Coloring agent, and production method of colored synthetic resin using the same

Abstract

To provide a coloring agent in which a water-soluble natural pigment is easily mixed with a synthetic resin, and which hardly gives harmful effect to moldability of a synthetic resin.SOLUTION: A coloring agent for coloring a synthetic resin contains: 10 mass% to 50 mass% of 1-2C monovalent alcohol; 5 mass% to 25 mass% of isoplpropyl alcohol; 0 mass% to 10 mass% of normalpropyl alcohol; 1 mass% to 10 mass% of 2-4C glycol; 0 mass% to 10 mass% of one or more kinds of ether selected from the group consisting of dipropylene glycol-n-butyl ether, tetrahydrofuran and diethylene glycol dimethyl ether; 1 mass% to 20 mass% of a water-soluble natural pigment; and water as the remainder.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a coloring agent containing a natural pigment, and particularly to a coloring agent containing a water-soluble natural pigment.

Background Art

[0002] As coloring agents, organic pigments synthesized from petroleum and the like, and inorganic pigments made from ores and metal oxides are known. These organic pigments and inorganic pigments are mixed with synthetic resins such as acrylic resins and urethane resins and are used in a wide range of applications such as inks, paints, and plastics.

[0003] On the other hand, as coloring agents other than organic pigments and inorganic pigments, natural pigments obtained from plants are also known. For example, curcumin, a natural pigment contained in turmeric, has been used for dyeing fabrics since ancient times, and a natural pigment contained in red perilla is used for coloring umeboshi. Thus, natural pigments are used for coloring foods and fabrics.

[0004] Recently, as represented by efforts towards SDGs, environmental issues and the effective utilization of energy resources have been strongly demanded. Based on such a situation, using natural pigments for coloring synthetic resins has also been studied (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Among natural pigments, there are water-soluble natural pigments. Among natural pigments, water-soluble natural pigments have a problem that they are difficult to blend into synthetic resins and result in non-uniform coloring.

[0007] On the other hand, there is also a technique of making a water-soluble dye less soluble in water and improving the compatibility of the water-soluble dye with the object to be colored by emulsifying or pigmenting the water-soluble dye. However, when using such a technique, there is a problem that processes for emulsification or pigmentation are required, resulting in an increase in cost. In addition, depending on the components blended to emulsify or pigment the water-soluble dye, it may also have an adverse effect on the moldability of the synthetic resin.

[0008] An object of the present invention is to provide a coloring agent in which a water-soluble natural dye is easily compatible with a synthetic resin and hardly has an adverse effect on the moldability of the synthetic resin.

Means for Solving the Problems

[0009] The gist of the present invention is as follows. [1] A coloring agent for coloring a synthetic resin, wherein the content of a monohydric alcohol having 1 to 2 carbon atoms is 10% by mass to 50% by mass, the content of isopropyl alcohol is 5% by mass to 25% by mass, the content of normal propyl alcohol is 0% by mass to 10% by mass, the content of a glycol having 2 to 4 carbon atoms is 1% by mass to 10% by mass, the content of one or more ethers selected from the group consisting of dipropylene glycol-n-butyl ether, tetrahydrofuran, and diethylene glycol dimethyl ether is 0% by mass to 10% by mass, the content of the water-soluble natural dye is 1% by mass to 20% by mass, and the balance is water, the coloring agent [2] The coloring agent according to [1], wherein the content of the monohydric alcohol is 20% by mass to 50% by mass. [3] The coloring agent according to [1], wherein the content of the isopropyl alcohol is 10% by mass to 25% by mass. [4] The coloring agent according to [1], wherein the content of the normal propyl alcohol is 2% by mass to 10% by mass. [5] The coloring agent according to [1], wherein the content of the ether is 1% by mass to 10% by mass. [6] A method for producing a colored synthetic resin, characterized by mixing the coloring agent according to [1] to [5] with a synthetic resin.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a coloring agent in which a water-soluble natural pigment is easily compatible with a synthetic resin and hardly affects the moldability of the synthetic resin.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described in detail. This embodiment is a coloring agent used for coloring a synthetic resin.

