JP2000085070A - Antibacterial transparent resin sheet - Google Patents

Abstract

(57) [Problem] To provide a biaxially stretched laminated sheet of a styrene-based resin containing an antibacterial agent, which exhibits a high antibacterial effect without impairing the basic performance as a styrene sheet. SOLUTION: An antibacterial layer is provided on one or both sides of a biaxially stretched styrene resin sheet, and the antibacterial layer has an average particle size of 7 μm.
As described above, soluble glass particles containing a Group IB element of 17 μm or less are blended.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a transparent resin sheet having antibacterial properties, and more particularly to a biaxially stretched laminated sheet of a styrene resin. More specifically, a styrene-based resin biaxially stretched styrene-based resin suitable as a molding material for a container for storing a food exhibiting an antibacterial effect while maintaining the inherent properties of the biaxially stretched styrene-based resin sheet such as transparency, rigidity, and moldability. The present invention relates to an axially stretched laminated sheet.

[0002]

2. Description of the Related Art Conventionally, biaxially stretched polystyrene resin sheets have excellent transparency, rigidity and moldability.
Widely used as packaging materials for various food products. However, in food applications, bacteria and molds are propagated under the influence of temperature and humidity during storage, and the contents may be spoiled.

[0003] For this reason, various attempts have recently been made to impart antibacterial properties to various packaging materials. That is, it is conventionally known that metals such as copper and silver have an antibacterial effect,
Utilizing this performance, a film containing a fine powder of a copper compound or a silver compound (JP-A-61-138658) has been proposed. JP-A-2-258256 discloses an invention relating to a film in which a layer in which particles obtained by blending a compound capable of eluting copper ions and / or silver ions into a soluble glass are dispersed on one side and / or both sides. Is described.

[0004]

However, in order to obtain antibacterial properties, a large amount of fine powder of a metal compound must be added, and when added to a biaxially stretched styrene resin sheet, the most advantageous of the styrene sheet is obtained. There has been a problem that transparency, which is a characteristic feature, is impaired, and the sheet strength is also reduced.

For example, Japanese Unexamined Patent Publication No. Hei.
In the report, as an example, 95 parts of low density polyethylene and core
1 part of forming agent and 4 parts of melting glass (average particle diameter 3 μm;
Ag _Two 0 to 5% by weight), and after heating and melting, T
-Foamed polyethylene fill of 100 μm thickness by die method
And 20 μm thick polyethylene, 15
The laminated film laminated with μm nylon is described.
However, a laminated film of such a thickness is
When applied to an axially stretched sheet, sufficient transparency cannot be obtained.
Not. In view of the above disadvantages, the present invention is stable and antibacterial.
Demonstrates performance and does not impair transparency or sheet strength
With the aim of providing a biaxially stretched styrene-based resin sheet
Is what you do.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, have found that the present invention is a soluble glass particle containing a group IB element such as silver and has a moderate average particle diameter. The present inventors have found that a sheet exhibiting a sufficient antibacterial effect can be obtained by using the antibacterial particles without impairing the transparency of the styrene resin, and have reached the present invention. That is,
The gist of the present invention is an antibacterial transparent resin sheet having a biaxially oriented polystyrene base material layer and at least one antibacterial resin surface layer, wherein the antibacterial resinous fat surface layer contains a group IB element. The antibacterial transparent resin sheet is characterized in that it contains soluble glass particles, and the average particle size of the soluble glass particles is 7 μm or more and 17 μm or less.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The styrenic resin biaxially stretched laminated sheet of the present invention has a base material layer (A) composed of a styrenic resin (a). The styrene resin (a) is not particularly limited,
Conventionally known various styrene resins can be appropriately selected and used. Representative examples include styrene such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, dimethylstyrene, α-methylstyrene, p-chlorostyrene, and 2,4-dichlorostyrene, and singly composed of derivatives thereof. At least one of a polymer, a copolymer, styrene or the above styrene derivative
Binary, ternary or quaternary or higher copolymers of the species with other monomers copolymerizable with these polymers are mentioned. In addition, a mixed composition in which two or more of these polymers are mixed is exemplified.

Other copolymerizable monomers include methacrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate and butyl methacrylate; methyl acrylate, ethyl acrylate, propyl acrylate and acrylic Acrylates such as butyl acrylate; unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile; unsaturated carboxylic anhydrides such as maleic anhydride and itaconic anhydride; unsaturated carboxylic acids such as acrylic acid and methacrylic acid; No.

