JPH0612303B2 - Discoloration time management layer - Google Patents

Description

The present invention relates to a discoloration time management layer. More specifically, the microcapsules are destroyed between the [A] layer containing the microcapsules of a liquid substance and the [B] layer containing a substance that causes discoloration upon contact with the components in the microcapsules. This is an indicator label for temperature control of articles that require strict temperature control, such as refrigerated or frozen foods, for controlling the time until the liquid substance flowing out and reaching the [B] layer and causing discoloration. Discoloration time management layer for use.

[Conventional technology]

Conventionally, it has been desired to develop a storage temperature control label that irreversibly discolors when the temperature exceeds a predetermined temperature for articles requiring temperature control. For items that require temperature control, there are, for example, frozen foods, chilled foods, fresh flowers, pharmaceuticals, etc., which are effective for detecting whether or not those items are kept at a normal control temperature during storage or transportation. No means have been found at this stage. Also, frozen,
Although it is necessary to strictly control the temperature of articles represented by refrigerated foods, it is difficult to know whether or not the articles will be stored under the necessary temperature control after the production of the articles and delivered to the user. Specific temperature control systems are required in related industries.

The inventors of the present invention previously conducted diligent studies in order to solve such problems, and applied a non-reversible color development system using a methine dye precursor and an oxidizing material to a temperature display unit, which is extremely characteristic and effective. A new unit (Japanese Patent Laid-Open No.
0-53984). That is, the unit uses (1) a hydrophobic organic substance having an arbitrary melting point, (2) a methine dye precursor, and (3) an oxidizing material represented by a benzoquinone derivative as an essential constituent material. A label for temperature control using a temperature control unit (1) microcapsules, (2) and (3), or (2) dissolved in (1) microcapsules and (3) as a support with an essential component It is held on top.

Such a unit is extremely effective in performing strict temperature control, but it still has the following problems in the actual distribution process. That is, when the target article is exposed to a temperature higher than the specified temperature, decomposition and deterioration due to propagation of various bacteria occur, but the target time of decay and deterioration varies depending on the property of the target article. Needless to say, therefore, an indicator is required to manage the discoloring time in accordance with the target time of decay and deterioration of the target article. Indicators (labels or tags) used for simplifying such temperature control are attached to the packaging surface where the target food, for example, meat or fish, is packaged with a polymer material in consideration of refrigerated food, for example. It is generally attached. In other words, the indicator is immediately exposed to the storage environment temperature, but the meat, fish, etc. that are the original management targets do not immediately follow the environment temperature due to their own specific heat or the effect of shielding by the packaging container, and the time Cause a delay. In addition, even if the target article follows the ambient temperature,
Not only those which become edible immediately due to decay and deterioration, but also those which become edible depending on the environmental conditions, that is, the degree of propagation of various bacteria, etc., over the course of several hours or tens of hours. Up to now, there are various kinds of target articles. In other words, there is an allowable edible storage time depending on the target.

Generally, chilled foods required by law are required to be stored at 10 ° C or lower. However, not all foods become inedible in a short time when exposed to an ambient temperature of 10 ° C or higher. On the contrary, in the case of certain pharmaceuticals, catalysts, etc., they extremely dislike the reaction and alteration of the product itself, so that a strict storage temperature must be maintained, and a system that discolors quickly beyond the storage temperature is required. It is useful. In other words, there is a permissible storage time for each target and there is a need for a system suitable for each. Therefore, it is desired to develop a system capable of freely controlling the time until the color changes depending on the purpose such as the decay and deterioration behavior of the target article.

The present inventors have found that the above-mentioned problems can be solved by a discoloration time management layer or the like made of a film produced from an emulsion of a polymer containing a specific amount of acrylonitrile or styrene, and previously filed a patent application. I went (Japanese Patent Application Sho 60-110297
No. 60-205375).

[Problems to be solved by the invention]

The present inventors have succeeded in developing a system capable of freely controlling the time until the color changes in accordance with the purpose such as the decay and deterioration behavior of the target article as described above. However, these polymer emulsions or the like have a coating roll bar or a layer [A] containing microcapsules of an oily substance and a layer [B] containing a substance which causes discoloration upon contact with the oily substance. The coating is carried out with an air knife, etc., but a special pigment layer is formed in the [B] layer in order to improve its function, and the wetting property becomes a problem when uniformly coating a general polymer emulsion. Become. Therefore, addition of a wetting agent or the like is essential for most polymer emulsions. However, many wetting agents cause a drop in the melting point of oily substances with a certain melting point. Further, a wetting agent that does not cause a melting point drop has many problems such as insufficient wetting characteristics.

