2i6oy melt flow index 5, 1 f / 10 min, melting point 181 °C (1) SC (
(Scanning speed) King endothermic peak temperature at 10° C./min) Part B8 was premixed and then subjected to percussive mixing to obtain a mixture.

After that, the inner diameter of the mixing chamber = 54m0, L
/D = 5.8 (1st stage), L/D
= 4.2 (2nd stage), a two-stage two-axis different direction continuous mixer (LCM- manufactured by Kobe Steel, Ltd.) with two stages of mixing rotors and a deaeration mechanism t-i between the two rotors.
50) and a single-screw extruder connected thereto, kneading, extrusion, and pelletizing were performed to obtain pellets of the composition (this is referred to as Composition 1). The mixing glow adopted at this time,
The tip clearance with the mixing chamber is 3■
The crosstalk temperature (outlet temperature) is 206°C to 22°C.
0°C, kneading time 30-40 seconds, rotor rotation speed 530-6
50 rpm and specific energy 0.3-0.6 KW
It was carried out in the range of b/kg. The melt flow index of this composition at 190°C and a load of 21609 was 4.4f.
It took 710 minutes (this time is the composition vJ1). Obtained pellets) A thin film with a thickness of approximately 100 μm was obtained using a heat press machine at 220° C. The state of dispersion of the powder in this thin film was observed using a light microscope. In order to improve the depth of focus, the magnification of the microscope was set to a smaller 50x, and the photo enlargement was set to 15x to obtain a photograph with an 800x magnification. The average diameter of particles having a major diameter of 10 μm or more in an area of 200 μ×200 μ was measured for 10 samples at different positions on the wall of the container, and the average diameter by body area was calculated to be 17.6 μ.

The above composition 1 was used as an intermediate layer, and the intrinsic viscosity (phenol 50
A multilayer film with an internal volume of 700 m1, with inner and outer layers made of polyethylene terephthalate mWIC (hereinafter abbreviated as PET■) with an [η] of 0.75 (measured at a temperature of 30°C dissolved in a mixed solvent of 5 ng% of tetrachloroethane and 5 ng% of tetrachloroethane). A stretch-blown container was multilayer injection molded. That is, two injection cylinders A and B
Using a multi-layer injection molding machine with 'i', PET ■ is charged into cylinder A (inner diameter 38) with a barrel temperature of 285°C.
Composition 1 was added to cylinder B (inner diameter 1
6). Next, the P
One part of ET■ was injected into the parison cavity set at a temperature of 20℃, and 1.2 seconds after the start of injection, the injection of PET■ was k 0.
．． At the same time as the 1 second pause, the composition 1 was concentrically injected into the parison cavity through the hot runner, from the nozzle opening, and through the mold gate. ,PET
In (2), after the injection was interrupted for 0.1 seconds, the injection was continued again with the E v OH composition. At this time, the amount of resin of PET ■ to be injected is set to be larger than the amount of resin of composition 1 to be injected at the same time, so that the flowing tip of composition 1 is finally wrapped by the flowing tip of PET ■, thereby forming a cavity. Fill it inside. Next, after stopping the injection of Composition 1, the injection of PE and T■ was stopped a little later, and the parison cavity was completely filled with the resin.
It was possible to completely enclose it with f P E T (,3). The total ejection time was 28 seconds.

After cooling under pressure, the mold was fully opened and the obtained multilayer parison was transferred to a fully temperature controlled pot, the temperature of the multilayer parison was controlled to 110°C, and then the temperature controlled multilayer parison was transferred to a blow mold, Stretched twice in the axial direction by a stretching rod, and at the same time approximately IQ
It was stretched 3 times in the circumferential direction using pressurized air at ly/- to fit the shape of the mold, and after cooling, a container with an output weight of 262 liters and a capacity of 700 liters was manufactured.

The total thickness of the circumferential side wall of the body of the obtained multilayer stretch blow container was 3
00μ, J-configuration is inner layer PET■ (160μ)/intermediate I
- Composition 1 (40μ)/outer layer PET ■ (100μ) (Example 1) 0 at the same time EV (Jl-1 composition instead of EVOH alone resin (containing ethylene units @32Mo) L
z%, 190° C., a load of 2160 f, a melt flow index of 5.1 r/10 min) k, and all multilayer containers were prepared and softened in substantially the same manner (Comparative Example 1).

