JP2006002162A - Styrenic resin sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin sheet roll imparting anti-fogging properties, sliding properties and releasability to a styrenic resin sheet and molded containers thereof, almost free from whitening of moldings and giving a container excellent in transparency, and to provide a method for producing the resin sheet roll. <P>SOLUTION: The anti-fogging styrenic resin sheet roll is covered, on one side by turns from the surface of the styrenic resin when rewinding the sheet roll, with 5-50 mg/m<SP>2</SP>anti-fogging agent and silicone oil thereon, and on the other side, substantially only with a silicone oil, wherein total silicone oil amount is within 1-50 mg/m<SP>2</SP>and silicone oil amount on the anti-fogging agent is 0-48%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an antifogging styrene-based resin sheet roll which is thermoformed mainly by a hot plate contact heating vacuum / pressure forming method and used as various packaging containers including food packaging containers and a method for producing the same.

  Conventionally, it is described in Patent Documents 1 to 4 and the like that a styrenic resin sheet is coated with an antifogging agent and silicone oil to impart antifogging properties and improve slipperiness, releasability, and the like. .

  In these methods, a mixture of an antifogging agent mainly composed of sucrose fatty acid ester and silicone oil is used to impart antifogging property, slipperiness and releasability to a styrene resin sheet, and the mixed solution is applied on one side. It is applied to. For example, in Patent Document 1, the surface tension is adjusted to 40 to 55 dynes / cm by corona discharge treatment for the purpose of simultaneously improving the non-blocking property and the antifogging property, and the antifogging agent and the silicone oil are uniformly attached. There is a proposed method. In Patent Document 2, for the purpose of improving antistatic properties in addition to antifogging properties and releasability, the surface tension of the sheet surface is adjusted to 50-60 dynes / cm by corona discharge treatment, and then sucrose. A method of applying a mixed solution of fatty acid ester, silicone oil, and coconut oil fatty acid diethanolamide has been proposed. Furthermore, Patent Document 3 and Patent Document 4 describe that the continuous antifogging property is improved and an antifogging film (sucrose fatty acid ester coating film) and a release film (silicone emulsion coating film) at the time of thermoforming, particularly at deep drawing. For the purpose of improving the anti-fogging property of molded products by preventing cutting, a method of applying a mixed solution of a sucrose fatty acid ester, a hydrophilic polymer and a silicone emulsion to a styrene resin sheet has been proposed.

  Sheets coated by such a method are usually rolled up and then thermoformed and used in large quantities as various containers, including food packaging. As a thermoforming method for a styrene-based resin sheet, particularly a biaxially stretched sheet, a method called a hot plate contact heating vacuum / pressure forming method (hereinafter referred to as hot plate / pressure forming) is generally employed. In most thermoforming methods, a sheet stretched in space is heated without contact, such as by radiant heating, but this method adheres the sheet to the hot plate by means of compressed air pressure from the mold side and vacuum pressure from the hot plate side. This is a method in which the sheet heated by the compressed air pressure from the hot plate side and the vacuum pressure from the mold side is pressed against the mold immediately after heating. At this time, the antifogging surface of the sheet is generally on the inner side of the molding container, that is, on the hot plate contact side.

The above-described conventional invention has been made in order to impart antifogging properties and releasability to a styrene resin sheet that is molded into a container mainly by a hot plate pressure forming method.
Japanese Patent Laid-Open No. 53-115781 Japanese Examined Patent Publication No. 61-36864 Japanese Examined Patent Publication No. 63-62538 JP-A-5-287097

Polystyrene-based resin sheets, especially biaxially-oriented polystyrene-based sheets, are widely used for various packaging materials, including food packaging applications, because they have high transparency, gloss, and elasticity (rigidity) compared to other materials. Is used. However, a polystyrene resin sheet mixed with a conventional anti-fogging agent and silicone oil and applied to the sheet surface is excellent in transparency and gloss at the sheet stage, but is whitened in a molded container after hot plate compression molding. There is a defect that transparency is lowered due to generation of a pattern and appearance defects (hereinafter, this phenomenon is referred to as molding whitening) often occur, and the characteristic transparency and gloss are lowered.
An object of the present invention is to provide a styrene-based resin sheet roll that does not cause such molding whitening phenomenon, and a method for producing the same.

  As a result of intensive studies, the inventor of the present invention tends to cause whitening of the styrene resin sheet during hot plate compression molding due to the interaction between the surface of the styrene resin sheet hot plate contact surface and the silicone oil during molding heating. As a result, the present invention was completed through further studies based on this finding.

That is, the present invention
(1) In the anti-fogging agent and antifogging styrenic resin sheet silicone oil is coated, anti-fogging agent on one side is coated at a coverage of 5 to 50 mg / m ^2, on the antifogging agent and the opposite surface A styrene-based resin sheet that is coated with silicone oil, the total coating amount of the silicone oil is 1 to 50 mg / m ² , and satisfies the following conditions:
0.05 ≦ A / (A + B) ≦ 0.48
(However, A is the amount of silicone oil coating on the anti-fogging agent, B is the amount of silicone oil coating on the opposite side)
(2) The antifogging agent is selected from a mixture of sucrose fatty acid ester and sucrose fatty acid ester (99 to 50% by weight) and polyglycerin fatty acid ester or sorbitan fatty acid ester (1 to 50% by weight). The present invention relates to the styrene-based resin sheet for hot plate pressure forming described in 1 above.

