Colorant for silicone products and preparation method thereof

Abstract

The invention discloses a colorant for silicone products and a preparation method thereof, belonging to the technical field of fine chemicals. The key points of the technical scheme are that the colorant comprises the following raw materials in parts by weight: 40-60 parts of inorganic pigments, 30-50 parts of silicone oils, and 2-7 parts of dispersants; the dispersant comprises modified sodium alginate and sodium dodecyl sulfate in a weight ratio of 1:(0.5-1.2), so as to solve the problem that inorganic pigments are easy to form agglomerates and have poor coloring effect.

Description

Technical Field

[0001] The present invention relates to the technical field of fine chemicals, and in particular to a colorant for organosilicon products and a preparation method thereof. Background Art

[0002] Silicone rubber has the characteristics of high and low temperature resistance, aging resistance, oil resistance and chemical resistance. It is widely used in medical and health, aviation, wire and cable, electronic appliances and automotive machinery. In the fields of medical and health and electronic appliances, silicone rubber needs to be colored, and colorant is a type of silicone rubber additive. Its function is to give rubber products the desired color. Selecting suitable colorant is the key to improving the appearance and overall quality of silicone products, so it is generally valued.

[0003] The colorants used in silicone rubber mainly include inorganic pigments and organic pigments. Organic pigment colorants have bright colors, strong coloring ability and are non-toxic. However, the migration resistance, heat resistance and light resistance of organic pigments are worse than those of inorganic pigments. Therefore, inorganic pigments are usually used as colorants for silicone products. However, the compatibility between inorganic pigments and resins is poor, resulting in poor dispersion of inorganic pigments in resins, which causes the problem of reduced coloring ability of inorganic pigments during application. Summary of the invention

[0004] In order to solve the problem that inorganic pigments are easy to form agglomerates and have poor coloring properties, the present invention provides a colorant for silicone products and a preparation method thereof.

[0005] The first object of the present invention is to provide a colorant for silicone products, using the following technical solution:

[0006] A colorant for silicone products, the colorant comprises the following raw materials in parts by weight: 40-60 parts of inorganic pigment, 30-50 parts of silicone oil, and 2-7 parts of dispersant; the dispersant comprises modified sodium alginate and sodium dodecyl sulfate in a weight ratio of 1: (0.5-1.2).

[0007] Preferably, the modified sodium alginate is obtained by the following preparation method: sodium alginate is mixed with water and a surfactant and stirred until the sodium alginate is completely dissolved, then a base is added to adjust the pH of the solution to 8.5-9.5, dodecyl glycidyl ether is added dropwise under a water bath temperature of 70-80°C, and refluxed at this temperature for 7.5-8.5h, after the reaction is completed, the solution is cooled and the pH is adjusted to 3.5-4.5 with an organic acid, washed with acetone, filtered and dried to obtain the modified sodium alginate, and the weight ratio of the sodium alginate to dodecyl glycidyl ether is 1:(0.7-1).

[0008] Preferably, the weight ratio of sodium alginate to water is 1:(25-35).

[0009] Preferably, the added amount of the surfactant is 3-6% by weight of the sodium alginate.

[0010] Preferably, the surfactant is polyethylene glycol ether.

[0011] Preferably, the inorganic pigment is an inorganic pigment that has been modified, and the modification method comprises the following steps: mixing the inorganic pigment and tetrahydrofuran, and then stirring and dispersing them evenly at a temperature of 60-70°C, and then adding a monomer mixture, stirring while adding dropwise, reacting for 2-3 hours after the addition is completed, and then filtering, washing, and drying at 60-70°C to obtain a modified inorganic pigment. The raw materials of the monomer mixture include acrylic acid, 2-hydroxyethyl methacrylate, silicon-containing acrylic monomer, butyl acetate and an initiator, and the weight ratio of acrylic acid, 2-hydroxyethyl methacrylate, silicon-containing acrylic monomer, and butyl acetate is 1: (1-1.5): (0.5-0.7): (0.2-0.4).

