JPH0647628B2 - Polyvinyl alcohol melt molding - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a melt-molded product comprising a composition of polyvinyl alcohol (hereinafter abbreviated as PVA) and a specific amount of a metal salt, or a layer comprising the composition. It relates to a multi-layer coextrusion product containing one layer.

2. Description of the Related Art PVA is a resin that is excellent in chemical resistance and physical properties, particularly oxygen gas barrier property, and is widely used industrially. However, since the crystal melting point (Tm) of PVA is higher than the decomposition onset temperature (Td), a simple melt extrusion method cannot be used like polyethylene, polyvinyl chloride, and polypropylene, and plasticizers such as glycerin and low-molecular-weight polyethylene glycol or water cannot be used. It is necessary to make pellets impregnated with and to perform extrusion film formation with an extruder having a special melting, kneading, and defoaming mechanism. ["Poval" published by Polymer Publishing Association 19
Reprinted April 25, 1984, p. 377, "Encyclopedia
Of Polymer Science and Engineering
(Encyclopedia of Polymer Science and Engineerin
g) ”John Wiley and Sons, Inc. 1989, Volume 17,
Pp. 186-187].

Therefore, industrially, PVA is generally made into an aqueous solution and then cast by a casting method, a wet spinning method or the like to obtain a film, a sheet,
It has been molded into fibers and the like.

Therefore, in order to easily perform hot melt molding of PVA, it has been devised to reduce the degree of saponification into a vinyl alcohol-vinyl acetate copolymer or a copolymer with ethylene. However, there are some problems such as reduced barrier properties.

On the other hand, the composition of PVA and a metal salt is disclosed in Japanese Examined Patent Publication No. 43-29660.
JP-A-49-45882, JP-A-56-25419, JP-A-61
-141916, Japanese Patent Laid-Open No. 1-230659, etc.,
The molding is a casting method, a wet spinning method, or a room temperature pressing method, and there is no disclosure about the influence of the metal salt on the decomposition temperature of PVA as well as the melt-molded product composed of PVA and the metal salt composition.

The present inventors have diligently studied a method of melt-molding PVA having a particularly high gas saponification degree and a high degree of saponification, which has been considered to be difficult to process in the past, without lowering the gas barrier property, and as a result, specified as PVA. By adding an amount of a metal salt, the decomposition initiation temperature (Td) of PVA can be made higher than its crystalline melting point (Tm) and flow initiation temperature (Tf), a melt-molded product can be easily obtained, and a gas barrier can be obtained. The present invention has been completed by finding that the property is not impaired.

Means for Solving the Problems The present invention relates to a melt-molded product comprising a polyvinyl alcohol composition containing 0.01 to 3.0 mmol of metal salt per 1 g of PVA and a multi-layer coextrusion product having at least one layer comprising the composition. is there.

The PVA used in the present invention generally has a degree of polymerization of 100 to 2000,
Preferably 200 to 1000 is used, and the degree of saponification is 80% or more, preferably 90% or more, and more preferably 95%.
% Or more is used. If the saponification degree is less than 80%, the barrier property is lowered, which is not preferable. The degree of polymerization is 10
If it is less than 0, the viscosity becomes low, and it is not suitable for ordinary molding equipment.

As the metal salt, any metal salt can be used as long as Td of PVA is higher than Tf and the difference can be 15 ° C. or more, preferably 20 to 70 ° C., but preferably lithium, sodium, Alkali metal salts such as potassium,
Alkaline earth metal salts such as calcium, magnesium, strontium, cobalt, tin, manganese, nickel,
Divalent to tetravalent heavy metal salts such as iron and titanium are used. Chlorides, halides such as bromides, inorganic salts such as carbonates, sulfates, nitrates, organics such as acetates, lactates and stearates. An acid salt or the like is used.

Further, these metal salts may be used alone or as a mixture.

The action is different depending on the kind of the metal salt. For example, lithium has an effect of lowering Tm and increasing Td,
Sodium and potassium tend to increase Td, and magnesium and calcium tend to decrease Tm.

The amount of the metal salt varies depending on the kind of the metal salt, but 0.01 mmol to 3.0 mmol, preferably 0.1 mmol to 2.0 mmol is used per 1 g of PVA. If it is less than 0.01 millimole, the effect of increasing Td is lowered, and if it is 3.0 millimole or more, Td is rather lowered and coloring due to thermal decomposition becomes severe, and it becomes impossible to make the difference between Td and Tf 15 ° C or more. When the amount is 2.0 mmol or less, PVA can further improve the gas barrier property, so that it is particularly preferable for applications using the gas barrier property. The improvement in the gas barrier property is 0.5 mmol / g, as is clear from FIG.
The lithium salt in the range of up to 2.0 mmol / g and the calcium salt in the range of 0.1 mmol / g to 0.1 mmol / g are particularly prominent and can be preferably used in the field where high barrier properties are required.