An object of the present invention is to provide a discoloration time management layer having excellent wetting characteristics.

[Means for solving problems]

As a result of intensive studies to solve the above problems, the present invention has found that a polymer emulsion obtained by copolymerizing a hydrophilic monomer as a discoloration time management layer has excellent wetting characteristics, and arrived at the present invention.

That is, the present invention interposes between the [A] layer containing the microcapsules of an oily substance and the [B] layer containing a substance that causes discoloration upon contact with the oily substance, In the irregular time management layer for controlling the time required for the oily substance that breaks down and flows out to reach the [B] layer and cause discoloration, the management layer is 2-hydroxyethyl (meth) acrylate. , 2-hydroxypropyl acrylate, (meth) acrylamide, N-methylol (meth)
Hydrophilic monomers consisting of one or more kinds of acrylamide, acrylonitrile, styrene, hard monomers consisting of one or more kinds of methyl methacrylate, ethyl acrylate, isobutyl (meth) acrylate, (meth ) An acrylic emulsion obtained by polymerizing, as an essential component, a soft monomer comprising one or more of normal butyl acrylate, hexyl acrylate, 2-ethylhexyl (meth) acrylic acid, and lauryl methacrylate. The proportion of these monomers is 1 to 30% by weight, 20 to 90% by weight, 20 to 90% by weight, and the weight ratio of the total amount of the monomers to the monomer is
A discoloration time control layer, which is a continuous film obtained by applying and drying a composition of 1:99 to 30:70.

The acrylic microcapsules used in the discoloration time management layer of the present invention can be obtained by various known polymerization methods such as photopolymerization method, thermal polymerization method, radiation polymerization method, ring-opening polymerization method and radical polymerization method. Of the various polymerization methods, the radical polymerization method is preferably used, and the emulsion polymerization method using a redox catalyst in a horizontal medium is most preferably used.

Examples of the hydrophilic monomer used in the present invention include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl acrylate, (meth) acrylamide, N-
Methylol (meth) acrylamide can be used, and one or more of these can be used.

Examples of the hard monomer used for copolymerization include acrylonitrile, styrene, and methyl methacrylate, and one or more of these can be used.

Furthermore, examples of soft monomers used for copolymerization include ethyl acrylate, isobutyl (meth) acrylate, normal butyl (meth) acrylate, hexyl acrylate, 2-ethylhexyl (meth) acrylic acid, and lauryl methacrylate. And one or more of these can be used.

The acrylic emulsion of the present invention is the above hydrophilic monomer,
Although it is a copolymer of hard and soft monomers,
In order to improve various properties such as particle size control, water dispersibility, mechanical stability, storage stability, and freeze stability, it is possible to copolymerize with another monomer, if necessary. Examples of such a monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid and crotonic acid, aromatic vinyl compounds such as vinyltoluene and divinylbenzene, methyl acrylate and methacrylic acid. Alkyl ester of (meth) acrylic acid such as ethyl, vinyl acetate, vinyl chloride,
Various monomer components such as vinylidene chloride and methacrylonitrile may be mentioned.

In the copolymer, the amount of hydrophilic monomer is 1 to 30% by weight, the amount of hard monomer is 20 to 90% by weight, and the amount of soft monomer is
20 to 90% by weight, and the ratio of the total amount of hard monomer and soft monomer to the amount of hydrophilic monomer is by weight.
It is 1:99 to 30:70, preferably 1:99 to 10:90.

These various components used for the copolymerization may be preliminarily mixed and polymerized, or the monomers may be added stepwise to perform block copolymerization or graft copolymerization. Further, two or more kinds of copolymers may be mixed and used.

The acrylic emulsion has an average particle size of 0.01 to 2.0.
It is a white water suspension of fine particles of μ, preferably 0.05 to 0.8 μ, which has the property of producing a uniform film by fusion of polymer particles by drying and evaporating water. preferable.

When the continuous film obtained by drying the acrylic emulsion thus obtained is used as the discoloration time management layer, the wetting property is improved without using a wetting agent and the object of the present invention is achieved.