  Since the sheet of the present invention is less likely to be whitened during hot plate compression molding, it provides a molded product with superior transparency compared to a molded product from a conventional sheet, and is also antifogging, slippery and releasable. There is an excellent effect. For this reason, it can be suitably used as a styrene resin sheet for forming various packaging containers including food packaging containers, particularly as a styrene resin sheet for hot plate pressure forming.

The present invention will be described in detail below.
Sheet roll of the present invention, one surface when rewound sheet rolls are anti-fogging agent is 5 to 50 mg / m ² coated on the styrene resin is a silicone oil 0~24mg / m ² coated thereon (Hereinafter, this surface is referred to as an anti-fogging surface), that is, the anti-fogging surface of the sheet roll of the present invention is placed between the two so that the styrenic resin and the silicone oil do not come into direct contact when unrolled. The anti-fogging agent is interposed between the two and the transfer amount is controlled (as a masking film). Thus, when the sheet roll of the present invention is rewound, one side is coated with the antifogging agent in order from the resin surface and further coated with silicone oil, and the opposite side is coated with only silicone oil. This structure prevents the interaction due to the direct contact between the styrene resin and the silicone oil, and is a molded container that keeps the transparency and gloss of the styrene resin sheet at a high level, which is the object of the present invention (mold whitening hardly occurs) Container). On the other hand, in the conventionally known sheet, an antifogging agent and silicone oil are mixed and coated on the styrene resin. That is, in the conventionally known sheet, since the silicone oil and the styrene resin are in direct contact with each other, even if the coating amounts of the antifogging agent and the silicone oil coincide with the sheet of the present invention, the styrene resin and the silicone oil Due to this interaction, the thermoformed product obtained by the hot plate compression molding method has a drawback that whitening is likely to occur.

  For example, when the numerical value evaluation is performed by the same method as the molding whitening evaluation method performed in the example without forming the sheet roll of Example 1 and the sheet roll of Comparative Example 1, both sheets are maximum. The line number was equivalent to an average of 180. However, the maximum numerical value of the container after hot plate compression molding shows an average value of 50 for the molded container from the sheet roll of Example 1 compared to the average of 110 for the molded container from the sheet roll of Example 1. Met. Also from this result, the drawbacks of the above-described conventional sheet and the effects of the present invention are clear.

  In the sheet roll of the present invention, for example, the antifogging agent is applied after corona treatment on one side of the sheet, the silicone oil is applied to the opposite side, and the silicone oil is prevented from being wound up in a roll shape. It is obtained by controlling the transfer onto the clouding agent surface. This makes it possible to corona-treat the sheet roll resin surface to make it hydrophilic, thereby preventing the transfer of the antifogging agent to the opposite surface, and uniformly covering the sheet roll resin surface with the antifogging agent. .

  The sheet roll of the present invention adopts the concept of two-stage drying, controls the transfer amount of silicone oil by combining with the corona treatment of the sheet surface by sufficiently drying before winding into a roll shape, and is not subject to double-sided This is achieved by controlling the transfer accurately and uniformly.

Next, the sheet roll of this invention is demonstrated.
The coating amount of the antifogging agent that directly covers one surface (antifogging surface) of the sheet roll of the present invention is 5 to 50 mg / m ² . If the coating amount of the antifogging agent is less than 5 mg / m ² , sufficient antifogging effect cannot be obtained, and the thickness of the silicone oil masking film is insufficient, and a part of the silicone oil is in direct contact with the styrene resin. This is a region that may cause whitening during molding. In addition, when the antifogging agent is coated in excess of 50 mg / m ² , no improvement in the antifogging property is observed. Further, stickiness of the sheet and thermoformed product, blocking, and transparency of the sheet due to excessive coating of the antifogging agent. This is a region where deterioration occurs. In particular, when the sheet roll is used for a thermoformed product having a drawing ratio (depth of the molded product / short side length or diameter of the molded product) of 0.2 or more, the antifogging durability after molding is improved. From the viewpoint of maintenance, the coating amount is preferably 10 mg / m ² or more, and from the viewpoint of not deteriorating the color tone of the recycled polymer of the sheet (preventing yellowing), the coating amount of the antifogging agent is preferably 30 mg / m ² or less.

The total silicone oil coverage of the unwound sheet is 1 to 50 mg / m ² . Below this lower limit, for example, even if silicone oil is applied to one side and the sheet roll of the present invention is obtained by transfer, the silicone oil does not transfer or is difficult to transfer uniformly, and the mold or hot plate is not used during sheet thermoforming. It is also an area where the releasability from the sheet becomes worse. On the other hand, when the upper limit is exceeded, sheet blocking and stickiness of the sheet and thermoformed product are felt and the merchantability is lowered. Further, from the viewpoint of improving the releasability of the thermoformed sheet without stacking, it is preferable that the total coating amount of the silicone oil is 5 mg / m ² or more, and the silicone oil is transferred to a hot plate or a mold. From the viewpoint of preventing contamination due to water, it is preferable that the total amount of the silicone oil is 20 mg / m ² or less.

Further, a silicone oil coverage Amg / m ² on the anti-fogging agent coating surface, the ratio of silicone oil coverage Bmg / m ² on the opposite side A / (A + B) is from 0 to 0.48, preferably Is 0.05 to 0.48, more preferably in the range of 0.1 to 0.35.

