JP2544755B2 - Polystyrene laminated structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a polyester amide having a Tg (glass transition point) of 50 ° C. or less and a saponified ethylene-vinyl acetate copolymer (hereinafter referred to as EVOH) on at least one surface of a polystyrene substrate. And a polystyrene laminated structure having a mixture layer of

B. Conventional Technology Polystyrene has a wide range of uses as a resin with well-balanced properties among general-purpose resins. However, not all properties can be satisfied by polystyrene alone. For example, when used in hollow containers for foods and non-foods, high gas barrier properties are required in fields where it is necessary to prevent oxidation of contents or retain scent. As a method for providing gas barrier properties, a method is known in which a multilayer structure (film, sheet, parison, etc.) in which EVOH and polystyrene are laminated is secondarily processed into a container or the like.

On the other hand, it is possible to form a coating with a relatively thin film thickness, to easily form a coating on a substrate having a complicated shape such as a hollow container, and to perform a coating operation with a relatively simple device.
At present, a solution coating method, in which a solution prepared by dissolving EVOH in a solvent is applied to a substrate, is drawing attention. Further, in the coating method, since EVOH is a resin having oil resistance, it is possible to impart oil resistance to polystyrene by forming an EVOH layer on the polystyrene surface.

EV with polystyrene layer using the solution coating method
When stacking the OH layer, the two will not adhere at all unless an adhesive layer is provided in the intermediate layer. As the adhesive used for such an application, a polyurethane type adhesive is mainly used, but usually, the adhesive solution is applied to polystyrene as a base material and dried, and then the EVOH solution is applied and dried to obtain EVOH. A laminated structure of polystyrene and polystyrene is obtained. However, the process of applying and drying the adhesive solution and the EVOH solution respectively requires complicated equipment and is disadvantageous in terms of cost.

Therefore, if a solution obtained by mixing an adhesive with an EVOH solution is used, it is very useful in terms of cost by simplifying the coating and drying process of the adhesive and omitting the solvent of the adhesive solution. As a method thereof, Japanese Patent Publication No. 30600/1985 proposes blending polyethyleneimine with an EVOH solution. However, this method adheres strongly to polyolefin-based polymers, but hardly to polystyrene.

In addition, USP4459400 (JP-A-60-144330) and U.S.P.
SP4481238 (Tokuyo Sho-60-501312) describes the use of polyesteramide as an interlayer adhesive between EVOH layer and PET layer. Polyesteramide has excellent adhesiveness to polystyrene. Is EV
There is no disclosure of laminating a mixture layer of OH and polyesteramide and a polystyrene layer, and by doing so, a laminated structure having excellent adhesion can be obtained.

C. Problems to be Solved by the Invention The present invention aims to provide a laminated structure in which polystyrene and EVOH are firmly adhered while simplifying the step of coating and drying the adhesive.

D. Means for Solving the Problems According to the present invention, the above object is to provide a polyester amide having a Tg (glass transition point) of 50 ° C. or lower and a saponified ethylene-vinyl acetate copolymer on at least one surface of a polystyrene substrate. This is accomplished by providing a polystyrene laminate structure having a mixture layer with a weight ratio of 5:95 to 35:65.

E. More Detailed Description of the Invention The most important feature of the present invention is that the mixture of polyesteramide and EVOH strongly adheres to the polystyrene layer.

The polyesteramide referred to in the present invention needs to have a Tg (glass transition point) of 50 ° C. or lower, preferably 40 ° C. or lower, particularly preferably 30 ° C. or lower. When Tg exceeds 50 ° C, not only the compatibility with EVOH decreases but also the adhesive strength with polystyrene and EVOH decreases.

Polyesteramide is a polymer composed of a reaction product of a diamine component, a diol component and a dicarboxylic acid component and having an ester repeating unit and an amide repeating unit in one polymer chain. The diamine component is composed of at least one diamine having about 2 to 14 carbon atoms and is preferably aliphatic, but aromatic diamine may be added within the range not departing from the spirit of the present invention. Suitable diamines include hexamethylene diamine, piperazine,
1-Aminoethylpiperazine, bisaminopropylpiperazine, 1,3-dipiperidyl propane, 1,4-cyclohexanebismethylamine, 1,2-ethanediamine, a mixture thereof and the like are included. The diol component is about 2
It consists of at least one diol containing up to 14 carbon atoms. Suitable diols include ethylene glycol, 1,4
-Butanediol, neopentyl glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol,
Or a mixture thereof and the like are included.

