JP7294110B2 - packaging material - Google Patents

Description

The present invention relates to food packaging materials, beverage packaging materials, pharmaceutical and medical packaging materials, chemical packaging materials, cosmetic packaging materials, toiletry packaging materials, industrial packaging materials, agricultural material packaging materials, and the like. A polystyrene-based film-like material that can be suitably used for materials, containers such as box-shaped containers, lidded containers, cups, trays, plates, and lids, and packaging materials and containers using this polystyrene-based film-like material. Regarding.

At present, polystyrene-based film materials, for example, transparent biaxially oriented polystyrene-based resin sheets made of general-purpose polystyrene-based resin (GPPS), etc., are used as food packaging materials and lid materials. In addition, unstretched sheets and biaxially stretched sheets of impact-resistant polystyrene resins (HIPS) such as rubber-modified polystyrene resins are superior in oil resistance and impact resistance compared to the above-mentioned transparent sheets, so they can be used in fresh and dried foods. , box-type containers for storing food such as sweets, containers with lids, cups, trays, plates and other lidless containers, lids, etc. (hereinafter collectively referred to as “containers, etc.”) there is

In addition, many beverages such as tea, juice, and coffee are sold in containers such as PET bottles. A heat-shrinkable film printed on the Polystyrene-based resins are often used as the material for this heat-shrinkable film.

On the other hand, in recent years, in order to realize a sustainable environment and society, the use of plant-derived resins and biodegradable resins has been active even in these packaging materials and containers. Among them, polylactic acid-based resin is a plant-derived resin made from lactic acid obtained by fermentation of starch. From this point of view, it is receiving more and more attention.

However, if polylactic acid-based resin is used as the constituent resin for packaging materials and containers made from polystyrene-based film materials that have been used in the past, it is not possible to satisfy the characteristics (for example, heat resistance) of packaging materials and containers. There are many good points. Therefore, attempts have been made to add polylactic acid-based resins to polystyrene-based resins in order to replace some of the polystyrene-based resins with polylactic acid-based resins, but polystyrene-based resins and polylactic acid-based resins are incompatible. Therefore, a film-like material made of a mixed resin of polystyrene-based resin and polylactic acid-based resin causes unevenness due to poor dispersion, and the contents cannot be clearly seen in packaging materials and containers made of this film-like material. There is a problem.

Conventionally, studies have been made to add a compatibilizing agent in order to improve compatibility in a mixed resin composition containing mutually incompatible resins. For example, Patent Documents 1 to 3 disclose heat-shrinkable films having a layer obtained by adding an oxazoline group-containing resin as a compatibilizer to a mixed resin composition of a polystyrene-based resin and a polyester-based resin.

JP 2010-241055 A JP 2010-264657 A JP 2011-56736 A

The polyester-based resin in the mixed resin composition of polyester-based resin and polystyrene-based resin disclosed in Patent Documents 1 to 3 is only an aromatic polyester-based resin having a terephthalic acid component. Aromatic polyester resin has an average refractive index close to that of polystyrene resin (both have an average refractive index of around 1.58), so a mixed resin of polystyrene resin and aromatic polyester resin The composition is relatively easy to maintain transparency.

On the other hand, the average refractive index of polylactic acid-based resin (around 1.45) deviates greatly from the average refractive index of polystyrene-based resin. However, due to the difference in average refractive index between the two, the transparency of the obtained film-like material is remarkably lowered compared to the film-like material of the polystyrene resin alone.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a film-like material that suppresses uneven dispersion of polystyrene-based resin and polylactic acid-based resin and has high transparency. Another object of the present invention is to provide a packaging material and a container using the film-like material.

As a result of intensive studies, the inventors of the present invention succeeded in obtaining a film-like material capable of solving the above-described problems of the prior art, and completed the present invention.
The gist of the present invention is as follows.

[1] A polystyrene-based film material having at least one layer containing a mixed resin composition of a polystyrene-based resin (A), a polylactic acid-based resin (B), and an oxazoline group-containing resin (C) as a main component, , a polystyrene-based film material that satisfies the following a) and b).
a) The mixing ratio when the mixed resin composition is 100% by mass is polystyrene resin (A) / polylactic acid resin (B) / oxazoline group-containing resin (C) = 50% by mass to 98% by mass / 1% to 30% by mass/1% to 20% by mass
b) The content of 2-isopropenyl-2-oxazoline is 4% by mass or more based on 100% by mass of the oxazoline group-containing resin (C)

[2] The polystyrene film material according to [1], wherein the oxazoline group-containing resin (C) has a weight average molecular weight of 5,000 or more and 300,000 or less.

[3] The polystyrene according to [1] or [2], wherein the polystyrene resin (A) contains at least one copolymer of a styrene monomer (a) and the following monomer (b) system film-like material.
Monomer (b): at least one selected from butadiene, isoprene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene a monomer that is a diene-based hydrocarbon of the species, a partially hydrogenated monomer of said diene-based hydrocarbon, or a fully hydrogenated monomer of said diene-based hydrocarbon

[4] The polystyrene-based film material according to any one of [1] to [3], wherein the polystyrene-based resin (A) contains a styrene-butadiene-styrene copolymer (SBS).

[5] A packaging material using the polystyrene-based film material according to any one of [1] to [4].

[6] A container using the polystyrene-based film material according to any one of [1] to [4].

According to the polystyrene-based film-like material of the present invention, it is possible to obtain a film-like material having high transparency by uniformly dispersing the polystyrene-based resin and the polylactic acid-based resin to suppress uneven dispersion. Therefore, the polystyrene-based film material of the present invention can be used as food packaging materials, beverage packaging materials, pharmaceutical and medical packaging materials, chemical packaging materials, cosmetic packaging materials, toiletry packaging materials, and industrial packaging materials. , packaging materials for agricultural materials, etc., and containers such as box-shaped containers, containers with lids, cups, trays, plates and lids.

1 is a TEM observation photograph of a film-like material obtained in Example 2. FIG. 4 is a TEM observation photograph of a film-like material obtained in Comparative Example 4. FIG. 4 is a TEM observation photograph of a film-like material obtained in Comparative Example 6. FIG.

Hereinafter, the polystyrene-based film material, packaging material, and container of the present invention will be described as an example of embodiments of the present invention. However, the scope of the present invention is not limited to the embodiments described below.