[0012] The coloring agent of this embodiment contains a monohydric alcohol having 1 to 2 carbon atoms (hereinafter, referred to as "C1-2 monohydric alcohol"). In other words, C1-2 monohydric alcohol is methanol and ethanol. That is, the coloring agent of this embodiment contains at least one of methanol and ethanol as the monohydric alcohol.

[0013] In the coloring agent of this embodiment, the content of the C1-2 monohydric alcohol is 10% by mass to 50% by mass. Here, the content of the C1-2 monohydric alcohol means the total amount of the C1-2 monohydric alcohol. That is, when the coloring agent of this embodiment contains both methanol and ethanol as the C1-2 monohydric alcohol, the content of the C1-2 monohydric alcohol means the total amount of their contents, and when the coloring agent of this embodiment contains only one of methanol and ethanol as the C1-2 monohydric alcohol, the content of the C1-2 monohydric alcohol means the content of that one.

[0014] In the coloring agent of this embodiment, the content of the C1-2 monohydric alcohol may be 10% by mass to 50% by mass, but is preferably 20% by mass to 50% by mass. When the content of the C1-2 monohydric alcohol in the coloring agent of this embodiment is 20% by mass to 50% by mass, the water-soluble natural pigment is more easily compatible with the synthetic resin and less likely to adversely affect the moldability of the synthetic resin as compared with the case outside this range.

[0015] In addition, in the present embodiment, the content of each component means the content with respect to 100% by mass of the coloring agent of the present embodiment.

[0016] The coloring agent of the present embodiment contains isopropyl alcohol. The content of isopropyl alcohol in the coloring agent of the present embodiment is 5% to 25% by mass.

[0017] In the coloring agent of the present embodiment, the content of isopropyl alcohol may be 5% to 25% by mass, but is preferably 10% to 25% by mass. When the content of isopropyl alcohol in the coloring agent of the present embodiment is 10% to 25% by mass, compared with the case outside the range, the water-soluble natural pigment is more compatible with the synthetic resin, and it is less likely to have an adverse effect on the moldability of the synthetic resin.

[0018] The coloring agent of the present embodiment has a content of normal propyl alcohol of 0% to 10% by mass. In the present embodiment, a content of 0% by mass means that the component is not contained. That is, the coloring agent of the present embodiment may or may not contain normal propyl alcohol, but when it contains normal propyl alcohol, its content is 10% by mass or less (more than 0% and 10% by mass or less).

[0019] In the coloring agent of the present embodiment, the content of normal propyl alcohol may be 0% to 10% by mass, but is preferably 2% to 10% by mass. When the content of normal propyl alcohol in the coloring agent of the present embodiment is 2% to 10% by mass, compared with the case outside the range, the water-soluble natural pigment is more compatible with the synthetic resin, and it is less likely to have an adverse effect on the moldability of the synthetic resin.

[0020] The colorant of this embodiment contains a glycol having 2 to 4 carbon atoms (hereinafter also referred to as "C2-4 glycol"). In this embodiment, glycol means a divalent alcohol in which two hydroxyl groups are bonded to different carbon atoms. Specific examples of the C2-4 glycol contained in the colorant of this embodiment include propylene glycol (alias: 1,2-propanediol), ethylene glycol (alias: 1,2-ethanediol), 1,3-propanediol, 1,2-butanediol, butylene glycol (alias: 1,3-butanediol), 1,4-butanediol, and diethylene glycol, and one or more of these can be contained. Among these C2-4 glycols, the C2-4 glycol contained in the colorant of this embodiment is preferably one or more selected from the group consisting of ethylene glycol (alias: 1,2-ethanediol), propylene glycol (alias: 1,2-propanediol), and butylene glycol (alias: 1,3-butanediol).

[0021] In the colorant of this embodiment, the content of C2-4 glycol is 1% by mass to 10% by mass. Here, the content of C2-4 glycol means the total amount of C2-4 glycol. That is, when the colorant of this embodiment contains two or more C2-4 glycols, the content of C2-4 glycol means the total amount of the contents of those two or more C2-4 glycols, and when the colorant of this embodiment contains only one kind of C2-4 glycol, it means the content of that one kind of C2-4 glycol.

