JP2000280416A - Anti-fog styrene resin sheet - Google Patents

Abstract

(57) [Problem] To provide an antifogging styrene resin sheet which does not cause poor antifogging property. SOLUTION: One side of the styrene resin sheet is an antifogging styrene resin sheet coated with an antifogging agent, or a mixture of an antifogging agent and silicone oil, wherein the antifogging agent, or On the surface of the layer of the mixture of the antifogging agent and the silicone oil, the content of carbon derived from the hydrophilic group of the antifogging agent is 30% or more of the total carbon present on the surface.
It is less than 0%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is mainly used in a hot plate contact heating vacuum press forming method (hereinafter referred to as a hot plate heating molding method), and is used as a food packaging container and other various packaging containers. The present invention relates to a technology for modifying an antifogging styrene resin sheet.

[0002]

2. Description of the Related Art Polystyrene-based resin sheets, especially biaxially oriented polystyrene-based resin sheets, have higher transparency, gloss and rigidity than other materials, and are widely used for various packaging materials, including food packaging containers. Used in

[0003] In order to impart antifogging property, lubricity and release property to a polystyrene resin sheet, a method of mixing an antifogging agent and silicone oil and applying (coating) the mixture to the surface of the polystyrene resin sheet is known. Was adopted.

[0004]

As described above, in order to impart anti-fog properties, lubricity and release properties to a polystyrene resin sheet, a polystyrene resin sheet is prepared by mixing an anti-fog agent and silicone oil. The method of applying to the surface is a drawback that often causes poor antifogging property in a molded container obtained by thermoforming a polystyrene resin sheet and a hot-plate hot-molding method as a food packaging container or other various packaging containers. There is.

An object of the present invention is to provide an antifogging styrene-based resin sheet which does not cause poor antifogging properties even in a food packaging container and a variety of other packaging containers after the sheet is subjected to hot plate heating and molding. It is the purpose.

[0006]

Means for Solving the Problems As a result of diligent studies, the present inventor has found that a poor antifogging property in a molded container after hot plate heat molding of a styrene resin sheet is caused by an antifogging agent or the above antifogging agent and silicone. The present invention was found to be attributable to the abundance ratio of carbon derived from the hydrophilic group of the anti-fogging agent on the surface of the layer of the oil mixture or to the surface exposure of the anti-fogging agent, and completed the present invention.

That is, the present invention provides a styrene resin sheet in which one surface of a styrene resin sheet is coated with an antifogging agent or a mixture of an antifogging agent and silicone oil, Alternatively, the ratio of carbon derived from the hydrophilic group of the antifogging agent on the surface of the layer of the mixture of the antifogging agent and the silicone oil is 30% or more of the total surface existing carbon.
It is characterized by being less than 0%. In the present invention, the sheet includes a so-called film.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
As the antifogging agent, a nonionic surfactant is preferable,
Examples of these include, for example, sucrose fatty acid esters, polyglycerin fatty acid esters, polyamide resin film oxyalkyls, polyoxyethylene alkyl ethers, polyoxyethylene fatty acid ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid One or a mixture of two or more surfactants selected from esters, polyoxyethylene sorbitan fatty acid esters, and the like. The HLB of the surfactant is 11 to 1
7 are preferred. When the HLB is less than 11, the water solubility, dispersibility, and wettability of the antifogging agent are deteriorated, and it is difficult to form a uniform antifogging agent film. When the HLB exceeds 17, the antifogging agent flows into water. This is because the antifogging property tends to be deteriorated. Among these surfactants, the antifogging agents used in the present invention include sucrose fatty acid esters and polyglycerin fatty acid esters that are approved as food additives.
Sorbitan fatty acids are preferred. A sucrose fatty acid ester containing 50 mol% or more of lauric acid as a fatty acid component, and a mixture of the sucrose fatty acid ester (99 to 50% by weight) and a polyglycerin fatty acid ester or a sorbitan fatty acid ester (1 to 50% by weight) It is particularly preferable because it has an excellent balance between product safety and antifogging properties and also has an excellent masking effect of silicone oil.

