JPH11277688A - Styrenic resin sheet and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a styrenic resin sheet capable of continuing anti-fogging properties at low temp. and high temp. for a long time. SOLUTION: An anti-fogging styrenic resin sheet is obtained by applying an anti-fogging agent containing sugar fatty acid ester and polyglycerine fatty acid ester with an HLB of about 11-18 to at least one surface of a styrenic resin sheet. The ratio of sugar fatty acid ester and polyglycerine fatty acid ester is about former/latter = 55/45-98/2 (pts.wt.). Polyglycerine fatty acid ester is constituted of about 12-26C fatty acid. The anti-fogging agent may contain about 0-50 pts.wt. of a nonionic surfactant and/or about 0-400 pts.wt. of a mold release agent per 100 pts.wt. of fatty acid esters. The styrenic resin sheet can be produced by applying the anti-fogging agent to at least one surface of the sheet and suitable for molding a container.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an antifogging styrene resin sheet and a method for producing the same. More specifically, the present invention relates to an antifogging styrene-based resin sheet useful for obtaining a food packaging container mainly by performing secondary processing such as hot plate molding, vacuum molding, and vacuum pressure molding, a method for producing the same, and a container.

[0002]

2. Description of the Related Art An antifogging styrene sheet coated with an antifogging agent is widely used as a food packing container including a lunch box lid, a food pack and the like. These sheets and films are coated with an antifogging agent containing a sucrose fatty acid ester as a main component in order to impart antifogging properties. Sucrose fatty acid ester is superior in short-term anti-fogging property as compared with many other anti-fog agents, and is a substance recognized as a food additive, and thus is preferable as an anti-fogging agent for food packaging containers. . However, with the expanding market and diversifying needs of consumers,
The performance required of these antifogging sheets is also increasing. For example, when a container containing water is stored in a refrigerator for a long time, dew condensation occurs. However, it is difficult for a container formed from a styrene-based antifogging sheet or film coated with a sucrose fatty acid ester to maintain the antifogging property against dew condensation or the like for a long time. In other words, it has been confirmed that sucrose fatty acid ester is easily removed from the surface due to the formed dew due to its high hydrophilicity, and as a result, the antifogging property of the container is reduced in a relatively short time. .

In order to improve long-term anti-fog properties, Japanese Patent Application Laid-Open No.
In JP-A-3-13641 and JP-A-3-182347, various water-soluble polymers are added. However, sheets coated with antifogging agents containing these water-soluble polymers are difficult to recycle, that these water-soluble polymers are not recognized as food additives, and that whitening occurs during secondary molding. Therefore, it is difficult to put it to practical use.

Japanese Patent Application Laid-Open No. Sho 59-19584 discloses a styrene-based composition coated with a mixture of a surfactant having an HLB of 13 or more and a sucrose fatty acid ester in order to prevent a decrease in anti-fogging property due to peeling of the anti-fogging agent. Resin sheets have been proposed.
In addition, antifogging styrene-based sheets with excellent low-temperature sustained antifogging properties
As a film, Japanese Patent Application Laid-Open No. 9-12751 proposes application of an antifogging agent containing a fatty acid ester of polyglycerin. Although these antifogging agents improve the practical long-term antifogging properties slightly, they have a high affinity for the silicone applied to the release surface with respect to the mold and inevitably set off when rolled up on a roll. When the degree of this set-off is severe, the tape peeling strength of the release surface and the anti-fog property of the anti-fog surface decrease,
Significant mold contamination during molding occurs.

[0005]

Accordingly, it is an object of the present invention to prevent appearance defects such as whitening at the time of secondary processing and to prevent the resin from being formed for a long time at a low temperature and a high temperature even after being molded into a container or the like. It is an object of the present invention to provide a styrene-based resin sheet for container molding capable of maintaining haze and a method for producing the same. Another object of the present invention is to include a release agent, do not show off when rolled up in a roll at the time of forming a sheet, and do not impair the appearance even when molded into a container or the like, and An object of the present invention is to provide an antifogging styrene resin sheet capable of suppressing contamination and a method for producing the same.

It is still another object of the present invention to provide a packaging container in which stored items (such as foodstuffs) can be effectively visually recognized even when stored at a low temperature for a long time, especially in the field of food packaging. .