[0022] In the colorant of this embodiment, the content of one or more ethers (hereinafter also simply referred to as "ether") selected from the group consisting of dipropylene glycol-n-butyl ether, tetrahydrofuran, and diethylene glycol dimethyl ether is 0% by mass to 10% by mass. That is, the colorant of this embodiment may or may not contain ether, but when it contains ether, its content is 10% by mass or less (more than 0% by mass and 10% by mass or less).

[0023] In the colorant of the present embodiment, the ether content means the total amount of ether. That is, when the colorant of the present embodiment contains two or more ethers, the ether content means the total amount of the contents of those two or more ethers, and when the colorant of the present embodiment contains only one kind of ether, it means the content of that one kind.

[0024] In the colorant of the present embodiment, the ether content may be 0% by mass to 10% by mass, but is preferably 1% by mass to 10% by mass. When the ether content in the colorant of the present embodiment is 1% by mass to 10% by mass, compared with the case where it is outside this range, the water-soluble natural pigment is more compatible with the synthetic resin, and it is less likely to have an adverse effect on the moldability of the synthetic resin.

[0025] The colorant of the present embodiment contains a water-soluble natural pigment. Here, the natural pigment means a pigment extracted from naturally occurring animals and plants, and the water-soluble natural pigment means a natural pigment that is soluble in water at 25°C (for example, 1 g or more is dissolved in 100 ml of water).

[0026] Specific examples of the water-soluble natural pigments contained in the pigment agent of the present embodiment include gardenia yellow pigment (crocin, crocetin), gardenia blue pigment (a mixture of iridoid compounds and protein hydrolysates), red radish pigment (pelargonidin acylglycoside), safflower yellow pigment (safflomin), red kojic yellow pigment (xanthomonascins), red kojic pigment (monascorubin, ankaflavin), red cabbage pigment (cyanidin acylglucoside), purple sweet potato pigment (peonidin / cyanidin acylglucoside), spirulina pigment (phycocyanin), beet red (betanin, isobetanin), grape skin pigment (various acylated anthocyanins), berry pigments (blueberry, blackberry, blackcurrant, bilberry, etc., various acylated anthocyanins), and one or more of these can be contained. Among these water-soluble natural pigments, the water-soluble natural pigment contained in the pigment agent of the present embodiment is preferably one or more selected from the group consisting of gardenia yellow pigment (crocin, crocetin), gardenia blue pigment, red radish pigment (pelargonidin acylglycoside), safflower yellow pigment (safflomin), red kojic yellow pigment (xanthomonascins), and red kojic pigment (monascorubin, ankaflavin).

[0027] The water-soluble natural pigment contained in the pigment agent of the present embodiment can be obtained, for example, by extracting animals and plants with a polar solvent such as water or alcohol (for example, ethyl alcohol and a mixed solution of water and ethyl alcohol (aqueous alcohol)). The extraction conditions are not particularly limited, and conventionally known extraction conditions can be used. In addition, commercially available products may be used for the water-soluble natural pigment contained in the pigment agent of the present embodiment.

[0028] Among natural pigments, there are also oil-soluble natural pigments that are insoluble in water at 25°C (for example, less than 1 g dissolves in 100 ml of water). As shown in the examples described later, oil-soluble natural pigments are easily compatible with synthetic resins, and problems such as uneven coloring of synthetic resins are less likely to occur. Specific examples of oil-soluble natural pigments include, for example, capsicum pigments (capsanthins), marigold pigments (xanthophyll (lutein)), turmeric pigments (curcumin), and algal carotenes (β-carotene).

[0029] The content of the water-soluble natural pigment in the pigment agent of the present embodiment is 1% by mass to 20% by mass. Here, the content of the water-soluble natural pigment means the total amount of the water-soluble natural pigment. That is, when the pigment agent of the present embodiment contains two or more water-soluble natural pigments, the content of the water-soluble natural pigment means the total content of those two or more water-soluble natural pigments. When the pigment agent of the present embodiment contains only one kind of water-soluble natural pigment, it means the content of that one kind of water-soluble natural pigment.

