JPH0356168B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a preform having a double coating that is impermeable to gases such as oxygen and aromatic components such as seasonings and fragrances, and a biaxially stretching and blowing method for biaxially stretching and blowing the preform. This invention relates to a gas-impermeable biaxially stretched hollow body obtained by axial stretching. More specifically, a coating of a solvent solution of saponified ethylene-vinyl acetate copolymer is formed on at least one wall of the preform, and then dried so that the volatile content in the coating is 0.05 to 5% by weight. The present invention relates to a gas-impermeable composite preform having a gas-impermeable coating and a gas-impermeable biaxially stretched composite hollow body obtained by biaxially stretching and blow molding the composite preform under biaxially stretching conditions.

In recent years, thermoplastic resins have made rapid progress in the field of hollow bodies. In particular, polyethylene terephthalate resin has mechanical properties (especially impact resistance and internal pressure resistance) that are improved by biaxial stretch blow molding of preforms.
It is well known that it has the remarkable properties of forming pins with excellent properties and can therefore be used advantageously for the filling of pressurized liquids and sparkling beverages. However, in the case of liquids that contain seasonings, fragrances, are sensitive to oxygen, contain carbon dioxide gas, or a combination of these, many thermoplastic resin hollow bodies are used. Their impermeability to gases and flavorings is inadequate, so that the filled products often remain in good condition for only a limited period of time. Polyethylene terephthalate resins, polypropylene resins, polystyrene resins, etc. are no exception. This phenomenon becomes more pronounced as the wall thickness of the hollow body becomes thinner and as the surface area ratio of the container to the volume of the contents increases. In order to reduce the permeability of the hollow body, it has been proposed to coat the surface of the hollow body with a barrier material having a lower gas permeability than the base material. In addition, polyvinyl alcohol is used as a surface coating barrier material for polyethylene biaxially oriented pins, and in this case, a water-insensitive and impermeable polymer is added to the polyvinyl alcohol coating to compensate for the shortcomings in high temperature atmospheres. 2
Measures such as applying a coating are already known. A method has also been proposed in which a preform, such as a parison with or without a bottom, is coated with polyvinyl alcohol and then made into a gas-impermeable biaxially stretched composite hollow body using a biaxially stretched blowing method. Additionally, in known methods, the coating is applied onto the finished container wall using a variety of techniques including dipping, spraying and other application methods, but the coating layer thickness is difficult to control due to the sometimes complex shape of the container. There are drawbacks. Furthermore, when polyvinyl alcohol is selected as the barrier material, when applied to the surface of the hollow product,
Regardless of whether the preform is coated with a barrier material coating or a biaxially stretched hollow body is obtained by a biaxially stretched blowing method, the water resistance of the coating is insufficient due to the characteristics of the material. There are unavoidable drawbacks that come with it. In order to eliminate this fatal drawback, a known method protects the first coating layer by providing a second coating layer of a water-insensitive and water-impermeable polymer on top of the first coating layer made of polyvinyl alcohol. Although measures have been taken to greatly reduce the permeability of gases etc. even in a humid atmosphere, this actually has the drawback of making drying control extremely difficult. In other words, if drying is prolonged, for example, moisture in the latex of the hydrophobic polymer on the surface layer rewets the polyvinyl alcohol layer below, which in combination with the drying of the second coating, which is the moisture-impermeable surface layer, results in moisture loss. A permeable film is formed and the underlying polyvinyl alcohol is incompletely dried. This phenomenon is inevitable because it is caused by the extremely high affinity between polyvinyl alcohol in the lower layer and water and the hydrophobicity of the polymer used in the surface layer.

