Dye composition for polylactic acid fiber and dying method

Abstract

To provide a dye composition for polylactic acid fibers excellent in dye exhaustion of each of a yellow disperse dye, a red disperse dye, and a blue disperse dye, excellent in reproducibility due to equal dyeing speed during dying of each color, and excellent in light-fastness, a dyed product using the same and a dying method.SOLUTION: The dye composition for polylactic acid fibers of the present invention contains a yellow disperse dye represented by compounds of formula (1) and / or formula (2) (DISPERSE ORANGE 61, DISPERSE ORANGE 155), a red disperse dye represented by compounds of formula (3) (DISPERSE RED 167, DISPERSE RED 167.1), and a blue disperse dye which includes compounds represented by formula (4) (DISPERSE BLUE 79, DISPERSE BLUE 79.1) and / or a mixture of two isomers represented by formula (5) (DISPERSE BLUE 54).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for dyeing polylactic acid fibers using a disperse dye, and more particularly to a dye composition containing a yellow disperse dye, a red disperse dye, and a blue disperse dye, and a method for dyeing polylactic acid fibers and the like using the same. [Background technology]

[0002] In light of recent environmental issues, polylactic acid fibers have been attracting attention as a non-petroleum-based biodegradable fiber. Unlike petroleum, which is the raw material for conventional plastics, polylactic acid fibers can be harvested annually from renewable plant resources such as corn, and are therefore expected to be a material that will contribute to the realization of a sustainable society (e.g., Non-Patent Document 1).

[0003] Since plant-derived synthetic fibers such as polylactic acid fibers are obtained by fixing carbon dioxide gas in the ecosystem, the carbon dioxide generated by combustion or biodegradation by microorganisms is simply returned to its original state from within the ecosystem and does not contribute to the carbon dioxide gas on Earth; in other words, they are carbon-neutral materials.

[0004] Besides its biodegradability, polylactic acid fibers also have new appealing features such as a soft feel, light weight, sweat absorption and quick drying, mild antibacterial properties, and a weak acidity that is gentle on the skin, making them comfortable and attractive, not found in conventional synthetic fibers, and they are highly anticipated as a versatile fiber to replace polyester (for example, Non-Patent Document 2).

[0005] It is known that the best way to dye polylactic acid fibers is with disperse dyes, but the dye exhaustion rate varies depending on the dye, making color matching difficult and not very reproducible.In addition, polylactic acid fibers have inferior heat resistance compared to polyester fibers, so there are problems with the texture becoming hard when heat treated, and hydrolysis occurring under high temperature (over 60°C) and high humidity conditions.

[0006] The conventional disperse dye compositions described in Patent Documents 1 to 3 are disperse dyes that can dye polylactic acid fibers, but are not satisfactory as tricolor dyes with excellent reproducibility. When dyeing using tricolor dyes, reproducibility is improved by making the dyeing speeds of the three primary colors approximately equal, which solves the problem of color differences between the laboratory and the field and the problem of poor reproducibility, leading to improved productivity. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 4346611 [Patent Document 2] Patent No. 4424466 [Patent Document 3] JP 2006-8871 A [Non-patent literature]

[0008] [Non-Patent Document 1] Journal of the Textile Machinery Society, 2003, Vol. 56, No. 3, pp. 133-136 [Non-Patent Document 2] Journal of Sen-i-Gakkaishi, 2003, Vol. 59, No. 10, pp. 329-332 Summary of the Invention [Problem to be solved by the invention]

[0009] In order to solve these problems, the present invention provides a dye composition for polylactic acid fiber, which has excellent dye exhaustion properties for each of yellow disperse dyes, red disperse dyes, and blue disperse dyes, has uniform dyeing results for each color, and is excellent in reproducibility and light fastness, and also provides a dyed product and a dyeing method using the same. [Means for solving the problem]

[0010] As a result of intensive research conducted by the inventors to solve the above problems, it was discovered that by combining a yellow disperse dye, a red disperse dye, and a blue disperse dye, a dye composition having excellent dye exhaustion properties for polylactic acid fibers, uniform dyeing properties during dyeing, and excellent light fastness can be obtained, and this has led to the completion of the present invention.

