JP4758926B2 - Thermoplastic multilayer resin sheet and molded container - Google Patents

Description

  The present invention relates to a thermoplastic multilayer resin sheet and a molded container formed by molding the same.

  Conventionally, styrenic resins having excellent thermoformability and rigidity have been used as containers for soft drinks, fruit juice drinks, and favorite foods and drinks. However, in recent years, an ethylene-vinyl alcohol copolymer resin layer is provided through an adhesive layer such as a modified olefin resin in the middle of the styrene resin layer as the outermost layer to provide oxygen barrier properties, and by oxidation of the contents A multilayer resin sheet in which deterioration in quality is suppressed and a multilayer container comprising the same are widely used (Patent Document 1).

  In recent years, the number of cases in which these containers are manufactured by an integrated process of molding, filling the contents, and sealing the lid material has increased. Patent Document 2 proposes a multilayer resin sheet in which a polystyrene resin layer and a polyolefin resin layer are laminated to prevent generation of resin whiskers during stamping in the process up to the final product.

JP-A-11-58619 JP 2006-21409 A

  However, the conventional multilayer resin sheet has a problem that the notch bendability after thermoforming is insufficient because the oxygen barrier resin is tough.

  Therefore, the present invention provides a thermoplastic multilayer resin sheet that has thermoformability, rigidity, and oxygen barrier properties, and that is easy to impart notch breakability after thermoforming, and a molded container comprising the same. Objective.

  The inventor of the present invention relates to a modified olefin polymer layer on a notch-forming surface side and a styrene resin in a multilayer resin sheet in which a styrene resin layer is laminated on both surfaces of an oxygen barrier resin layer via a modified olefin polymer layer. It has been found that the above-mentioned problems can be solved by adjusting the thickness of the resin layer, and the present invention has been completed.

  That is, the thermoplastic multilayer resin sheet of the present invention is a multilayer resin sheet in which a notch is formed from one surface side, and a styrene resin is interposed on both surfaces of the oxygen barrier resin layer via a modified olefin polymer layer. The layers are laminated, and the total thickness of the modified olefin polymer layer and the styrene resin layer on the one surface side is 50 to 400 μm.

  The thermoplastic multilayer resin sheet of the present invention has thermoformability, rigidity, and oxygen barrier properties, and easily imparts notch breakability after thermoforming.

  In addition, the molded container of the present invention has rigidity and oxygen barrier properties, and is excellent in notch breakability.

<Oxygen barrier resin layer>
Typical examples of the oxygen barrier resin constituting the oxygen barrier resin layer include ethylene-vinyl alcohol copolymer resins and polyamide resins. Among these, ethylene-vinyl alcohol copolymer resin is preferable in terms of processability and moldability.

  The ethylene-vinyl alcohol copolymer resin is usually obtained by saponifying an ethylene-vinyl acetate copolymer, and has an ethylene content of 10 to 10 in order to have oxygen barrier properties, workability, and moldability. It is preferably 65 mol%, preferably 20 to 50 mol%, and a saponification degree of 90% or more, preferably 95% or more.

  Examples of the polyamide resin include lactam polymers such as caprolactam and laurolactam, polymers of aminocarboxylic acids such as 6-aminocaproic acid, 11-aminoundecanoic acid and 12-aminododecanoic acid, hexamethylenediamine, decamethylenediamine, Aliphatic diamines such as dodecamethylenediamine, 2,2,4- or 2,4,4-trimethylhexamethylenediamine, 1,3- or 1,4-bis (aminomethyl) cyclohexane, bis (p-aminocyclohexylmethane) ) Alicyclic diamines such as m- or p-xylylenediamine, diamine units such as aromatic diamines, aliphatic dicarboxylic acids such as adipic acid, suberic acid and sebacic acid, and alicyclics such as cyclohexanedicarboxylic acid Aromatic dica, such as dicarboxylic acid, terephthalic acid, isophthalic acid Polycondensates of a dicarboxylic acid units, such as carbon acid, and copolymers thereof, and the like.

  Specifically, nylon 6, nylon 9, nylon 11, nylon 12, nylon 66, nylon 610, nylon 611, nylon 612, nylon 6T, nylon 6I, nylon MXD6, nylon 6/66, nylon 6/610, nylon 6 / 6T, nylon 6I / 6T, etc., among which nylon 6 and nylon MXD6 are preferred.