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and have found that an antifogging agent containing a sucrose fatty acid ester and a polyglycerin fatty acid ester is used.
By applying to at least one surface of the sheet, it has been found that the anti-fogging property of the styrene resin sheet, and thus the anti-fogging property of the container obtained by molding this sheet, can be maintained for a long time, and the present invention has been completed. .

That is, the styrenic resin sheet of the present invention has an anti-fogging composition comprising a sucrose fatty acid ester and a polyglycerin fatty acid ester having an HLB (Hydrophilic-Lipophilic Balance) of about 11 to 18 on at least one surface of the sheet. The agent has been applied. The ratio of the sucrose fatty acid ester to the polyglycerin fatty acid ester is about the former / the latter = 55/45 to 98/2 (parts by weight). The polyglycerin fatty acid ester has 12 to 26 carbon atoms.
It may be composed of fatty acids to some degree. The anti-fog agent may further include a nonionic surfactant and / or a release agent (such as silicone oil) other than the sucrose fatty acid ester and the polyglycerin fatty acid ester,
These ratios are based on 100 parts by weight of the total amount of the sucrose fatty acid ester and the polyglycerin fatty acid ester.
0 to 50 parts by weight of a nonionic surfactant, 0 to 50 parts by weight of a release agent
It is about 400 parts by weight. The styrene resin sheet can be manufactured by applying the anti-fogging agent to at least one surface of the sheet.

The present invention also includes a molded article such as a container obtained by subjecting the styrene resin sheet to secondary processing.

[0010] In the present specification, "sucrose fatty acid ester" means an ester mainly composed of a monoester in which one molecule of fatty acid is bonded to one molecule of sucrose.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the styrene resin sheet of the present invention, at least one surface of the sheet is coated with an antifogging agent containing sucrose fatty acid and polyglycerin fatty acid ester by coating or the like.

HL of the polyglycerin fatty acid ester
B is about 11-18, preferably about 12-18. Such polyglycerin fatty acid ester,
It has good solubility in water, can be easily mixed with sucrose fatty acid ester to form an aqueous dispersion or aqueous solution, and does not require the use of an organic solvent, so that a coating solution can be prepared safely and stably. As an HLB determination method, for example, Griffin
The following equation, proposed by the authors, can be used. HLB = 20 (1-S / A) (where S represents the saponification value of the ester and A represents the acid value of the fatty acid.) The polyglycerin fatty acid ester is obtained by partially esterifying polyglycerin with a fatty acid. Alternatively, it may be obtained by reacting a fatty acid with glycidol in the presence of an acidic catalyst, as described in JP-A-8-109153. The position of the ester bond in these fatty acid esters is not particularly limited as long as a part of the hydroxyl group of polyglycerin is ester-bonded to the fatty acid. The average degree of polymerization n of polyglycerin is
n = about 2 to 20, preferably about 3 to 15, particularly 4 to
It may be about 10. In addition, polyglycerin is not limited to a straight chain, and may have a crosslinked structure.

The fatty acid constituting the polyglycerin fatty acid ester has 12 or more carbon atoms (for example, 12 to
26), preferably about 14 to 22, especially 14 to 2
Fatty acids that are around 0 are preferred. The polyglycerin fatty acid ester composed of such a long-chain fatty acid is applied to a styrene-based resin sheet and can be firmly adhered to the surface thereof. Therefore, the polyglycerin fatty acid ester as described above has a relatively high affinity for water, makes it easy to prepare a coating solution, and after application, when dried, shows strong adhesion, which is practically sufficient. Water resistance can be imparted, and high antifogging properties can be exhibited for a long time.

The fatty acids constituting the fatty acid ester include saturated fatty acids having about 12 to 26 carbon atoms, such as lauric acid, myristic acid, palmitic acid, stearic acid, 1,2-hydroxystearic acid and behenic acid. Examples thereof include unsaturated fatty acids having about 12 to 24 carbon atoms, such as toleic acid, oleic acid, linoleic acid, and linolenic acid. Preferred fatty acids are C _12-22 saturated fatty acids or C
_16-20 unsaturated fatty acids. These fatty acids can be used alone or as a mixture of two or more.