[0011] That is, the present invention provides the following <1> ~ <8> Regarding. <1> A yellow disperse dye which is a compound represented by the following formula (1) and / or the following formula (2), A red disperse dye which is a compound represented by the following formula (3), A blue disperse dye which is a compound represented by the following formula (4) and / or a mixture of two isomers represented by the following formula (5), A dye composition for polylactic acid fibers comprising: [ka] [ka] [ka] (In the formula, R 1 represents a methyl group or an ethyl group. [ka] (In the formula, R 2 represents a methyl group or an ethyl group. [ka] (In the formula, X 1 and X 2 One represents NO2 and the other represents OH.)

[0012] <2> The composition further comprises a mixture of two dye compounds represented by the following formula (6): The content of the mixture is less than 5 parts by mass when the total amount of the yellow disperse dye, the red disperse dye, and the blue disperse dye is 100 parts by mass. <1> The dye composition for polylactic acid fibers according to claim 1. [ka] (In the formula, R 3 represents a methyl group or a methoxyethyl group.

[0013] <3> The yellow disperse dye, the red disperse dye, and the blue disperse dye are dispersed by a dispersant. <1> or <2> The dye composition for polylactic acid fibers according to claim 1.

[0014] <4> the dispersant is one or more compounds selected from the group consisting of a formalin condensate of naphthalenesulfonic acid and an alkylbenzenesulfonic acid, a formalin condensate of naphthalenesulfonic acid, a formalin condensate of cresolsulfonic acid, a formalin condensate of cresol and 2-naphthol-6-sulfonic acid, a formalin condensate of alkylnaphthalenesulfonic acid, a formalin condensate of creosote oil sulfonic acid, ligninsulfonic acid, a block copolymer of ethylene oxide and propylene oxide, an ethylene oxide adduct of an alkylphenol, and an ethylene oxide adduct of polystyrenated phenol; <3> The dye composition for polylactic acid fibers according to claim 1.

[0015] <5> The content of quinoline contained as an impurity derived from the dispersant is less than 1000 ppm; <3> or <4> The dye composition for polylactic acid-based fibers according to claim 1.

[0016] <6> <1> ~ <5> 2. A polylactic acid fiber dyed product obtained by dyeing using the dye composition for polylactic acid fiber according to claim 1.

[0017] <7> <1> ~ <5> A step of diluting the dye composition for polylactic acid fiber according to any one of the above to prepare a dye dispersion; A step of immersing polylactic acid fibers in the dye dispersion; A method for dyeing polylactic acid fibers comprising the steps of:

[0018] <8> In the immersion step, the temperature of the dye dispersion is set to 110 to 120°C. <7> A method for dyeing polylactic acid fiber according to claim 1. Effect of the Invention

[0019] According to the present invention, it is possible to provide a dye composition for polylactic acid fiber which has excellent dye exhaustion properties for each of yellow disperse dyes, red disperse dyes, and blue disperse dyes, has uniform dyeing results for each color when dyeing, is excellent in reproducibility, and is also excellent in light fastness, and a dyed product and a dyeing method using the same. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The present invention will be described in detail below. The dye composition for polylactic acid fiber of the present invention contains a yellow disperse dye, a red disperse dye, and a blue disperse dye.

[0021] The yellow disperse dye is a compound represented by the following formula (1) and / or the following formula (2).

[0022] [ka]

[0023] [ka]

[0024] The compound represented by the above formula (1) is CIDISPERSE ORANGE 61, which can be produced by a method known in the literature or by applying the same, but a commercially available compound may also be used. The compound represented by the above formula (2) is CIDISPERSE ORANGE 155, which can be produced by a method known in the literature or by applying the same, but a commercially available compound may also be used.

[0025] The red disperse dye is a compound represented by the following formula (3).

[0026] [ka] (In the formula, R 1 represents a methyl group or an ethyl group.

[0027] The compound represented by the above formula (3) is CIDISPERSE RED 167 or CIDISPERSE RED 167.1, and can be produced by a method known in the literature or by applying the method, but a commercially available compound may also be used.

[0028] The blue disperse dye is a compound represented by the following formula (4) and / or a mixture of two isomers represented by the following formula (5).

[0029] [ka] (In the formula, R 2 represents a methyl group or an ethyl group.

