JP2000085069A - Antibacterial transparent resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially oriented laminated sheet of styrene resin, containing an antibacterial agent, which shows a high antibacterial effect without impairing basic performance as a sheet. SOLUTION: This antibacterial transparent resin sheet has a biaxially oriented polystyrene base material layer and at least, one piece of an antibacterial resin surface layer. In this case, the antibacterial resin surface layer contains dissolving glass particles containing a group IB element. Further, the product obtained by multiplying the total thickness of the antibacterial resin surface layer by the weight % of the dissolving glass particle content is 1.5 μm.wt.% or above and 25 μm.wt.% or below.

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 suitable as a molding material for a container for storing food, which maintains the inherent properties of a biaxially stretched styrene-based resin sheet, such as transparency, rigidity, and moldability, and exhibits an antibacterial effect. The present invention relates to a biaxially 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, food products may be affected by temperature and humidity during storage, and bacteria and fungi may proliferate, causing the contents to spoil.
For this reason, in recent years, various attempts have been made to impart antibacterial properties to various packaging materials. In other words, IB such as copper and silver
It is known that group metals have an antibacterial action, and a film containing a fine powder of a copper compound or a silver compound (Japanese Patent Laid-Open No. 61-138658) has been proposed by utilizing this performance. 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.

[0003]

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 Patent Application Laid-Open No. 2-258256 discloses, as an example, blending of 95 parts of low-density polyethylene, 1 part of a nucleating agent, and 4 parts of a soluble glass (containing 5% by weight of Ag ₂₀ ). After heating and melting, the thickness is 10 by the T-die method.
0 μm foamed polyethylene film, and a thickness of 2
Although a laminated film in which polyethylene having a thickness of 0 μm and nylon having a thickness of 15 μm are laminated is described, sufficient transparency cannot be obtained when a laminated film having such a thickness is applied to a styrene-based resin biaxially stretched sheet. The present invention, in view of the above disadvantages, stably exhibit antibacterial performance, and,
It is an object of the present invention to provide a biaxially stretched styrene-based resin sheet that does not impair transparency or sheet strength.

[0005]

Means for Solving the Problems The present inventors diligently studied to solve the above-mentioned problems, and the content of the soluble glass particles containing the antibacterial agent and the thickness of the antibacterial resin surface layer have a specific relationship. At this time, it was found that the above object could be satisfied, and the present invention was completed. 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 resin surface layer contains a group IB element. The product of the total thickness of the antibacterial resin surface layer and the content (% by weight) of the soluble glass particles is 1.5 μm ·% by weight or more and 25 μm ·% by weight or less. An antimicrobial transparent resin sheet characterized by the following.

[0006]

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 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)
The same styrene resin as that used for the base material layer (A) is used as the resin used in (1). Specifically, silver is preferable as the group IB element.

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 antibacterial agent (b1) concentration in the antibacterial resin layer (B) is 0.05 to 2% by weight,
Preferably it is 0.08 to 1.3% by weight. If the concentration of the antibacterial agent is less than 0.08%, a sufficient antibacterial effect may not be obtained. If the concentration exceeds 1.3%, the antibacterial effect is sufficient, but the transparency of the laminated sheet itself is reduced. Since the silver-glass antibacterial agent itself is expensive, it may not be practical and not suitable.

The thickness of the antibacterial resin layer (B) is from 10 to 200
μm, preferably 15 to 150 μm. When the thickness of the antibacterial resin layer (B) is small, the antibacterial resin layer may be broken at the time of thermoforming, which contributes to the dispersion of the antibacterial properties.
On the other hand, if it is too thick, it becomes difficult to expose an antibacterial agent having a particle size that is usually used to the sheet surface, so that the antibacterial effect is reduced and the transparency is also 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) preferably has a thickness of usually 15 to 60 μm, particularly preferably 20 to 40 μm.