In the present specification, the term "main component" refers to a component that accounts for 50% by mass or more when the total of the components constituting each layer is 100% by mass, and this percentage is preferably 60% by mass or more. , more preferably 70% by mass or more.
In addition, when described as “X to Y” (X and Y are arbitrary numbers), unless otherwise specified, “X or more and Y or less”, “preferably larger than X” and “preferably smaller than Y ” is included.
In addition, the upper limit and lower limit of the numerical range in this specification, even if slightly deviating from the numerical range specified by the present invention, as long as it has the same effect as within the numerical range, the present invention shall be included in the equivalent range of

[Polystyrene-based film material]
The polystyrene-based film-like material of the present invention (hereinafter sometimes referred to as "the film-like material of the present invention") includes a polystyrene-based resin (A), a polylactic acid-based resin (B), and an oxazoline group-containing resin (C ), which has at least one layer containing the mixed resin composition of ) as a main component, and which satisfies the following a) and b).
a) The mixing ratio when the mixed resin composition is 100% by mass is polystyrene resin (A) / polylactic acid resin (B) / oxazoline group-containing resin (C) = 50% by mass to 98% by mass / 1% to 30% by mass/1% to 20% by mass
b) The content of 2-isopropenyl-2-oxazoline is 4% by mass or more based on 100% by mass of the oxazoline group-containing resin (C)

Here, the term "film-like object" refers to planar objects such as thin films (thickness of about 0.1 μm to 200 μm), sheets (thickness of about 200 μm to 1000 μm), and thick plates (thickness of about 1 mm to 3 mm). It is a planar object having a large length direction (also referred to as MD) and width direction (also referred to as TD) with respect to the thickness described above. The film may be subjected to orientation imparting treatment such as stretching or rolling treatment, or surface treatment such as embossing or corona treatment. Moreover, it may have a tubular shape obtained by molding such as inflation molding. Furthermore, a film roll obtained by winding the film-like material around a core or the like is also included in the "film-like material" in the present invention.
Further, hereinafter, the content of structural units derived from monomers in the resin component is simply referred to as "monomer content". For example, the styrene content in the polystyrene resin (A) refers to the content of structural units derived from styrene in the polystyrene resin (A).

<Polystyrene resin (A)>
The polystyrene resin (A) in the present invention is a resin containing a styrene monomer (a) as a main monomer component, and usually the styrene monomer (a) is 50% by mass or more in the resin. It contains 100% by mass or less. This polystyrene-based resin (A) may be a homopolymer of the styrene-based monomer (a), and contains the styrene-based monomer (a) as a main monomer component and other monomers. It may be a copolymer.

When the polystyrene-based resin (A) is a copolymer, if the styrene-based monomer (a) is the main monomer component, a multi-component copolymer containing two or more of the above-described other monomer components May be combined. Further, the copolymer may be in any copolymer form such as a random copolymer, a block copolymer, or a graft copolymer.

Further, the polystyrene-based resin (A) may be a linear polystyrene-based resin or a multi-branched polystyrene-based resin.
In the film-like material of the present invention, the polystyrene resin (A) may be of one kind, or two or more kinds of different monomer component types, composition ratios, physical properties, etc. may be mixed and used. .

Examples of the styrene-based monomer (a) include styrene and derivatives thereof. For example, styrene, α-methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, diethylstyrene, triethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene, alkylstyrene such as octylstyrene, fluorostyrene, chlorostyrene, bromo Halogenated styrenes such as styrene, dibromostyrene and iodostyrene, nitrostyrene, acetylstyrene, methoxystyrene and the like can be mentioned.
Among them, styrene and α-methylstyrene are preferred, and styrene is particularly preferred, from the viewpoint of heat resistance and workability.

Examples of other monomers used in the copolymer include (meth) acrylic acid, (meth) acrylic acid ester, maleic anhydride, vinyl acetate, acrylonitrile, butadiene, isoprene, 2-methyl- Diene hydrocarbons such as 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, ethylene, propylene, 1-butene, 1-hexene, 4 α-olefins such as -methyl-1-pentene and 1-octene.

When the film-like material of the present invention is used as a container, from the viewpoint of rigidity and workability, the styrene-based monomer (a) in the polystyrene-based resin (A) is preferably styrene, and styrene is contained in the resin. It is preferably a homopolymer (general-purpose polystyrene, GPPS) containing 100% by mass. In addition, when used for applications requiring higher heat resistance than GPPS, the polystyrene-based resin (A) preferably has styrene as the styrene-based monomer (a), and is used for the styrene-based resin (A). The monomer preferably contains at least one monomer selected from α-methylstyrene, (meth)acrylic acid, (meth)acrylic acid ester, maleic anhydride, and acrylonitrile, α-methylstyrene, It is more preferable to contain at least one monomer selected from (meth)acrylic acid and (meth)acrylic acid ester, and it is particularly preferable to contain (meth)acrylic acid.

(Meth)acrylates as other monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, (meth) ) t-butyl acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, stearyl (meth)acrylate, (meth)acrylic octadecyl acid, phenyl (meth)acrylate, benzyl (meth)acrylate, chloromethyl (meth)acrylate, 2-chloroethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, (meth)acrylic acid 3 -hydroxypropyl, 2,3,4,5-tetrahydroxypentyl (meth)acrylate, aminoethyl (meth)acrylate, propylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, (meth)acrylate ethylaminopropyl acrylate, phenylaminoethyl (meth)acrylate, cyclohexylaminoethyl (meth)acrylate, glycidyl (meth)acrylate and the like.
Among them, it is preferable to use methyl (meth)acrylate as another monomer used in the copolymer from the viewpoint of suppressing the dehydration reaction of the copolymer, improving the mechanical strength, light resistance, surface hardness, and the like.

When the film-like material of the present invention is used as a container, an impact-resistant polystyrene-based resin can also be suitably used as the polystyrene-based resin (A) from the viewpoint of rigidity and impact resistance. As the impact-resistant polystyrene resin, a rubber component described below is graft-polymerized with a styrene monomer described below (hereinafter sometimes referred to as "graft-type HIPS"). can be used. Graft-type HIPS can be formed, for example, by dissolving a rubber component in a styrene-based monomer and then graft-polymerizing the styrene-based monomer to the rubber component. It is preferable to form a salami structure dispersed in the Within the salami structure, the rubber component is bound to a portion of the polystyrene outside the salami.