It is also a well-known fact that saponified ethylene-vinyl acetate copolymer (abbreviated as EVOH) resins also have high barrier properties against gases such as oxygen and carbon dioxide, and aromatic components. It also has better moisture resistance than other thermoplastic resins, and is used in combination with other thermoplastic resins as a suitable barrier material for molded products such as films. However, these molded products can be laminated with other thermoplastic resins, for example by coextrusion technology, dry lamination, etc., and used as is without being co-stretched, or they can be applied to other resin films or containers, and
After drying, an EVOH resin coating is provided on the surface of the container, etc., and the container is used for various purposes. Also
To obtain a preformed product laminated with EVOH resin and co-stretch it to improve the properties of the laminate, and to obtain a hollow body by biaxial stretching blowing method from a parison obtained by coextrusion technology. is published in Japanese Patent Application Publication No. 1973-
It is only slightly disclosed in Publication No. 108162, etc., and can hardly be found. In particular, as mentioned above, for example, polyethylene terephthalate resins have been improved in mechanical properties by biaxial stretch blow molding of preforms and have begun to be suitably used as hollow containers for pressurized liquids and foamed beverages. EVOH for the purpose of improving the impermeability of gases etc. in the humid atmosphere of the body
No preform has been found that can be suitably co-stretched during biaxial stretch blow molding in which resins are laminated. There are various possible reasons for this, but one is that the crystallization rate of the EVOH resin is extremely high, and because it is a preformed product, the EVOH coating layer must be thick enough to achieve the desired coating thickness after stretching. As a result, when preforms with such a coating are obtained by laminating them by coextrusion technology, it is extremely difficult to prevent or sufficiently delay the crystallization of the EVOH resin by quenching, etc. - It is extremely difficult to maintain the crystallinity to a level that allows co-stretching with other thermoplastic resins such as terephthalate. The method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 53-108162 and the like does not go beyond this range.

EVOH resin is used as a barrier material that is water resistant and has suitable gas impermeability in a humid atmosphere, and is composited with thermoplastic resin, especially polyethylene terephthalate resin, and is a preliminary material that can be suitably co-stretched. Molded products are strongly desired.

The present inventors eliminate the drawbacks of the prior art and obtain a biaxially stretched hollow body that is water resistant and exhibits sufficient impermeability to gases such as oxygen and carbon gases and aroma components even in a humid atmosphere. For this purpose, we focused on the co-stretchability of laminates of EVOH resin, which is a barrier material, and thermoplastic resins such as polyethylene terephthalate resin, polypropylene resin, polystyrene resin, and polyvinyl chloride resin. As a result of extensive research, we have completed a preform for manufacturing biaxially stretched hollow bodies that has a composite structure of EVOH resin and other thermoplastic resin that can be co-stretched, and has water resistance. This makes it possible to provide a biaxially stretched hollow body that has suitable impermeability to oxygen and the like even in a humid atmosphere. That is, in the composite preform and biaxially stretched composite hollow body of the present invention, at least one wall surface is coated with a solvent solution of EVOH resin, and then the volatile content in the coating is 0.05 to 5% by weight. The composite hollow body is obtained by co-stretching the preform under biaxial stretching conditions.

Here, the volatile content in the present invention is a value on a dry basis. The solvent is relatively low temperature below 100℃.
A solvent that can dissolve the EVOH resin is preferably used from the viewpoint of workability in applying the resin solution. For example, alcohol solvents include methanol/water,
Examples include ethanol/water system, n-propyl alcohol/water system, i-propyl alcohol/water system, t-butyl alcohol/water system, and mixtures of two or more of these alcohols and water can also be suitably used. In addition, these alcohol aqueous solutions contain aliphatic alcohols that partially dissolve water, such as n-butyl alcohol, i-butyl alcohol, sec-butyl alcohol, etc., in a uniformly mixed composition region, and the alcohols that are less soluble. , for example, n-, i-, and t-amyl alcohols. However, when water and alcohol that is partially soluble or poorly soluble coexist, a composition region may be reached that does not uniformly dissolve in the partially dried water of the composite preform, resulting in a decrease in the transparency of the resulting coating. In some cases, the range of suitable use is quite narrow.

In addition, the above n- stands for normal, i- stands for iso,
sec- means secondary and t- means tertiary.