In the present invention, the silicone oil coated on the antifogging agent is in the range of 0 to 24 mg / m ^{2 in} the region satisfying the above relationship. However, when the silicone oil coating amount is less than 0.05 mg / m ² , the sheet easily adheres to the hot plate when the sheet is subjected to hot plate pressure forming, and the surface of the sheet is roughened. Since the appearance may be deteriorated, it is preferably 0.05 mg / m ² or more. When the silicone oil is coated in excess of 24 mg / m ² , the silicone oil film is too thick and antifogging. In addition, the masking effect of the sheet surface by the antifogging agent becomes insufficient, and the sheet and the silicone oil partly contact with each other due to the hot plate contact pressure at the time of hot plate pressure forming, resulting in molding whitening Therefore, it is preferably 24 mg / m ² or less. Furthermore, from the viewpoint of improving the peelability between the thermoformed products of the sheet and preventing the hot plate contamination due to the transfer of the silicone oil to the hot plate of the molding machine, the coating amount of the silicone oil is 0.1-17.5 mg / m ^2. More preferably, it is 0.25-10 mg / m < ² >.

Further, the surface opposite to the antifogging surface is substantially covered only with silicone oil, and the amount of the silicone oil coating is in the range of 0.52 to 50 mg / m ^{2 in} the region satisfying the above relationship. If the silicone oil is less than 0.52 mg / m ^2, it is not only a region where the releasability between the sheet and the molding die is reduced during thermoforming, and a region where stickiness is felt when the upper limit is exceeded. Dirt becomes severe and the transparency of the molded product is reduced. Further, from the viewpoint of improving the peelability between the thermoformed products of the sheet and preventing the contamination of the mold due to the transfer of the silicone oil to the mold, the silicone oil coating amount is set to 0.75 to 37.5 mg / m ^2. Preferably, it is 2.5 to 20 mg / m ² . Here, “substantially covered only with silicone oil” means that the level of components other than the silicone oil and the emulsifier derived from the silicone emulsion is not quantified by the analysis method described later (antifogging agent). Is outside the limit of quantification). As described above, in the present invention, when the sheet roll is rewound, the coating amount of the silicone oil is not intended for both sides, and the coating amount of the silicone oil on the antifogging surface side is necessary for the release property of the hot plate surface and the sheet. The amount of coating required for releasability and slipperiness when taking out one by one after using the product after stacking during mold transportation or securing the mold on the opposite surface. Is ensured.

  The sheet of the present invention is coated, for example, on the one side of the sheet with an antifogging agent and on the opposite side with a silicone oil, wound up in a roll shape with a winding tension of 10 to 40 kg / m, and the silicone oil on the opposite side. It is obtained by transferring onto the applied anti-fogging agent film. In this case, the transfer amount of the silicone oil to the anti-fogging surface changes with time, and it takes 5 days or more at 23 ° C. for the transfer amount to be balanced. Accordingly, the silicone oil coating amount of the sheet of the present invention is preferably measured by unwinding the roll after aging the sheet roll at 23 ° C. for 5 days or more.

  The quantitative analysis of the silicone oil coating amount can be performed by fluorescent X-ray analysis, FTIR analysis (ATR) or the like. Quantitative analysis of the amount of anti-fogging agent can be carried out by washing sheets and films, collecting the washings, and performing the weight method, gas chromatography method, high performance liquid chromatography method, etc., or FTIR analysis method (ATR method). Etc.

  The antifogging agent used in the present invention is a nonionic surfactant such as sucrose fatty acid esters, polyglycerin fatty acid esters, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl ethers, polyoxyethylene alkyl ethers, One or a mixture of surfactants selected from oxyethylene fatty acid ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, etc., and having an HLB of 11 to 17. When the HLB is less than 11, the water-solubility, dispersibility, and wettability of the antifogging agent are deteriorated, and it is a region where it is difficult to form a uniform antifogging agent film. In addition, when the HLB exceeds 17, the antifogging agent tends to be washed away into the water, so that the continuous antifogging property is lowered. Of these, sucrose fatty acid esters, polyglycerin fatty acid esters, and sorbitan fatty acid esters that are approved as food additives are preferred as antifogging agents for polystyrene resin sheets that are frequently used for food packaging applications. A sucrose fatty acid ester containing 50 mol% or more of lauric acid as a component, and a mixture of the sucrose fatty acid ester (99 to 50% by weight) and a polyglycerin fatty acid ester or sorbitan fatty acid ester (1 to 50% by weight) It is particularly preferable because it has an excellent balance between safety and anti-fogging property and also has an excellent masking effect of silicone oil (when the polyglycerol fatty acid ester is mixed in an amount of more than 100% by weight or 50% by weight, the masking effect is slightly lowered, The anti-molding whitening effect tends to be inferior).

  The silicone oil used in the present invention is an organic polysiloxane such as dimethylpolysiloxane, methylphenylpolysiloxane, diphenylpolysiloxane and the like, and dimethylpolysiloxane is particularly preferable in terms of product safety and economy. The viscosity of the silicone oil is preferably 100 to 100000 CS, and the upper limit is to ensure the stability of the emulsion when the silicone oil is used in an emulsion, and the lower limit is the slipperiness of the sheet, between the hot plate and the sheet. This level is necessary for improving the peelability. Furthermore, in order to improve the mold releasability between thermoformed products and prevent mold contamination due to silicone oil, it is preferable to use silicone oil having a viscosity of 500 to 50,000 CS, more preferably 1000 to 20000 CS. For these silicone oils, a known silicone emulsion is preferably used from the viewpoint of ease of handling and coating.