[0030] [ka] (In the formula, X 1 and X 2 One represents NO2 and the other represents OH.)

[0031] The compound represented by the above formula (4) is CIDISPERSE BLUE 79 or CIDISPERSE BLUE 79.1, and can be produced by a method known in the literature or by applying the method, but a commercially available compound may also be used.

[0032] The mixture of two isomers represented by the above formula (5) is CIDISPERSE BLUE 54, which can be produced by a method known in the literature or by applying the method, but a commercially available compound may also be used.

[0033] The dye composition for polylactic acid fibers is a dye mixture containing a yellow disperse dye which is a compound represented by the above formula (1) and / or the above formula (2), a red disperse dye which is a compound represented by the above formula (3), and a blue disperse dye which is a compound represented by the above formula (4) and / or a mixture of two isomers represented by the above formula (5). For example, the dye composition preferably contains 10 to 90 mass% of the yellow disperse dye, 2 to 90 mass% of the red disperse dye, and 10 to 90 mass% of the blue disperse dye, more preferably 20 to 50 mass% of the yellow disperse dye, 2 to 40 mass% of the red disperse dye, and 20 to 70 mass% of the blue disperse dye, and even more preferably 20 to 40 mass% of the yellow disperse dye, 2 to 40 mass% of the red disperse dye, and 20 to 58 mass% of the blue disperse dye.

[0034] The dye composition for polylactic acid fibers may further contain a mixture of two dye compounds represented by the following formula (6).

[0035] [ka] (In the formula, R 3 represents a methyl group or a methoxyethyl group.

[0036] The color rendering of the dyed product can be improved by containing a mixture of two dye compounds represented by the above formula (6). The mixture of two dye compounds represented by the above formula (6) is CIDISPERSE BLUE 204, and can be produced by a method known in the literature or by applying the method, but a commercially available compound may also be used. The content of the mixture of two dye compounds represented by the above formula (6) in the dye composition for polylactic acid fiber is preferably less than 5 parts by mass, and more preferably 0.1 parts by mass or more and less than 5 parts by mass, when the total amount of the above yellow disperse dye, the above red disperse dye, and the above blue disperse dye is 100 parts by mass.

[0037] The dye composition for polylactic acid fiber preferably further contains a dispersant, and the disperse dye is preferably dispersed by the dispersant. Examples of the dispersant include one or more compounds selected from the group consisting of formalin condensates of naphthalenesulfonic acid and alkylbenzenesulfonic acid, formalin condensates of naphthalenesulfonic acid, formalin condensates of cresolsulfonic acid, formalin condensates of cresol and 2-naphthol-6-sulfonic acid, formalin condensates of alkylnaphthalenesulfonic acid, formalin condensates of creosote oil sulfonic acid, ligninsulfonic acid, block copolymers of ethylene oxide and propylene oxide, ethylene oxide adducts of alkylphenols, and ethylene oxide adducts of polystyrenated phenols. These dispersants are available on the market. The disperse dye can be dispersed by using these dispersants. The content of the dispersant in the dye composition for polylactic acid fiber is preferably 30 to 80% by mass, more preferably 50 to 80% by mass, calculated as solid content. The disperse dye can be dispersed by a known method.

[0038] The amount of quinoline contained as an impurity derived from the dispersant is preferably less than 1000 ppm in the dye composition for polylactic acid fibers. Quinoline appears as a contaminant in the dispersant and is classified as a carcinogen. It is also highly water-soluble and toxic to aquatic life. In recent years, it has become a subject of regulated substances under REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) and bluesign (registered trademark).

[0039] The dye composition for polylactic acid fiber can be prepared by mixing a disperse dye, optionally a dispersant, and optionally other components. The dye composition for polylactic acid fiber is preferably one that has been subjected to a microparticulation treatment. The microparticulation treatment can be carried out by thoroughly wet-pulverizing the dye composition for polylactic acid fiber in the presence of a small amount of water using a pulverizer such as a ball mill or a sand mill until the average particle size (D50) is usually about 0.2 to 1.0 μm. The dye composition for polylactic acid fiber can be in the form of a liquid or paste as it is microparticulated, or in the form of a powder dried by a spray drying method or the like.