An alcohol/water based EVOH resin composition for obtaining a transparent coating can be obtained by dissolving the resin in an n-propyl alcohol/water system, an i-propyl alcohol/water system, or a t-butyl alcohol/water system. However, even in these alcohol/aqueous solvents, a transparent coating film cannot be formed unless the composition is selected depending on the ethylene content of the EVOH resin. n-propyl alcohol, i
- In the case of propyl alcohol and t-butyl alcohol, the suitable composition range of alcohol/aqueous solvent in relation to the ethylene content of the resin is disclosed in Japanese Patent Publication No. 47-48489. This publication also discloses that it is known to apply EVOH resin to a molded product such as a film or a bottle and dry it to obtain a molded product with improved barrier properties against oxygen and the like. In this case, care is taken to keep the volatile content after drying in the extremely low range of usually 0.3% or less, preferably 0.1% or less, because when the EVOH resin contains moisture, its gas impermeability decreases. , it is customary to further perform heat treatment. For this purpose, the composite preform which is the object of the invention is simply
A hollow body obtained by applying an alcohol/water based composition of EVOH resin to form a coating of the resin on another thermoplastic resin, and then co-stretching this using a biaxial stretching blowing method to improve properties. As mentioned above, obtaining
The crystallization rate of EVOH-based resins is high and it is extremely difficult to solve this problem, which remains a serious problem that still needs to be solved.
That is, for example, since the EVOH resin in the composite sheet has a high degree of crystallinity after drying, co-stretching cannot be suitably performed. In addition, the present inventors applied a resin solution of an alcohol in the composition range to, for example, polyethylene terephthalate resin in order to obtain a preform for manufacturing a biaxially stretched hollow body made of thermoplastic resin coated with a layer of EVOH resin. When dried, the resulting composite preform, such as a bottomed or bottomless balisong, was stretched in a biaxial stretching blowing operation under biaxial stretching conditions, and only the polyester resin portion was stretched, resulting in an EVOH resin. The coating layer of
It was hardly stretched. Even more surprisingly, after application in this operation, the volatile content in the coating layer was reduced to 0.3
When the drying operation was controlled to keep the amount from 5 to 5% by weight, it showed completely satisfactory co-stretchability in the biaxial stretching blowing operation, was transparent, and had satisfactory gas impermeability in a humid atmosphere. It has been found that a biaxially stretched hollow body can be obtained. Conventional
It is widely known that in order to obtain a biaxially stretched film of EVOH resin, the film cannot be stretched properly unless the film is re-humidified and the moisture content is regulated. However, in order to obtain the biaxially stretched hollow body, an EVOH resin solution is applied to the preform, dried to a volatile content of 0.1% by weight, and then water is added again to reduce the volatile content to 0.3 to 5% by weight. When the preform was adjusted to the desired weight percentage and then subjected to a biaxial stretching blowing operation, the co-stretchability was extremely unsatisfactory compared to the case of using the preform of the present invention, and the result was that it could hardly be stretched or could not be stretched. The degree of uniformity was extremely high, and there were parts that were not stretched, parts that were only half-stretched, etc. in the medullary region, and the coating was torn. In the present invention, the above-mentioned drawbacks can be overcome by using a two-component alcohol/water solvent in forming the coating, and by allowing a suitable amount of volatile matter to remain after drying. can. Although the details of this are not clear, it is believed that this is due to the inclusion of the alcohol component in the volatile matter. This means that if the solvent is alcohol/water-based and the volatile content is less than 0.05% by weight, it will be difficult to achieve the desired effect. When a small amount of a high boiling point non-alcoholic solvent is added and used, these components tend to remain in the residual volatile matter, reducing the amount of residual volatile matter necessary for imparting co-stretchability during partial drying of the composite preform. This is also suggested by the fact that it can be caused.

When an alcohol/aqueous solvent is used in the present invention, the volatile content after partial drying of the preform is 0.05
Preferably the composite preform is biaxially stretched under biaxial stretching conditions when the amount is 5% by weight, preferably 0.1-5% by weight, more preferably 0.3-5% by weight, optimally 0.5-5% by weight. Co-stretching can be performed by an axial stretching-blow method. If the volatile content is 0.05% by weight or less, good co-stretchability is not exhibited, and if it is 5% by weight or more,
There is a risk of foaming during molding of the hollow body, and furthermore, improvement in coating properties due to the biaxial stretching effect cannot be expected.