Further, as the impact-resistant polystyrene-based resin, polystyrene obtained by polymerizing styrene-based monomers described below and a rubber component described below are kneaded (hereinafter referred to as "blend type HIPS”) can also be used. Polystyrene in this case can be obtained by bulk polymerization or suspension polymerization of styrenic monomers. As a kneading method, heat kneading using a general-purpose kneader such as a single-screw extruder or a multi-screw extruder or a Banbury mixer can be employed.

The graft-type HIPS can be obtained by polymerizing at least a styrenic monomer in the presence of a rubber component. Examples of rubber components include polybutadiene, polyisoprene, chloroprene rubber, styrene-isoprene copolymers, styrene-isoprene-butadiene copolymers, random or block polymers of butadiene and other copolymerizable monomers, and the like. can. Monomers copolymerizable with butadiene include vinyl aromatic compounds such as styrene and α-methylstyrene, unsaturated carboxylic acids such as acrylic acid and methacrylic acid and their esters, vinyl compounds such as acrylonitrile and methacrylonitrile. Cyanide compounds may be mentioned.

These rubber components may be used alone or in combination of two or more. Of the rubber components, diene rubbers are preferred, and polybutadiene, polyisoprene, and random or block styrene-butadiene copolymers are particularly preferred. The styrene content in this styrene-butadiene copolymer is preferably 10% by mass to 50% by mass, more preferably 10% by mass to 30% by mass. High-cis polybutadiene having a cis-1,4 structure of 90 mol % or more is particularly preferable as the rubber component, from the viewpoints of thermal stability and recyclability when used as an impact-resistant polystyrene resin.

Styrenic monomers to be graft-polymerized include styrene, alkylstyrene such as o-, m-, p-methylstyrene, p-ethylstyrene and pt-butylstyrene, α-methylstyrene, Examples include vinyl aromatic compounds such as α-alkylstyrenes such as α-ethylstyrene. These styrenic monomers can be used alone or in combination of two or more. Among them, styrene is preferred.

The diene content in the rubber component contained in the impact-resistant polystyrene resin in the present invention is preferably 2.0% by mass to 12.0% by mass. Further, the diene content in the rubber component is more preferably 3.0% by mass to 12.0% by mass, even more preferably 4.0% by mass to 12.0% by mass.

When the diene content in the rubber component is 2.0% by mass or more, the high-speed moldability during thermoforming is improved, and the impact resistance and tear strength of the impact-resistant polystyrene resin are easily improved, which is preferable. . Further, when the diene content in the rubber component is 12.0% by mass or less, it is preferable because the rigidity of the impact-resistant polystyrene resin can be easily maintained.

The diene content in the rubber component can be measured by potentiometric titration using iodine monochloride, potassium iodide and sodium thiosulfate standard solutions. Analysis methods are described, for example, in "New Edition Polymer Analysis Handbook" edited by the Japan Society for Analytical Chemistry Polymer Analysis Research Roundtable, Kinokuniya Shoten (1995 edition), p. 659, "(3) Rubber content", and can be measured by this method.

The average particle size of the rubber component contained in the impact-resistant polystyrene resin is not limited, but is preferably 0.5 μm to 10.0 μm. By setting the average particle size within the above range, the impact resistance and tear strength of the impact-resistant polystyrene-based resin are likely to be improved, which is preferable. The average particle size of the rubber component contained in the impact-resistant polystyrene resin is more preferably 1.0 μm to 8.0 μm, further preferably 2.0 μm to 6.0 μm.

The average particle size of the rubber component is obtained by taking a 10,000-fold enlarged photograph using a transmission electron microscope by the ultra-thin section method, measuring the particle size of about 1,000 particles of the rubber component taken, and calculating the following formula: , rubber average particle size [μm]=(ΣniDi ⁴ )/(ΣniDi ³ ). In this formula, ni indicates the number of rubber particles having a particle diameter of Di. Further, since the particles of the rubber component are not perfectly circular, the particle size can be calculated by measuring the major axis and the minor axis and arithmetically averaging them.

When the film-like material of the present invention is used as a packaging material, the styrene-based monomer (a) in the polystyrene-based resin (A) is preferably styrene from the viewpoint of imparting appropriate rigidity and flexibility. . Other monomers used in the styrene-based resin (A) include the following monomers (b).
Monomer (b): at least one selected from butadiene, isoprene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene a monomer that is a diene-based hydrocarbon of the species, a partially hydrogenated monomer of said diene-based hydrocarbon, or a fully hydrogenated monomer of said diene-based hydrocarbon

Among the monomers (b) described above, butadiene and isoprene are particularly preferred for imparting heat-shrinkability to the packaging material.

When the film-like material of the present invention is used as a packaging material, the polystyrene resin (A) preferably used includes styrene-butadiene-styrene copolymer (SBS). From the viewpoint of achieving both the rigidity and flexibility of the film-like material required for packaging materials, the SBS preferably has a styrene/butadiene mass% ratio of about (95 to 60)/(5 to 40), and (93 ~60)/(7 to 40) is more preferable, and about (90 to 60)/(10 to 40) is even more preferable.

Furthermore, from the viewpoint of the melt fluidity during molding and the dimensional accuracy of the film-like material, the measured value of the melt flow rate (MFR) of SBS (measurement conditions: temperature 200 ° C., load 49 N) is preferably 2 g / 10 minutes or more. is 3 g/10 min or more and 15 g/10 min or less, preferably 10 g/10 min or less, more preferably 8 g/10 min or less.

Further, when the film-like material of the present invention is used as a packaging material, the polystyrene resin (A) may be a styrene-isoprene-butadiene-styrene copolymer (SIBS), a styrene-isoprene-butadiene block copolymer ( SIBS) is also preferably used.

In SIBS, the mass% ratio of styrene/isoprene/butadiene is preferably (60-90)/(5-40)/(5-30), (60-85)/(10-30)/( 5 to 25), more preferably (60 to 80)/(10 to 25)/(5 to 20).
If the butadiene content is higher and the isoprene content is lower than the above range, butadiene heated in the extruder or the like causes a cross-linking reaction, which may increase the amount of gel. On the other hand, if the butadiene content is less than the above range and the isoprene content is greater than the above range, the cross-linking reaction of butadiene may be suppressed, and the gel-like substance may be suppressed.

Furthermore, the melt flow rate (MFR) measurement value of SIBS (measurement conditions: temperature 200 ° C., load 49 N) is 2 g / 10 minutes or more, preferably 3 g / 10 minutes or more, and 15 g / 10 minutes or less, preferably It is desirable to be 10 g/10 minutes or less, more preferably 8 g/10 minutes or less.