The term "carbon derived from a hydrophilic group of the antifogging agent" as used in the present invention refers to carbon in an organic atom group having strong interaction with water in the antifogging agent. When sucrose fatty acid ester is used, it refers to carbon in the following atomic groups a to c contained in the sucrose fatty acid ester.

Embedded image

[0010] An antifogging styrene resin sheet in which one surface of a styrene resin sheet is coated with an antifogging agent or a mixture of an antifogging agent and silicone oil, and the other surface is preferably coated with silicone oil. Wherein the ratio of carbon derived from hydrophilic groups of the anti-fogging agent on the surface of the layer of the anti-fogging agent or the mixture of the anti-fogging agent and the silicone oil is 30% or more and 60% or more of the total surface existing carbon. The feature is to use those less than. By having such a configuration, the present invention can prevent defective antifogging properties and supply a sheet and a molded container having a high level of antifogging properties. On the other hand, a conventionally known sheet having a coating ratio of 30% or more of carbon derived from a hydrophilic group derived from the antifogging agent on the sheet surface is used even if the application of the antifogging agent and the silicone oil to the sheet are the same. Is not an indispensable requirement, so that antifoggant defects are likely to occur.

The silicone oil is an organic polysiloxysan such as dimethylpolysiloxysan, methylphenylpolysiloxysan and diphenylpolysiloxysan, and dimethylpolysiloxysan is particularly preferred from the viewpoint of product safety and economy. The viscosity of the silicone oil used in the present invention is 100 to 100 to ensure the stability of the emulsion and to improve the slipperiness of the sheet and the separation of the hot plate and the sheet.
100,000 cst is preferable, and 20,000 cs
Those having a thickness of about t are particularly preferable because the releasability is improved.

The styrenic resin used in the present invention is obtained, for example, by polymerizing the following monomers. That is, as the styrene monomer constituting the styrene resin, styrene, alkyl-substituted styrene (for example, o-methylstyrene, p-methylstyrene, m-methylstyrene,
4-dimethylstyrene, p-ethylstyrene, pt-
Butylstyrene, etc.), α-alkyl-substituted styrene (eg, α-methylstyrene, α-methyl-p-methylstyrene, etc.), and halogenated styrene (eg, o-chlorostyrene, p-chlorostyrene, etc.). Preferred styrene monomers are styrene, o-methylstyrene and p-methylstyrene, and styrene is particularly preferred.
These styrene monomers may be used singly or as a mixture of two or more.

The styrenic resin of the present invention can be appropriately selected from transparent styrenic monomers. In addition, for the transparent styrene-based monomer, for example, acrylic acid, (meth) acrylic acid such as methacrylic acid, (meth) acrylic acid ester such as methyl methacrylate, ethyl acrylate, butyl acrylate, and the like, A copolymerizable monomer such as maleic anhydride or acrylonitrile may be copolymerized as long as the transparency is not impaired. Of these, polystyrene is particularly preferable as the styrene resin used in the present invention in terms of cost.

The styrenic resin of the present invention may contain additives such as a flame retardant, an antioxidant, an ultraviolet absorber, an antistatic agent, a coloring agent, and a filler, as long as the transparency is not impaired. it can. Further, these resins can be produced by a conventional polymerization method.

The sheet made of the above-mentioned styrene resin is
It may be a single-layer sheet or a multilayer sheet in which a plurality of layers are laminated. In the multilayer sheet, the lamination method and the number of layers are not particularly limited, and the material forming each layer may be the same or different depending on the layer. The thickness of the sheet made of the styrene-based resin is not particularly limited, but is preferably 0.13 to 0.50 mm.

The method for producing the sheet made of the styrene resin is not particularly limited, and may be appropriately selected according to the material to be used. When performing biaxial stretching, a method generally used can be used. The production of the unstretched sheet may be carried out by a known method, and there is no particular limitation.

In the present invention, it is necessary that the proportion of carbon derived from hydrophilic groups of the antifogging agent on the surface of the layer of the antifogging agent or the mixture of the antifogging agent and the silicone oil is 30% or more. is there. The abundance ratio of carbon derived from the hydrophilic group of the antifogging agent on the surface is calculated from the result measured by X-ray photoelectron spectroscopy.