The polyglycerol fatty acid ester used in the present invention is, for example, tetra-, penta-, hexa-,
Esters (mono-, di- and trifatty acid esters) of polyglycerol having an average degree of polymerization of about 4 to 20, such as hepta, octa, nona, deca, undeca, dodecaglycerin, and the above-mentioned saturated and unsaturated fatty acids Etc.) can be used. Examples of the ester include tetraglycerin C _12-26 saturated fatty acid esters such as tetraglycerin stearate and tetraglycerin laurate, tetraglycerin C _12-20 unsaturated fatty acid esters such as tetraglycerin oleate, hexaglycerin laurate, hexaglycerin 1 , 2-hydroxy stearate, hexaglycerol C _12-26 saturated fatty acid esters such as hexaglycerin monostearate, hexaglycerin C _12-20 unsaturated fatty acid esters such as hexaglycerin oleate, octaglycerol monolaurate, octaglycerol 1,2 hydroxystearate, octaglycerol C _12-26 saturated fatty acid esters, such as octaglycerol monostearate, octaglycerol C _12-20 unsaturated fatty acid esters, such as octaglycerol oleate, decaglycerol Rumiteto, decaglycerin laurate, decaglycerol 1,2 hydroxystearate, decaglycerol monostearate, decaglycerol C _12-26 saturated fatty acid esters such as decaglycerol behenate, decaglycerol oleate, such as decaglycerol linoleate deca Glycerin C _12-20 unsaturated fatty acid ester can be exemplified. In particular, an average degree of polymerization of 4
About 15 (e.g., about 4 to 12) and polyglycerin, such as esters of C _12-24 fatty acids (particularly C _{12 -20} fatty acids) are preferred.

To obtain a suitable HLB value as described above,
Polyglycerin monofatty acid ester, polyglycerin difatty acid ester, polyglycerin trifatty acid ester and the like can be used, and it is particularly effective to use polyglycerin monofatty acid ester (monosubstituted). Commercially available polyglycerin monofatty acid esters are generally monosubstituted as a main component and are mixtures with unsubstituted polyglycerin, polyglycerin difatty acid ester (disubstituted), and polyglycerin trifatty acid ester (trisubstituted). . When these commercially available products are used, the composition thereof is not particularly limited, but the content of the monosubstitute in the mixture is 20% by weight or more, preferably 30% by weight or more. Polyglycerol fatty acid esters containing polyglycerin as di-glyceride and triglyceride as main components generally have an HL of 4 or less.
It has a B value, is highly hydrophobic, and is not easily dispersed in water even by ultrasonic treatment, and is not very suitable for the polyglycerin fatty acid ester used in the antifogging agent of the present invention. As a method for quantifying monoglyceride in polyglycerin fatty acid ester, a conventional method, for example, JP-A-8-1091
No. 53, high performance liquid chromatography (HP
LC) method or the like.

The polyglycerin fatty acid ester has a relatively high solubility in water, and a coating solution can be prepared in the form of an aqueous solution. Since it is an amphiphilic compound having a hydrophobic group and a hydrophilic group in the molecule, an antifogging agent containing this is dispersed in water and applied in the form of a dispersion to a styrene resin sheet to produce an antifogging sheet. it can. Dispersion can be carried out by a conventional method such as stirring, vibration, and the like.To uniformly and easily disperse the antifogging agent in water,
It may be dispersed by sonication. In such a case,
The antifogging agent forms a micellar structure and stabilizes after dispersion. Once the micelle structure is obtained, the structure is not destroyed by mechanical operations such as stirring, vibration, mixing, and dilution, and the state is maintained. Thus, even if the solubility in water is relatively low, since the antifogging agent can be directly dispersed in water, it is not necessary to use an organic solvent,
An antifogging agent containing a polyglycerin fatty acid ester can be safely and stably applied to a styrene resin sheet.
In addition, since the constituent fatty acids of the polyglycerol fatty acid ester are long-chain fatty acids as described above, after coating and drying, they have excellent water resistance, and even at low temperatures, can maintain high antifogging properties for a long time, and During secondary processing such as container molding, appearance defects such as whitening, peeling, and set-off do not occur.

Sucrose fatty acid ester is a substance recognized as a food additive, and has a short-term antifogging property (initial antifogging property)
Because of its excellent high-temperature anti-fog property, it can be sufficiently combined with the above-mentioned polyglycerin fatty acid ester having high long-term anti-fog property and low-temperature anti-fog property over a wide time and temperature range required for food packaging applications. Develops antifog properties and can maintain it. The fatty acid constituting the sucrose fatty acid ester includes, for example, the fatty acid constituting the polyglycerin fatty acid ester. When importance is placed on the solubility in water, a fatty acid having about 12 to 18 carbon atoms such as lauric acid is used as a main component. Is preferred.