Further, silver contained in the antibacterial resin layer (B)
The average particle size of the glass antibacterial agent (b1) is preferably in the range of 5 to 15 μm. If it is less than 5 μm, it becomes difficult to expose the antibacterial agent on the sheet surface. On the other hand, if it exceeds 15 μm, the roughness of the sheet surface becomes large, and the surface properties such as transparency are reduced. In the present invention, the product of the total of the thickness of the antimicrobial resin surface layer and the content% by weight of the soluble glass particles,
An essential requirement is 1.5 μm · weight% or more and 25 μm · weight% or less, and within this range, both transparency and antibacterial effect can be achieved. If necessary, an antimicrobial resin surface layer may be provided only on one surface of the base material layer, or may be provided on both surfaces. When provided on both surfaces, the product of the total thickness of the antimicrobial resin surface layer and the content% by weight of the soluble glass particles is 1.5
It may be at least μm · weight% and at most 25 μm · weight%. In order to obtain sufficient transparency, the product of the total thickness of the antibacterial resin surface layer and the content% by weight of the soluble glass particles is 15
It is preferably at most μm ·% by weight.

Further, the amount of the rubber-modified impact-resistant styrene resin blended in the antibacterial resin layer (B) of the present invention is 0.1.
The content is preferably from 1 to 4% by weight, more preferably from 0.2 to 4% by weight.
2% by weight. If the amount is less than 0.1% by weight, the releasability of the 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 styrenic resin used in the present invention 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.

The orientation relaxation stress is ASTM D-1.
504 was measured. In the sheet of the present invention,
The transparency of the sheet measured according to ASTM D-1003 is preferably 80% or more. More preferably,
Transparency is 90% or more. When the transparency is less than 80%, the appearance becomes poor when used as a food container.

The layer structure of the biaxially stretched styrenic resin laminated sheet of the present invention is not limited as long as the food storage side of the container becomes the antibacterial resin layer (B) when the container is molded. Those having a layer structure and a three-layer structure are preferred. Specifically, a two-layer structure of the antibacterial resin layer (B) / the base material layer (A),
Alternatively, a three-layer structure of an antimicrobial resin layer (B) / a base material layer (A) / an antimicrobial resin layer (B) may be used. 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 they are still in the 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 the biaxially stretched sheet made of the resin composition (b) for the conductive resin layer (B), and bonding these biaxially stretched sheets using an adhesive, etc. Is mentioned.

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 styrenic 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.

[0021]

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 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) Evaluation of antibacterial properties and transparency was performed by the following methods.

(1) Evaluation method of antibacterial property The obtained biaxially stretched 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 air-dried to obtain a sample. 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. These were stored at 35 ° C., and the viable cell count of the sample 24 hours after storage was measured, and expressed by the following evaluation criteria.

[0024]

[Table 1]: <10 △: 10 or more and less than 10 ³ ×: 10 ³ or more

(2) Method of Evaluating Transparency The light transmittance of the sheet was measured in accordance with ASTM D-1003, and the ratio to the transmittance (100) in the absence of a sample was expressed by the following evaluation criteria.

[0026]

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

Example 1 GPPS was used as the styrene resin (a) for the base material layer (A).
Using 100 parts, the antibacterial resin layer (B) is GPPS,
100 parts of a composition (b) was used in which the silver-glass antibacterial agent (b1) was 0.1% and the rubber-modified impact-resistant styrene resin (b2) was 1%. Next, using two extruders, a feed block for two kinds and two layers and a T die were attached thereto, and the GPPS charged into each extruder and the blended pellet (b) were coextruded to form a 1.3 mm-thick. An unstretched two-layer sheet is obtained, and then the unstretched two-layer sheet is rolled by a roll-type longitudinal stretching machine, and then by a tenter transverse stretching machine.
By stretching about 2.5 times in the vertical direction and about 2.5 times in the horizontal direction, the thickness of the base material layer (A) is 190 μm, the thickness of the antibacterial resin layer (B) is 20 μm, and the total thickness is 210 μm. An axially stretched sheet was obtained. With respect to the obtained biaxially stretched sheet, the orientation relaxation stress was measured in accordance with ASTM D-1504. As a result, it was 6.0 kg / cm ² . The obtained biaxially stretched sheet was evaluated for antibacterial properties and transparency. The results obtained 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 also 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 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 5 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 7 μm. Was. Table 1 shows the evaluation results. Example 6 In Example 1, an unstretched sheet was obtained by changing to a feed block for two kinds and three layers, and subsequently stretched lengthwise and widthwise to obtain a base layer (A) having a thickness of 170 μm and antibacterial resin layers on both sides thereof A three-layer biaxially stretched sheet (B) having a thickness of 20 μm and a total thickness of 210 μm was obtained. Table 1 shows the evaluation results.