In the present invention, a non-alcoholic solvent can also be used as the solvent. Suitable non-alcoholic solvents include dimethylsulfoxide, N-methyl-2-pyrrolidone, dimethylformamide,
0 to 20% by weight hydrated phenol, metacresol,
Examples include ethylene chlorohydrin. These non-alcoholic solvents are excellent as solvents for EVOH resins, superior to alcoholic solvents in terms of solubility, and can always easily provide a transparent coating. However, due to its high boiling point, heat resistance of thermoplastic resins such as polyethylene terephthalate, polypropylene, polystyrene, polyvinyl chloride, etc. is In addition, in the former case, there is a drawback that drying at a relatively low temperature is required due to other constraints from the viewpoint of crystallization of the resin, and thus drying under reduced pressure must be used in many cases. For example, when drying a preform such as a composite parison made of polyethylene terephthalate, the temperature is about 130°C or less, and when removing the residual solvent component in the coating of a biaxially stretched hollow body obtained from the parison, the temperature is about 70°C or less. It is necessary to carry out the drying at the temperature of the resin, and, for example, in the case of dimethyl sulfoxide (boiling point 85-87°C/25 mmHg), drying is required under considerable reduced pressure.

In the case of non-alcoholic solvents, the composite preform is preferably biaxially stretched under biaxial stretching conditions when the volatile content of the composite preform after partial drying is 0.05 to 3% by weight, preferably 0.1 to 3% by weight. Co-stretching can be performed using the axial stretching blowing method. However, if the volatile content is less than 0.05% by weight, good co-stretchability is not exhibited, and if it is more than 3% by weight, no improvement in the properties of the coating due to the biaxial stretching effect can be expected. As described above, in the case of the non-alcoholic solvent, there is a suitable range in the low volatile content region compared to the case of alcohol/aqueous solvents. This is because the solvent properties are superior to alcohol/aqueous solvents. In addition, a small amount of the non-alcoholic solvent is added to the alcohol/
It is preferable to use it by adding it to an aqueous solvent in order to impart good co-stretchability, and in this case, good co-stretchability is exhibited even in a region where the volatile content after partial drying of the composite preform is low.

The solvent solution of the EVOH resin used in the present invention has a resin concentration of 5 to 30% by weight, preferably 10% by weight.
25% by weight can be suitably used. Although EVOH resins are superior to polyvinyl alcohol in terms of water resistance in compositions with low ethylene content, their barrier properties in humid atmospheres are still unsatisfactory, and in compositions with high ethylene content. Although it has excellent water resistance, it is unsatisfactory due to a decrease in barrier properties. In the present invention, an EVOH resin having an ethylene content of 25 to 60 mol% is preferably used. In the case of a single coating layer, if the target is a field of application that emphasizes barrier properties against oxygen, etc., a low ethylene content region (B) ethylene content of 25 to 35 mol%, saponification, etc. Every time
When using EVOH resins with an EVOH content of 96 mol% or more, and in applications where moisture resistance is important, high ethylene content areas within the composition range, such as (C) ethylene content of 40 to 60 mol%, saponification An EVOH resin having a concentration of 96 mol% or more is preferably used. In the above case, in order to further suppress the deterioration of barrier properties against oxygen etc. in a humid atmosphere,
The EVOH resin coating layer should have a two-layer structure, that is, (B) ethylene content of 25 to 35 mol%, saponification degree
Covered with EVOH resin of 96 mol% or more, then
(C) It is more preferable to coat with an EVOH resin having an ethylene content of 40 to 60 mol% and a saponification degree of 96 mol% or more. Which layer is provided on the inside is determined by the nature and condition of the material to be filled in the hollow body, the type of thermoplastic resin used to coat the hollow body, the atmosphere with which the outer surface of the hollow body comes into contact, and other factors. For example, when the content is an aqueous mixture such as beer or cola, the moisture permeability of the thermoplastic resin part is
If the thermoplastic resin layer is smaller than either of the thermoplastic resin layers, it is preferable to provide the low ethylene content EVOH resin (B) layer on the inside and the high ethylene content EVOH resin (C) layer on the outside. If the moisture permeability of the EVOH resin layer with a low ethylene content is lower than that of the EVOH resin layer with a high ethylene content, two types of EVOH resin layers may be placed in opposite positions to those in the above case. It is preferable to provide one.
A two-layer coating of EVOH resin involves first applying the first layer to the preform, pre-drying it, then applying the second layer, and drying it. By adjusting the amount to 0.05 to 5% by weight, a two-layer coating can be obtained.