The ratio between the sucrose fatty acid ester and the polyglycerin fatty acid ester depends on the desired antifogging level,
It can be selected according to the application (for example, requirements for initial antifogging property and long-term antifogging property, high temperature antifogging property and low temperature antifogging property). When the balance of the above properties is taken into consideration, the ratio of the sucrose fatty acid ester to the polyglycerin fatty acid ester is, for example, about the former / the latter = 55/45 to 98/2 (parts by weight), preferably 60/40 to 98 /. About 2 (parts by weight) (for example, 6
About 5/35 to 95/5 (parts by weight), more preferably about 70/30 to 95/5 (parts by weight). If the proportion of the polyglycerin fatty acid ester is less than 2% by weight with respect to 100% by weight of the antifogging agent composed of sucrose fatty acid ester and polyglycerin fatty acid ester, remarkable improvement in long-term antifogging property cannot be expected, If it exceeds 45% by weight, set-off of the polyglycerin fatty acid ester to the release surface becomes remarkable, the release property of the release surface and the tape peeling strength are reduced, the antifogging property of the antifogging surface is reduced, and Contamination of the mold or the hot plate.

In addition to the initial or long-term anti-fog properties at low and high temperatures as described above, heat stability,
In consideration of dispersibility in water, transferability, antistatic property, cost, and the like, a nonionic surfactant other than the sucrose fatty acid ester and polyglycerin fatty acid ester is used in combination to further add these properties. Is also possible. In the present specification, the term "nonionic surfactant" is used to mean a nonionic surfactant excluding the sucrose fatty acid ester and polyglycerin fatty acid exemplified above. Examples of such nonionic surfactants include polyglycerol fatty acid esters other than the above-described polyglycerin fatty acid esters, propylene glycol fatty acid esters, polyhydric alcohol esters of fatty acids such as sorbitan fatty acid esters, and polyoxyalkylene glycerin fatty acid esters (for example, Polyoxy C _2-4 alkylene glycerin mono C _8-22 saturated fatty acid ester such as polyoxyethylene glycerin monostearate; polyoxyalkylene sorbitan fatty acid ester (eg polyoxy C _2-4 such as polyoxyethylene sorbitan monolaurate)
Alkylene oxide adducts of polyhydric alcohol esters of fatty acids such as alkylene sorbitan mono-C _8-22 saturated fatty acid esters), polyoxyethylene polyoxypropylene glycol, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, fatty acid alkanolamide, etc. Is mentioned. Preferred nonionic surfactants have, for example, polyoxyalkylene units such as polyoxy C _2-4 alkylene glycerin mono C _8-22 saturated fatty acid ester and polyoxy C _2-4 alkylene sorbitan mono C _8-22 saturated fatty acid ester. Nonionic surfactants and the like. The nonionic surfactants can be used alone or in combination of two or more.

The amount of the nonionic surfactant used is from 0 to 50 parts by weight (for example, 0.1 to 40 parts by weight) based on 100 parts by weight of the total amount of the sucrose fatty acid ester and the polyglycerin fatty acid ester. It is preferably about 1 to 30 parts by weight, particularly about 3 to 20 parts by weight (for example, about 5 to 20 parts by weight).

The styrenic resin sheet of the present invention can be produced by applying the anti-fogging agent to at least one surface of the styrenic resin sheet. In addition, a release agent may be used for the styrene-based resin sheet in order to improve the slip property of the sheet, the releasability from a mold or the like during molding, and the releasability of a molded product. The release agent may be coated on the surface of the sheet, or a release agent may be added to the antifogging agent in advance to impart release properties.

In the present invention, the antifogging agent preferably contains a release agent in advance within a range that does not impair the antifogging property. As the release agent, a conventional release agent or lubricant can be used. Examples of these release agents and lubricants include hydrocarbons such as paraffin and chlorinated paraffin, higher alcohols such as stearyl alcohol and cetyl alcohol, fatty acids such as stearic acid and oleic acid, oils and fats, monohydric and polyhydric alcohol esters. Fatty acid salts such as Ca, Zn and Ba salts such as lauric acid and stearic acid; ethers such as polypropylene glycol alkyl ether; and silicone oil. It is preferable to use a silicone oil or the like from the viewpoint of improving the releasability and slipperiness of the antifogging surface of the styrene resin sheet.