The polystyrene resin (A) has a weight average molecular weight (Mw) of 100,000 or more, preferably 150,000 or more, and 1,000,000 or less, preferably 800,000 or less, more preferably 600,000 or less is desirable. If the weight average molecular weight (Mw) of the polystyrene resin (A) is 100,000 or more, it is preferable because there is no defect such as deterioration of the film. Further, if the polystyrene resin (A) has a molecular weight of 1,000,000 or less, it is preferable because there is no need to adjust the flow characteristics and there is no drawback such as deterioration of extrudability. The weight average molecular weight of the polystyrene resin (A) can be measured by gel permeation chromatography (hereinafter referred to as "GPC").

<Polylactic acid resin (B)>
The polylactic acid resin (B) used in the present invention is a resin containing D-lactic acid or/and L-lactic acid as a main monomer component, and D-lactic acid or/and L-lactic acid is contained in the resin at 50%. % or more and 100% or less by mass. When 100% by mass of D-lactic acid and L-lactic acid are contained in the resin, poly(D-lactic acid) whose structural unit is D-lactic acid, poly(L-lactic acid) whose structural unit is L-lactic acid, and further There is poly(DL-lactic acid) which is a copolymer of L-lactic acid and D-lactic acid. A plurality of polylactic acid resins having different copolymerization ratios of D-lactic acid and L-lactic acid can also be used.

The above copolymer of L-lactic acid and D-lactic acid has a copolymer mass% ratio of D-lactic acid and L-lactic acid (D-lactic acid/L-lactic acid, hereinafter abbreviated as "D/L ratio"). is preferably (0.1 to 15)/(99.9 to 85) or (99.9 to 85)/(0.1 to 15).
When the copolymer mass% ratio of D-lactic acid is higher than 99.9 or less than 0.1, it has a high melting point and crystallinity, so the molding temperature for melt mixing with the polystyrene resin (A) It is not preferable because it becomes necessary to raise the temperature and supercooling is necessary to suppress the crystallization of the film-like material. On the other hand, when the copolymerization mass% ratio of D-lactic acid is less than 85 or higher than 15, the crystallinity is almost completely lost. This is not preferable because the viscosity of the system resin (B) may excessively decrease or the decomposition may be accelerated.

The polylactic acid-based resin (B) is a resin containing D-lactic acid and/or L-lactic acid as a main monomer component, and D-lactic acid and/or L-lactic acid is contained in the resin in an amount of 50% by mass or more. A copolymer containing other monomers may be used as long as it contains 100% by mass or less. Other monomer components include α-hydroxycarboxylic acids other than lactic acid, non-aliphatic dicarboxylic acids such as terephthalic acid, aliphatic dicarboxylic acids such as succinic acid, non-aliphatic diols such as ethylene oxide adducts of bisphenol A, and at least one selected from the group consisting of aliphatic diols such as ethylene glycol. A small amount of a chain extender such as a diisocyanate compound, an epoxy compound, an acid anhydride, etc. may also be used for the purpose of increasing the molecular weight.

Examples of α-hydroxycarboxylic acids other than lactic acid include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, and 2-hydroxy-3-methyl Examples include bifunctional aliphatic hydroxycarboxylic acids such as butyric acid, 2-methyllactic acid and 2-hydroxycaproic acid, and lactones such as caprolactone, butyrolactone and valerolactone.

Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid. Examples of the aliphatic diol include ethylene glycol, 1,4-butanediol, 1 , 4-cyclohexanedimethanol and the like.

The copolymerization mass% ratio [lactic acid/(α-hydroxycarboxylic acid, diol, or dicarboxylic acid other than lactic acid)] of a copolymer of lactic acid and an α-hydroxycarboxylic acid other than lactic acid, a diol, or a dicarboxylic acid is (100 to 50) / (0 to 50) is preferred, (100 to 60) / (0 to 40) is more preferred, (100 to 70) / (0 to 30) More preferred. If the copolymer mass % ratio is within the above range, a film-like material having a good balance of physical properties such as rigidity, transparency and impact resistance can be obtained. Structures of these copolymers include random copolymers, block copolymers, and graft copolymers, and any structure may be used.

The weight average molecular weight (Mw) of the polylactic acid resin (B) is preferably 20,000 or more, more preferably 40,000 or more, and even more preferably 60,000 or more. Also, it is preferably 800,000 or less, more preferably 600,000 or less, and even more preferably 400,000 or less. When the weight-average molecular weight is 20,000 or more, an appropriate resin cohesive force can be obtained, and insufficient strength and brittleness of the film-like material can be suppressed. On the other hand, if the weight average molecular weight is 800,000 or less, the melt viscosity can be lowered, which is preferable from the viewpoint of production and productivity improvement. Here, the weight-average molecular weight of the polylactic acid-based resin (B) is the result of measurement by GPC after dissolving in chloroform, and shown in terms of polystyrene (PS).

As a method for polymerizing the polylactic acid-based resin (B), known methods such as condensation polymerization and ring-opening polymerization can be employed. For example, in the condensation polymerization method, D-lactic acid, L-lactic acid, or a mixture thereof can be directly subjected to dehydration condensation polymerization to obtain a polylactic acid resin having an arbitrary composition. Further, in the ring-opening polymerization method, lactide, which is a cyclic dimer of lactic acid, is subjected to ring-opening polymerization in the presence of a predetermined catalyst, using a polymerization modifier as necessary, to form a poly having an arbitrary composition. A lactic acid-based resin can be obtained. The lactide includes DL-lactide, which is a dimer of L-lactic acid, and by mixing and polymerizing these as necessary, a polylactic acid resin having any composition and crystallinity can be obtained. can.

<Oxazoline group-containing resin (C)>
The oxazoline group-containing resin (C) used in the film material of the present invention is a resin having a 2-isopropenyl-2-oxazoline monomer component in its structure.

Since the 2-isopropenyl-2-oxazoline monomer component has an oxazoline group in the side chain, it exhibits high reactivity with the polylactic acid resin (B), and since the reaction mechanism is an addition reaction, it can be used with water or water. Since reaction by-products such as carbon dioxide are not generated, it is difficult to cause air bubbles and acceleration of resin decomposition in the film-like material.
Therefore, by further including the oxazoline group-containing resin (C) in the mixed resin composition containing the polystyrene resin (A) and the polylactic acid resin (B), the oxazoline group-containing resin (C) becomes the polystyrene resin ( It works as a compatibilizer that uniformly disperses the domains of the polylactic acid resin (B) in the matrix of A), making it possible to suppress poor dispersion of the film-like material.