Example 7 In Example 6, an unstretched sheet was prepared by changing the extrusion ratio of two extruders, and then stretched lengthwise and widthwise to obtain a base material layer (A) having a thickness of 110 μm. A three-layer biaxially stretched sheet having a thickness of 50 μm on both sides of the antibacterial resin layer (B) and a total thickness of 210 μm was obtained. Table 1 shows the evaluation results.

Example 8 In Example 6, the antimicrobial agent (b) in the antimicrobial resin layer (B) was used.
Example 6 except that the average particle size of 1) was changed to 7 μm.
In the same manner as described above, the thickness of the base material layer (A) is 170 μm, the thickness of the antibacterial resin layer (B) on both sides thereof is 20 μm, and the total thickness is 210 μm.
A three-layer biaxially stretched sheet of μm was obtained. Table 1 shows the evaluation results.

Example 9 In Example 1, a non-stretched sheet was obtained by changing to a feed block for two and three layers, and subsequently stretched lengthwise and widthwise to obtain a base material layer (A) having a thickness of 190 μm, An antimicrobial resin layer (B) having a thickness of 10 μm and a total thickness of 210 μm was obtained as a three-layer biaxially stretched sheet. Table 1 shows the evaluation results.

Comparative Example 1 GPPS was used as the styrene resin (a) of the base material layer (A), and the antibacterial resin layer (B) contained a silver-glass antibacterial agent (b1) and rubber particles (b2). Without compounding, only GPPS was used. These were extruded using two extruders,
The unstretched sheet having a thickness of 1.3 mm was obtained by co-extrusion using a layer feed block and a T-die. The sheet was stretched 5 times and about 2.5 times in the transverse direction to obtain a biaxially stretched sheet having a total thickness of 210 μm. The evaluation results of the obtained biaxially stretched sheet are shown in Table 1.

Comparative Example 2 In Example 1, the antimicrobial agent (b) in the antimicrobial resin layer (B) was used.
A two-layer biaxially stretched sheet was obtained in the same manner as in Example 1 except that the amount of 1) was changed to 0.07%. Table 1 shows the evaluation results. Comparative Example 3 In Example 1, the antibacterial agent (b) in the antibacterial agent resin layer (B) was used.
A two-layer biaxially stretched sheet was obtained in the same manner as in Example 1, except that the amount of 1) was changed to 1.5%. First evaluation result
It is shown in the table.

[0036]

[Table 3]

[0037]

The biaxially stretched styrene-based resin sheet having antibacterial properties obtained by the present invention has a high antibacterial effect without impairing the basic performance, particularly transparency, of the conventional biaxially stretched styrene-based resin sheet. It can be played efficiently.

 ──────────────────────────────────────────────────の Continuing on the front page F term (reference) 4F100 AA36B AA36C AB17B AB17C AB17H AB25B AB25C AB25H AG00B AG00C AG00H AK01B AK01C AK12A BA02 BA03 BA06 BA10B BA10C BA13 DE01B DE01C DE01H EH20 EJ38A00 J00B00 J20Y00 J20Y00 J00YC BC041 BC061 BC071 BC081 BC091 BC111 BH011 BN141 BN142 DA076 DL006 FD186 GF00 GG01

Claims (4)

[Claims] 1. An antibacterial transparent resin sheet having a biaxially oriented polystyrene base layer and at least one antibacterial resin surface layer, wherein the antibacterial resin surface layer contains a IB group-containing solution. The product of the total thickness of the antibacterial resin surface layer and the content (% by weight) of the soluble glass particles is not less than 1.5 μm ·% by weight and not more than 25 μm ·% by weight. An antibacterial transparent resin sheet characterized by the following. 2. The antibacterial transparent resin sheet according to claim 1, wherein an antibacterial resinous surface layer is provided on both sides of the biaxially oriented polystyrene base material layer. 3. The antibacterial transparent resin sheet according to claim 1, wherein the product of the total thickness of the antibacterial resin surface layer and the content% by weight of the soluble glass particles is 15 μm ·% by weight or less. . 4. An alignment relaxation stress of 3 kg / cm ² or more,
Antibacterial transparent resin sheet according to any one of claims 1 to 3, characterized in that 0 kg / cm ² or less.