When silicone oil is used as a release agent, it is preferable to add an emulsion type silicone oil to an aqueous antifogging liquid (antifogging agent) from the viewpoint of disaster prevention and the working environment. Representative silicone oils include dimethylpolysiloxane. The viscosity of the silicone oil may be about 100 to 50,000 сSt (preferably about 1,000 to 20,000 cSt).

The ratio of the release agent is from 0 to 400 parts by weight (for example, from 5 to 400 parts by weight) based on 100 parts by weight of the total amount of the polyglycerin fatty acid ester and the sucrose fatty acid ester.
Parts by weight), preferably 10 to 400 parts by weight (for example, 1
0 to 300 parts by weight), more preferably about 10 to 200 parts by weight (for example, 10 to 100 parts by weight), usually about 10 to 100 parts by weight.
It is about 50 parts by weight.

When constituting an antifogging agent containing the above-mentioned nonionic surfactant or release agent, the proportion of sucrose fatty acid ester in the antifogging agent is, for example, 60 to 80% by weight (preferably 55 to 80% by weight). 70% by weight) and the proportion of the polyglycerol fatty acid ester can be selected from, for example, about 1 to 50% by weight (preferably 1 to 45% by weight), and the remainder is 0 to 20% by weight of the nonionic surfactant. (Preferably 0-10
%), A release agent of 0 to 40% by weight (preferably 10% by weight).
(About 35% by weight).

The antifogging agent may be applied to the sheet in a form containing no solvent, or in the form of a dispersion (including an emulsion) dispersed in the solvent by stirring, ultrasonic treatment, or the like, or may be uniformly dissolved. It may be applied in the form of a prepared solution. When using a solvent, an organic solvent may be used.
From the viewpoints of working environment and environmental hygiene, aqueous solvents are preferred. Wherein the aqueous solvent, water means a solvent system is used as a solvent, may be used water alone as a solvent, methanol in water, such as C _1-4 alcohols and acetone, such as ethanol C _1- A hydrophilic (particularly water-soluble) organic solvent such as _4- dialkyl ketone may be added to increase the compatibility between the fatty acid esters and water.

The concentration of the non-volatile component of the anti-fogging agent can be selected at a concentration suitable for imparting anti-fogging properties according to the purpose and application.
It also depends on the coating agent containing the anti-fog agent, the coating method, or the speed of the work line. Usually, the concentration is from 0.01 to 10
% By weight, preferably 0.1 to 5% by weight (for example,
0.1 to 2% by weight).

The anti-fogging agent may contain various additives as required, for example, stabilizers (UV absorbers, antioxidants, etc.), plasticizers, reinforcing agents, fillers, slip agents, anti-blocking agents, It may contain a nucleating agent, a crosslinking agent, an antistatic agent, a flame retardant, a light-shielding agent such as titanium oxide, a coloring agent (a pigment, a dye, and the like).

The application of the anti-fogging agent is preferably carried out uniformly on a styrene resin sheet. However, depending on the purpose and application, it is also possible to apply the anti-fogging agent only to the site or region where the anti-fogging property is to be imparted. It may also be non-uniform depending on the desired level of anti-fogging properties. The anti-fogging agent may be formed by a conventional casting or coating method, for example, a roll coater, knife coater, air knife coater, blade coater, rod coater, comma coater, gravure coater, spray coater, dip coater method, etc. Cast or coated on top. The anti-fogging agent applied by the above method is dried after application, if necessary, and is fixed on a sheet. When drying, the drying temperature is usually about 40 to 120 ° C., preferably 60 to 10 ° C.
It is about 0 ° C.

When a container is formed using a styrene-based resin sheet in which the antifogging agent is applied only to one side of the sheet, the coated surface is usually used on the side where fogging may occur when used as a container. For example, for food packaging, it is molded so that it is on the food side during refrigeration and outside during warming.