  Next, the manufacturing method of the styrene-type resin sheet roll of this invention is demonstrated with reference to FIG. FIG. 1 is a schematic diagram of an example of the production method of the present invention by off-line, but a set of coating apparatuses may be incorporated into a sheet deposition line and produced by on-line coating. In FIG. 1, 1 is a sheet roll, 2 is a styrene resin sheet, 3 and 4 are corona treatment machines, 5 and 7 are coaters, 6, and 8 are first-stage dryers, and 9 is a second-stage dryer. Machine 10 represents a sheet roll after coating.

  The sheet roll of the present invention is produced by forming a sheet (film formation), applying a corona treatment to a wetting coefficient of 45 to 65 dynes / cm with a corona treatment machine 3 or 4, and then applying an antifogging agent aqueous solution or a silicone emulsion with a coater 5. After drying in one stage by a dryer 6, an anti-fogging agent aqueous solution or a silicone emulsion (which differs from the opposite surface) is applied by a coater 7 and sufficiently dried by dryers 8 and 9 and then wound by a winder with a winding tension of 10 to 10. The roll-up resin sheet roll 10 is made under the condition of 40 kg / m. Further, the corona treatment machine 4-1 in FIG. 1 may be changed to the position 4-2, one side may be subjected to corona treatment, and the coating may be performed by performing corona treatment on the opposite surface after the coating is completed. Among these production methods, the corona treatment and the drying method are particularly important and are the characteristics of the present invention.

  In the production method of the present invention, the drying after applying the antifogging agent aqueous solution and the silicone emulsion is sufficiently performed so that when a part of the silicone oil is transferred onto the antifogging agent at the time of winding the roll later, it is sufficiently transferred. Must be done. When the moisture is insufficiently dried, the transfer of the silicone oil becomes non-uniform, so that the desired styrene resin sheet roll cannot be obtained.

  Therefore, the drying method employed in the production method of the present invention is, for example, after one side is coated and then dried normally by the dryer 6 (one-stage drying), then coated on the opposite side, and the coated surface is usually dried by the dryer 8. After drying (1 step drying), it is sufficiently dried by two-step drying through the dryer 9 again. By performing such two-stage drying, the moisture taken into the antifogging agent and the emulsifier in the silicone emulsion is more completely dried, and the drying level of the antifogging agent and the silicone oil application surface is improved and uniformly. Dried. As a result, it becomes possible to control the uniformity of the transfer amount of the silicone oil to the antifogging surface, and a substantially uniform transfer silicone film is formed on the antifogging agent. On the other hand, the conventionally known drying method (when two-stage drying is not performed) that has been conventionally performed is not sufficient for drying, and in this case, uneven transfer occurs in the silicone oil, and the sheet roll of the present invention Is difficult to obtain stably (for example, the difference between Example 6 and Comparative Example 7 in Table 3).

  The conditions for drying the coated sheet vary greatly depending on the coating liquid coating amount, sheet production speed, etc., and cannot be specified unconditionally. It is common to pass through a hot air dryer at 5 ° C. for about 5 to 20 seconds. Also in the present invention, it is preferable to select conditions under which water normally evaporates in the dryers 6 and 8, and to perform two-stage drying with the dryer 9 under the same conditions as the dryers 6 and 8. In FIG. 1, the dryers 8 and 9 are separated, but one-stage drying and two-stage drying are performed with one dryer having a length more than twice that of the dryer 6. Is also possible. Although there is no restriction | limiting in particular in the kind of dryer, It is common to use a warm air dryer.

  Corona treatment is carried out by adjusting the surface tension of the sheet to 45 to 65 dynes / cm (mN / m) in terms of the wetting coefficient measured according to ISO 8296. When the wetting coefficient is less than 45 dynes / cm, the antifogging agent aqueous solution and the silicone emulsion are not uniformly coated and uneven coating occurs, resulting in non-uniform antifogging properties and releasability. If the surface tension exceeds 65 dynes, blocking is likely to occur, and static electricity is likely to be generated during sheet manufacturing and sheet molding in a low temperature and low humidity environment. In addition, since the silicone oil needs to be uniformly coated and transferred to the antifogging surface, and the wettability is worse than that of the antifogging agent, the surface to which the silicone emulsion is applied is particularly preferably 50 to 65 dynes / cm. The corona treatment may be performed before coating with the treatment liquid, and is not particularly limited.

There is no particular limitation on the coating method of the antifogging agent and silicone oil, and it can be carried out by a generally known method such as a spray coater, gravure coater, air knife coater, roll coater, knife coater or the like. At this time, the concentration of the antifogging agent aqueous solution is suitably about 0.05% to 5%, and it is appropriate to apply about 1 to 10 g / m ^{2 by} wet. The silicone emulsion also is suitable for application to the opposite surface of 1 to 10 g / m ² approximately antifogging surface wet and similarly diluted with water so as to be 0.01 to 4% as the silicone oil concentrations. Further, for the purpose of preventing foaming of the antifogging agent at the time of coating, a surfactant having an HLB of 1 to 8 as an antifoaming agent together with the antifogging agent, such as sorbitan fatty acid esters, polyoxyethylene polyoxypropylene block copolymers, Particularly preferably, sorbitan fatty acid esters which are food additives may be added in an amount of 5 to 30 parts by weight with respect to 100 parts by weight of the antifogging agent.