[0030] The balance of the pigment agent of the present embodiment consists of water. Here, the balance consisting of water means that water is contained in such a content that the total content of each component containing water becomes 100% by mass. That is, the pigment agent of the present embodiment contains water, and the total amount becomes 100% by mass by including the water. The content of water is determined according to the volume of the balance, and the lower limit can be, for example, 1% by mass or more, 10% by mass or more, or 15% by mass or more, and the upper limit can be, for example, 50% by mass or less.

[0031] The pigment agent of the present embodiment can be manufactured by mixing each component so that each component contained in the pigment agent of the present embodiment has the above-described content. The mixing process for mixing each component may be any process that can mix (mix so that each component becomes uniform) so that each component is not unevenly distributed, and conventionally known mixing conditions and mixing methods can be used. The mixing process may be performed while heating. Also, the mixing process may be performed using a conventionally known device such as a stirrer, a homogenizer, a bead mill, or a ball mill.

[0032] The mixing process of mixing the components may be a process of mixing all the components contained in the colorant of the present embodiment at the same time. However, among the components contained in the colorant of the present embodiment, a part of the components (hereinafter, also simply referred to as "a part of the components") and the remaining components (hereinafter, also simply referred to as "the remaining components") are mixed separately, and then, a process of mixing the mixture of a part of the components and the mixture of the remaining components may be performed.

[0033] According to the colorant of the present embodiment described above, the water-soluble natural pigment is easily compatible with the synthetic resin, and uneven coloring of the synthetic resin by the water-soluble natural pigment can be suppressed. Further, the colorant of the present embodiment hardly affects the moldability of the synthetic resin. In addition, since the water-soluble natural pigment in the colorant of the present embodiment is easily compatible with the synthetic resin without being emulsified or pigmented, a process for emulsifying or pigmenting the water-soluble natural pigment is not necessarily required, so that an increase in cost can also be suppressed.

[0034] The colorant of the present embodiment can be used for coloring a synthetic resin. The synthetic resin colored with the colorant of the present embodiment (hereinafter, also referred to as "colored synthetic resin") can be produced by mixing the colorant of the present embodiment and the synthetic resin. The mixing process of the colorant and the synthetic resin may be any process as long as the colorant of the present embodiment can be mixed so as not to be unevenly distributed in the synthetic resin (the colorant and the synthetic resin are uniformly mixed), and conventionally known mixing conditions and mixing methods can be used. The mixing process may be performed while heating to 30 to 60°C. Further, the mixing process may be performed using a conventionally known device such as a stirrer, a homogenizer, a bead mill, or a ball mill.

[0035] The synthetic resin colored with the coloring agent of the present embodiment can be exemplified by, for example, acrylic resin, urethane resin, epoxy resin, polyester resin, polyamide resin, vinyl acetate resin, phenol resin, olefin, ethylene-vinyl acetate copolymer resin, polyvinyl acetal resin, natural rubber, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, vinyl acetate-acrylic copolymer, ethylene-ethyl acrylate copolymer, polyester polyol, polyester polyurethane polyol, polyether polyurethane polyol, and may be a resin containing two or more of these. Since the water-soluble natural pigment becomes more familiar and is less likely to adversely affect the moldability of the synthetic resin, the synthetic resin colored with the coloring agent of the present embodiment is preferably an acrylic resin and / or a urethane resin.

[0036] The mixing ratio of the coloring agent and the synthetic resin of the present embodiment can be appropriately set according to the desired color shade. For example, with respect to 100 parts by mass of the coloring agent of the present embodiment, the synthetic resin can be 10 parts by mass to 100 parts by mass, and with respect to 100 parts by mass of the coloring agent of the present embodiment, the synthetic resin can also be 30 parts by mass to 55 parts by mass.

[0037] The mixture obtained by mixing the coloring agent and the synthetic resin (hereinafter, also referred to as "the mixture obtained by the mixing process") may be used as the colored synthetic resin as it is, or may be used as the colored synthetic resin after drying.

[0038] The drying process of the mixture obtained by the mixing process may be any process that can remove the volatile components from the mixture, and conventionally known drying conditions and drying methods can be used. As a specific drying process, for example, a process of leaving it at room temperature (0 to 30°C) for 12 hours to 72 hours can be exemplified.