In the styrene resin sheet of the present invention,
The coating amount of the anti-fogging agent is preferably 5 to 50 mg / m ^2.
And more preferably about 10 to 30 mg / m ² . When the coating amount of the anti-fog agent is less than 5 mg / m ² ,
If the anti-fogging property cannot be achieved, and if it exceeds 50 mg / m ² , the set-off of the anti-fogging agent when the sheets are stacked cannot be ignored, and the sheet becomes sticky, and furthermore, when molding such as mold stains and clouding, etc. Problem may occur.

The styrene resin sheet of the present invention includes:
A styrene resin sheet or film formed from a conventional styrene resin into a sheet or film by a conventional method can be used. The sheet or film may be a stretched sheet (a uniaxially stretched sheet, a biaxially stretched sheet, etc.) or an unstretched sheet. Examples of the method for forming a sheet or film include an extrusion method (such as a T-die method and an inflation method), a stretching method using a tenter method, a tube method, and an inflator method (such as a uniaxial stretching method and a biaxial stretching method). . The sheet may be a single-layer sheet, a laminated sheet of a plurality of resin layers composed of a styrene-based resin or a styrene-based resin having a different composition of an antifogging agent, and a layer composed of a styrene-based resin layer. It may be a laminated sheet with another resin layer (for example, an olefin-based resin such as polyethylene or polypropylene). The laminated sheet can be prepared by a technique such as coextrusion, heat lamination, or dry lamination.

The styrenic resin used in the styrenic resin sheet of the present invention can be composed of an aromatic vinyl compound alone or a copolymer, or a copolymer of an aromatic vinyl compound and a copolymerizable vinyl monomer.

Examples of the aromatic vinyl compound include styrene, alkylstyrene (for example, vinyltoluenes such as o-, m- and p-methylstyrene, p-ethylstyrene, p-isopropylstyrene, butylstyrene, p-styrene).
-T-butylstyrene, etc.), α-alkylstyrene (eg, α-methylstyrene), halostyrene (eg, o-, m- and p-chlorostyrene, p-bromostyrene, etc.). These aromatic vinyl monomers can be used alone or in combination of two or more. Preferred styrene monomers include styrene, vinyltoluene, α-methylstyrene and the like, and styrene is particularly preferred.

As the copolymerizable vinyl monomer, for example,
(Meth) acrylonitrile, alkyl (meth) acrylate, vinyl ester-based monomer (eg, vinyl acetate), hydroxyl group-containing monomer [hydroxy C ₁ such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, etc. _-4 alkyl (meth) acrylate, etc.], glycidyl group-containing monomer [glycidyl (meth) acrylate, etc.], carboxyl group-containing monomer [(meth) acrylic acid, maleic anhydride, fumaric acid, etc.], imide monomer Monomers (maleimide, N-methylmaleimide, N-phenylmaleimide, etc.). The alkyl (meth) acrylate includes methyl (meth) acrylate, ethyl (meth) acrylate,
Butyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate,
_C1-20 alkyl (meth) acrylates such as lauryl (meth) acrylate are included. These vinyl monomers can be used alone or in combination of two or more.

Preferred styrene resins include, for example, polystyrene, acrylonitrile styrene copolymer (AS resin), styrene- (meth) acrylic acid copolymer, styrene-maleic anhydride copolymer, styrene-
(Meth) acrylic acid ester copolymer (styrene-methyl methacrylate copolymer, etc.), styrene- (meth) acrylic acid ester- (meth) acrylic acid copolymer (styrene-methyl methacrylate- (meth) acrylic acid) Copolymers), styrene- (meth) acrylate-maleic anhydride copolymers (styrene-methyl methacrylate-maleic anhydride copolymer) and the like. Further, the styrene resin may be composed of a rubber-modified styrene resin. The rubber-modified styrenic resin includes at least a polymerizable monomer composed of the aromatic vinyl compound (a polymerizable monomer composed of an aromatic vinyl compound alone or an aromatic vinyl compound and a copolymerizable monomer). Copolymer) and a rubber component (particularly, a diene rubber component such as butadiene rubber, isoprene rubber, ethylene-vinyl acetate copolymer, acrylic rubber, and ethylene-propylene rubber (EPDM)), for example, a graft copolymer. Polymers (graft rubbers), block copolymers and the like are included. Usually, a graft copolymer obtained by grafting a styrene monomer (aromatic vinyl monomer) to a diene rubber component such as polybutadiene is preferable.