Coating to the preform can be carried out by any known means such as dipping, doctor coater, spraying, atomizing, etc. To facilitate wetting and adhesion,
For example, corona discharge treatment and preliminary surface treatment for fire treatment can be performed. Further, it is more suitable to adopt a method such as providing an adhesive layer on the wall surface of the preform in advance. As the adhesive, ethylene-vinyl acetate copolymers, modified products of the copolymers such as graft products of unsaturated carboxylic acids or anhydrides thereof, polyurethane resins, and the like can be suitably used.

As an inner layer of the EVOH resin layer, (A)
Providing an EVOH resin layer with an ethylene content of 25 to 60 mol% and a saponification degree of 85 to 95 mol% improves adhesion with other thermoplastic resins when no other adhesive layer is previously provided. This is more preferable because it can further improve the performance.

The EVOH resin used in the present invention is obtained by saponifying an ethylene-vinyl acetate copolymer in the presence of an alkali, etc., as is known in the art.
It is preferably 96 mol% or more, preferably 98 mol% or more. When the degree of saponification is less than 96 mol%, the barrier properties against oxygen and the like and water resistance decrease, resulting in unsatisfactory results.

The amount of coating composition applied should be selected to take into account the thickness reduction that occurs during the biaxial stretch-blow operation of the composite preform. The coating weight on the preform is generally on a dry material basis, e.g.
It is 200g/ ^m2 . As the drying means, it is possible to use high temperature air, an inert gas such as nitrogen, or a device using infrared radiation of a desired wavelength (for example, an average wavelength of 2 μm). Biaxially stretched EVOH
The formation of a thin film of the resin based on the volatile content is 0.05 to 5.
% by weight, preferably from 0.3 to 5% by weight in the case of the alcohol/aqueous solvent, optimally from 0.5 to 5% by weight in the case of the non-alcoholic solvent.
This can be easily done by controlling drying to 0.05 to 3% by weight, optimally 0.1 to 3% by weight, and the coating of the preform after partial drying has good co-stretchability. Motsu. The drying conditions can be arbitrarily selected so as to satisfy the requirements and to obtain a continuous phase coating without causing phenomena such as foaming. When using the alcohol/aqueous solvent, it is preferable to maintain the temperature of the coating layer at 50° C. or higher and below the boiling point of the solvent. Further, it is necessary to perform the treatment in a temperature range below the crystallization temperature of the thermoplastic resin in order to suppress crystallization of both resins.

The composite preform thus obtained is then processed in a conventional manner, such as by placing a bottomed parison in the mold of a blow molding machine, heating it, and biaxially stretching it to a predetermined magnification. Under pressure and temperature conditions, for example in the case of polyethylene terephthalate resins, within the range of the glass transition temperature and the crystallization temperature, ie between 80 DEG and 130 DEG C., the conversion into biaxially oriented hollow bodies occurs.
After the formation of the hollow body, the coating is dried to remove residual volatiles and, if necessary, heat-treated. The drying and heat treatment must be carried out at a temperature below the heat resistance temperature of the biaxially stretched thermoplastic resin part forming the hollow body, and in the case of polyethylene terephthalate, for example, the temperature of the resin part must be carried out so that the temperature does not exceed about 70°C. .

The resulting hollow body has extremely good barrier properties against oxygen and the like, and has low humidity dependence.

The details of the present invention will be explained below based on Examples, but the scope thereof is not limited. Note that parts in the examples mean parts by weight.

Example 1 85 parts of a solvent consisting of 60 parts of n-propyl alcohol and 40 parts of water, with an ethylene content of 32 mol% and a degree of saponification.
15 parts of 99.8 mol % EVOH resin was added and dissolved under stirring at a temperature of 80 to 85°C to prepare a transparent solution. After corona treatment of the outer surface of a bottomed polyethylene terephthalate parison with an intrinsic viscosity (measured in 1% chloroform solution at 25°C) of 0.81 dl/g obtained by injection molding with a length of 160 mm, an outer diameter of 25 mm, and a wall thickness of 25 mm. The EVOH resin was applied to the outer surface of the parison by a dipping method by immersing it in the coating solution prepared above and maintained at 60°C. After coating, while making sure that the temperature of the coating layer is 55℃ or higher and that the coating solution does not foam, preliminary drying is performed using infrared radiation (average wavelength: 2μ), and then drying is carried out using hot air at 105℃. Dry. The volatile content in the coating of the composite bottomed parison was 2.6% by weight, and the pure coating amount of the resin was 46 g/m ² . The obtained composite preform having the coating layer was heated to a temperature of 108° C., and a biaxially stretched composite hollow body having an internal volume of about 1.5 was obtained by a biaxially stretched blowing method. After drying with hot air at 80°C while being careful not to let the temperature of the polyethylene terephthalate resin part of the hollow body rise above 70°C,
The coating was heat treated at 190°C for a few seconds. The thickness of the coating layer was 4.6μ. The oxygen permeability coefficient of the hollow body is
2.1×10 ^-13 cm ³ at 40℃ and 45% relative humidity.
cm/ ^cm2・seccmHg. Co-stretchability was good.