[0039] According to the manufacturing method described above, a colored synthetic resin colored with a water-soluble natural pigment can be manufactured. The manufactured colored synthetic resin has suppressed non-uniform coloring (is uniformly colored) and has excellent moldability. The colored synthetic resin can be used, for example, in applications such as films, coatings, and gel nails.

Examples

[0040] Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to these examples.

[0041] [Evaluation 1] Each component was mixed at the contents shown in Table 1 below to produce the colorants of Reference Examples 1-2, Examples 1-14, and Comparative Examples 1-8. The mixing of each component was carried out using a Lab Revolution manufactured by Primix Corporation, and mixing was performed for about 10 minutes under the conditions of normal temperature (about 20°C) and 300 rpm.

[0042] In Tables 1-6 described later, EtOH refers to ethanol, IPA refers to isopropyl alcohol, nPA refers to normal propyl alcohol, PG refers to propylene glycol (1,2-propanediol), and DPnB refers to dipropylene glycol-n-butyl ether. Also, in Evaluations 1-6, Nichino Color YN-30 manufactured by Nihon Nohyaku Co., Ltd. was used as Gardenia yellow pigment, Nichino Color R-R500SP(S) manufactured by Nihon Nohyaku Co., Ltd. was used as Akadaiikon pigment, Nichino Color Benibana 500A manufactured by Nihon Nohyaku Co., Ltd. was used as Safflower yellow pigment, Nichino Color R-D manufactured by Nihon Nohyaku Co., Ltd. was used as Kojic red pigment, Nichino Color BLUE-L manufactured by Nihon Nohyaku Co., Ltd. was used as Gardenia blue pigment, and Nichino Color Paprika pigment 30S manufactured by Nihon Nohyaku Co., Ltd. was used as Cayenne pepper pigment. All of these pigments are natural pigments that have not been emulsified or pigmented, and the natural pigments other than the cayenne pepper pigment were water-soluble natural pigments.

[0043] The colorants of each reference example, example, and comparative example were each mixed with an acrylic resin. The mixing ratio of the colorant and the acrylic resin was 42.9 parts by mass of the acrylic resin with respect to 100 parts by mass of the colorant. Further, the mixing of the colorant and the acrylic resin was carried out by using a Lab Revolution manufactured by Primix Corporation and mixing for about 10 minutes under the conditions of normal temperature (about 20°C) and 300 rpm.

[0044] The acrylic resins mixed with the colorants of Reference Examples 1 to 2, Examples 1 to 14, and Comparative Examples 1 to 8 (hereinafter, also referred to as "colored synthetic resins of Reference Examples 1 to 2, Examples 1 to 14, and Comparative Examples 1 to 8" respectively) were put into a mold for molding, left at room temperature to dry, and then evaluated for "color unevenness" and "moldability".

[0045] The evaluation of "color unevenness" was carried out according to the following evaluation criteria. After 24 hours had elapsed since the start of drying (left at room temperature), the colored synthetic resins of each reference example, example, and comparative example were visually confirmed from a distance of 30 cm. The evaluation of "moldability" was carried out by taking out the colored synthetic resins of each reference example, example, and comparative example from the mold for molding and checking whether they could be molded into a predetermined shape (specifically, a plate shape with a thickness of 1 mm). The results are shown in Table 1. 〈Evaluation Criteria for Color Unevenness〉 ◎: No color unevenness is observed (no color unevenness can be confirmed at all). 〇: Almost no color unevenness is observed (color unevenness can be confirmed at 1 to 3 places). △: Color unevenness is observed (color unevenness can be confirmed at 4 or more places). ×: The synthetic resin and the natural pigment are separated (pigment accumulation can be confirmed). 〈Evaluation Criteria for Coloring Unevenness〉 ◎: Molded into a predetermined shape within less than 24 hours after the start of drying (after leaving at room temperature). 〇: Molded into a predetermined shape within 24 to 72 hours after the start of drying (after leaving at room temperature). △: Molded into a predetermined shape within 24 to 72 hours after the start of drying (after leaving at room temperature), but the molded body is brittle and cracks when taken out of the mold. ×: Cannot be molded into a predetermined shape even after 72 hours have elapsed since the start of drying (after leaving at room temperature).