[0040] The dye composition for polylactic acid fiber may contain other components such as a dustless agent, a mildewproofing agent, a defoaming agent, a penetrating agent, a pH adjuster, etc. As these components, general ones can be used. The content in the dye composition for polylactic acid fiber can be appropriately adjusted as long as the dyeability to polylactic acid fiber is not impaired.

[0041] Next, a method for dyeing polylactic acid fibers will be described, but the method for dyeing polylactic acid fibers is not limited to the following description.

[0042] The method for dyeing polylactic acid fibers is characterized by including a step of immersing polylactic acid fibers in a dye dispersion. The dye dispersion can be prepared by adding a dye composition for polylactic acid fibers to water and mixing. The pH of the dye dispersion is preferably adjusted to 4 to 5. The pH can be adjusted by adding a commonly used pH adjuster such as acetic acid or sodium acetate. The content of the disperse dye in the dye dispersion is preferably adjusted to 0.005 to 10% owf based on the mass of the polylactic acid fiber to be dyed.

[0043] Dyeing conditions, etc., may be according to known conditions and are not particularly limited. For example, it is preferable to immerse polylactic acid fibers and dye them under pressure at a temperature of preferably about 110 to 120°C, more preferably 115 to 120°C, for 30 minutes to 1 hour. By increasing the temperature, the dye exhaustion rate increases, making it easier to obtain a deep or black hue. In addition, by increasing the dye exhaustion rate, the dye solution remaining in the residual bath decreases, resulting in better reproducibility.

[0044] After the dyeing process, it is desirable to perform processes such as rinsing, soaping, reduction cleaning, etc. on the dyed polylactic acid fiber in order to remove unadsorbed dye on the fiber surface. Soaping, reduction cleaning, etc. should be performed at 60°C or less. If the process is performed at 65°C or more, the disperse dye that has been adsorbed may fall off from the polylactic acid fiber, causing a decrease in concentration.

[0045] According to the dyeing method, it is possible to obtain dyed products having sufficient performance for practical use, for example, high light fastness and washing fastness, good color, and sufficient dyeing reproducibility.

[0046] Next, we will explain about polylactic acid fibers. The polylactic acid fibers used this time are made from corn, and the raw material grade is suitable for fiber grade, so they have enough strength to withstand use as materials for apparel products. In addition, while conventional polylactic acid fibers harden when the dyeing temperature is 100 to 110°C or higher, we have confirmed that they do not harden even when the dyeing temperature is as high as 120 to 130°C. EXAMPLES

[0047] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited thereto. In the examples, "%" means "mass %". Also, CIDISPERSE means color index generic name.

[0048] [Dyeing suitability of disperse dyes for polylactic acid fiber] The disperse dyes used were Nos. 1 to 44. Commercially available disperse dyes were used as the disperse dyes Nos. 1 to 44.

[0049] [1] Each dye compound shown in Table 1 was mixed with an equal amount of a dispersant composed of a formalin condensate of naphthalenesulfonic acid and sodium ligninsulfonate, a small amount of a dustless agent was added, and the mixture was subjected to a microparticulation treatment in a conventional manner and then dried to prepare a dye composition for polylactic acid fiber.

[0050] [2] Dyeing of polylactic acid fiber The amount of the dyed product with 1.0% owf of disperse dye was measured, and 0.5 g / L of dispersing and leveling agent KP Leveler AL (manufactured by Nippon Kayaku Co., Ltd., anionic surfactant) was added, and then the mixture was added to water adjusted to pH 4.5 with acetic acid and sodium acetate to adjust the total amount to 100 mL. 5 g of white polylactic acid cloth (manufactured by Hichem Co., Ltd.) was immersed in this dye bath (dye dispersion) and dyed at 120 ° C for 60 minutes. The dyed polylactic acid cloth was subjected to reduction washing at 60 ° C for 10 minutes (hydrosulfite was added at 60 ° C) in a bath containing 3 g / L of soda ash, 3 g / L of hydrosulfite, 1 g / L of Sunmol RC-700E (manufactured by Nicca Chemical Co., Ltd., anionic surfactant) and water to a total amount of 100 mL, and then washed with water and dried to obtain a dyed product.