Example 2 In Example 1, an adhesive consisting of a maleic anhydride-modified ethylene vinyl acetate copolymer with a vinyl acetate content of 26% by weight and a maleic anhydride content of 1.5% by weight was prepared.
Using a bottomed parison made of polyethylene terephthalate coated on the outer surface with an ^amount of 10 g/m2,
When preparing the EVOH resin solution, use n-amyl alcohol as an n-propyl alcohol/water mixed solvent.
The same procedure as in Example 1 was carried out except that 3 parts per 100 parts of the resin was added and the coating amount was 85 g/m ² based on the pure amount of the resin. The coating operation is done in 2 steps with preliminary drying in between.
Conducted twice. The volatile content of the coating after drying was 4.2% by weight, and the composite parison was subjected to biaxial stretching-blowing. The co-stretchability was good, the thickness of the coating layer of the obtained composite hollow body was 8.6μ, and the oxygen permeability coefficient of the hollow body was 35°C and 45% relative humidity.
It was 1.1×10 ^-13 cm ³・cm/cm ²・sec.cmHg.

Example 3 After applying EVOH resin in Example 1,
The procedure of Example 1 was repeated, except that the moisture content in the coating of the dried preform was partially dried to 0.8% by weight, 3.2% by weight, and 4.7% by weight, respectively. The thicknesses of the coatings were 4.5μ, 4.7μ, and 4.6μ, respectively, and the co-stretchability was good. The oxygen permeability coefficient of the hollow body was approximately the same as that in Example 1.

Example 4 79 parts of a solvent consisting of 70 parts of i-propyl alcohol and 30 parts of water with an ethylene content of 45 mol% and a degree of saponification
21 parts of 99.5 mol % EVOH resin was added and dissolved by stirring at a temperature of 75°C to prepare a transparent coating solution. After the outer surface of the same parison as in Example 1 was subjected to corona treatment, the EVOH resin was applied to the outer surface of the parison by immersion in the above-adjusted coating solution maintained at 60° C. by a dipping method. After coating, while making sure that the temperature of the coating layer is 55°C or higher and that the coating solution does not foam, pre-drying is carried out using infrared radiation.
It was dried with hot air at 105°C. The volatile content in the coating of the composite bottomed parison is 3.1% by weight,
The coating amount of the resin on a pure basis was 51 g/m ² .
The resulting composite preform with the coating layer was heated at 100°C.
heated to a temperature of approximately 1.5 mm by biaxial stretching blowing method.
A biaxially stretched composite hollow body with an internal volume of . Co-stretchability was good. After drying with hot air at 80°C while being careful not to allow the temperature of the polyethylene terephthalate resin portion of the hollow body to exceed 70°C, the coating was heat-treated at 190°C for several seconds. The thickness of the coating layer was 5.2μ. The oxygen permeability coefficient of the hollow body is 2.6×10 ^-13 at 35℃ and 45% relative humidity.
cm ³ cm/cm ² seccmHg.