[0046]

Table 1

[0047] From the results of Reference Example 1 shown in Table 1, it was understood that for oil-soluble natural pigments (capsicum pigments), even when mixed with a synthetic resin, there was no problem of poor compatibility with the synthetic resin (acrylic resin). On the other hand, from the results of Reference Example 2 shown in Table 1, it was understood that for water-soluble natural pigments (gardenia yellow pigments), when mixed with a synthetic resin, there was a problem of poor compatibility with the synthetic resin (acrylic resin). In this regard, although the colored synthetic resins of Comparative Examples 1 to 8 tended to have slightly improved "color unevenness" compared to the colored synthetic resin of Reference Example 2, the evaluation of at least one of "color unevenness" and "moldability" was △ or ×. On the other hand, for the colored synthetic resins of Examples 1 to 14, the evaluations of both "color unevenness" and "moldability" were ○ or ◎. From this result, it was understood that the pigment agent of the present embodiment has the characteristics that water-soluble natural pigments are easily compatible with synthetic resins and are less likely to have an adverse effect on the moldability of synthetic resins.

[0048] [Evaluation 2] Except for using each component in the content shown in Table 2 below, pigment agents of Examples 15 to 28 and Comparative Examples 9 to 13 were produced under the same conditions as in Evaluation 1.

[0049] Except for using the pigment agents of Examples 15 to 28 and Comparative Examples 9 to 13 instead of the pigment agent used in Evaluation 1, colored synthetic resins of Examples 15 to 28 and Comparative Examples 9 to 13 were produced in the same manner as in Evaluation 1, and "color unevenness" and "moldability" were evaluated. The results are shown in Table 2.

[0050]

Table 2

[0051] As shown in Table 2, the colored synthetic resins of Examples 15 to 28 all received an evaluation of ◎ for both "color unevenness" and "moldability". On the other hand, the colored synthetic resins of Comparative Examples 9 to 13 received an evaluation of △ for at least one of "color unevenness" and "moldability". From these results, it was understood that with the colorant of this embodiment, no matter what water-soluble natural pigment was used, the water-soluble natural pigment was easily compatible with the synthetic resin and was less likely to have an adverse effect on the moldability of the synthetic resin.

[0052] [Evaluation 3] The colorants of Examples 29 to 31 were produced under the same conditions as in Evaluation 1, except that each component was used in the contents shown in Table 3 below. In Table 3, MeOH refers to methanol.

[0053] The colored synthetic resins of Examples 29 to 31 were produced in the same manner as in Evaluation 1, except that the colorants of Examples 29 to 31 were used instead of the colorant used in Evaluation 1, and "color unevenness" and "moldability" were evaluated. The results are shown in Table 3.

[0054]

Table 3

[0055] As shown in Table 3, the colored synthetic resins of Examples 29 to 31 all received an evaluation of ○ or ◎ for both "color unevenness" and "moldability". From these results, it was understood that with the colorant of this embodiment, even if methanol was used instead of ethanol, which is a C1-2 monohydric alcohol, the water-soluble natural pigment was easily compatible with the synthetic resin and was less likely to have an adverse effect on the moldability of the synthetic resin.

[0056] [Evaluation 4] The colorants of Examples 32 to 34 were produced under the same conditions as in Evaluation 1, except that each component was used in the contents shown in Table 4 below. In Table 4, EG refers to ethylene glycol (1,2-ethanediol), and BG refers to butylene glycol (1,3-butanediol).

[0057] The colored synthetic resins of Examples 32 to 34 were produced in the same manner as in Evaluation 1, except that the colorants of Examples 32 to 34 were used instead of the colorant used in Evaluation 1, and the "color unevenness" and "moldability" were evaluated. The results are shown in Table 4.

[0058]

Table 4

[0059] As shown in Table 4, for the colored synthetic resins of Examples 32 to 34, the evaluations of both "color unevenness" and "moldability" were ◎. From these results, it was understood that in the colorant of this embodiment, even if ethylene glycol (1,2 - ethanediol) or butylene glycol (1,3 - butanediol) was used instead of propylene glycol (1,2 - propanediol), which is a C2 - 4 glycol, the water - soluble natural pigment was easily compatible with the synthetic resin and was less likely to have an adverse effect on the moldability of the synthetic resin.