  The order of coating is not particularly limited. For example, the antifogging agent is first applied and then dried, the silicone emulsion is applied to the opposite surface, and the two-stage drying method is applied, or the silicone emulsion is first applied and dried. Any method, such as applying an antifogging agent to the opposite surface and drying in two steps, may be used.

  After drying, the sheet coated with the coating agent is taken up as a wound sheet roll with a winding tension of 10 to 40 kg / m. When the winding tension is less than 10 kg / m, the sheet roll is liable to occur and the sheet roll is in the form of a bamboo shoot or is easily damaged when transported. In addition, when the winding tension exceeds 40 kg / m, paper crushing and gauge bands are likely to occur strongly, and undulation at the time of rewinding is also likely to occur. More preferably, the sheet is wound by the above method, and after aging for 1 to 3 days, the sheet roll is rewound into a sheet shape, and then wound again into a roll shape with a winding tension of 10 to 40 kg / m. Although there is a difference in the transfer speed of the silicone oil between the winding core and the winding surface of the sheet roll, rewinding (rewinding the sheet roll once wound on the roll into a sheet and winding it again on the roll) By doing so, it is possible to equilibrate the transfer of the silicone oil on the entire sheet roll in a short time.

  The styrenic resin used in the styrenic resin sheet roll of the present invention is a homopolymer of styrenic monomers selected from styrene, alkyl styrenes, halogenated styrenes and the like, copolymers thereof, and conjugated dienes. (Butadiene, isoprene, etc.), block, random, graft copolymer of rubber component such as styrene-conjugated diene copolymer and the above styrene monomer, and copolymer of styrene monomer and other monomer And these rubber graft copolymers. In addition, known additives such as plasticizers such as mineral oil, terpenes, petroleum resins, antistatic agents, and ultraviolet absorbers may be added to these styrene resins.

  Among these, preferred resins are styrene-alkyl (meth) such as styrene homopolymer (GPPS), styrene-methacrylic acid copolymer, styrene-maleic anhydride copolymer, styrene-butyl (meth) arylate copolymer, and the like. Acrylate copolymers and blends thereof with GPPS, styrene-conjugated diene block copolymers (SBBC), blends of SBBC with GPPS and styrene-alkyl (meth) acrylate copolymers, and the like.

  The original sheet used in the styrene resin sheet roll of the present invention may be a single layer sheet made of the above styrene resin or a known multilayer sheet containing one or more layers of the above styrene resin. As the multilayer sheet, for example, GPPS (surface layer) / GPPS + SBBC (inner layer), heat-resistant styrene copolymers such as styrene-methacrylic acid copolymer (surface layer) / GPPS (inner layer), GPPS (surface layer) / styrene-alkyl (Meth) acrylate copolymers (inner layer), high molecular weight GPPS (outer layer) / medium to low molecular weight GPPS (inner layer), GPPS + SBBC (outer layer) / GPPS (inner layer), GPPS (outer layer) / plasticized GPPS (inner layer), etc. A known sheet having two layers, three layers, or four or more layers can be used. The raw sheet may be unstretched or may be stretched uniaxially or biaxially, and may be selected as appropriate depending on the desired physical properties of the sheet / film. The stretching may be carried out by a known bubble method, tenter method or the like, and is not particularly limited. The production of the non-stretched sheet is not particularly limited as long as it is performed by a known method.

The following examples illustrate the invention.
The performance evaluation of the sheets and films in the examples and comparative examples was performed according to the following criteria (“◯” or more is the acceptable level of the present invention unless otherwise specified).

(1) Whitening by molding A lid with a flat top of 80mm x 130mm x 15mm is molded by hot plate compression molding (set the sheet so that the antifogging surface of the sheet becomes the hot plate contact surface. , Molded at a heating temperature of 132 ° C., a heating time of 1.2 seconds, and a molding cycle of 6 seconds.The sheet of Production Example 2 was molded at a heating temperature of 108 ° C., a heating time of 2.2 seconds, and a molding cycle of 8 seconds). Ten pieces of randomly selected molded products were cut out from molded products free of dirt and scratches, and the test pieces were obtained by stacking and fixing the periphery with tape. Next, place a line meter published by the Japan Society of Printing Press on the table, place a test piece 10 cm above it, and measure the maximum number of lines that can be identified visually from 20 cm above the test piece (each of the n monitors by 5 monitors). = 4, a total of 20 samples were tested), and molding whitening was evaluated based on the average value (rounded to one decimal place). The smaller the value, the more severe the whitening.

(2) Formability (adhesion between sheet and hot plate, releasability between sheet and mold, mold contamination)
A container was molded by the same method as the molding whitening measurement method. From the appearance evaluation of the molded product obtained, the adhesion between the sheet and the hot plate (the surface of the antifogged surface of the molded product, the occurrence of adhesion marks), the releasability between the sheet and the mold (generation of sound during mold release, The occurrence of scratches due to defective mold release) and mold stains (the number of shots until stains and dents occur on the non-fogged surface of the molded product) were evaluated according to the following criteria.