The polyesteramide further comprises a dicarboxylic acid component. The dicarboxylic acid component consists of at least one dicarboxylic acid containing up to about 5 to 14 carbon atoms and is preferably aliphatic, but addition of an aromatic dicarboxylic acid within the scope of the present invention is not critical. Is also good. Suitable dicarboxylic acids are sebacic acid, azelaic acid, adipic acid,
A mixture thereof and the like are included.

The polyesteramide referred to in the present invention is synthesized by a method generally known in the art for producing a polyesteramide. Usually, it is produced by a melt phase polymerization method from a diamine component, a diol component and a dicarboxylic acid component in the presence of a catalyst (preferably a titanium compound). Examples include JP-A-60-144330, JP-A-61-501312, and the like. The polyesteramide used in the present invention is an ester component and an amide component in the polymer chain of 5:95 ~.
The resin is contained in a molar ratio range of 40:60, preferably 10:90 to 30:70. If the ester component content is 5 mol% or less, the adhesive strength with polystyrene will decrease, while 40 mol%
Above, the compatibility with EVOH decreases.

EVOH used in the present invention has an ethylene content of 20 to 60 mol%,
Preferably 25 to 55 mol%, the degree of saponification of the vinyl acetate component is 90
% Or more, preferably 95% or more. 20 ethylene content
When it is at most mol%, the gas barrier property at high humidity will be lowered, or the water resistance will be lowered. On the other hand, if it is 60 mol% or more, sufficient gas barrier properties cannot be obtained. . Further, when the saponification degree is 90% or less, the gas barrier property and the moisture resistance decrease.

EVOH is also a small amount of propylene, isobutene, α
An α-olefin such as octene, an unsaturated carboxylic acid or a salt thereof, a partial alkyl ester thereof, a complete alkyl ester thereof, a nitrile thereof, an amide thereof, an anhydride thereof,
It may contain a comonomer unit such as an unsaturated sulfonic acid or a salt thereof.

Regarding the blending ratio of polyesteramide and EVOH, if the blending ratio of polyesteramide is low, the adhesiveness with polystyrene is poor, and a satisfactory composite structure cannot be obtained, while if the blending ratio of polyesteramide is too high, the gas barrier properties descend. Therefore, the blending ratio of polyesteramide is 5 based on the total weight of polyesteramide and EVOH
˜35 wt%, preferably 10 to 30 wt%.

The most effective method for providing the mixture layer of polyesteramide and EVOH on at least one surface of the polystyrene base material is to dissolve polyesteramide and EVOH in a common solvent for these and apply the solution. Here, the common solvent is a monohydric alcohol such as methyl alcohol, ethyl alcohol, propyl alcohol or butyl alcohol, or 2 such as ethylene glycol or propylene glycol.
Polyhydric alcohols, trihydric alcohols such as glycerin, phenols such as cresol, phenols such as ethylenediamine and trimethylenediamine, acids such as formic acid, dimethylsulfoxide, dimethylacetamide, N-methylpyrrolidone, etc. The water-containing material and the like are used alone or in admixture of two or more. Particularly preferably used solvents are water-alcohol-based mixed solvents such as water-normal propyl alcohol, water-isopropyl alcohol and water-methyl alcohol.

The concentration of the mixed solution of polyesteramide and EVOH can be applied at any concentration, but normally, it is preferably about 2 to 20% by weight.

As a method for applying a solution of a mixture of polyesteramide and EVOH, any known method such as a roller coating method, a spray coating method, a dip coating method, or the like can be applied. The polystyrene substrate has one coated surface and two coated surfaces.
Either the surface or the entire surface may be used.

After applying a mixed solution of polyesteramide and EVOH to a polystyrene substrate, drying is performed. Drying temperature is 30 ~
It may be heated at a temperature of 200 ° C., preferably about 50 to 150 ° C. for about 10 seconds to 10 minutes. The coating can be dried until the volatiles are almost eliminated, but the volatiles can be added to the coating to prevent cracking of the coating and to maintain the transparency and interlayer adhesion of the coating for a long period of time. 0.
It is advantageous to leave 5 to 5% by weight.

In the present invention, a mixture of EVOH and polyesteramide may be appropriately blended with additives such as a weather resistance stabilizer, an antioxidant, a filler, a reinforcing agent (such as glass fiber), a colorant, a surfactant, and a soluble inorganic salt. You can

In the present invention, the film thickness (thickness after evaporation of the solvent) of the mixture layer of polyesteramide and EVOH applied to the polystyrene substrate is practically about 0.5 to 20 μm. 0.5μ
In the following, sufficient gas barrier properties will be obtained, while in the case of 20 μm or more, operations such as increasing the number of coatings will be required to obtain a film having a target film thickness, resulting in a problem that productivity is significantly reduced.