[0012] Preferably, the added amount of the initiator is 2% of the total amount of acrylic acid, 2-hydroxyethyl methacrylate and silicon-containing acrylic monomer, and the initiator is dibenzoyl peroxide.

[0013] Preferably, the weight ratio of the total amount of acrylic acid, 2-hydroxyethyl methacrylate, and silicon-containing acrylic monomer to the inorganic pigment is (1-1.5):1.

[0014] Preferably, the weight ratio of the inorganic pigment to tetrahydrofuran is 1:(6-10).

[0015] The inventors found that by using modified sodium alginate and sodium dodecyl sulfate as dispersants to disperse silicon-containing acrylic polymer modified pigments, the obtained colorant has good dispersibility and can exist stably for a long time in silicone products, thereby greatly improving the uniformity and stability of coloring. This may be because, on the one hand, sodium alginate has a hydrophobic long chain obtained by modification with dodecyl, which can have better compatibility in organic bodies such as silicone oil and play a better dispersing effect. In addition, it has the same hydrophobic chain as sodium dodecyl sulfate and obtains similar compatibility, thereby improving the contact between the two, improving the electrostatic repulsion effect, and being more conducive to the dispersion of inorganic pigments; on the other hand, the inorganic pigment has improved compatibility in silicone oil and dispersion through modification with silicon-containing polyacrylate, and sodium dodecyl sulfate and sodium alginate modified with dodecyl can achieve a certain entanglement with the polymer chain on the surface of the pigment through the alkane long chain, and further based on the repulsion effect, the inorganic pigment can stably maintain a good dispersion, and the compatibility between the components is also improved, so that the obtained colorant is uniform and stable.

[0016] The second object of the present invention is to provide a method for preparing the above-mentioned colorant for silicone products, comprising the following steps:

[0017] S1. Add inorganic pigment and dispersant into silicone oil and stir to mix;

[0018] S2. Grind the mixture obtained in step S1 at a temperature of 50-60° C. for 20-30 minutes to obtain a colorant for silicone products having a viscosity of 25000-30000 mPa·s.

[0019] In summary, the present invention has the following beneficial effects:

[0020] 1. In the present application, the dispersant is composed of modified sodium alginate and sodium dodecyl sulfate, which can effectively improve the dispersibility of inorganic pigments. The reason is that the combination of modified sodium alginate and sodium dodecyl sulfate can provide electrostatic repulsion and spatial barrier for inorganic pigments, thereby making them more stable in the system and reducing the probability of agglomeration. In addition, the combination of modified sodium alginate and sodium dodecyl sulfate can increase the compatibility between inorganic pigments and silicone resins, thereby providing a guarantee for the effective dispersion of inorganic pigments in silicone resins.

[0021] 2. In the preparation process of modified sodium alginate in the present application, the water content also has a relatively important influence on the modification of sodium alginate. When the water content is relatively low, the sodium alginate solution is relatively viscous, and its contact area with dodecyl glycidyl ether is very small, and it is relatively difficult to undergo a grafting reaction, resulting in a poor modification effect of the sodium alginate. When the water content is relatively high, since dodecyl glycidyl ether is insoluble in water, dodecyl glycidyl ether is easily aggregated together and is not easy to undergo a grafting reaction with sodium alginate. Therefore, in the present application, when the weight ratio of sodium alginate to water is limited to 1:25-35, the reaction efficiency of sodium alginate and dodecyl glycidyl ether can be effectively improved.

[0022] 3. In the preparation process of modified sodium alginate, the addition of surfactant can increase the solubility of dodecyl glycidyl ether in sodium alginate solution, so that the contact area between dodecyl glycidyl ether and sodium alginate increases, which is beneficial to the grafting reaction. However, when the addition amount of surfactant is relatively large, the yield of modified sodium alginate will be reduced. The reason is that when the concentration of surfactant is higher than its critical micelle concentration, a certain amount of core-shell micelles will be formed in the sodium alginate solution, thereby wrapping dodecyl glycidyl ether in the core of the micelle, reducing the contact area between dodecyl glycidyl ether and sodium alginate, resulting in a decrease in the yield of modified sodium alginate.