・ Adhesion between sheet and hot plate ◎: There is a surface on the anti-fogging surface and there is no adhesion mark ×: There is an adhesion mark on the anti-fogging surface ・ Releasability between sheet and mold ◎: Sound is generated during release No, there is no scratch on the molded product. ○: A little loud noise is generated at the time of mold release, but there is no scratch on the molded product. ×: A loud noise is generated at the time of mold release, or a scratch is generated on the molded product. No mold contamination over shot: ○: Mold contamination occurs after 1500 to 1999 shots △: Mold contamination occurs after 1000 to 1499 shots ×: Mold contamination occurs after 999 shots or less

(3) Antifogging property A drawing ratio of 0.1 (80 mm × 130 mm × 8 mm) and a drawing ratio so that the antifogging surface is on the water surface side at 40 mm from the water surface on a constant temperature water bath controlled at 85 ± 1 ° C. A molded product of 0.3 (90 mmΦ × 27 mm) was placed, and adhesion of water droplets after 3 minutes (initial antifogging property) and after 1 hour (sustained antifogging property) was evaluated according to the following criteria. Anti-fogging property of ○ or higher is desirable for molded products with a drawing ratio of 0.1, and the anti-fogging property of ○ or higher is desirable for molded products with a drawing ratio of 0.3.

A: A mirror-like water film is seen on the entire surface, and the entire surface is transparent and the inner surface is completely transparent.
○: A partially continuous water film is seen, and the whole is somewhat “slightly hazy”, but there are no water droplets and the inside is visible.
(Triangle | delta): A big water drop about 10-20 mm in diameter is seen, and an inside is a little hard to see.
X: A small water droplet of about 5 mm or less is seen in an area of 10% or more of the whole, and the inside is very difficult to see.

(4) Peelability of molded product Using a hot plate heated air pressure molding machine, food packs (pack inner surface is anti-fogging surface) are molded from a test sheet, and eight sets of punched 25 shots are stacked. After leaving for a minute, the detachment of the main body when the hood was lifted one by one was evaluated according to the following criteria: ◎: good peeling in 98% or more molded product: good peeling ○: 90% or more molding The product can be peeled well and does not lift by overlapping 4 sheets or more: Peelable at a practical level. Δ: 80 to 90% of molded products can be peeled well, or 90% or more is good but 4 sheets or more overlap. May be lifted: Poor peelability (however, depending on the shape of the molded product, there is a possibility of practical use).
X: Less than 80% of molded products that can be peeled well: no peelability

(5) Blocking resistance of sheet Five sheets cut into A4 size were stacked so that the antifogging agent-coated surface and the antifogging agent non-coated surface were in contact with each other, and treated at 60 ° C. under a pressure of 200 kg / cm ² for 3 minutes. The back sheet was peeled off and evaluated according to the following criteria. ◎: Peelable without resistance and no whitening ○: Slightly resistant but can be peeled off without whitening △: Peelable but the sheet whitened ×: Sheet Is stuck and cannot be peeled off or the sheet is torn

(6) Quantification of silicone coverage The infrared absorption spectrum of the sheet surface was measured by FTIR using the ATR method (ATR crystal ZnSe, accumulated 16 times), absorption of about 1263 cm- ¹ silicone oil (dimethylpolysiloxane) and polystyrene of was quantified silicone coating amount than the ratio of the absorption (using approximately 1372 and 1069cm ~ ¹⁾ (a calibration curve was prepared from the known concentration of the standard sample, quantitative).

(7) Transfer uniformity of silicone oil Twenty measurement samples were randomly cut out from 10 m ² of the sheet antifogging surface, and the silicone coating amount was quantified by the above FTIR method. Transfer uniformity was determined from the variation in the coating amount (transfer amount). Evaluation based on the criteria.
◎: Variation in silicone oil coverage is within ± 15% of average ○: Variation in silicone oil coverage is ± 15 to ± 30% of average
X: Variation in silicone oil coverage is greater than ± 30% of the average

(8) Quantification of coating amount of antifogging agent FTIR is used to measure the difference spectrum between the sheet surface and polystyrene by ATR method (ATR crystal ZnSe, cumulative number of times: 64), and the silicone oil coated with the antifogging agent is used as an internal standard. as (quantitative silicone oil in the same manner as in (6)), characteristic absorption of the carbonyl group of the anti-fogging agents: was quantified antifog agent amount than (about 1735 cm ~ ¹ when sucrose fatty acid ester).

The following antifogging agents were used.
B-1: Sucrose fatty acid ester, lauric acid as a fatty acid component is 68 mol%, monoester is 30 mol%, HLB is 15.2
B-2: Decaglycerin laurate, monoester is 66 mol%, and HLB is 13.2.
B-3: Hexaglycerin laurate, monoester is 62 mol%, HLB is 15.4
The following silicone oil was used.
S-1: Dimethylpolysiloxane (emulsion with a viscosity of 5000 cs and an effective solid content of 30% by weight)
S-2: Dimethylpolysiloxane (emulsion with a viscosity of 1000 cs and an effective solid content of 30% by weight)
S-3: Dimethylpolysiloxane (emulsion having a viscosity of 50000 cs and an effective solid content of 30% by weight)

Production Example 1
Polystyrene is fed into an extruder, extruded from a T-die, and the extruded sheet is cast, then stretched three times longitudinally by the speed ratio of a roller heated to 130 ° C, and then stretched three times by a tenter with an oven temperature of 135 ° C. Thus, a biaxially stretched sheet having a thickness of 0.18 mm was obtained.

Production Example 2
A styrene-butyl acrylate copolymer (87% by weight of styrene) and a styrene-butadiene block copolymer (70% by weight of styrene) are mixed in a weight ratio of 55/45, supplied to an extruder, and extruded from a T-die. The extruded sheet was cooled with a casting roll to obtain an unstretched sheet having a thickness of 0.3 mm.