[0060] [Evaluation 5] The colorants of Examples 35 to 37 and Comparative Examples 14 to 15 were produced under the same conditions as in Evaluation 1, except that each component was used in the contents shown in Table 5 below. In Table 5, THF refers to tetrahydrofuran, DGM refers to diethylene glycol dimethyl ether, DEE refers to diethyl ether, and PE refers to petroleum ether.

[0061] The colored synthetic resins of Examples 35 to 37 and Comparative Examples 14 to 15 were produced in the same manner as in Evaluation 1, except that the colorants of Examples 35 to 37 and Comparative Examples 14 to 15 were used instead of the colorant used in Evaluation 1, and the "color unevenness" and "moldability" were evaluated. The results are shown in Table 5.

[0062]

Table 5

[0063] As shown in Table 5, the colored synthetic resins of Examples 35 to 37 both received an evaluation of ◎ for "color unevenness" and "moldability". From these results, it was understood that with the pigment agent of this embodiment, even if tetrahydrofuran or diethylene glycol dimethyl ether was used instead of dipropylene glycol-n-butyl ether which is an ether, the water-soluble natural pigment was easily compatible with the synthetic resin and was less likely to have an adverse effect on the moldability of the synthetic resin. On the other hand, the colored synthetic resins of Comparative Examples 14 to 15 both received an evaluation of △ for "color unevenness" and "moldability". From these results, it was understood that if an ether other than dipropylene glycol-n-butyl ether, tetrahydrofuran, and diethylene glycol dimethyl ether was used as the ether contained in the pigment agent, the water-soluble natural pigment would be less likely to be compatible with the synthetic resin and would have an adverse effect on the moldability of the synthetic resin.

[0064] [Evaluation 6] The pigment agents of Examples 38 to 42 were produced under the same conditions as in Evaluation 1, except that each component was used in the content shown in Table 6 below.

[0065] The colored synthetic resins of Examples 38 to 42 were produced in the same manner as in Evaluation 1, except that the pigment agents of Examples 38 to 42 were used instead of the pigment agent used in Evaluation 1, and 42.9 parts by mass of urethane resin was used instead of the acrylic resin (42.9 parts by mass of acrylic resin with respect to 100 parts by mass of the pigment agent) used in Evaluation 1, and "color unevenness" and "moldability" were evaluated. The results are shown in Table 6.

[0066]

Table 6

[0067] As shown in Table 6, the colored synthetic resins of Examples 38 to 42 both received an evaluation of ◎ for "color unevenness" and "moldability". From these results, it was understood that with the pigment agent of this embodiment, even when mixed with a urethane resin, the water-soluble natural pigment was easily compatible and was less likely to have an adverse effect on the moldability of the urethane resin.

Claims

1. A colorant for coloring synthetic resins, wherein the content of monohydric alcohols having 1 to 2 carbon atoms is 10% to 50% by mass, the content of isopropyl alcohol is 5% to 25% by mass, the content of normal propyl alcohol is 0% to 10% by mass, the content of glycols having 2 to 4 carbon atoms is 1% to 10% by mass, the content of one or more ethers selected from the group consisting of dipropylene glycol - n - butyl ether, tetrahydrofuran, and diethylene glycol dimethyl ether is 0% to 10% by mass, the content of water - soluble natural pigments is 1% to 20% by mass, and the balance is water, the colorant.

2. The colorant according to claim 1, wherein the content of the monohydric alcohol is 20% to 50% by mass.

3. The colorant according to claim 1, wherein the content of the isopropyl alcohol is 10% to 25% by mass.

4. The colorant according to claim 1, wherein the content of the normal propyl alcohol is 2% to 10% by mass.

5. The colorant according to claim 1, wherein the content of the ether is 1% to 10% by mass.

6. A method for producing a colored synthetic resin, characterized by mixing the colorant according to any one of claims 1 to 5 with a synthetic resin.

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