  The thickness of the oxygen barrier resin layer is preferably 10 to 50 μm, more preferably 20 to 40 μm. If it is less than 10 μm, there is a possibility that the oxygen barrier performance to the extent that quality deterioration due to oxidation of the contents of the molded container is suppressed cannot be obtained, and if it exceeds 50 μm, resin whiskers are generated when the thermoformed container is punched. Or notch breakage may be insufficient.

<Modified olefin polymer layer>
Examples of the modified olefin polymer constituting the modified olefin polymer layer include homopolymers of olefins having about 2 to 8 carbon atoms such as ethylene, propylene, and butene-1, and these olefins and ethylene, propylene, and butene-1. Other olefins having about 2 to 20 carbon atoms such as 3-methylbutene-1, pentene-1, 4-methylpentene-1, hexene-1, octene-1, decene-1, etc., vinyl acetate, vinyl chloride, acrylic acid Olefin resins such as copolymers with vinyl compounds such as methacrylic acid, acrylic acid esters, methacrylic acid esters and styrene, ethylene-propylene copolymers, ethylene-propylene-diene copolymers, ethylene-butene-1 Olefin rubbers such as copolymers, propylene-butene-1 copolymers, acrylic acid, methacrylic acid, Unsaturated carboxylic acids such as rotonic acid, isocrotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid and tetrahydrophthalic acid, or derivatives thereof such as acid halides, amides, imides, anhydrides and esters, specifically Typical examples include those modified with maleyl chloride, maleimide, maleic anhydride, citraconic anhydride, monomethyl maleate, dimethyl maleate, glycidyl maleate and the like under the graft reaction conditions.

  Among these, an ethylene-based resin, a propylene-based resin, or an ethylene-propylene or butene-1 copolymer rubber modified with an unsaturated dicarboxylic acid or an anhydride thereof, particularly maleic acid or an anhydride thereof, is preferable.

  The thickness of the modified olefin polymer layer is preferably 10 to 50 μm, more preferably 20 to 40 μm on either side. If it is less than 10 μm, sufficient interlayer adhesion strength may not be obtained, and if it exceeds 50 μm, resin whiskering may occur when punching a thermoformed container, or notch breakability may be insufficient. There is.

<Styrenic resin layer>
Examples of the styrene resin constituting the styrene resin layer include styrene monomers such as styrene, α-methyl styrene, p-methyl styrene, dimethyl styrene, pt-butyl styrene, and chlorostyrene, or copolymers thereof. Copolymers of styrenic monomers and other monomers, such as styrene-acrylonitrile copolymers (AS resin), or other polymers such as styrene-based monomers, such as polybutadiene, styrene-butadiene copolymers, poly Examples include graft polymers obtained by graft polymerization in the presence of diene rubbery polymers such as isoprene and polychloroprene, such as high impact polystyrene (HIPS resin) and styrene-acrylonitrile graft polymer (ABS resin).

  Among these, polystyrene (GPPS resin) and high impact polystyrene (HIPS resin) are preferable from the viewpoint of the rigidity and moldability of the molded container.

  The styrene resin preferably contains 4 to 8% by mass of a butadiene rubber component. The butadiene rubber component content is a simple method of adjusting by blending GPPS and HIPS, but it may be adjusted at the manufacturing stage of HIPS. If it is less than 4% by mass, a practically sufficient container strength may not be obtained. If it exceeds 8% by mass, problems such as adhesion of a hot platen may occur during thermoforming.

  In the styrene resin layer, if necessary, a colorant such as a pigment or a dye, a release agent such as silicon oil or an alkyl ester, or a fibrous reinforcing agent such as glass fiber, as long as the effects of the present invention are not impaired. Additives such as particulate lubricants such as talc, clay and silica, salt compounds of sulfonic acid and alkali metals, antistatic agents such as polyalkylene glycol, UV absorbers and antibacterial agents can be added. Moreover, the scrap resin generated in the production process of the multilayer resin sheet or molded container of the present invention can be mixed and used.