In order to obtain the above effect of the 2-isopropenyl-2-oxazoline monomer component, the 2-isopropenyl-2-oxazoline monomer component contained in 100% by mass of the oxazoline group-containing resin (C) used in the present invention It is most important in the present invention that the content (2-isopropenyl-2-oxazoline content) is 4% by mass or more. The content of 2-isopropenyl-2-oxazoline contained in 100% by mass of the oxazoline group-containing resin (C) is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 10% by mass or more. There is no upper limit to the content of 2-isopropenyl-2-oxazoline, and although it may be 100% by mass, it is preferably 80% by mass or less, more preferably 60% by mass or less, from the viewpoint of thermal stability during molding. .

As described above, the oxazoline group-containing resin (C) functions as a compatibilizer that uniformly disperses the domains of the polylactic acid-based resin (B) in the matrix of the polystyrene-based resin (A). By uniformly dispersing the domains of the polylactic acid-based resin (B), it is possible to suppress uneven dispersion of the film-like material and to make it possible to clearly show the contents in packaging materials and containers made of the film-like material. However, on the other hand, the average refractive index of the polystyrene resin (A) is around 1.58, while the average refractive index of the polylactic acid resin (B) is around 1.45, so the polystyrene resin Even if the polylactic acid-based resin (B) is uniformly dispersed in (A), the transparency of the obtained film-like material is lowered because the average refractive indices of the two differ greatly.

Since the average refractive index of polystyrene resin (A) and polylactic acid resin (B) is due to the monomer skeleton of each resin, polylactic acid resin ( It is important to disperse the domain size of B) below the wavelength order of visible light. From the viewpoint of reducing the domain size, it is most important in the present invention that the content of 2-isopropenyl-2-oxazoline contained in 100% by mass of the oxazoline group-containing resin (C) is 4% by mass or more. Become. When the 2-isopropenyl-2-oxazoline content is 4% by mass or more, the domain size of the polylactic acid-based resin (B) can be reduced, and the transparency of the film material can be improved.

Moreover, the weight average molecular weight (Mw) of the oxazoline group-containing resin (C) is preferably 5,000 or more, more preferably 10,000 or more, and even more preferably 15,000 or more. Also, it is preferably 300,000 or less, more preferably 200,000 or less, and even more preferably 150,000 or less. If the weight-average molecular weight is 5,000 or more, the reduction in strength of the film can be suppressed. On the other hand, if the weight-average molecular weight is 300,000 or less, in functioning as a compatibilizer, it is possible to increase the mobility of polymer chains during melt-mixing and promote the reaction with the polylactic acid-based resin (B). It is preferable because it can Here, the weight-average molecular weight of the oxazoline group-containing resin (C) is a value obtained by dissolving in chloroform and measuring the result by GPC in terms of polystyrene (PS).

In the oxazoline group-containing resin (C) used in the present invention, the monomers other than the 2-isopropenyl-2-oxazoline monomer component constituting the resin are not particularly limited, but polystyrene resins ( From the viewpoint of compatibility with A), it is preferable to use the styrenic monomer (a) described above, and it is particularly preferable to use styrene.

In the film-like material of the present invention, the oxazoline group-containing resin (C) may be of one type, or two or more types having different monomer component types, composition ratios, physical properties, etc. may be used in combination. good.

<Content ratio of each resin>
In the film-like material of the present invention, the mixing ratio of the mixed resin composition of the polystyrene resin (A), the polylactic acid resin (B), and the oxazoline group-containing resin (C) is polystyrene resin (A)/polylactic acid Resin (B) / oxazoline group-containing resin (C) = 50% by mass to 98% by mass / 1% by mass to 30% by mass / 1% by mass to 20% by mass (however, polystyrene resin (A) and polylactic acid resin The total of (B) and the oxazoline group-containing resin (C) is assumed to be 100% by mass.).
This mixing ratio is polystyrene resin (A) / polylactic acid resin (B) / oxazoline group-containing resin (C) = 60% by mass to 98% by mass / 1% by mass to 25% by mass / 1% by mass to 15% by mass %, polystyrene resin (A) / polylactic acid resin (B) / oxazoline group-containing resin (C) = 75% by mass to 98% by mass / 1% by mass to 20% by mass / 1% by mass More preferably 15% by mass, polystyrene resin (A)/polylactic acid resin (B)/oxazoline group-containing resin (C) = 80% by mass to 98% by mass/1% by mass to 15% by mass/1 More preferably, it is in the range of 15% by mass to 15% by mass.

When the film-like material of the present invention is used for packaging materials or containers, in order to maintain basic physical properties such as rigidity, heat resistance, and flexibility required for each application, 100% by mass of the mixed resin composition On the other hand, it is important that the polystyrene resin (A) is 50% by mass to 98% by mass.

On the other hand, in order to use the polylactic acid-based resin (B), which is a plant-derived resin and a biodegradable resin, and improve the biomass degree of the film-like material, the mixed resin composition must include the polylactic acid-based resin (B) However, if the polylactic acid-based resin (B) exceeds 30% by mass with respect to 100% by mass of the mixed resin composition, it becomes difficult to suppress poor dispersion. Therefore, it is important that the polylactic acid-based resin (B) accounts for 1% by mass to 30% by mass with respect to 100% by mass of the mixed resin composition.

Furthermore, when the oxazoline group-containing resin (C) is less than 1% by mass with respect to 100% by mass of the mixed resin composition, poor dispersion of the polylactic acid-based resin (B) occurs, and uneven dispersion occurs in the film-like material. do. On the other hand, when the oxazoline group-containing resin (C) exceeds 20% by mass with respect to 100% by mass of the mixed resin composition, the mechanical strength of the film-like product decreases, and the film-like product when used as a packaging material is easily torn. It is not preferable because it tends to cause problems such as the film-like material being easily cracked when used as a container. Therefore, it is important that the oxazoline group-containing resin (C) is 1% by mass to 20% by mass with respect to 100% by mass of the mixed resin composition.