Table 1 shows the T when various metal salts are added to PVA.
The effect on f, Tm and Td is shown.

Tf is indicated by the temperature at which the sample melts and flows under the conditions of heating rate 6 ° C./min, load 50 kg, nozzle: diameter 1 mmφ using a Koka type flow tester (manufactured by Shimadzu Corporation). Tm is TAS100 system manufactured by Rigaku Co., Ltd., and the sample is about 5 mg.
Obtained by increasing the temperature in a nitrogen atmosphere at a heating rate of 20 ° C / min
It is shown by the temperature showing the maximum value of the TA curve. For Td, using the same device, about 5 mg of the sample was heated in a nitrogen atmosphere at a heating rate of 20
In the TG curve obtained by increasing in ° C / min, the temperature is shown as the temperature decreasing by 1% from the weight at room temperature.

Single PVA without metal salt as shown in Table 1
In the case of, Td-Tf is -15 ° C, and in the melt molding,
Thermal decomposition occurs, making melt molding difficult. Metal salt is PVA
When 0.1 to 3.0 mmol is contained per 1 g, Td becomes higher than Tf, and melt molding becomes possible. Td-Tf is preferably 15 ° C or higher, more preferably 20 to 70 ° C or higher for melt molding.

It is also an excellent advantage of the present invention that the gas barrier property of PVA is improved when the amount of the metal salt added is 2.0 mmol or less per 1 g of PVA as described above.

The PVA-metal salt composition is molded into an arbitrary molded article such as a film, a sheet, a tube or a container by melt molding such as hot press molding, injection, extrusion molding (T-die, blow, inflation molding). Next, a case of forming a film by extrusion will be described as an example.

The PVA and the metal salt may be mixed by uniformly mixing the raw materials with a mixer such as a tumbler or a Henschel mixer.
The metal salt aqueous solution may be added to PVA to be pelletized and dried using a Banbury mixer, a single screw extruder, a twin screw extruder, or the like, or PVA may be dissolved in the metal salt aqueous solution and dried.

The PVA-metal salt composition thus obtained is fed to an extruder, melt-kneaded, and formed into a film or sheet at a die temperature of 170 to 270 ° C. by a T die or the like connected to the extruder.

The melt-formed product of the present invention may be a single layer or a multilayer. In the case of a multi-layer, at least one layer may be a layer composed of the PVA-metal salt composition, and a co-extruded multi-layer molded product is preferable from the viewpoint of processing. A film as a multilayer molded product,
Sheets, tubes, containers, etc. are exemplified.

A coextrudable thermoplastic resin is preferable as the other layer forming the multilayer, and polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate are preferable. Olefin resins such as copolymers and ionomers, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamides, polycarbonates and the like are used.

Among the coextruded multilayer molded products, a multilayer molded product in which a layer of PVA-metal salt composition is used as a core layer and both outer layers are thermoplastic resin corrugated layers is preferable, and when the thermoplastic resin is an olefin resin, a PVA composition is used. The influence of external moisture on the physical layer can be prevented, and the gas barrier property can be maintained even under high humidity, which is particularly preferable.

In the case of a coextruded multilayer molded article, a meltable adhesive is used, and an adhesive layer can be provided between each layer. In the case of co-extrusion multi-layer molding, for example, multi-layer film molding, each component is melt-kneaded by a plurality of extruders and then introduced into a laminating annular die or a T-die, for example, an outer layer / adhesive layer / core layer (P
VA-metal salt composition) / adhesive layer / outer layer are laminated in this order and coextruded. The coextrusion film is rapidly cooled with a cold water shower ring or roll of 5 to 30 ° C. to obtain a multi-layer film.

Further, within a range not impairing the object of the present invention, PVA
-Plasticizers, stabilizers, lubricants, antioxidants, pigments etc. can be added to the metal salt composition.

EFFECTS OF THE INVENTION In the present invention, a melt-molded product of PVA, which has been considered difficult in the past, could be obtained by adding a specific amount of a metal salt to PVA and performing melt-molding without impairing the gas barrier property.

Since the molded product of the present invention is a melt-molded product, it can be industrially easily manufactured as compared with the casting method and the like, and particularly when the amount of the metal salt is within a certain range, the gas barrier property of PVA can be improved. .

Further, the coextrusion multilayer molded product obtained by the coextrusion method is easy to manufacture, and when the PVA-metal salt composition is the core layer and the thermoplastic resin layer is the outer layer, it exhibits excellent gas barrier properties under high humidity. You can Since the sheet, film and container of the present invention are excellent in oxygen gas barrier property, foods such as meat, ham and
Suitable for packaging materials such as sausage.