The antifogging styrenic resin sheet of the present invention comprises:
An antifogging agent or a mixture of an antifogging agent and silicone oil is applied to one side of the sheet, the silicone oil is applied to the other side of the sheet, and then dried by a commonly used method, and the winding tension is 10 to 60 kg / m. It is obtained by winding into a roll shape and cutting it into a predetermined shape from a take-up roll by a commonly used method such as slitting or cutting.

The method of applying the antifogging agent layer applied to one surface of the styrene resin sheet alone or mixed with silicone oil and the silicone oil layer applied to the other surface of the styrene resin sheet are described below. The method is not particularly limited, and a generally used method can be used.

The thickness of the antifogging agent layer applied to one surface of the styrene resin sheet alone or mixed with silicone oil, and the thickness of the silicone oil layer applied to the other surface of the styrene resin sheet Is not particularly limited, but preferably has a thickness of about several hundreds of degrees. The winding tension is preferably from 20 to 40 kg / m.

Hereinafter, the present invention will be described in more detail with reference to Test Examples, Production Examples, and Examples, but the present invention is not limited to these Examples.

Test Example 1. Test method (1) Anti-fogging styrene resin sheet The anti-fogging styrene resin sheet obtained in Example 1-3 and Comparative Example 1-3 was cut into 100 mm x 150 mm,
The water was adhered to the upper portion of a transparent acrylic container containing 30 ml of hot water at 30 ° C., and the state of water droplets attached to the sheet after 2 minutes was visually evaluated. The visual evaluation of the antifogging property of the antifogging styrene resin sheet was performed according to the following criteria. （(Good): Water droplets form a substantially uniform liquid film, and the contents are clearly visible. Δ (Slightly good): Water droplets became uneven, and the contents were slightly hard to see. X (poor): Water droplets became uneven, and the contents were not seen at all.

(2) Antifogging property of molded container manufactured by hot plate contact heating vacuum pressure molding method using styrene resin sheet (a) Low temperature antifogging container (12 × 18 cm, depth 2 cm) Water at 23 ℃
100 ml, cover with the lid (12 × 18 cm, depth 3 cm) obtained in Example 4-6 and Comparative Example 4-6, and in a 5 ° C. environment, the state of water droplets attached to the lid surface after 30 minutes in an environment of 5 ° C. Was visually evaluated. The visual evaluation of the antifogging property of the molded container was performed according to the following criteria. （(Good): Water droplets form a substantially uniform liquid film, and the contents are clearly visible. Δ (Slightly good): Water droplets became uneven, and the contents were slightly hard to see. X (poor): Water droplets became uneven, and the contents were not seen at all.

(B) High-temperature anti-fog property A container (12 × 18 cm, depth 2 cm) is filled with water at 70 ° C.
100 ml, cover with the lids (12 × 18 cm, depth 3 cm) obtained in Example 4-6 and Comparative Example 4-6, and put at 20 ° C.
5 minutes later, the state of water droplets adhered to the lid surface was visually evaluated under the above environment. The visual evaluation of the antifogging property of the molded container was performed according to the following criteria. （(Good): Water droplets form a substantially uniform liquid film, and the contents are clearly visible. Δ (Slightly good): Water droplets became uneven, and the contents were slightly hard to see. X (poor): Water droplets became uneven, and the contents were not seen at all.

2. Test Results Table 1 shows the results of the test (1), and Table 2 shows the results of the test (2).

[Table 1]

[0026]

[Table 2]

[0027]

EXAMPLES The presence of surface carbon derived from hydrophilic groups by X-ray photoelectron spectroscopy of the antifogging styrene resin sheet and the container obtained by molding the antifogging styrene resin sheet in Examples and Comparative Examples The ratio was calculated by the following method.

X-ray photoelectron spectroscopy The sheet and the molded product were cut out, attached to a special sample holder, and subjected to X-ray photoelectron spectroscopy. Equipment used PHI 5800system (manufactured by ULVAC-PHI) Al-kα monochromator: 150W. The sample was measured using an electron beam neutralizing gun (PHISICAL ELECTRON
ICS 11-066 type Ion Gan), and the pressure in the analysis chamber is 1
× 10 ⁻⁸ Pa or less.