The formation of the composite structure is not limited to solution coating and can be performed by a method called hot pressing or coextrusion. For example, the composite structure can be formed by pressing a molten blend film of EVOH and polyesteramide and a polystyrene film under heating, or by coextruding a mixture of EVOH and polyesteramide and polystyrene.

When laminating a mixture of EVOH and polyester amide on a polystyrene base material, it is desirable that the surface of the polystyrene base material is previously subjected to surface treatment such as corona discharge treatment or fire treatment for the purpose of an adhesive structure, and then laminated. As for the degree of surface treatment, it is desirable that the wetting index of the substrate is 40 dyn / cm or more, preferably 45 dyn / cm or more, based on the result of the method of JIS K6768.

In the present invention, polystyrene means polystyrene,
Styrene and other monomers capable of copolymerizing it (eg,
Copolymers with acrylonitrile, butadiene (for example, styrene-acrylonitrile copolymer, styrene-
p-divinyl benzene copolymer, styrene-butadiene copolymer, styrene-butadiene-acrylonitrile copolymer) and the like. Suitably, a rubber-blended polystyrene resin for polymerizing styrene in the presence of butadiene-styrene rubber, which is widely known in the industry as styrene, and an acrylonitrile-butadiene-styrene resin which is widely known as ABS in the industry. Polystyrene such as styrene-butadiene block copolymer having a large amount of styrene component known as high-impact polystyrene is used. The polystyrene base material may be any material such as a film, a sheet, a hollow bottle, and a tube.

In addition to these uses, the laminate of the present invention can be used for foods, beverages, medicines, packaging materials for medicines, containers and the like. It is also possible to coat or laminate a mixture of EVOH and polyesteramide on a polystyrene base material, and then draw and / or heat-treat to obtain a desired molded product.

Further, if necessary, a moisture-proof layer can be formed on the EVOH-polyesteramide layer of the composite structure by vinylidene chloride resin coating, vinyl chloride-vinyl acetate copolymer coating, or the like. In addition to the composite structure, the composite material laminated on polyester, polyolefin or the like can be used as a packaging material for foods, beverages, medicines, medical treatments, containers or the like.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. All percentages and parts are by weight unless otherwise specified. Also, Tg (glass transition point)
Was measured using a Perkin-Elmer DSC-2 differential scanning calorimeter.

F. Examples Examples 1 to 4 Polyesteramide (Tg: 20.5) composed of azelaic acid / cyclohexanedimethanol / piperazine = 0.50 / 0.09 / 0.41 (molar ratio; ester component: amide component = 18: 82)
℃) and ethylene content 32 mol%, saponification degree 99.5% EVOH in a weight ratio of 5:95, 10:90, 15:85, 20:80 10 parts of a mixture of 35% water, 65% n-propyl alcohol Mixed solvent containing 90
And added to each part and stirred at 70 to 80 ° C. for about 2 hours to obtain 4 kinds of transparent solutions. After cooling these solutions to a liquid temperature of 25 ° C, they were previously treated with corona discharge (corona discharge output: 1k
w, Processing speed: 20m / min., Wetting speed: 48dyn / cm) Polystyrene film 50μ (Styro film: Asahi Kasei Corp.)
The above melt is applied to the above by the applicator coating method, and the temperature is 70 ° C.
Was dried for 10 minutes to form a coating film of EVOH (film thickness 5 μm) having a volatile content of about 3%.

 Various performances of the composite structure are shown in Table 1.

Example 5 Azelaic acid / ethylene glycol / piperazine = 0.
50 / 0.13 / 0.37 (molar ratio; ester component: amide component = 2
6:74) polyester amide (Tg: -2.3 ° C) and EVOH with an ethylene content of 32 mol% and a saponification degree of 99.5%
10 parts of a mixture of 5:85 was added to 90 parts of a mixed solvent containing 30% of water and 70% of n-propyl alcohol, and stirred at 70 to 80 ° C for about 2 hours to obtain a transparent solution. Liquid temperature of this solution
After cooling to 25 ℃, corona discharge treatment was performed in advance (corona discharge output: 1kw, treatment speed: 20m / min. Wetting index: 48dyn / cm)
Polystyrene film 50μ (Styro film: Asahi Kasei Corp.) was coated with the above solution by an applicator coating method and dried at 80 ° C for 5 minutes to obtain an EVO with a volatile content of 1.5%.
A coating film of H (film thickness 2 μ) was formed.