The discoloration time management layer of the present invention specifically comprises a layer [A] comprising microcapsules of an oily substance provided on a support and a substance which causes discoloration upon contact with components in the microcapsules. It is provided between the layer [B] and As the support, a flexible film-like material such as paper or polymer is generally used, on which [A] layer or [B] is formed.
The layer is generally coated by various coating methods such as air knife coating, bar coating, blade coating, gravure coating, roll coating, or various printing methods such as gravure printing, flexographic printing, offset printing, and screen printing. Set by the method. Further, the acrylic emulsion of the present invention is coated or printed by the above-mentioned method, and generally, the coating method is used.

In a preferred embodiment, when the discoloration time management layer of the present invention is used, a low-viscosity aqueous suspension is obtained, and thus a coating method suitable for applying a low-viscosity coating liquid such as an air knife coater or a bar coater is generally preferred. Used in

The discoloration time management layer of the present invention has a dry thickness of 0.01 to 20 μm,
It is preferably an extremely thin continuous film having a thickness of about 0.05 to 10 μm, and is provided by applying the acrylic emulsion by the above-mentioned coating method and then drying by heating to a temperature at which a continuous film can be sufficiently formed. Further, a [B] layer or [A] layer is provided on the upper layer. These layers are also provided by coating or printing.

In the label-like product provided with the discoloration time management layer of the present invention, the time-controlled discolored portion is often required to be in the form of characters or patterns, so the printing method particularly includes microcapsules. When printing a layer, a printing method that may cause destruction of the microcapsules due to pressure is inconvenient, and a screen printing method is most preferably used.

Acrylic emulsion is a composition that is the main component of the discoloration time management layer provided between the oil substance microcapsule layer and the color developer layer, and has the property of controlling the swelling, diffusion, and permeation of the oil substance. It must have been done. By the way, a resin film having only a large barrier effect is not suitable as a discoloration time management layer of the present invention because it does not permeate an oily substance, and a resin film having a too small barrier effect allows an oily substance to pass through. However, it is also unsuitable as the discoloration time management layer of the present invention. In other words, as a condition that can be the discoloration time management layer required in the present invention, it must have both properties of appropriate barrier property and appropriate carrier property, and it can be obtained by using a dry film of the acrylic emulsion. The purpose is achieved. It goes without saying that one or more kinds of other polymer emulsions, latexes, water-based polymers and the like can be added to the acrylic emulsion depending on the purpose of modification.

In the present invention, as a means for causing discoloration, for example, color development by a methine dye precursor and a benzoquinone derivative or color development by a phthalide derivative and an organic or inorganic solid acid as proposed in JP-A-60-53984 is used. be able to. For example, one of these color-forming components is dissolved in an oily substance having a melting point in the vicinity of a temperature requiring control, microcapsule is formed by a known method, and this is contained in the [A] layer, and the other is contained in the [B] layer. You may make it contain in. Further, the above oily substance may be microencapsulated and contained in the [A] layer, and both coloring components may be contained in the [B] layer. Moreover, these modifications are also used. Although various oily substances are used according to the purpose, for example, n-caprate-n-butyl, n-ethyl caprate, acetic acid as an oily substance having a sharp melting point in the range of -30 ° C to + 50 ° C. -N-dodecyl, ethyl n-undecanoate, n-decylbenzene,
Undecyl caproate, heptyl caprate, -n-butyl laurate, -n-butyl myristate, n-dodecylbenzene, methyl laurate, ethyl myristate, isobutyl palmitate, -n-butyl palmitate, methyl myristate, etc. Can be given. Of course, the oily substance used is not limited to these exemplified compounds. Moreover, you may use it in mixture of 2 or more types as needed.

The layers [A] and [B] are, in addition to the microcapsules and the substances that cause discoloration, natural or synthetic polymer binders and solvents, inorganic or organic fillers for the purpose of improving coating and printability. It is common to include.

The temperature indicating label provided with the discoloration time management layer of the present invention destroys the microcapsules by roll pressure, impact pressure, etc. when used. When the temperature exceeds the control temperature, the substance in the microcapsule melts, and the discoloration time control layer of the present invention dissolves, penetrates,
Discoloration starts after passing through diffusion or the like. Since the time required to start the anomaly changes depending on the viscosity, polarity, molecular weight, etc. of the oily substance in the microcapsules, the monomer composition of the time management layer used according to the time required to start the required color change,
Change the particle size, molecular weight, film thickness, etc. to correspond.