Example 5 Same as in Example 1 and Example 4
Two types of EVOH resin coating solutions were prepared. First, the same coating solution as in Example 4 was applied to the same bottomed parison as in Example 1 by the dipping method. After coating, preliminary drying was performed using infrared radiation (average wavelength: 2μ) to prevent re-dissolution of the first coating, and then the same coating solution as in Example 1 was applied onto the first coating in the same manner as in Example 1. It was applied by dipping method. After application,
It was dried in the same manner as in Example 1 to obtain a composite bottomed parison having a two-layered coating. The volatile content of the two-layer coating was 2.8% by weight, and the pure coating weight of the resin was 93 g/m ² . The obtained composite parison was subjected to a biaxial stretching blowing method according to Example 1.
After obtaining a biaxially stretched composite hollow body of 1.5 mm, it was dried and heat treated. The thickness of the two-layer coating is
It was 9.4μ. The oxygen permeability coefficient of the hollow body is 1.2×10 ^-13 cm ³ cm/cm 2 cm ² sec at 35°C and relative humidity 45%.
It was cmHg. Co-stretchability was good.

Example 6 The bottomed parison used in Example 1 was used. 85 parts of a mixed solvent consisting of 78 parts of t-butyl alcohol and 12 parts of water with an ethylene content of 55 mol% and a degree of saponification.
15 parts of 90 mol% EVOH was added and stirred at 80°C to prepare a transparent coating solution. First, the above-prepared coating solution was applied to the parison by the dipping method as in Example 1. (In order to measure the coating amount, the measurement sample was dried and the coating amount was confirmed. It was 15 g/ ^m2 .) After the coating, preliminary drying was performed using infrared radiation (average wavelength: 2 μ). Thereafter, in the same manner as in Example 5, two types of coating liquids of the same EVOH resin as in Examples 1 and 4 were applied and partially dried to obtain a composite parison having a three-layered coating. The volatile content of the three-layer coating was 4.5% by weight, and the pure coating amount of the resin was 107 g/m ² . The obtained composite parison was subjected to a biaxial stretching/blowing method according to Example 1 to obtain a composite hollow body which was biaxially stretched to a diameter of about 1.5, and then dried and heat treated. The thickness of the three-layer coating is
It was 10.6μ. The oxygen permeability coefficient of the hollow body is 35℃,
0.95×10 ^-13 cm ³ cm/ under conditions of relative humidity 45%
It was ^cm2・seccmHg.

Example 7 In Example 6, the EVOH used in Example 1
A composite parison having a two-layer coating was obtained according to Example 6 without applying the resin solution. The volatile content of the two-layered coating layer after partial drying is 1.5% by weight, and the coating amount based on the pure amount of the resin is 65g/
It was ^m2 . The obtained composite parison was prepared in Example 1.
A biaxially stretched composite hollow body of about 1.5 was obtained by a biaxially stretched blowing method according to the method, and then dried and heat treated.
The thickness of the two-layer coating was 6.6μ. The oxygen permeability coefficient of the hollow body was 3.3×10 ^-13 cm ³ ·cm/cm ² seccmHg under the conditions of 35° C. and 45% relative humidity.

Example 8 The same procedure as in Example 2 was carried out, except that 0.5% by weight of dimethyl sulfoxide was added to the n-propyl alcohol/water mixed solvent instead of n-amyl alcohol. The volatile content of the coating after drying was 1.2% by weight. The composite parison was subjected to biaxial stretching and blowing. The co-stretchability was good, the thickness of the coating layer of the obtained composite hollow body was 8.5μ, and the oxygen permeability coefficient of the hollow body was 35.
1.2×10 ^-13 cm ³ cm/ under conditions of ℃ and 45% relative humidity.
It was ^cm2・sec・cmHg.

Claims (1)