  The thickness of the styrene-based resin layer on the surface side where the notch is formed is preferably 30 to 300 μm, more preferably 100 to 200 μm. If it is less than 30 μm, the styrene-based resin layer is cut off when it is stretched through thermoforming, and the modified olefin-based polymer layer is exposed, which may impair the proper printing on the container surface. Moreover, when it exceeds 300 micrometers, it is necessary to enlarge the insertion depth of the blade at the time of forming a notch, and there exists a possibility that the holding | maintenance performance and container strength of a container shape may fall.

  The thickness of the styrene-based resin layer on the side where no notch is formed is preferably 300 to 800 μm, more preferably 400 to 700 μm. If it is less than 300 μm, the rigidity of the container obtained by thermoforming may be insufficient, and if it exceeds 800 μm, the notch breakability after forming the notch may be lowered.

<Thermoplastic multilayer resin sheet>
The layer structure of the thermoplastic multilayer resin sheet of the present invention is basically a styrene resin layer / modified olefin polymer layer / oxygen barrier resin layer / modified olefin polymer layer / styrene resin layer, In addition, for example, a multilayer resin sheet of the present invention or a layer of scrap resin generated in the manufacturing process of the molded container may be laminated on the opposite side where the notch is formed.

  In the thermoplastic multilayer resin sheet of the present invention, the total thickness of the modified olefin polymer layer and the styrene resin layer on the surface side where the notch is formed is 40 to 350 μm, preferably 120 to 240 μm. If it is less than 40 μm, the thickness of the styrenic resin layer on the surface side where the notch is relatively formed becomes thin, and the styrenic resin layer breaks when stretched through thermoforming, thereby impairing the appearance and strength of the container. There is a possibility. Moreover, when it exceeds 350 micrometers, it is necessary to enlarge the insertion depth of the blade at the time of forming a notch, and there exists a possibility that the holding | maintenance performance and container strength of a container shape may fall.

  The thickness of the thermoplastic multilayer resin sheet is preferably 500 to 1200 μm, more preferably 700 to 1000 μm. If it is less than 500 μm, the strength of the container obtained by thermoforming may be insufficient, and if it exceeds 1200 μm, the production cost of the container may increase.

  A method for forming the thermoplastic multilayer resin sheet is not particularly limited, and a general method can be used. For example, each raw resin is melt-extruded using four or more single-screw extruders, and a multilayer resin sheet is obtained using a feed block and a T die, or a multilayer resin sheet is obtained using a multi-manifold die Is mentioned.

<Molded container>
1 and 2 show an example of the molded container of the present invention.

  The molded container of the present invention is formed by thermoforming the thermoplastic multilayer resin sheet of the present invention. The thermoforming method includes general vacuum forming, pressure forming, and the plug assist method in which a plug is brought into contact with one side of the sheet as a form of application, and a pair of male and female dies are brought into contact with both sides of the sheet. A method called so-called “match mold molding” and the like, in which the molding is performed, is exemplified, but is not limited thereto. In addition, as a method for heating and softening the sheet before molding, a known sheet heating method such as radiation heating with an infrared heater or the like which is non-contact heating can be applied.

  The molded container of the present invention has a notch 1. The notch 1 has a V-shaped cross section and is heated on one surface side, that is, on the side where the total thickness of the modified olefin polymer layer and the styrene resin layer is 50 to 400 μm by a hot plate method or the like. It can be formed by inserting a letter-shaped blade.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to the content of an Example etc. at all.

The resin raw materials used in the examples are as follows.
(1) Oxygen barrier resin layer Ethylene-vinyl alcohol copolymer “EVAL J-102B” (manufactured by Kuraray Co., Ltd., ethylene content 32 mol%, saponification degree 99% or more)
(2) Modified olefin polymer layer “Modic F502” (Mitsubishi Chemical Corporation)
(3) Styrenic resin layer HIPS resin: “Toyostyrene H850” (Toyo Styrene Co., Ltd., butadiene content: 9.0% by mass)
GPPS resin: “HRM23” (manufactured by Toyo Styrene Co., Ltd.)

<Example 1>
Three 40mm single-screw extruders were used, and by feed block method, styrene resin layer A 80 μm / modified olefin polymer layer A 20 μm / oxygen barrier resin layer 30 μm / modified olefin polymer layer B 20 μm / styrene resin layer A multilayer resin sheet having a layer configuration of B550 μm and a thickness of 700 μm (the total thickness of the styrene resin layer A and the modified olefin polymer layer A was 100 μm) was obtained.