Further, there may be mentioned an impact-resistant styrene resin modified by adding a small amount of a rubber component to the above homopolymer, copolymer or mixed resin composition.
Among these, polystyrene, styrene-acrylonitrile copolymer, copolymer of styrene and methyl methacrylate, copolymer of styrene and α-methylstyrene,
Copolymers of styrene and maleic anhydride, copolymers of styrene and acrylic acid, and rubber-modified products thereof are preferred. Particularly, homopolymers of styrene (general-purpose polystyrene) are excellent in transparency and available. Is most preferable because it is easy and inexpensive.

The base material layer (A) has a thickness of 80 to 700 μm.
m, more preferably 100 to 50
0 μm. When the thickness is less than 80 μm, the rigidity of the entire laminated sheet when formed is reduced, and may not be practically used as a food storage container. The styrene-based resin biaxially stretched laminated sheet of the present invention has an antibacterial resin layer (B) formed on at least one surface of the base material layer (A) and exhibits an antibacterial effect when used as a food storage container. I do.

This antibacterial resin layer (B) contains an antibacterial agent (b1) composed of soluble glass particles containing a group IB element, and usually further contains rubber particles having a weight average particle diameter of 1 to 10 μm. Rubber-modified impact-resistant styrenic resin (b
It is composed of a resin obtained by mixing 2). (B)
As the resin to be used, a styrene resin similar to the base layer (A) is usually used. As the IB group element,
Specifically, silver is preferred.

As the antibacterial agent (b1), commercially available glass particles obtained by blending a compound capable of eluting silver ions into a soluble glass are preferably used. The concentration of the silver-glass antibacterial agent in the antibacterial resin layer (B) is 0.05 to 2%, preferably 0.08 to 1.3%. And the thickness of the antibacterial resin layer (B) is 10 to 200 μm, preferably 15 to 150 μm.
It is. When the concentration of the antibacterial agent is less than 0.08%, a sufficient antibacterial effect may not be obtained. When the concentration exceeds 1.3%, the antibacterial effect is sufficient, but the transparency of the laminated sheet itself may be reduced. In addition, since the silver-glass antibacterial agent itself is expensive, it is not practical and not suitable.

In the present invention, the silver-glass antibacterial agent (b1) contained in the antibacterial resin layer (B) has an average particle diameter of 7 to 17 μm. If the average particle size is less than 7 μm, it becomes difficult to expose the antibacterial agent to the sheet surface, and a sufficient antibacterial effect cannot be obtained. On the other hand, when the particle size exceeds 17 μm, the roughness of the sheet surface is increased, and the surface properties such as transparency are reduced. It is preferable that the thickness of the antibacterial resin layer (B) is appropriately selected depending on the use of the container to be molded in relation to the thickness of the base material layer (A).
For example, when the thickness of the base material layer (A) is 180 to 250 μm, the antibacterial resin layer (B) usually has a thickness of 15 to 60 μm,
Particularly, the thickness is preferably 20 to 40 μm.

The thickness of the antibacterial resin layer (B) is from 10 to 200
μm, more preferably 15 to 1 μm.
50 μm. If it is less than 10 μm, the antibacterial resin layer may be broken at the time of thermoforming, which may contribute to antibacterial dispersion. On the other hand, if it exceeds 200 μm, it becomes difficult to expose the antibacterial agent having the above particle size to the sheet surface, and the antibacterial effect may be reduced.

The amount of the rubber-modified impact-resistant styrenic resin blended in the antibacterial resin layer (B) of the present invention is preferably 0.1 to 4% by weight, more preferably 0.2 to 2% by weight.
It is. If it is less than 0.1% by weight, the releasability as a food storage container is not improved, and if it exceeds 4% by weight, the transparency of the obtained laminated sheet is undesirably reduced. The rubber particles in the rubber-modified impact-resistant styrene resin preferably have a weight average particle diameter of 1 to 10 μm. More preferably, it is 1 to 5 μm. If the particle size is too small, the releasability of the food storage container will not be improved, and if it is too large, the transparency of the obtained laminated sheet will be reduced. The weight average particle diameter of the rubber particles was measured by a Coulter counter (manufactured by Coulter Electronics, USA).