〔Example〕

Hereinafter, the present invention will be described with reference to synthesis examples, examples and comparative examples. In addition,% and parts are% by weight and parts by weight unless otherwise specified.

Samples [I] to [III] were prepared by the method described below.

Synthesis Example 1 A round bottom flask equipped with a heating device was equipped with a stirrer and a fixed charge pump, charged with 560 g of water, 8 g of sodium dodecylbenzenesulfonate as an emulsifier, 0.9 g of ammonium persulfate and 0.45 g of sodium hydrogen sulfite,
After slowly raising the temperature to 55 ° C with stirring, a mixture of acrylonitrile monomer 170.5g, styrene monomer 118.2g as a hard monomer, butyl acrylate monomer 145.5g as a soft monomer, and acrylic acid 5.9g was further mixed using a charge pump. It was added at a rate of 5 g per minute, and a white and cloudy acrylic copolymer emulsion was obtained 7 hours after charging the monomer. The average particle size of this product was 0.3 μm. This is designated as sample [I].

Synthesis Example 2 The same apparatus as in Synthesis Example 1 was charged with 547 g of water, 8 g of sodium dodecylbenzenesulfonate as an emulsifier, 0.9 g of ammonium persulfate and 0.45 g of sodium hydrogen sulfite as a catalyst, and the mixture was slowly heated to 55 ° C. Acrylonitrile monomer 170.5g as hard monomer, styrene monomer 118.2g, butyl acrylate monomer 145.5g as soft monomer, acrylic acid as hydrophilic monomer
A mixture of 7 g of 2-hydroxyethyl, 6 g of acrylamide, and 5.9 g of acrylic acid was added at a rate of 5 g per minute using a charge pump, and a white and cloudy acrylic copolymer emulsion was obtained 7 hours after charging the monomer. . The average particle size of this product was 0.28 μm. This is designated as sample [II].

Synthesis Example 3 The same apparatus as in Synthesis Example 1 was charged with 552 g of water, 8 g of sodium dodecylbenzenesulfonate as an emulsifier, 0.9 g of ammonium persulfate and 0.45 g of sodium bisulfite, and slowly heated to 55 ° C. with stirring. , 153 g of acrylonitrile monomer as a hard monomer, 106 g of styrene monomer, 131 g of butyl acrylate monomer as a soft monomer, 20 g of 2-hydroxyethyl acrylate as a hydrophilic monomer, 20 g of acrylamide, 5 g of N-methylol acrylamide, and 5.3 g of acrylic acid. 5 g / min was added using a charge pump to obtain a white and cloudy acrylic copolymer emulsion 6 hours after the monomer was charged. This product had a slightly higher viscosity. The average particle size of this product was 0.22μ. This is designated as sample [III].

Synthesis Example 4 A 200 ml stainless beaker was charged with 100 g of 10% polyvinyl alcohol, and 1 g of 2,5-di-n-butoxycarbonyl-3,6-diphenylsulfonyl-1,4-benzoquinone was added thereto.
Was added and atomization was performed for 3 hours by high-speed stirring (1000 RPM) to obtain a developer dispersion.

In a separate container, 50 g of water, 20 g of calcium carbonate and 20 g of 10% starch were added, 10 g of the developer dispersion was added and mixed with stirring to obtain a coating liquid having a solid content of 23% and a viscosity of 150 centipoise. This is designated as sample [IV].

Synthesis Example 5 4,4'-Bis-dimethylamino- "3" -methyl-4 "-ethoxy-triphenylmethane dissolved in 2% of notimalbutyl myristate was coated with a melamine resin film by a known In-Situ polymerization method. Thus, a microcapsule slurry was obtained (average particle size 4.0 μ, solid content 50%) 100 parts of the microcapsule slurry, 20 parts of styrene butadiene latex and 100 parts of water were mixed to obtain a capsule-containing coating liquid. This is designated as sample [V].

Acrylic copolymer emulsions of Samples [I] to [III] obtained in Synthesis Examples 1 to 3, a color developer of Sample [IV] obtained in Synthesis Example 4, and a dye of Sample [V] obtained in Synthesis Example 5. A coating test was conducted using a combination of precursor microcapsules.

Example 1 On a general high-quality paper (basis weight 80 g / m ² ), the developer of Sample [IV] was applied.
5 g / m ^{2 in} solid content using No. 10 coating roll bar
And was dried at 80 ° C. for 1 minute to obtain a developer layer.