The calculation of the surface carbon abundance derived from the hydrophilic group was performed by curve fitting (waveform separation) of the C1s spectrum obtained by X-ray photoelectron spectroscopy. In the curve fitting (waveform separation), the C1s spectrum obtained by X-ray photoelectron spectroscopy is subjected to background correction using the Shirley equation, and then the Lorentz function ratio is 10% or less using the Gauss-Lorentz function. Curve fitting was performed.

The respective binding energy values of the carbon species at the time of peak fitting are as follows:

Embedded image And The peak half width of each split peak is 1.0 to 1.0.
The range was 2 eV.

The surface carbon abundance derived from the hydrophilic group was calculated by setting the total area of the C1s spectrum obtained by X-ray photoelectron spectroscopy (the sum of the peak areas of the divided peaks to 100) as 100 It was calculated from the split peak of the carbon species derived from hydrophilicity obtained by the fitting and the peak split ratio.

(Equation 1)

Production Example Polystyrene (trade name: Daicel Styrol, manufactured by Daicel Chemical Industries, Ltd.) was supplied to an extruder, extruded from a T-die, and the extruded sheet was cast. After longitudinal stretching twice, the film was laterally stretched three times with a tenter at an oven temperature of 135 ° C. to obtain a biaxially stretched sheet having a thickness of 0.18 mm.

Example 1 On one side of the styrene resin sheet produced in the production example, 30 mg / m ² of sucrose fatty acid ester having 68 mol% of lauric acid, 30 mol% of monoester and 15.2 of HLB as a fatty acid component. , Viscosity is 20,000cs on one side
dimethylpolysiloxane silicone oil 20m
After applying g / m ² , it is dried and wound up with a tension of 20 kg / m. Thereafter, slitting was performed at a tension of 20 kg / m to obtain an antifogging styrene resin sheet. The surface carbon abundance ratio of the antifogging agent layer of the antifogging styrene resin sheet was calculated using X-ray photoelectron spectroscopy.

Example 2 On one surface of the styrene resin sheet produced in the production example, sucrose fatty acid ester of 25 mol / m ² containing 68 mol% of lauric acid, 30 mol% of monoester, and HLB of 15.2 as a fatty acid component, and having a viscosity of 25 mol / m ² . Is applied with 5 mg / m ² of 20,000 cst dimethylpolysiloxane silicone oil and 20 mg / m ^{2 of} silicone oil on one side, then dried and wound up at a tension of 20 kg / m. After that, 20kg
/ M, to obtain a styrene resin sheet having antifogging properties. The surface carbon abundance ratio of the antifogging agent layer of the antifogging styrene resin sheet was calculated using X-ray photoelectron spectroscopy.

Example 3 One side of the styrene resin sheet produced in the production example was decaglycerin laurate ester and the monoester was 66 m
ol%, a polyglycerol fatty acid ester having an HLB of 13.2 is 30 mg / m ² , and the viscosity is 20,000 cst on one side.
Dimethylpolysiloxane silicone oil 20mg
/ M ² , dried and wound up at a tension of 20 kg / m. Thereafter, slitting was performed at a tension of 20 kg / m to obtain an antifogging styrene resin sheet. The surface carbon abundance ratio of the antifogging agent layer of the antifogging styrene resin sheet was calculated using X-ray photoelectron spectroscopy.

Examples 4, 5, 6 The antifogging styrenic resin sheets of Examples 1, 2 and 3 were heated at a hot plate temperature of 130 ° C., and vacuum-pressed to 12 × 18 c.
m, a fitting lid material having a depth of 3 cm was obtained. The surface carbon abundance ratio of the anti-fogging agent layer of the fitting lid material was calculated using X-ray photoelectron spectroscopy.

COMPARATIVE EXAMPLE 1 One side of the styrene resin sheet produced in the production example was 20 mg / m ² of sucrose fatty acid ester containing 68 mol% of lauric acid, 30 mol% of monoester and 15.2 of HLB as a fatty acid component on one side. Dimethylcylsiloxane silicone oil with a viscosity of 20,000 cst
After applying m ² , it is dried and wound up at 20 kg / m. Thereafter, slitting was performed at 20 kg / m to obtain an antifogging styrene resin sheet. The surface carbon abundance ratio of the antifogging agent layer of the antifogging styrene resin sheet was calculated using X-ray photoelectron spectroscopy.