  In addition, as styrene resin, what mixed HIPS resin and GPPS resin by mass ratio 80/20 (HIPS / GPPS) was used (butadiene rubber component content: 7 mass%).

The multilayer resin sheet was processed in a series of steps from molding, notch formation, and container punching (FIG. 3) under the following conditions to obtain the container shown in FIG. In addition, about the notch, it formed from the styrene-type resin layer A side, and the depth of the notch was adjusted with the heating temperature of the notch formation part.
Equipment used: CFF-300 (manufactured by CKD Corporation)
Upper heating plate temperature: 165 ° C
Lower heating plate temperature: 165 ° C
Notch partial heating temperature: 160 ° C
Notch depth: 350 μm
Container punching blade upper structure: male blade container punching blade lower structure: gap between upper and lower sides of female blade container punching blade: 20 μm

  Various evaluations of the obtained multilayer resin sheet and container were performed by the following methods. The results are shown in Table 1.

(1) Oxygen permeability The oxygen permeability of the sheet was measured by the following method and evaluated according to the following criteria.
[Measuring method]
Equipment used: OX-TRAN oxygen transmission rate measuring device (manufactured by Mocon)
Measurement method: JIS K7126-B method Measurement conditions: Temperature 25 ° C., relative humidity 65%
[Evaluation criteria]
○: Less than 3.0 ml / m ² · day · atm ×: 3.0 ml / m ² · day · atm or more

(2) Thermoformability The moldability when the container was thermoformed was evaluated according to the following criteria.
○: Good formability ×: Hot plate adherence occurs during heating, causing molding defects

(3) Punchability The cut surface of the container was visually observed and evaluated according to the following criteria.
○: No resin whiskers are seen on the cut surface.
Δ: Some resin whiskers are seen on the cut surface.
X: Generation of resin whiskers on the cut surface is remarkable.

(4) Notch foldability The notch formation part was bent in the bending direction shown in FIG. 2, and evaluated according to the following criteria.
○: Can be broken by bending once.
Δ: Divided by bending several times.
X: It does not crack even if it bends many times.

(5) Container rigidity The rigidity of the molded container was measured by the following method and evaluated according to the following criteria.
[Measuring method]
Equipment used: Strograph VE (manufactured by Toyo Seiki Co., Ltd.)
Measurement conditions: JIS K7181 compliant, test speed 50 mm / min
[Evaluation criteria]
○: Compressive strength 30N or more ×: Compressive strength 30N or less

(6) Comprehensive Judgment A case where all the above evaluation results were “good” was evaluated as “good”, and a case other than that was “good”.

<Examples 2 to 10 and Comparative Examples 1 to 9>
A multilayer resin sheet was molded in the same manner as in Example 1 except that the composition of the styrene resin and the thickness of each layer were changed as shown in Table 1. In Comparative Example 9, a single-layer sheet having only a styrene resin layer was used.

  Moreover, the container was shape | molded like Example 1 using the obtained multilayer resin sheet.

  The evaluation results are shown in Table 1.

It is a schematic perspective view which shows an example of the shaping | molding container of this invention. It is a schematic side view which shows an example of the shaping | molding container of this invention. It is the schematic explaining the punching process of a container.

Claims (6)

  A multilayer resin sheet in which a notch is formed from one surface side, wherein a styrene resin layer is laminated on both surfaces of an oxygen barrier resin layer via a modified olefin polymer layer, and the one surface side A total thickness of the modified olefin polymer layer and the styrene resin layer is 40 to 350 μm.   The thermoplastic multilayer resin sheet according to claim 1, wherein the oxygen barrier resin layer is made of an ethylene-vinyl alcohol copolymer resin.   The thermoplastic multilayer resin sheet according to claim 1 or 2, wherein the modified olefin polymer layer has a thickness of 10 to 50 µm.   The thermoplastic multilayer resin sheet according to any one of claims 1 to 3, wherein the oxygen barrier resin layer has a thickness of 10 to 50 µm.   5. The thermoplastic multilayer resin sheet according to claim 1, wherein the styrene resin layer is made of a styrene resin containing 4 to 8 mass% of a butadiene rubber component.   A molded container comprising a notch formed from the one surface side by thermoforming the thermoplastic multilayer resin sheet according to any one of claims 1 to 5.

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