The present invention will be described below with reference to examples. These examples are illustrative, and the present invention is not limited to these examples.

Examples 1 to 20 and Comparative Examples 1 to 4 Metal aqueous solutions were treated with PVA [Kuraray Co., Ltd. Poval PVA]
105, degree of polymerization 500, degree of saponification 98.5%] were mixed at a ratio of 1: 1 (weight ratio) so that the amounts shown in Table 2 were obtained, and the mixture was impregnated at room temperature overnight and then at 110 ° C. for 3 days. After drying for an hour, PVA with metal salt added was obtained. This metal salt-added PVA is a 30φ single screw extruder with a T die set (L /
D = 22), melt extruding, cooling and thickness
A 20 μm film was obtained. The soybean temperature is as shown in Table 2. The cylinder temperature of the extruder follows the standard method,
The temperature was 80 to 230 ° C. The extrusion rate was 40 g / min. Regarding Examples 1 to 20, there were no phenomena such as foaming and coloring, and the melt extrusion moldability was extremely good. In the case of PVA (no addition), vigorous foaming occurred due to thermal decomposition, and hot melt molding was completely impossible. When the addition amount of the metal salt was 5 mmol / g (Comparative Examples 1 to 3), the coloring became strong and the melt extrudability was insufficient.

The oxygen permeability coefficient and carbon dioxide permeability coefficient of these films were measured using a gas permeability tester Yanako GTR-10A manufactured by Yanagimoto Seisakusho under the conditions of 30 ° C. and 0% RH. The results are shown in Table 2.

Also, the oxygen permeability coefficient of PVA and the added metal salt PVA1
The relationship with the millimoles per g is shown in FIG. As is clear from the figure, the oxygen gas permeability coefficient of the film formed by adding the metal salt is smaller than that of the non-added film (cast film) when the added amount is 2.0 mmol or less, and the gas barrier property is improved by adding the metal salt. I understand that The cast film was obtained by casting a 10% aqueous solution of Poval PVA105 on a glass plate and then drying it. Its oxygen permeability coefficient is 9.5 × 10 ^-15 cc · cm / cm ² sec · cm
Hg, carbon dioxide permeability coefficient is 3.8 × 10 ^-14 cccm / cm ² seccm
It was Hg.

Examples 21 to 31, Comparative Examples 5 to 7 In the same manner as in Examples 1 to 20, PVA-metal salt compositions having the addition amounts in the proportions shown in Table 3 were obtained. Example 1 for PVA
The same as ~ 20 was used.

The first layer of polyethylene is a 35φ single screw extruder (L / D = 2
2), polyethylene of the 3rd layer is 40φ single screw extruder (L / D
= 22) and the second layer of PVA-metal salt composition was applied to a T-die (feed block) having a width of 35 mm.
The PVA-metal salt composition was co-extruded in a melt extrusion feed block from a 25φ single screw extruder to form a core layer. The extrusion rate was 200 g / min, and a three-layer laminated film was manufactured by cooling with a cooling roll directly below the die.
As the polyethylene of the first layer and the third layer, low density polyethylene Sumikasen F 114-1 manufactured by Sumitomo Chemical Co., Ltd. was used. Table 3 shows the die temperature and the adapter temperature as the extrusion temperature.

The laminated film had a thickness of 120 μm, the polyethylene layer had a thickness of 50 μm, and the PVA layer had a thickness of 20 μm.

Regarding Examples 21 to 31, there were no phenomena such as foaming and coloring, and the melt extrusion moldability was good.

In the case of Comparative Example 5, severe foaming occurred due to thermal decomposition, and coextrusion molding could not be performed.

In Comparative Examples 6 to 7, the amount of the metal salt added was large and the melt molding was difficult, and coloring occurred.

The oxygen permeability and carbon dioxide permeability of these films were measured using Yanamoto GTR-10A gas permeability tester manufactured by Yanagimoto Seisakusho.
It was measured under the conditions of 30 ° C. and 0% RH.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the oxygen permeability coefficient of a film made of a PVA-metal salt composition and the amount of metal salt added.

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display area B29L 7:00 4F

Claims (2)

[Claims] 1. 0.01 to 3.0 per 1 g of polyvinyl alcohol
A melt-formed product comprising a polyvinyl alcohol composition containing mmol of a metal salt. 2. 0.01 to 3.0 per 1 g of polyvinyl alcohol
A multilayer coextrusion having at least one layer of a polyvinyl alcohol composition containing millimoles of metal salt.