[Claims] 1. A coating of a solvent solution of a saponified ethylene-vinyl acetate copolymer is formed on at least one wall of the preform, and then the volatile content in the coating is 0.05 to 5% by weight. Composite preform with a dry gas-impermeable coating. 2. The composite preform according to claim 1, wherein the volatile content in the coating is 0.1 to 5% by weight. 3. The composite preform according to claim 1, wherein the solvent is a mixture of aliphatic alcohol and water, and the volatile content is 0.3 to 5% by weight. 4. The composite preform according to claim 3, wherein the solvent is n-propyl alcohol, i-propyl alcohol, t-butyl alcohol, or a mixture of water of two or more of these alcohols. 5. The composite preform according to claim 3 or 4, wherein the volatile content in the coating is 0.5 to 5% by weight. 6. The composite preform according to any one of claims 1 to 5, wherein the preform is made of a polyethylene terephthalate resin. 7. The composite preform according to any one of claims 1 to 6, wherein the saponified ethylene-vinyl acetate copolymer has an ethylene content of 25 to 60 mol% and a saponification degree of 96 mol% or more. 8 The coating is (B) a saponified ethylene-vinyl acetate copolymer layer with an ethylene content of 25 to 35 mol% and a saponification degree of 96 mol% or more, and (C) an ethylene content of 40 to 60 mol% and a saponification degree of 96 mol % or more of saponified ethylene-vinyl acetate copolymer layers. 9 The coating comprises (A) a saponified ethylene-vinyl acetate copolymer layer having an ethylene content of 25 to 60 mol% and a saponification degree of 85 to 95 mol%, and (B) an ethylene content of 25 to 35 mol% and a saponification degree of 96. Saponified ethylene-vinyl acetate copolymer layer with mole% or more and (C) ethylene content 40
Claims 1 to 6 consist of a saponified ethylene-vinyl acetate copolymer layer with a saponification degree of 96 mol% or more and a saponification degree of 96 mol% or more, the innermost layer being (A).
Composite preform according to any of paragraphs. 10 The coating includes a saponified ethylene-vinyl acetate copolymer layer having an ethylene content of 25 to 60 mol% and a saponification degree of 96 mol% or more, and (A) a saponified ethylene-vinyl acetate copolymer layer having an ethylene content of 25 to 60 mol% and a saponification degree of 85 to 95 mol%. It consists of a saponified ethylene-vinyl acetate copolymer layer, and the inner layer is (A).
A composite preform according to any one of claims 1 to 6. 11 A coating of a solvent solution of a saponified ethylene-vinyl acetate copolymer is formed on at least one wall surface of the preform, and then the volatile content in the coating is 0.05 to 5.
A gas-impermeable biaxially stretched composite hollow body which is dried to a weight percentage and then bi-stretched and blow-molded under biaxially stretched conditions. 12. The composite hollow body according to claim 11, wherein the volatile content in the coating is 0.1 to 5% by weight. 13. The composite hollow body according to claim 11, wherein the solvent is a mixture of aliphatic alcohol and water, and the volatile content is 0.3 to 5% by weight. 14. The composite hollow body according to claim 13, wherein the solvent is n-propyl alcohol, i-propyl alcohol, t-butyl alcohol, or a mixture of two or more of these alcohols and water. 15. The composite hollow body according to claim 13 or 14, wherein the volatile content in the coating is 0.5 to 5% by weight. 16. The composite hollow body according to any one of claims 11 to 15, wherein the preform is made of a polyethylene terephthalate resin. 17 Claims 11 to 1, wherein the saponified ethylene-vinyl acetate copolymer has an ethylene content of 25 to 60 mol% and a saponification degree of 96 mol% or more.
The composite hollow body according to any one of Item 6. 18 The coating has (B) an ethylene content of 25 to 35 mol%,
A saponified ethylene-vinyl acetate copolymer layer with a saponification degree of 96 mol% or more, and (C) an ethylene content of 40 to 60
The composite hollow body according to any one of claims 11 to 16, comprising two saponified ethylene-vinyl acetate copolymer layers having a saponification degree of 96 mol% or more by mol%. 19 The coating has (A) an ethylene content of 25 to 60 mol%,
A saponified ethylene-vinyl acetate copolymer layer with a saponification degree of 85 to 95 mol% and (B) an ethylene content of 25 to 95 mol%.
A saponified ethylene-vinyl acetate copolymer layer with an ethylene content of 35 mol% and a saponification degree of 96 mol% or more, and (C) an ethylene-vinyl acetate copolymer layer with an ethylene content of 40 to 60 mol% and a saponification degree of 96 mol% or more. The composite hollow body according to any one of claims 11 to 16, which is made of a compound layer, and the innermost layer is (A). 20 The coating has a saponified ethylene-vinyl acetate copolymer layer with an ethylene content of 25 to 60 mol% and a saponification degree of 96 mol% or more, and (A) an ethylene content of 25 to 60 mol% and a saponification degree of 85 to 95 mol%. It consists of a saponified ethylene-vinyl acetate copolymer layer, and the inner layer is (A).
A composite hollow body according to any one of claims 11 to 16.