By adjusting the content ratio of the polystyrene resin (A), the polylactic acid resin (B), and the oxazoline group-containing resin (C) to the above range, the matrix of the polystyrene resin (A) has improved biomass content. After uniformly dispersing the domains of the polylactic acid resin (B) for the film, it has excellent basic physical properties such as mechanical strength, rigidity, heat resistance, and flexibility, and is also excellent in transparency. can be a thing.

<Other ingredients>
The film-like material of the present invention has at least one layer composed mainly of a mixed resin composition of a polystyrene-based resin (A), a polylactic acid-based resin (B), and an oxazoline-containing resin (C). is. In the layer containing the mixed resin composition as the main component, it is allowed to contain other resins and thermoplastic elastomers other than the mixed resin composition as the main component within a range that does not impair the effects of the present invention. can be done.

Other resins include polyolefin-based resins, polyvinyl chloride-based resins, polyvinylidene chloride-based resins, chlorinated polyethylene-based resins, polyester-based resins other than polylactic acid-based resins (B), polycarbonate-based resins, polyamide-based resins, fluorine polymethylpentene resin, polyvinyl alcohol resin, cyclic olefin resin, polybutylene succinate resin, polyacrylonitrile resin, polyether resin, cellulose resin, polyimide resin, polyurethane resin, polyphenylene sulfide resin, polyphenylene ether resin, polyvinyl acetal resin, polybutadiene resin, polybutene resin, polyamideimide resin, polyamide bismaleimide resin, polyarylate resin, polyetherimide resin, polyetheretherketone resin, Examples include polyetherketone-based resins, polyethersulfone-based resins, polyketone-based resins, polyacetal-based resins, polysulfone-based resins, aramid-based resins, and the like.

Examples of thermoplastic elastomers include styrene-based thermoplastic elastomers, amide-based thermoplastic elastomers, ester-based thermoplastic elastomers, olefin-based thermoplastic elastomers, urethane-based thermoplastic elastomers, dynamic vulcanization-based thermoplastic elastomers, chloride Vinyl thermoplastic elastomers, acrylic thermoplastic elastomers, lactic acid thermoplastic elastomers, fluorothermoplastic elastomers, silicone thermoplastic elastomers, ionomers, and their blends, alloys, modified products, dynamically crosslinked products, blocks Examples include copolymers, graft copolymers, random copolymers, core-shell type multi-layer structure rubbers, and the like.

In addition to the components described above, the layer containing the mixed resin composition as a main component may contain additives that are generally blended in resin compositions, as appropriate, within a range that does not significantly impair the effects of the present invention. can. Examples of the additives include recycled resin generated from trimming loss such as selvage, silica, talc, kaolin, and calcium carbonate, which are added for the purpose of improving and adjusting molding processability, productivity, and various physical properties of laminated films. Inorganic particles such as titanium oxide, pigments such as carbon black, flame retardants, weather stabilizers, heat stabilizers, antistatic agents, melt viscosity improvers, cross-linking agents, lubricants, nucleating agents, plasticizers, anti-aging agents, Additives such as antioxidants, light stabilizers, ultraviolet absorbers, neutralizers, anti-fogging agents, anti-blocking agents, slip agents, and colorants are included.

<Layer structure>
The film material of the present invention is a layer (hereinafter referred to as (I) layer) mainly composed of a mixed resin composition of a polystyrene resin (A), a polylactic acid resin (B), and an oxazoline group-containing resin (C). ) at least one layer.

The film-like material of the present invention may be a single layer (I), a two-kind two-layer structure of (I) layer/(II) layer, or (I) layer/(II) layer/(I) Layer, (II) layer / (I) layer / (II) layer two kinds of three-layer structure, (I) layer / (II) layer / (III) layer, (II) layer / (I) layer / (III) ) layer, and (II) layer / (III) layer / (I) layer / (III) layer / (II) layer, (I) layer / (III) layer / (II) layer / (III) layer / (I) layer, (II) layer / (I) layer / (III) layer / (I) layer / (II) layer, such as a three-kind five-layer configuration can be adopted. , The number of layers, the above (II) layer, (III) layer in the case of a multilayer structure, and further the other layers ((IV) layer, (V) layer, (VI) layer, etc.) are not limited. .

When the film-like material of the present invention has a multi-layer structure, each layer may be formed into a laminated film by co-extrusion, or films obtained in separate processes may be laminated by pressing, lamination, or the like. In addition, non-woven fabric, paper, metal, etc. may be laminated as the other layers described above.

<Thickness>
In the film material of the present invention, the thickness of the layer (I), which is mainly composed of a mixed resin composition of a polystyrene resin (A), a polylactic acid resin (B), and an oxazoline group-containing resin (C), is Depending on whether the film-like material of the present invention is a monolayer film or a laminated film, and also depending on the application of the film-like material of the present invention, the thickness is usually 0.1 μm or more and 3000 μm or less, preferably 1 μm or more and 1000 μm or less. , more preferably 10 μm or more and 500 μm or less.

<Manufacturing method of film-like material>
The film-like material of the present invention can be produced by appropriately changing the conditions in a conventionally known production method, and the production method is not particularly limited. In addition, the film-like material of the present invention may be either planar or tubular. A planar configuration is preferred.

As a method for producing a planar film, for example, the resin or resin composition used in the extruded layer is melted using an extruder, extruded or coextruded from a T die, cooled and solidified with a chilled roll to form a film. A method of obtaining an object can be exemplified. In addition, the obtained film-like material is roll-stretched in the longitudinal direction and tenter-stretched in the transverse direction, and then uniaxially or biaxially stretched by annealing, cooling, and, if necessary, corona discharge treatment, etc. A method for manufacturing a film-like material that has been coated can be exemplified.

A method of cutting open a film produced by an inflation method or a tubular method to produce a film-like product can also be applied.

In addition, since the film-like material of the present invention may have a laminated structure, the resins constituting each layer are made into films separately, and then laminated using a press method, a roll nip method, or the like to be sequentially produced. can also

The film-like material is cooled by cooling rolls, air, water, etc., and then reheated by a suitable method such as hot air, hot water, infrared rays, etc., and is subjected to roll stretching, tenter stretching, tubular stretching, and long-distance stretching. It is preferable that the film is uniaxially or biaxially stretched simultaneously or sequentially by, for example. In biaxial stretching, MD and TD stretching may be carried out at the same time, but sequential biaxial stretching in which either one is carried out first is effective, and either MD or TD may be carried out first. The stretching temperature needs to be changed depending on the softening temperature of the resin constituting the film-like material and the application required for the film-like material. It is controlled within the range of 120°C or less. The draw ratio in the main shrinkage direction (preferably TD) is 2 times or more, preferably 3 times or more, more preferably 4 times or more, depending on the film constituents, drawing means, drawing temperature, and desired product form, It is appropriately determined within the range of 7 times or less, preferably 6 times or less. Further, whether to use uniaxial stretching or biaxial stretching is determined depending on the intended use of the product.