The rubber content of the rubber-modified impact-resistant styrene resin is preferably 3 to 15% by weight. More preferably, it is 6 to 10% by weight. If the rubber content is too low, the releasability of the food storage container will not be improved, and if it is too high, the transparency of the sheet will decrease, which is not preferable. The biaxially stretched styrenic resin laminated sheet of the present invention is stretched such that the orientation relaxation stress is 3 to 10 kg / cm ^{2 in} both the flow direction and the direction perpendicular thereto, and has both strength and formability. . If the orientation relaxation stress is less than 3 kg / cm ² , a molded product having practical strength cannot be obtained, and if it exceeds 10 kg / cm ² , only a molded product having poorly determined mold can be obtained. Note that the orientation relaxation stress is A
It measured according to STM D-1504.

In the sheet of the present invention, ASTM D-
The transparency of the sheet measured according to 1003 is preferably at least 70%. More preferably, the transparency is 80%.
That is all. If the transparency is less than 70%, the appearance becomes poor when used as a food container. The layer structure of the biaxially stretched styrene-based resin laminate sheet of the present invention is such that the food storage side of the container is the antibacterial resin layer (B) when the container is subjected to molding.
There is no particular limitation as long as it is satisfied, but a two-layer structure and a three-layer structure are preferable. Specifically, a two-layer structure of the antibacterial resin layer (B) / base layer (A), or a three-layer structure of antibacterial resin layer (B) / base layer (A) / antibacterial resin layer (B) Structure. With such use, the two-layer structure exhibits antibacterial properties on the inner surface of the container, and the three-layer structure exhibits antibacterial effects on the inner surface of the container and the outer surface of the container.

If necessary, an adhesive layer and a recycled product may be used within a range that does not impair the characteristics of the present invention.
% Or an additional layer made of another resin may be added. The biaxially stretched styrenic resin laminated sheet of the present invention is prepared by preparing a styrenic resin (a) for the base material layer (A) and a resin composition (b) for the antibacterial resin layer (B), respectively. It can be easily manufactured according to a more well-known method for manufacturing a biaxially stretched laminated sheet. Specifically, (a) a styrene resin (a) and a resin composition (b) are melt-extruded from two extruders, respectively, and a two-layer or three-layer multilayer T
A method of obtaining the unstretched laminated sheet having the two-layer structure or the three-layer structure by a die, and then stretching the sheet in the biaxial direction by a conventionally known method. (B) Using two extruders, respectively, using a styrene resin (a ) And the resin composition (b) are melt-extruded, and the base material layer (A) is formed by two or three single-layer T dies.
And one or two molten sheets for the antibacterial resin layer (B) are obtained separately, and they are pressure-bonded and laminated while still in a molten state to form the two-layer structure or the three-layer structure. A method of obtaining an unstretched laminated sheet having a layer structure and then stretching in a biaxial direction by a conventionally known method, (c) a biaxially stretched sheet made of a styrene resin (a) for the base material layer (A), and antibacterial A method of separately producing two types of biaxially stretched sheets of a biaxially stretched sheet composed of the resin composition (b) for the conductive resin layer (B), and bonding these biaxially stretched sheets using an adhesive;
And the like.

Further, an antifogging agent, a release agent, an antistatic agent and the like can be applied alone or as a mixture to the biaxially stretched styrene resin laminate sheet of the present invention. It is preferable to use a sucrose fatty acid ester as an anti-fogging agent from the viewpoint of safety for stored food, and it is effective to use a dimethyl silicone emulsion as a release agent. As a coating method, various types of coating apparatuses such as a roll coater and a spray coater used for normal coating can be used.

[0020]

Next, the present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited to the description of these examples unless it exceeds the gist of the present invention. In addition,
In the following examples, “%” and “parts” mean by weight unless otherwise specified. The resins used in the examples and comparative examples are as follows. Styrene resin (a): manufactured by Mitsubishi Chemical Corporation, trade name Dialex HH-102 (hereinafter referred to as GPPS) Silver-glass antibacterial agent (b1): manufactured by Koa Glass Co., Ltd., trade name: biocomposite glass fine particles Rubber-modified impact-resistant styrenic resin (b2): manufactured by Mitsubishi Chemical Corporation, trade name Dialex HT-516 (weight average particle diameter of rubber particles 4 μm, rubber content 7.5%) (hereinafter referred to as HIPS) , Antibacterial properties and transparency were evaluated by the following methods.

(1) Evaluation method of antibacterial activity The obtained biaxially stretched laminated sheet was cut into a square having a side of about 5 cm, and the surface was lightly wiped with absorbent cotton impregnated with ethanol, and then air-dried. 0.5 ml of Escherichia coli and Staphylococcus aureus bacterial solutions were each dropped onto the sample, and a polyethylene film was covered thereon and brought into close contact with each other. This was stored at 35 ° C., and the viable cell count of the sample after 24 hours of storage was measured and expressed by the following evaluation criteria.