[0051] [3] Residual dyeing of polyester fibers The total volume of the dye solution remaining in the pot was adjusted to 80 mL, and 4 g of Polyester Tropical (manufactured by Shikisen Co., Ltd.) was immersed in the solution and dyed at 135° C. for 30 minutes.

[0052] The dyeing suitability of each disperse dye for polylactic acid fiber is shown in Table 1.

[0053] [Table 1]

[0054] (Judgment method) The dye exhaustion was judged from the dyed product of the polylactic acid fiber and the dyed product of the polyester obtained by residual dyeing. Dye exhaustion: ◯: good, △: slightly poor, ×: poor.

[0055] From the results in Table 1, it was found that the dyed materials obtained with Nos. 1 to 22 had good dyeability, while the dyed materials obtained with Nos. 23 to 44 had poor dye exhaustion. This result showed that the dyed materials obtained with Nos. 1 to 22 had good dye exhaustion for polylactic acid fibers.

[0056] [Example 1: Dye composition for polylactic acid fiber] Yellow, red, and blue dyes were mixed in the ratios shown in Table 2, and this dye mixture was mixed with a dispersant composed of an equal amount of a formalin condensate of naphthalenesulfonic acid and sodium ligninsulfonate. A small amount of a dustless agent was added, and the mixture was subjected to a microparticulation treatment by a conventional method and then dried to prepare a dye composition for polylactic acid fiber.

[0057] [Examples 2 to 7: Dye compositions for polylactic acid fibers] A dye composition for polylactic acid fiber was prepared in the same manner as in Example 1, except that the dye was changed to the dye shown in Table 2.

[0058] [Comparative Examples 1 to 6: Dye compositions for polylactic acid fibers] A dye composition for polylactic acid fiber was prepared in the same manner as in Example 1, except that the dye was changed to the dye shown in Table 3.

[0059] [STEP DYEING TEST] The amount of dye composition for polylactic acid fiber that can give a dyed product with a total of 1.0% owf (see Table 2 for the composition ratio) was measured, and 0.5 g / L of a dispersing and leveling agent KP Leveler AL (manufactured by Nippon Kayaku Co., Ltd., an anionic surfactant) was added, and then the mixture was added to water adjusted to pH 4.5 with acetic acid and sodium acetate to adjust the total amount to 100 mL. 5 g of polylactic acid white cloth ("Hilacto" (registered trademark), manufactured by HiChem Co., Ltd.) was immersed in this dye bath (dye dispersion liquid), and the temperature was raised from 50°C at a rate of 1°C / min. The polylactic acid dyed product was removed from the dye bath at each of the following times: 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 120°C for 30 minutes, and 120°C for 60 minutes, and dyeing at each temperature was completed. After dyeing, the polylactic acid dyed fabric was subjected to reduction cleaning at 60°C for 10 minutes (hydrosulfite was added at 60°C) in a bath containing 3 g / L soda ash, 3 g / L hydrosulfite, 1 g / L Sunmol RC-700E (manufactured by Nicca Chemical Co., Ltd., anionic surfactant) and water to a total volume of 100 mL, then rinsed with water and dried to obtain the dyed product.

[0060] [Residual dyeing of polyester fibers] The remaining dye solution from the pots removed at each temperature was adjusted to a total volume of 80 mL, and 4 g of Polyester Tropical (manufactured by Shikisen Co., Ltd.) was immersed therein and dyed for 30 minutes at 135° C. The blending values ​​in Table 2 represent mass %.

[0061] (How to determine if the feet are dyed) The dyeing strength of the dyed polylactic acid fiber obtained by dyeing at each temperature and the dyed polyester obtained by residual dyeing was judged. The dyeing strength of each dye composition for polylactic acid fiber on polylactic acid fiber is shown in Tables 2 and 3. -Dyeing criteria- A: The dyed legs are very uniform. B: The dyed legs are relatively uniform. C: The dyed legs are somewhat uniform. D: The dyed legs are not very uniform. E: The dyed feet are significantly not uniform.