The acrylic copolymer emulsion of sample [II] was applied to this using a No. 10 coating roll bar so that the solid content was 2 g / m ^2, and dried at 80 ° C. for 1 minute. This is sample (a).

On top of that, the microcapsules of sample [V] are added in a solid content of 6 g / m 2.
^It was coated using a No. 10 coating roll bar so as to be ^2, and dried at 80 ° C. for 1 minute. As described above, a sample including a developer layer, a color change time management layer, and a microcapsule layer was obtained. This is designated as sample [A].

Example 2 A sample (b) and a sample [B] were obtained in the same manner as in Example 1 except that the sample [III] was used as the acrylic copolymer emulsion.

Comparative Example 1 A sample [C] was obtained in the same manner as in Example 1 except that a 5% carboxymethylcellulose solution was used instead of the acrylic copolymer emulsion of the sample [II].

Comparative Example 2 A sample [D] was obtained in the same manner as in Example 1 except that the acrylic copolymer emulsion was not applied at all. That is, this is one in which a microcapsule layer is directly provided on the developer layer, and does not have a color change time management layer.

Comparative Example 3 A sample (C) and a sample [E] were obtained in the same manner as in Example 1 except that the sample [I] was used as the acrylic copolymer emulsion.

A wettability test was conducted on the acrylic copolymer emulsions of Samples [I] to [III] obtained in Synthesis Examples 1 to 3 and Samples (A) to (C).

A color change test was conducted on Samples [A] to [E].

(Staining property test) Prepare 3 pieces of washed glass pieces having a length of 10 cm, a width of 5 cm, and a thickness of 2 mm, and keep them horizontal. Next, [I] to [III] of the acrylic copolymer emulsion was applied to each glass piece in an amount of 2 μm.
Apply once using an applicator roll.

Dry at room temperature, visually observe cissing per 4 cm ² ,
It is represented by the number of repellents.

Samples (a) to (c) are cut into a length of 10 cm and a width of 10 cm, and the repellency per 10 cm ² is visually observed and expressed by the number of repellants.

(Discoloration test conditions) 1) Microcapsule destruction machine: Super calendar (Line pressure 10
0kg / cm) 2) Microcapsule breaking temperature: normal temperature 3) Temperature history: After breaking microcapsule, leave it for 5 minutes at normal temperature, then put it in a freezer at 0 ° C for 2 hours and then raise it to 5 ° C, then 5 Keep at ℃.

4) Color measurement: Visually (check at any time) Next, the results of the smearing property test are shown in Table-1, and the results of the color change test are shown in Table-2.

[Effect of the invention] From Table 1, the discoloration time management layer of the present invention has excellent coating uniformity with respect to the developer layer, has no cissing or unevenness, and does not require the addition of a wetting agent at a predetermined melting point. It can be understood that the coating property is improved without causing the melting point of the oily substance to drop and the discoloration becomes uniform and the function as the discoloration time management layer is sufficiently exerted.

Incidentally, in the sample (E) of Comparative Example 3 in which the hydrophilic monomer was not copolymerized, cissing unevenness was generated and discoloration unevenness was generated.

Claims (1)

[Claims] 1. A microcapsule which is interposed between a layer [A] containing microcapsules of an oily substance and a layer [B] containing a substance which causes discoloration upon contact with the oily substance. In the discoloration time management layer for controlling the time required for the oily substance that breaks down and flows out to reach the [B] layer and cause discoloration, the management layer is 2-hydroxyethyl (meth) acrylate. , One or more hydrophilic monomers consisting of one or more of 2-hydroxypropyl acrylate, (meth) acrylamide, N-methylol (meth) acrylamide, acrylonitrile, styrene, methyl methacrylate Hard monomers consisting of and ethyl acrylate, isobutyl (meth) acrylate, normal butyl (meth) acrylate, hexyl acrylate, (meth) acrylic acid 2 -Acrylic emulsion obtained by polymerizing, as an essential component, a soft monomer consisting of one or more of ethylhexyl and lauryl methacrylate, wherein the proportion of these monomers is 1 to
30% by weight, 20 to 90% by weight, 20 to 90% by weight, and a composition in which the weight ratio of the total amount of the monomers to the monomers is 1:99 to 30:70 is applied and dried. A discoloration time management layer, which is a continuous film obtained by