[0022]

[Table 1]: <10 △: 10 or more and less than 10 ² ×: 10 ² or more

(2) Method for Evaluating Transparency The light transmittance of the obtained biaxially stretched sheet was measured according to ASTM D.
The measurement was carried out in accordance with -1003, and the ratio to the transmittance (100%) when there was no sample was represented by the following evaluation criteria.

[0024]

[Table 2] ○: 90% or more △: 80% or more, less than 90% ×: less than 80%

Example 1 As a styrene resin (a) for the base material layer (A), GPPS was used.
Using 100 parts, the antibacterial resin layer (B) is GPPS,
100 parts of a composition (b) containing 0.1% of the silver-glass antibacterial agent (b1) and 1% of the rubber-modified impact-resistant styrene resin (b2) was used. Next, using two extruders, a feed block for two kinds and two layers and a T-die were attached thereto, and the GPPS charged in each extruder and the blended composition (b) were coextruded to a thickness of 1.3 mm. , And subsequently, the unstretched two-layer sheet is stretched about 2.5 times in the longitudinal direction and about 2.5 times in the transverse direction by a roll type longitudinal stretching machine and then a tenter transverse stretching machine. Thus, a biaxially stretched sheet having a thickness of 190 μm of the base material layer (A), a thickness of 20 μm of the antibacterial resin layer (B), and a total thickness of 210 μm was obtained. About the obtained biaxially stretched sheet,
The orientation relaxation stress was measured according to ASTM D-1504. As a result, it was 6.0 kg / cm ² . Then
The obtained biaxially stretched sheet was evaluated for antibacterial properties and transparency. The results are shown in Table 1.

Example 2 In Example 1, an unstretched sheet was prepared by changing the extrusion ratio of the two extruders, and then stretched lengthwise and widthwise to obtain a base material layer (A) having a thickness of 110 μm and an antibacterial property. A biaxially stretched sheet having a thickness of 100 μm of the conductive resin layer (B) and a total thickness of 210 μm was obtained. Table 1 shows the evaluation results.

Example 3 In Example 1, the antibacterial agent (b) of the antibacterial resin layer (B) was used.
A two-layer biaxially stretched sheet was obtained in the same manner except that the amount of 1) was changed to 1%. Table 1 shows the evaluation results. Example 4 In Example 1, the antibacterial agent (b) of the antibacterial resin layer (B) was used.
A two-layer biaxially stretched sheet was obtained in the same manner except that the blending amount of 1) and the thickness ratio of the layers (B) and (A) were changed. Table 1 shows the evaluation results.

Example 5 In Example 1, the amount of HIPS (b2) was changed to 3.5.
% In the same manner as in Example 1 except that the biaxially stretched sheet was obtained. Table 1 shows the evaluation results. Example 6 A two-layer biaxially stretched sheet was obtained in the same manner as in Example 1, except that HIPS (b2) was changed to HIPS having an average particle diameter of 1.8 μm. Table 1 shows the evaluation results.

Example 7 A two-layer biaxially stretched sheet was obtained in the same manner as in Example 1, except that the average particle size of the antimicrobial agent particles in the antimicrobial resin layer (B) was changed to 7 μm. Was. Table 1 shows the evaluation results. Example 8 A two-layer biaxially stretched sheet was obtained in the same manner as in Example 1, except that the average particle size of the antibacterial agent particles in the antibacterial resin layer (B) was changed to 13 µm. Table 1 shows the evaluation results.

Example 9 In Example 1, an unstretched sheet was prepared by changing the extrusion amount of two units, and subsequently stretched lengthwise and widthwise to obtain a base material layer (A) having a thickness of 405 μm and an antibacterial resin layer ( A biaxially stretched sheet of B) having a thickness of 45 μm and a total thickness of 450 μm was obtained. Table 1 shows the results of evaluation performed in the same manner as in Example 1.

Example 10 In Example 1, the antibacterial agent (b) of the antibacterial resin layer (B) was used.
The thickness of the base material layer (A) was changed by changing the compounding amount of 1) to 1%, changing the extruding amount ratio of the two extruders to prepare an unstretched sheet, and subsequently stretching the sheet vertically and horizontally. 405μ
m, the thickness of the antimicrobial resin layer (B) is 45 μm, and the total thickness is 45
A two-layer biaxially stretched sheet of 0 μm was obtained. Table 1 shows the results of evaluation performed in the same manner as in Example 1.