COMPARATIVE EXAMPLE 2 One side of the styrene resin sheet produced in the production example was a sucrose fatty acid ester containing 68 mol% of lauric acid, 30 mol% of monoester and HLB of 15.2 as a fatty acid component at 30 mg / m ² , 20,000 cst viscosity on one side
20m of dimethylpolysiloxane silicone oil
After applying g / m ² , it is dried and wound up at 40 kg / m. Thereafter, slitting was performed at 40 kg / m to obtain an antifogging styrene resin sheet. The surface carbon abundance ratio of the antifogging agent layer of the antifogging styrene resin sheet was calculated using X-ray photoelectron spectroscopy.

Comparative Example 3 One side of the styrene resin sheet produced in the Production Example was decaglycerin laurate ester and the monoester was 66 m
ol%, HLB is dried after the polyglycerol fatty acid ester 20 mg / m ² and a viscosity of 13.2 was applied silicone oil 10 mg / m ² of dimethylpolysiloxane 20000Cst, wound with 40 kg / m. Thereafter, slitting was performed at 40 kg / m to obtain an antifogging styrene resin sheet. The surface carbon abundance ratio of the antifogging agent layer of the antifogging styrene resin sheet was calculated using X-ray photoelectron spectroscopy.

Comparative Examples 4, 5, and 6 The antifogging styrene resin sheets of Comparative Examples 1, 2, and 3 were heated at a hot plate temperature of 130 ° C., and subjected to vacuum pressure air forming to form 12 × 18 c.
m, a fitting lid material having a depth of 3 cm was obtained. The surface carbon abundance ratio of the antifogging agent layer of the fitting lid material was measured by X-ray photoelectron spectroscopy.

Calculated using the X-ray photoelectron spectroscopy of Example 1-6 and Comparative Example 1-6. The measurement results are shown in Tables 1 and 2 above.

[0042]

The antifogging styrenic resin sheet of the present invention and the molded container obtained by molding from the antifogging styrenic resin sheet have a high level of antifogging property because of the above-mentioned constitution.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 3E035 AA15 BA05 BB03 BC02 BD10 CA04 4F006 AA15 AB03 AB39 BA10 CA07 DA04 4F100 AH02B AH02H AK12A AK52B CA10B DA02 EH46 GB16 GB23 JA20B JN01 YY00B 4F208 AA13 AGA MBA MK15

Claims (8)

[Claims] 1. An antifogging styrene resin sheet in which one surface of a styrene resin sheet is coated with an antifogging agent or a mixture of an antifogging agent and silicone oil, wherein the antifogging agent or The antifogging agent characterized in that the proportion of carbon derived from hydrophilic groups of the antifogging agent on the surface of the layer of the mixture of the antifogging agent and silicone oil is 30% or more and less than 60% of the total carbon present on the surface. Styrene resin sheet. 2. The antifogging styrene resin sheet according to claim 1, wherein the antifogging agent is a sucrose fatty acid ester. 3. The antifogging styrene resin sheet according to claim 1, wherein the silicone oil is dimethylpolysiloxane. 4. A molded container obtained by molding the antifogging styrene resin sheet according to claim 1. Description: 5. The molded container according to claim 4, which is obtained by molding by hot plate contact heating vacuum pressure molding. 6. The container according to claim 4, wherein the molded container is a food packaging container.
Or the molded container according to 5. 7. Carbon derived from the hydrophilic group of the antifogging agent on the surface of the layer of the mixture of the antifogging agent and the silicone oil in the molded container according to any one of claims 4 to 6. Wherein the abundance ratio of the carbon is 25% or more of the total carbon present on the surface. 8. Molding of a food packaging container or the like, wherein the antifogging styrene resin sheet according to any one of claims 1 to 3 is molded by a hot plate contact heating vacuum pressure molding method or the like. Container manufacturing method.