Example 1
One side of the sheet manufactured in Production Example 1 was corona treated so that the wetting coefficient was 63 dynes / cm, and then a 96-fold diluted aqueous solution of silicone oil S-1 (silicone oil concentration: 0.3125% by weight) was sprayed on this side. After 4 g / m ² (silicone oil 12.5 mg / m ² ) was applied by a coater, it was passed through a hot air dryer at 120 ° C. for 8 seconds. Next, the opposite surface was treated with corona so that the wetting coefficient was 58 dynes / cm, and then a 0.5 wt% aqueous solution of antifogging agent B-1 was applied to this surface with a spray coater at 4 g / m ² (antifogging agent 20 mg / cm ² ). m ² ) After coating, it was passed through a hot air dryer at 120 ° C. for 8 seconds and then passed through a hot air dryer at 120 ° C. for 8 seconds (two-stage drying). The obtained sheet was wound with a winding tension of 15 to 20 kg / m to obtain a sheet roll. The sheet roll was aged at 23 ° C. for 1 day, and then the sheet was rewound (winding tension at the time of rewinding: 15 to 20 kg / m) and further aged at the same temperature for 4 days. After aging, transfer of the antifogging agent was not confirmed, and the silicone oil was coated on the antifogging agent coated surface on an average of 4.2 mg / m ² and the silicone oil coated surface was coated on an average of 8.3 mg / m ^2. It was confirmed by FTIR (ATR method). The results of evaluating the physical properties of this sheet are shown in Table 1.

Examples 2-4
The corona treatment strength of the silicone coating surface is 56 dynes / cm, the corona treatment strength of the antifogging agent coating surface is 60 dynes / cm, and the concentration of the antifogging agent aqueous solution is 0.2% by weight (antifogging agent 8 mg / m ² : Example 2), 0.4 wt% (antifogging agent 16 mg / m ² : Example 3), 1.0 wt% (antifogging agent 36 mg / m ² : Example 4) It carried out similarly and obtained the sheet roll. None of the sheets was able to confirm the transfer of the antifogging agent after aging, and the silicone oil coated an average of 4.3 mg / m ² on the antifogging agent coated surface, and the average of 8.2 mg / m ² on the silicone oil coated surface. ^{2 The} coating was confirmed by FTIR (ATR method). The results of evaluating the physical properties of this sheet are shown in Table 1.

Examples 5-7
Silicone oil dilution ratio: 480 times (silicone oil application amount 2.5 mg / m ² : Example 5), 60 times (silicone oil application amount 20 mg / m ² : Example 6), 30 times (silicone oil application amount 40 mg) / M ² : A sheet roll was obtained in the same manner as in Example 1 except that Example 7) was used. After aging, transfer of the antifogging agent could not be confirmed, and the silicone oil had an average of 0.4 / 2.1, 6.4 / 13.6, in order of the antifogging agent coated surface / silicone oil coated surface from Example 5. It was confirmed by FTIR (ATR method) that 16.8 / 23.2 mg / m ^{2 was} coated. The results of evaluating the physical properties of this sheet are shown in Table 1.

Example 8
One side of the sheet prepared in Production Example 1 was subjected to corona treatment so that the wetting coefficient was 60 dynes / cm, and then the half-faced surface was similarly treated. Then, after applying 4.8 g / m ² (antifogging agent 24 mg / m ² ) of a 0.5% by weight aqueous solution of an antifoggant B-1 and B-2 80/20 (weight ratio) mixture on one side using a spray coater. And passed through a hot air dryer at 110 ° C. for 10 seconds. Next, a 100-fold diluted aqueous solution of silicone oil S-2 (silicone oil concentration: 0.3%) was applied to a half face of the anti-fogging agent coating surface with a spray coater at 3.5 g / m ² (silicone oil 10.5 mg / m ² ). After coating, it was passed through a hot air dryer at 110 ° C. for 20 seconds. The obtained sheet was wound with a winding tension of 20 to 25 kg / m to obtain a sheet roll. The sheet roll was aged at 23 ° C. for 5 days. After aging, the transfer of the antifogging agent was not confirmed, and the silicone oil was transferred to the antifogging agent coated surface on an average of 3.7 mg / m ^2, and the silicone oil coated surface was coated on the average of 6.8 mg / m ^2. It was confirmed by FTIR (ATR method). The results of evaluating the physical properties of this sheet are shown in Table 1.

Example 9
The coating coefficient of the sheet antifogging agent coating surface is 54 dynes / cm, the antifogging agent is a 65/35 (weight ratio) mixture of B-1 and B-3, the silicone oil is S-3, and the winding tension of the sheet A sheet roll was obtained in the same manner as in Example 8 except that the amount was set to 15 to 20 kg / m. After aging, transfer of the antifogging agent could not be confirmed, and the silicone oil was transferred to the surface on which the antifogging agent was applied on average of 2.9 mg / m ^2, and the surface on which the silicone oil was applied was coated in an average range of 7.6 mg / m ² This was confirmed by FTIR (ATR method). The results of evaluating the physical properties of this sheet are shown in Table 1.