Example 11 In Example 1, an unstretched sheet was obtained by changing to a feed block for two and three layers, and then stretched lengthwise and widthwise to obtain a base layer (A) having a thickness of 170 μm and antibacterial properties on both sides thereof. A three-layer biaxially oriented sheet having a thickness of the conductive resin layer (B) of 20 μm and a total thickness of 210 μm was obtained. Table 1 shows the results of evaluation performed in the same manner as in Example 1.

Example 12 In Example 11, an unstretched sheet was prepared by changing the extrusion ratio of two extruders, and subsequently stretched lengthwise and widthwise to obtain a base material layer (A) having a thickness of 110 μm. The thickness of the antimicrobial resin layers (B) on both sides is 50 μm, and the total thickness is 210 μm
To obtain a three-layer biaxially stretched sheet. Table 1 shows the evaluation results.

Example 13 In Example 11, the antibacterial agent (b) of the antibacterial resin layer (B) was used.
Except that the amount of 1) was changed to 1%, in the same manner as in Example 11, the thickness of the base layer (A) was 170 μm, the thickness of the antibacterial resin layers (B) on both sides was 20 μm, and the total thickness was 210 μm.
A biaxially stretched sheet of layers was obtained. Table 1 shows the evaluation results.

Example 14 In Example 11, the antibacterial agent (b) of the antibacterial resin layer (B) was used.
By changing the blending amount of 1) to 1%, changing the extruding amount ratio of the two extruders to prepare an unstretched sheet, and subsequently stretching the sheet vertically and horizontally, the thickness of the base material layer (A) is 110 μm, The antimicrobial resin layers (B) on both sides have a thickness of 50 μm and a total thickness of 2
A 10-μm three-layer biaxially stretched sheet was obtained. Table 1 shows the evaluation results.

Example 15 In Example 11, the antibacterial agent (b) of the antibacterial resin layer (B) was used.
Example 1 except that the average particle size of 1) was changed to 7 μm.
1, the thickness of the base layer (A) was 170 μm, the thickness of the antibacterial resin layer (B) on both sides was 20 μm, and the total thickness was 21 μm.
A three-layer biaxially stretched sheet of 0 μm was obtained. First evaluation result
It is shown in the table.

Example 16 In Example 11, the antibacterial agent (b) of the antibacterial resin layer (B) was used.
Except that the average particle size in 1) was changed to 13 μm, the thickness of the base layer (A) was 170 μm, the thickness of the antibacterial resin layer (B) on both sides was 20 μm, and the total thickness was 2 in the same manner as in Example 11.
A 10-μm three-layer biaxially stretched sheet was obtained. Table 1 shows the evaluation results.

Comparative Example 1 A two-layer biaxially stretched sheet was obtained in the same manner as in Example 1, except that the average particle size of the antimicrobial agent particles in the antimicrobial resin layer (B) was changed to 5 μm. Was. Table 1 shows the evaluation results. Comparative Example 2 A two-layer biaxially stretched sheet was obtained in the same manner as in Example 1, except that the average particle size of the antibacterial agent particles in the antibacterial resin layer (B) was changed to 20 μm. Table 1 shows the evaluation results.

[0039]

[Table 3]

[0040]

The biaxially stretched styrene-based resin sheet having antibacterial properties obtained by the present invention impairs the transparency, moldability, rigidity, etc., which are the basic performances of the conventional biaxially stretched styrene-based resin sheet. And a high antibacterial effect can be efficiently exhibited.

 ──────────────────────────────────────────────────の Continuing on the front page F term (reference) 4F100 AA17H AA25H AA36B AA36C AA36H AB17B AB17C AB25B AB25C AG00B AG00C AG00H AK01B AK01C AK12A BA02 BA03 BA06 BA10B BA10C BA13 DE01B DE01C DE01H EH20J01 JE20C 4J002 BC031 BC041 BC061 BC071 BC081 BC091 BC111 BN141 BN142 DA076 DL006 FD186 GF00 GG01

Claims (1)

[Claims] 1. An antibacterial transparent resin sheet having a biaxially stretched polystyrene base layer and at least one antibacterial resin surface layer, wherein the antibacterial resin surface layer contains a IB group-containing soluble material. An antibacterial transparent resin sheet containing glass particles, wherein the average particle size of the soluble glass particles is 7 μm or more and 17 μm or less.