The total thickness of the circumferential side wall of the body of this container is 300μ, and the layer structure is as follows:
Inner layer PET ■ (160μ)/middle layer EV (Jl ((40
μ)/outer layer PET (100μ).

Next, the bottles were filled with water containing carbon dioxide gas, and all changes in carbon dioxide permeability over time were measured, and the results are shown in Table A1.

Evaluation method ■ Fill a container with saturated carbon dioxide gas water with a vapor pressure of 4 atm at 20°C, seal the container tightly, and store the container in a sealed lees, 65
Purge the homolog with nitrogen gas adjusted to %Ri-1, and remove the charcoal that permeated through the container wall.
The number of days until the carbon dioxide in the scooping container decreased to 15% was measured using a Permatran C-■ carbon dioxide gas permeability measuring device manufactured by ROLLS. (Average of n=2) Results all 1st
Shown in the table.

From Table 1, it can be seen that the containers of the present invention have improved storage stability.

Example 2 and Comparative Example 2 A, B, C: A multilayer injection device ft'c having three injection cylinders was used, and polypropylene (2
Melt flow index at 30℃ and load 21t30'/=7.0.23℃ specific gravity -0.91) was charged, and maleic anhydride graft-modified polypropylene (maleic anhydride modified with -0.01 mol %) was charged in cylinder B. , 230
Melt flow index at ℃, load 3i2160F =
7. Specific gravity at 0.23°C = 0.91)k was charged, and Composition 1 prepared in Example 1 was charged into cylinder 〇.

As a molding mold, a 4-cavity cup mold (cup opening 72 fins, bottom diameter 65cm, daylight 35W + wall thickness 2)
85μ) was installed and the temperature was set at 20°C, the barrel temperature of the A cylinder and B cylinder was set at 240°C, and that of the C cylinder was set at 220°C.

First, all of the polypropylene is injected from cylinder A through a hot runner block set at 240°C and the gate so as not to fill the mold capacity of 85 inches.Next, all of the modified polypropylene is injected from cylinder B, which also has a mold capacity of 7.5 inches. Then, from cylinder 〇, a mold capacity of 7.5% composition 1 is similarly injected, and finally, a small amount of polypropylene is again injected from cylinder A to close the bottom outer layer with polypropylene, and the pressure is kept and After cooling, the mold was opened and four multilayer cup-shaped containers were taken out. The layer structure of the cross section of the container wall is: from the outside: PP225μ/modified PP20μ/composition 140
μ/modified PP20μ/PP225μ Total thickness=530μ
Met.

Next, EVOH (ethylene content 32 mo/
A cup was produced by multilayer injection in almost the same manner except that a melt flow index of 5.1 f (710 minutes) at 190° C. and a load of 2160 f was used (Comparative Example 2).

The layer structure of the side wall cross section is PP225μ/modified PP20 from the outside.
μ/EVOH40μ/denatured PP20μ/PP225μ. This container was heat-sealed with a lid containing aluminum foil, and heated with steam in a retort pot at 120°C for three different lengths of 30 minutes, 60 minutes, and 120 minutes.Then, the container was taken out and water was poured inside the cup. In this state, the opening of the cup was connected to an oxygen gas permeation measurement device to measure the oxygen permeation rate. The results are shown in Table 2.