Comparative Example 1
One side of the sheet produced in Production Example 1 was corona treated so that the wetting coefficient was 62 dynes / cm, and then 96 times that of silicone oil S-1 containing 0.5% by weight of antifogging agent B-1 on this side. A diluted aqueous solution (silicone oil concentration: 0.3125% by weight) was applied at 4 g / m ² (antifogging agent 20 mg / m ² , silicone oil 12.5 mg / m ² ) with a spray coater, and then heated in a 120 ° C. hot air dryer. Passed for 8 seconds. The obtained sheet was wound with a winding tension of 15 to 20 kg / m to obtain a sheet roll. The sheet roll was aged at 23 ° C. for 3 days, and then the sheet was rewound (winding tension at the time of rewinding was 15 to 20 kg / m) and further aged at the same temperature for 7 days. After aging, the transfer of the anti-fogging agent can not be confirmed, also silicone oils, average 6.7 mg / m ² coated anti-fogging agent coating surface, are averaged 5.8 mg / m ² transfer coated on the opposite surface This was confirmed by FTIR (ATR method). The results of evaluating the physical properties of this sheet are shown in Table 2.

Comparative Example 2
A sheet roll was obtained in the same manner as in Example 1 except that the dilution ratio of the silicone oil was 20 times (silicone oil coating amount 60 mg / m ² ). After aging, transfer of the antifogging agent could not be confirmed, and the silicone oil was transferred to the antifogging agent coated surface on an average of 27.5 mg / m ² and the silicone oil coated surface was coated on an average of 32.5 mg / m ² . This was confirmed by FTIR (ATR method). The results of evaluating the physical properties of this sheet are shown in Table 2.

Comparative Example 3
A sheet roll was obtained in the same manner as in Example 8, except that the dilution ratio of the silicone oil was 1200 times (silicone oil coating amount 0.875 mg / m ² ). After aging, the transfer of the antifogging agent could not be confirmed, and the silicone oil transferred to the antifogging agent coating surface was less than 0.05 mg / m ² , and the silicone oil coating surface averaged about 0.85 mg / m ² The coating was confirmed by FTIR (ATR method). The results of evaluating the physical properties of this sheet are shown in Table 2.

Comparative Example 4
A sheet roll was obtained in the same manner as in Example 1 except that the concentration of the antifogging agent aqueous solution was 0.075 wt% (antifogging agent 3 mg / m ² ). After aging, transfer of the antifogging agent could not be confirmed, and the silicone oil was coated on the antifogging agent coated surface with an average of 5.0 mg / m ² and the silicone oil coated surface was coated with an average of 7.5 mg / m ^2. It was confirmed by FTIR (ATR method). The results of evaluating the physical properties of this sheet are shown in Table 2.

Comparative Example 5
A sheet roll was obtained in the same manner as in Example 1 except that the concentration of the antifogging agent aqueous solution was 1.75% by weight (antifogging agent 70 mg / m ² ). About 25% of the applied antifogging agent is transferred to the opposite surface, and the silicone oil is transferred to the antifogging agent coated surface on an average of 6.1 mg / m ^2, and the silicone oil coated surface is averaged on 6.4 mg / m 2. ^{2 The} coating was confirmed by FTIR (ATR method). The results of evaluating the physical properties of this sheet are shown in Table 2. This sheet was particularly sticky and reduced the commercial value.

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Examples 10 and 11
A sheet roll was obtained in the same manner as in Example 6 except that the wettability coefficient on both surfaces of the sheet was 54 dynes / cm (Example 10) and 48 dynes / cm (Example 11). Table 3 shows the results of evaluating the transfer uniformity of the silicone oil of the obtained sheet.

Comparative Example 6
A sheet roll was obtained in the same manner as in Example 6 except that the corona treatment was performed so that the coating coefficient on both sides of the sheet was 43 dynes / cm. Table 3 shows the results of evaluating the transfer uniformity of the silicone oil of the obtained sheet.

Comparative Example 7
A sheet roll was obtained in the same manner as in Example 6 except that the two-stage drying was not performed after the antifogging agent was applied (only one-stage drying was performed). Table 3 shows the results of evaluating the transfer uniformity of the silicone oil of the obtained sheet.

・

Example 12
A sheet roll was obtained in the same manner as in Example 1 except that the sheet prepared in Production Example 2 was used. In the obtained sheet, transfer of the antifogging agent was not confirmed, and the silicone oil was transferred to the antifogging agent coated surface on an average of 4.4 mg / m ² and the silicone oil coated surface was averaged on 8.1 mg / m2. ^{2 The} coating was confirmed by FTIR (ATR method). The molding whitening evaluation result of this sheet showed a line value of 80, and other evaluation items were at the same level as the sheet of Example 1.

1 is a schematic diagram of an example manufacturing method of the present invention by off-line coating.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, Sheet raw fabric 2, Styrenic resin sheet 3, 4, Corona processing machine 5, 7, Coater 6, 8, First stage dryer 9, Second stage dryer 10, Sheet roll after coating

Claims (2)

In an antifogging styrene resin sheet coated with an antifogging agent and silicone oil, one side is coated with an antifogging agent at a coating amount of 5 to 50 mg / m ² , and silicone oil is coated on the antifogging agent and on the opposite side. A styrene resin sheet for hot-plate pressure forming that is coated and has a total silicone oil coating amount of 1 to 50 mg / m ² and satisfies the following conditions.
0.05 ≦ A / (A + B) ≦ 0.48
(However, A is the amount of silicone oil coating on the anti-fogging agent, B is the amount of silicone oil coating on the opposite side) The antifogging agent is selected from a mixture of sucrose fatty acid ester and sucrose fatty acid ester (99 to 50% by weight) and polyglycerin fatty acid ester or sorbitan fatty acid ester (1 to 50% by weight). The styrene resin sheet for hot plate pressure forming of Claim 1.

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