In the case of a copolymer, the form of the copolymer is not particularly limited, and may be, for example, a random, block, tapered block, graft copolymer or the like. Further, these copolymers may be completely or partially hydrogenated products, or may be polymer blends with other polymers or polymer alloys. These styrenic resins are
They can be used alone or in combination of two or more.

If necessary, the styrene resin may contain various additives such as stabilizers such as an ultraviolet absorber or an antioxidant, a plasticizer, a reinforcing agent, a filler, a slip agent, an antiblocking agent, and a nucleating agent. , Crosslinking agents, antistatic agents, flame retardants, light shielding agents such as titanium oxide, coloring agents, etc.) and mineral oil, etc., and various properties such as heat resistance, cold resistance, impact resistance, flame retardancy, moldability, etc. Or may be improved.

The styrene resin sheet may be subjected to a surface treatment such as a corona discharge treatment or an undercoat treatment, if necessary, in order to improve the adhesion of the antifogging agent, depending on the purpose and application.

When molding a container or the like, the thickness of the styrene resin sheet before the application of the antifogging agent can be determined according to the molding conditions and the like. The thickness is 0.05
About 2 mm, 0.1 to 1.5 mm (for example, 0.1 to
1 mm).

The styrenic resin sheet is coated with an antifogging agent, dried if necessary, and rolled up. Can be greatly improved. Therefore, the anti-fogging sheet is suitable to be subjected to secondary processing such as container molding by heating or the like, without impairing the anti-fogging property, even if rolled once. For the secondary processing, a conventional molding method applied to a plastic sheet or film can be used. As a method of the secondary processing, for example,
Examples include vacuum forming, compressed air forming (compressed air pressure forming), and hot plate forming. The antifogging styrene resin sheet of the present invention is formed into a molded product (particularly, a container for food packaging) by secondary processing.
It is useful as an anti-fogging sheet that can maintain anti-fogging property even when molded into a sheet.

[0043]

According to the present invention, the sucrose fatty acid ester and the polyglycerin fatty acid ester are divided into the former / the latter = 55/4.
Since the antifogging agent containing 5 to 98/2 (parts by weight) is applied to the styrenic resin sheet, it can be used in the form of a sheet, or even after molding into a container or the like, at high or low temperature. The anti-fogging property can be achieved, and the anti-fogging property can be maintained for a long time. When the polyglycerin fatty acid ester is combined with a sucrose fatty acid ester, the polyglycerin fatty acid ester can be applied onto a sheet without using an organic solvent. Because the food can be clearly seen and the water resistance is high,
It is possible to provide a safe packaging container and an anti-fogging sheet / film which do not cause the anti-fogging agent to flow out due to water droplets and contaminate the food. Further, set-off of the antifogging agent to the sheet, which occurs when the roll is wound after the sheet is formed, can be effectively suppressed.

[0044]

EXAMPLES The present invention will be described below in more detail with reference to Examples, but the present invention is not limited to these Examples.

The sucrose fatty acid ester, polyglycerin fatty acid ester, nonionic surfactant, release agent and styrene resin sheet used in the examples and comparative examples are as follows.

1. 1. Sucrose fatty acid ester (a-1): sucrose monolaurate (containing 72% by weight of monosubstituted product) Polyglycerin fatty acid ester (b-1): hexaglycerin monolaurate (HL
B: 12.0) (b-2): decaglycerin monolaurate (HLB:
15.5) (b-3): Decaglycerin monostearate (HL
B: 12.0) (b-4): decaglycerin monooleate (HLB: 1)
2.0) 3. 3. Nonionic surfactant (c-1): polyoxyethylene glycerin monostearate (HLB: 14.3) (c-2): polyoxyethylene sorbitan monolaurate (HLB: 16.7) 4. Release agent (d-1): silicone oil (added as emulsion) Styrene resin sheet (e-1): biaxially stretched polystyrene sheet (thickness 0.2
5 mm) In the styrene-based resin sheets and containers obtained in Examples and Comparative Examples, the following characteristics were evaluated.

[Anti-fogging property] The anti-fogging property of the molded container at low and high temperatures was visually evaluated according to the following time after the test. ◎ No clouding ○ Small clouding △ Small water droplets × Water droplets

[Offset property] A silicone oil (0.5% by weight emulsion) alone was applied as a release agent, and a dried styrene-based resin sheet was prepared. / Cm ² . The sheet after pressing was peeled off, and the tape peeling strength (using KOKUYO Super Clear, width 24 mm as a tape) of the sheet to which the release agent was applied was measured to evaluate the set-off property of the antifogging agent.