<Transparency>
The transparency of the film-like material of the present invention is evaluated by the haze value measured according to JIS K7105, and the haze value is preferably 50% or less, more preferably 40% or less, and 30% or less. is more preferable, and 15% or less is most preferable. If the haze value is 50% or less, the visibility of the contents when the film material is used as a packaging material or container is excellent.

[Packaging materials]
The film-like material of the present invention can be used as food packaging materials, beverage packaging materials, pharmaceutical and medical packaging materials, chemical packaging materials, cosmetic packaging materials, toiletry packaging materials, industrial packaging materials, and agricultural material packaging materials. It can be suitably used for packaging materials such as materials, and containers such as box-shaped containers, containers with lids, cups, trays, plates and lids.

The contents of the present invention will be described in more detail below with reference to examples, but the present invention is not limited by these examples.
Various measurements and evaluations of the film-like materials shown in this specification were carried out as follows.

(1) Confirmation of Visibility (Unevenness of Dispersion) Visibility was judged by the following judgment criteria when the scenery was visually confirmed through the film-like materials collected in Examples and Comparative Examples.
◯: No dispersion unevenness was observed in the film-like material, and the outline of the landscape was clearly visible.
Δ: Uneven dispersion is observed in the film-like material, and the outline of the landscape looks slightly blurred.
x: A large amount of dispersion unevenness is observed in the film-like material, and the outline of the landscape appears blurred.

(2) Haze value measurement The haze values of the film-like materials obtained in Examples and Comparative Examples were measured according to JIS K7136.

(3) Confirmation of dispersibility by transmission electron microscope (TEM) A cross-section of the film-like material obtained in Example 2, Comparative Examples 4 and 6 in the thickness direction was cut, and polylactic acid was examined by a transmission electron microscope (TEM). Dispersibility of the system resin (B) was confirmed.

The raw materials used in each example and comparative example are as follows.

<Polystyrene resin (A)>
・Styrene-butadiene-styrene copolymer (hereinafter abbreviated as "A-1")
Styrene content: 83% by mass
Butadiene content: 17% by mass
Melt flow rate (MFR): 5.5 g/10 minutes (measurement conditions: temperature 200° C., load 49 N)
Weight average molecular weight (Mw): 248,000

<Polylactic acid resin (B)>
・ Poly (DL-lactic acid) (hereinafter abbreviated as “B-1”)
Product name: Ingeo4060D (manufactured by NatureWorks)
D/L ratio: 12% by mass/88% by mass
Weight average molecular weight (Mw): 220,000

<Oxazoline group-containing resin (C)>
・Styrene/2-isopropenyl-2-oxazoline copolymer (hereinafter abbreviated as “C-1”)
2-isopropenyl-2-oxazoline content: 6% by mass
Weight average molecular weight (Mw): 40,000
・Styrene/2-isopropenyl-2-oxazoline copolymer (hereinafter abbreviated as “C-2”)
2-isopropenyl-2-oxazoline content: 30% by mass
Weight average molecular weight (Mw): 20,000
・Styrene/2-isopropenyl-2-oxazoline copolymer (hereinafter abbreviated as “C-3”)
2-isopropenyl-2-oxazoline content: 3% by mass
Weight average molecular weight (Mw): 30,000
・Styrene/2-isopropenyl-2-oxazoline copolymer (hereinafter abbreviated as “C-4”)
2-isopropenyl-2-oxazoline content: 3% by mass
Weight average molecular weight (Mw): 70,000
・Styrene/2-isopropenyl-2-oxazoline copolymer (hereinafter abbreviated as “C-5”)
2-isopropenyl-2-oxazoline content: 3% by mass
Weight average molecular weight (Mw): 110,000
・Styrene/2-isopropenyl-2-oxazoline copolymer (hereinafter abbreviated as “C-6”)
Product name: Epocross RPS-1005 (manufactured by Nippon Shokubai Co., Ltd.)
2-isopropenyl-2-oxazoline content: 3% by mass
Weight average molecular weight (Mw): 160,000

<Resin having a reactive group other than an oxazoline group (maleic anhydride group-containing resin)>
・Maleic anhydride-modified styrene-ethylene-butylene-styrene copolymer (hereinafter referred to as “D-1”)
Product name: Dynaron 8660P (manufactured by JSR)
Styrene content: 25% by mass

<Example 1>
As shown in Table 1, 90% by mass of polystyrene-based resin "A-1", 5% by mass of polylactic acid-based resin "B-1", and 5% by mass of oxazoline group-containing resin "C-1" were set at a temperature of 200. The resin was introduced into a twin-screw extruder at a temperature of ° C. and melt-kneaded, and the molten resin was taken out from a T-die (mouthpiece) with a cast roll and cooled and solidified to obtain a film-like material having a thickness of 50 μm. Table 1 summarizes the visibility evaluation results and haze measurement results of the obtained film-like material.

<Example 2>
As shown in Table 1, 90% by mass of polystyrene resin "A-1", 5% by mass of polylactic acid resin "B-1", 5% by mass of oxazoline group-containing resin "C-2", and a set temperature of 200 The resin was introduced into a twin-screw extruder at a temperature of ° C. and melt-kneaded, and the molten resin was taken out from a T-die (mouthpiece) with a cast roll and cooled and solidified to obtain a film-like material having a thickness of 50 μm. Table 1 summarizes the visibility evaluation results and haze measurement results of the obtained film-like material. Further, FIG. 1 shows a TEM observation photograph of the obtained film-like material.

<Comparative Example 1>
As shown in Table 1, 90% by mass of polystyrene resin "A-1", 5% by mass of polylactic acid resin "B-1", 5% by mass of oxazoline group-containing resin "C-3", and a set temperature of 200 The resin was introduced into a twin-screw extruder at a temperature of ° C. and melt-kneaded, and the molten resin was taken out from a T-die (mouthpiece) with a cast roll and cooled and solidified to obtain a film-like material having a thickness of 50 μm. Table 1 summarizes the visibility evaluation results and haze measurement results of the obtained film-like material.