The oxygen permeation rate after retorting is less than three times the value of the oxygen permeation rate of the container that has not been retorted, and the gas permeation resistance is good enough to preserve food.Table 2 Oxygen permeation Speed measurement using Modern Controls
Using a 0X-TRAN 100 type oxygen permeability measuring device manufactured by Co., Ltd., internal 100 cm RH1 external 65% ftH at 20℃
Example 3 Using a multilayer injection molding machine with three injection cylinders, 3ai of resin was placed in an inverted conical mold with an opening of 65μ1 and a height of 65μ. Injection, polypropylene/
5 of adhesive resin/composition/adhesive resin/polypropylene
A pariso layer having a layered structure was formed. The polypropylene used here was E-103D manufactured by Ube Industries ■, and the adhesive resin was Atmar QB530 manufactured by Mikata Petrochemical Industries ■.
The composition is EVO containing the desiccant fine particles shown in Example 1)
1 (composition 1). This parison was subjected to direct blow molding to produce a substantially cylindrical container with 65 openings and a height of 70 fi. Constituent thickness is 300/8/45
/8/300μ. Water was poured into this container using a metal lid, the n-end was double-sealed, and the mixture was heated in a retort pot at 120°C for 30 minutes, 60 minutes, and 120 minutes. After that, with water in the cup, two pipes were attached to the lid of the container, and the pipe was connected to an oxygen gas permeation measuring device to measure the amount of M gas permeation. The results are shown in Figure 3.

Cut out a part of the container before retorting, and put it in xylene.
The polypropylene and adhesive resin were melted out by heating at 20°C to obtain a film of the composition in the container. The state of dispersion of powder = 37- in this film was observed using a Kuji microscope. The average diameter of particles having a major diameter of 10μ or more in an area of f'L 200μ×200μ was measured for 10 samples at different positions on the wall of the container, and the average diameter by body area was calculated to be 17.5μ.

Example 4 In Example 3, a multilayer injection molding machine with two injection cylinders was used to prepare polypropylene/composition of Example 1.
A container having a thickness structure of 300/45/300μ was produced by carrying out the same molding method as in Example 3, except that a parison having a three-layer structure of 11/polypropylene was used. A metal lid was also attached to this container, and the amount of oxygen permeation was measured after retorting.

The results are shown in Table 3.

Comparative Examples 3 and 4, Example 5 Same as Example 3 except that EVOH (ethylene unit content 33 mol%, melt flow index at 190°C 5.1 r/10 min) was used instead of the composition. Containers having a construction thickness of 300/45/45/45/300μ were created by the method described in (Comparative Example 3).

In addition, in Comparative Example 3, a desiccant (
Comparative Example 2 except that an adhesive resin (Atomer QB53Q) containing 10% more fine powder (disodium phosphate) was used.
A container having the same thickness structure was obtained (Comparative Example 4).

All of the containers of Comparative Examples 3 and 4 were fitted with metal lids in the same manner as the containers of Example 3, and the amount of permeation through mature trees after retort was measured. The results are shown in Table 3.

Compared to Comparative Examples 3 and 4, the oxygen permeability of the containers of Examples 3 and 4 after retort is 1fi lower, and the storage stability is excellent. If a multi-layered container requires retort processing, should it not be retorted because it has a low barrier property due to low water absorption (EVUH)? (If there is no -, even if the tV (J) J- is made thinner, the final shelf life of the contents is maintained, the interlayer M property is also good, and since it is injection molded, most of the original waste is generated. In this respect as well, they are very similar to each other, and the significance of the 1st chestnut of 7 is profound.

Claims (6)

[Claims] (1) In manufacturing a multilayer container that includes thermoplastic resin layers as inner and outer layers and at least one layer in which desiccant particles are dispersed in an ethylene-vinyl alcohol copolymer matrix as an intermediate layer, multiple injection machines are used. A method for manufacturing a multilayer container, comprising the step of performing multilayer injection molding in one mold clamping operation using a cylinder. (2) Claim 1, characterized in that among the desiccant particles dispersed in the matrix of the ethylene-vinyl alcohol copolymer, the particles having a major diameter of 10μ or more have a body area average diameter of 30μ or less. A method for manufacturing multilayer containers. (3) The method for manufacturing a multilayer container according to claim 1 or 2, which includes a blow molding step after the multilayer injection step. (4) The method for manufacturing a multilayer container according to claim 1 or 2, which includes a stretch blow molding step after the multilayer injection step. (5) The method for manufacturing a multilayer container according to claim 1, 2, or 3, wherein the thermoplastic resin is a polypropylene resin. (6) The method for manufacturing a multilayer container according to claim 1, 2, or 4, wherein the thermoplastic resin is a saturated polyester resin.