When the transparency of the composite structure was measured, the Haze degree was 3.8.
%, Indicating good transparency.

The oxygen permeability of the composite structure was measured under the condition of 20 ° C-65% RH, and it was 9.3cc / m ² · day · atm (EV
OH layer only).

Furthermore, when the 180 degree peel strength between the polystyrene film of the composite structure and the EVOH coating film was measured, it was 120 g / 15 mm.
It was a width.

Example 6 Sebacic acid / neopentyl glycol / piperazine =
0.50 / 0.05 / 0.45 (molar ratio; ester component: amide component =
10:90) polyester amide (Tg: 23.3 ° C) and EVOH with an ethylene content of 44 mol% and a saponification degree of 99.6% have a weight ratio of 1
10 parts of the mixture of 0:90 was added to 90 parts of a mixed solvent containing 30% of water and 70% of n-propyl alcohol, and stirred at 70 to 80 ° C. for about 2 hours to obtain a transparent solution. Liquid temperature of this solution
After cooling to 25 ℃, corona discharge treatment was performed in advance (corona discharge output: 1kw, treatment speed: 20m / min. Wetting index: 48dyn / cm)
Polystyrene film 50μ (Styro film: Asahi Kasei Kogyo Co., Ltd.) is coated with the above solution by an applicator coating method and dried at 80 ° C for 5 minutes to form an EVOH (thickness 2μ) coating film with a volatile content of 1.2%. Let

When the transparency of the composite structure was measured, the Haze degree was 3.4.
%, Indicating good transparency.

Further, when the oxygen permeability of the composite structure was measured under the condition of 20 ° C.-65% RH, it was 18.2 cc / m ² · day · atm (E
VOH layer only).

Furthermore, when the 180 degree peel strength between the polystyrene film and the EVOH coating film of the composite structure was measured, it was 60 g / 15 mm.
It was a width.

Comparative Examples 1 to 2 Various performances of the composite structure in which the mixing ratio of polyesteramide and EVOH is 2:98, 40:60 are shown by the same coating film forming method as shown in Examples 1 to 4. Shown in 1.

In Comparative Example 1, the Haze degree indicating transparency and the oxygen permeability indicating gas barrier property were comparable to those in Examples 1 to 4, but the 180 degree peel strength indicating adhesive strength was very small, which was a problem in practical use. there were.

In Comparative Example 2, there was no problem in the adhesive strength and transparency, but the gas barrier property was extremely lowered.

G. Effect of the Invention According to the present invention, it is possible to obtain a polystyrene laminated structure having excellent gas barrier properties and oil resistance, and having EVOH strongly adhered to polystyrene as a base material.

Claims (6)

(57) [Claims] 1. Tg on at least one side of a polystyrene substrate
The weight ratio of polyesteramide (glass transition point) below 50 ℃ and saponified ethylene-vinyl acetate copolymer is 5:95 to 3
Polystyrene laminate structure having a 5:65 mixture layer. 2. A polyesteramide having at least one repeating unit of a diamine component having 2 to 14 carbon atoms, at least one repeating unit of a diol component having 2 to 14 carbon atoms, and a dicarboxylic acid component having 5 to 14 carbon atoms. The polystyrene laminated structure according to claim 1, which comprises at least one repeating unit of the above, and contains the ester component and the amide component in the polyesteramide in a molar ratio of 5:95 to 40:60. 3. A saponification product of an ethylene-vinyl acetate copolymer having an ethylene content of 20 to 60 mol%, and a saponification degree of a vinyl acetate component of 90.
The polystyrene laminated structure according to claim 1, wherein the polystyrene laminated structure is at least%. 4. The polystyrene laminated structure according to claim 1, wherein the film thickness of the mixture layer of the polyesteramide and the saponified product of the ethylene-vinyl acetate copolymer is 0.5 to 20 μm. 5. The polystyrene laminated structure according to claim 1, wherein the surface of the polystyrene base material has been previously subjected to corona discharge treatment or fire treatment. 6. A mixture layer of polyesteramide and a saponified product of ethylene-vinyl acetate copolymer, which is obtained by coating a mixed solution of a polyesteramide and a saponified product of ethylene-vinyl acetate copolymer and drying. The polystyrene laminated structure according to item 1.