<Comparative Example 2>
As shown in Table 1, 90% by mass of polystyrene resin "A-1", 5% by mass of polylactic acid resin "B-1", and 5% by mass of oxazoline group-containing resin "C-4" were set at a temperature of 200. The resin was introduced into a twin-screw extruder at a temperature of ° C. and melt-kneaded, and the molten resin was taken out from a T-die (mouthpiece) with a cast roll and cooled and solidified to obtain a film-like material having a thickness of 50 μm. Table 1 summarizes the visibility evaluation results and haze measurement results of the obtained film-like material.

<Comparative Example 3>
As shown in Table 1, 90% by mass of polystyrene resin "A-1", 5% by mass of polylactic acid resin "B-1", and 5% by mass of oxazoline group-containing resin "C-5" were set at a temperature of 200. The resin was introduced into a twin-screw extruder at a temperature of ° C. and melt-kneaded, and the molten resin was taken out from a T-die (mouthpiece) with a cast roll and cooled and solidified to obtain a film-like material having a thickness of 50 μm. Table 1 summarizes the visibility evaluation results and haze measurement results of the obtained film-like material.

<Comparative Example 4>
As shown in Table 1, 90% by mass of polystyrene resin "A-1", 5% by mass of polylactic acid resin "B-1", and 5% by mass of oxazoline group-containing resin "C-6" were set at a temperature of 200. The resin was introduced into a twin-screw extruder at a temperature of ° C. and melt-kneaded, and the molten resin was taken out from a T-die (mouthpiece) with a cast roll and cooled and solidified to obtain a film-like material having a thickness of 50 μm. Table 1 summarizes the visibility evaluation results and haze measurement results of the obtained film-like material. Further, FIG. 2 shows a TEM observation photograph of the obtained film-like material.

<Comparative Example 5>
As shown in Table 1, 90% by mass of polystyrene resin "A-1", 5% by mass of polylactic acid resin "B-1", maleic anhydride group-containing resin "D-1" having a reactive group that is not an oxazoline group ”5% by mass is introduced into a twin-screw extruder with a set temperature of 200 ° C., melt-kneaded, the molten resin is drawn from the T die (mouthpiece) with a cast roll, cooled and solidified to form a film with a thickness of 50 μm. got stuff Table 1 summarizes the visibility evaluation results and haze measurement results of the obtained film-like material.

<Comparative Example 6>
As shown in Table 1, 95% by mass of polystyrene resin "A-1" and 5% by mass of polylactic acid resin "B-1" were introduced into a twin-screw extruder with a set temperature of 200 ° C. and melt-kneaded. Then, the molten resin was taken out from the T-die (mouthpiece) with a cast roll and cooled and solidified to obtain a film-like material having a thickness of 50 μm. Table 1 summarizes the visibility evaluation results and haze measurement results of the obtained film-like material. A TEM observation photograph of the obtained film-like material is shown in FIG.

It can be seen from Table 1 that the films of the present invention obtained in Examples 1 and 2 have higher transparency than the films of Comparative Examples 1-6. Further, in the film-like material of the present invention obtained in Example 2, it can be seen from the TEM observation photograph of FIG. 1 that the polylactic acid-based resin (B) is uniformly dispersed in nano-order. From this, it can be seen that the content of 2-isopropenyl-2-oxazoline contained in the oxazoline-containing resin (C) defined by the present invention is 4% by mass or more, thereby suppressing uneven dispersion of the obtained film-like material. and transparency can be achieved at the same time.

On the other hand, in Comparative Examples 1 to 4, the content of 2-isopropenyl-2-oxazoline contained in the oxazoline-containing resin (C) deviates from the range defined by the present invention, so it contributes to improve the dispersibility to some extent. However, the transparency of the obtained film-like material was low. As can be seen from the TEM observation photograph of the film-like material obtained in Comparative Example 4 shown in FIG. This is because the difference in refractive index between A) and the polylactic acid-based resin (B) resulted in a decrease in transparency.

In addition, in Comparative Example 5, since a resin having a reactive group different from the oxazoline group was used, the suppression of dispersion unevenness was insufficient, and the transparency of the obtained film-like material was also insufficient.

Furthermore, in Comparative Example 6, since no compatibilizing agent was used, uneven dispersion and transparency were remarkably lowered. As can be seen from the TEM observation photograph of the film-like material obtained in Comparative Example 6 shown in FIG. This is due to the fact that they are not dispersed.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, the invention is not limited to the embodiments disclosed herein. However, it can be changed as appropriate within the scope not contrary to the gist of the invention that can be read from the scope of claims and the entire specification, or the idea, and the film-like material that accompanies such changes is also included in the technical scope of the present invention. must be understood as

The film-like material of the present invention is excellent in uniform dispersibility of polystyrene resin and polylactic acid resin and has high transparency. Suitable for packaging materials such as packaging materials for cosmetics, packaging materials for toiletries, packaging materials for industrial use, packaging materials for agricultural materials, and containers such as box-shaped containers, containers with lids, cups, trays, plates and lids. can be used.

Claims (4)

A polystyrene-based film-like material having at least one layer containing a mixed resin composition of a polystyrene-based resin (A), a polylactic acid-based resin (B), and an oxazoline group-containing resin (C) as a main component, wherein the following a ) and b) using a polystyrene-based film material.
a) The mixing ratio when the mixed resin composition is 100% by mass is polystyrene resin (A) / polylactic acid resin (B) / oxazoline group-containing resin (C) = 50% by mass to 98% by mass / 1% to 30% by mass/1% to 20% by mass
b) The content of 2-isopropenyl-2-oxazoline is 4% by mass or more based on 100% by mass of the oxazoline group-containing resin (C) The packaging material according to claim 1, wherein the oxazoline group-containing resin (C) has a weight average molecular weight of 5,000 or more and 300,000 or less. The packaging material according to claim 1 or 2, wherein the polystyrene resin (A) contains at least one copolymer of a styrene monomer (a) and the following monomer (b).
Monomer (b): at least one selected from butadiene, isoprene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene a monomer that is a diene-based hydrocarbon of the species, a partially hydrogenated monomer of said diene-based hydrocarbon, or a fully hydrogenated monomer of said diene-based hydrocarbon The packaging material according to any one of claims 1 to 3, wherein the polystyrene resin (A) comprises a styrene-butadiene-styrene copolymer (SBS).

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