[0062] [Light fastness test] A dye composition for polylactic acid fiber of 3.0% owf (see Table 2 for composition ratio) was weighed out and 0.5 g / L of a dispersing and leveling agent KP Leveler AL (manufactured by Nippon Kayaku Co., Ltd., anionic surfactant) was added, and then the mixture was added to water adjusted to pH 4.5 with acetic acid and sodium acetate to adjust the total amount to 100 mL. 5 g of white polylactic acid cloth ("Hilacto", manufactured by Hichem Co., Ltd.) was immersed in this dye bath (dye dispersion), and after 60 minutes at 120 ° C., the polylactic acid dyed cloth was removed from the dye bath, completing the dyeing at each temperature. After dyeing, the polylactic acid dyed cloth was subjected to reduction washing at 60 ° C. for 10 minutes (hydrosulfite was added at 60 ° C.) in a bath containing 3 g / L of soda ash, 3 g / L of hydrosulfite, 1 g / L of Sunmol RC-700E (manufactured by Nicca Chemical Co., Ltd., anionic surfactant) and water to a total amount of 100 mL, and then washed with water and dried to obtain a dyed cloth.

[0063] The light fastness test was carried out using a Suga Test Instruments Co., Ltd. xenon fade meter NX75 under the conditions of JIS L 0843:2006 "Test method for color fastness to xenon arc lamp light" method A. Discoloration of the irradiated area was judged using the blue scale of JIS L 0841:2004. The results are shown in Tables 2 and 3. When high light fastness is required, grade 4 or higher is desirable.

[0064] [Table 2]

[0065] [Table 3]

[0066] The results in Table 2 show that the dyed products obtained in Examples 1 to 7 have good dyeing foot, excellent light fastness, and excellent performance as polylactic acid dyed products. The results in Table 3 show that the dyed products obtained in Comparative Examples 1 to 6 have inconsistent dyeing foot and poor reproducibility. The color rendering of the dyed product obtained in Example 2 was also improved.

Claims

1. A yellow disperse dye which is a compound represented by the following formula (1) and / or the following formula (2), A red disperse dye which is a compound represented by the following formula (3), A blue disperse dye which is a compound represented by the following formula (4) and / or a mixture of two isomers represented by the following formula (5): A dye composition for polylactic acid fibers comprising: 【Chemistry 1】 【Chemistry 2】 【Chemistry 3】 (In the formula, R １ represents a methyl group or an ethyl group.) 【Chemistry 4】 (In the formula, R ２ represents a methyl group or an ethyl group.) 【Chemistry 5】 (In the formula, X １ and X ２ One side is NO ２ , the other represents OH.)

2. The composition further comprises a mixture of two dye compounds represented by the following formula (6):

2. The dye composition for polylactic acid fiber according to claim 1, wherein the content of the mixture is less than 5 parts by mass when the total amount of the yellow disperse dye, the red disperse dye, and the blue disperse dye is 100 parts by mass. 【Chemistry 6】 (In the formula, R ３ represents a methyl group or a methoxyethyl group.

3. The dye composition for polylactic acid fibers according to claim 1 , wherein the yellow disperse dye, the red disperse dye, and the blue disperse dye are dispersed with a dispersant.

4. The dye composition for polylactic acid fiber according to claim 3, wherein the dispersant is one or more compounds selected from the group consisting of formalin condensates of naphthalenesulfonic acid and alkylbenzenesulfonic acid, formalin condensates of naphthalenesulfonic acid, formalin condensates of cresolsulfonic acid, formalin condensates of cresol and 2-naphthol-6-sulfonic acid, formalin condensates of alkylnaphthalenesulfonic acid, formalin condensates of creosote oil sulfonic acid, ligninsulfonic acid, block copolymers of ethylene oxide and propylene oxide, ethylene oxide adducts of alkylphenols, and ethylene oxide adducts of polystyrenated phenols.

5. 4. The dye composition for polylactic acid fibers according to claim 3, wherein the content of quinoline contained as an impurity derived from the dispersant is less than 1000 ppm.

6. A polylactic acid fiber dyed with the dye composition for polylactic acid fiber according to any one of claims 1 to 5.

7. A step of diluting the dye composition for polylactic acid fiber according to any one of claims 1 to 5 to prepare a dye dispersion; A step of immersing polylactic acid fibers in the dye dispersion; A method for dyeing polylactic acid fibers comprising the steps of:

8. The method for dyeing polylactic acid fiber according to claim 7, wherein the temperature of the dye dispersion is set to 110 to 120°C in the immersion step.

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