Examples 1 to 8 A mixture of the above-mentioned polyglycerin fatty acid ester and sucrose fatty acid ester having an HLB in the range of 11 to 18 was diluted with water according to the ratio shown in Table 1, and a 0.5% by weight aqueous dispersion was prepared. Prepared. The aqueous dispersion was applied to one surface of the corona discharge-treated styrene resin sheet with a Mayer bar (# 3) and dried at 80 ° C. for 30 minutes. A container (opening 120 mm × 90 mm, bottom 10 m) using a sheet single-pressure air forming machine (Asano Seisakusho Co., Ltd.) such that the surface coated with the antifogging agent becomes the inner surface.
m × 65 mm, depth 35 mm), and the antifogging properties of the sheet and this container were evaluated. Sheet (100mm x 1
50 mm) in a transparent acrylic container (100 mm long × 150 mm wide × 80 mm deep) containing 30 ml of water at 15 ° C
Immediately after attaching to the upper part of the sheet, it was put into a refrigerator (inside temperature, 5 ° C.), taken out after a lapse of a predetermined time, and observed for the state of water droplets / liquid film adhering to the inner surface of the sheet (low-temperature antifogging property). Table 2 shows the results. Furthermore, the sheet was held over the hot water bath heated to 80 ° C., and the state of the attached water droplets and liquid film was observed (high-temperature antifogging property). Table 3 shows the results.

Comparative Examples 1 to 4 Using a polyglycerol fatty acid ester, a sucrose fatty acid ester, a nonionic surfactant and a release agent in the proportions shown in Table 1, a 0.5% by weight aqueous dispersion of these mixtures was prepared. did. Subsequent production of sheets and containers and evaluation of antifogging properties were performed in the same manner as in Examples 1 to 8.

Examples 9 to 12 Polyglycerin fatty acid ester, sucrose fatty acid ester, nonionic surfactant and release agent were added to water in the proportions shown in Table 1, and 0.5% by weight of the mixture was added. % Aqueous solution was prepared and applied to a sheet in the same manner as in Examples 1 to 8, and the low-temperature antifogging property and the set-off property were evaluated. Table 2 shows the results.

Comparative Examples 5 to 8 Sucrose fatty acid esters and mold release agents were added to water at the ratios shown in Table 1 to prepare 0.5% by weight aqueous dispersions of these mixtures. The composition was applied to a sheet in the same manner as in Examples 1 to 8, and the low-temperature antifogging property and the set-off property were evaluated. Table 2 shows the results.

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[Table 1]

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[Table 2]

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[Table 3]

As is clear from Table 2, compared to the comparative example,
In the examples, the use of a combination of a sucrose fatty acid ester and a polyglycerin fatty acid ester improved the low-temperature antifogging property over a long period of time. Further, in the example, a larger peel strength was required than in the comparative example, and the set-off property was reduced. As is clear from Table 3, even after 5 minutes, high anti-fogging property is maintained in Examples.

Claims (6)

[Claims] 1. A sucrose fatty acid ester having an HLB of 11
An anti-fog sheet comprising a styrene resin sheet and an anti-fog agent containing a polyglycerin fatty acid ester of -18 to -18, wherein the ratio of the sucrose fatty acid ester to the polyglycerin fatty acid ester is the former / Styrene resin sheet with the latter being 55/45 to 98/2 (parts by weight). 2. The styrene resin sheet according to claim 1, wherein the fatty acid constituting the polyglycerin fatty acid ester has 12 to 26 carbon atoms. 3. The method according to claim 1, further comprising a silicone oil.
The styrene resin sheet according to the above. 4. The method according to claim 1, further comprising 0 to 50 parts by weight of a nonionic surfactant and 0 to 400 parts by weight of a release agent based on 100 parts by weight of the total amount of the sucrose fatty acid ester and the polyglycerin fatty acid ester. Styrene resin sheet. 5. A method for producing a styrene resin sheet, wherein the antifogging agent according to claim 1 is applied to at least one surface of the sheet. 6. A container formed of the styrene resin sheet according to claim 1.