[0023] 4. This application further modifies the inorganic pigments by polymer encapsulation, which can effectively improve the compatibility of the inorganic pigments with the silicone resin and reduce the probability of agglomeration of the inorganic pigments in the silicone resin. At the same time, after the inorganic pigments are modified by polymer encapsulation, the coloring effect of the silicone products and the migration resistance of the colorant can be effectively improved. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below with reference to the embodiments.

[0025] The raw materials used in the examples and comparative examples of the present application are all commercially available.

[0026] For the purpose of illustration, titanium dioxide is used as the inorganic pigment in this application.

[0027] Example 1

[0028] A method for preparing a colorant for silicone products comprises the following steps:

[0029] S1, adding 4 kg of inorganic pigment and 0.2 kg of dispersant into 3 kg of silicone oil and stirring and mixing for 10 minutes, wherein the dispersant comprises modified sodium alginate and sodium dodecyl sulfate in a weight ratio of 1:0.5;

[0030] The modified sodium alginate is obtained by the following preparation method: 1 kg of sodium alginate is mixed with 25 kg of water and 0.03 kg of a surfactant (polyethylene glycol ether) and stirred until the sodium alginate is completely dissolved, then sodium hydroxide is added to adjust the pH value of the solution to 8.5, under the condition that the water bath temperature is 70°C, 0.7 kg of dodecyl glycidyl ether is added dropwise, and refluxed at this temperature for 7.5 hours, after the reaction is completed, the solution is cooled to room temperature and the pH value of the solution is adjusted to 3.5 with acetic acid, washed with acetone, filtered and dried to obtain the modified sodium alginate, wherein the weight ratio of sodium alginate to dodecyl glycidyl ether is 1:0.7, and the weight ratio of sodium alginate to water is 1:25;

[0031] S2. Grind the mixture obtained in step S1 at a temperature of 50° C. for 30 minutes to obtain a colorant for silicone products with a viscosity of 25000 mPa·s.

[0032] Example 2

[0033] A method for preparing a colorant for silicone products comprises the following steps:

[0034] S1. Add 5 kg of inorganic pigment and 0.5 kg of dispersant into 4 kg of silicone oil and stir for 10 minutes, wherein the dispersant comprises modified sodium alginate and sodium dodecyl sulfate in a weight ratio of 1:0.5;

[0035] The modified sodium alginate is obtained by the following preparation method: 1 kg of sodium alginate is mixed with 25 kg of water and 0.03 kg of a surfactant (polyethylene glycol ether) and stirred until the sodium alginate is completely dissolved, then sodium hydroxide is added to adjust the pH value of the solution to 8.5, under the condition that the water bath temperature is 70°C, 0.7 kg of dodecyl glycidyl ether is added dropwise, and refluxed at this temperature for 7.5 hours, after the reaction is completed, the solution is cooled to room temperature and the pH value of the solution is adjusted to 3.5 with acetic acid, washed with acetone, filtered and dried to obtain the modified sodium alginate, wherein the weight ratio of sodium alginate to dodecyl glycidyl ether is 1:0.7, and the weight ratio of sodium alginate to water is 1:25;

[0036] S2. Grind the mixture obtained in step S1 at a temperature of 55° C. for 25 minutes to obtain a colorant for silicone products with a viscosity of 27500 mPa·s.

[0037] Example 3

[0038] A method for preparing a colorant for silicone products comprises the following steps:

[0039] S1. Add 6 kg of inorganic pigment and 0.7 kg of dispersant into 5 kg of silicone oil and stir for 10 minutes, wherein the dispersant comprises modified sodium alginate and sodium dodecyl sulfate in a weight ratio of 1:0.5;

[0040] The modified sodium alginate is obtained by the following preparation method: 1 kg of sodium alginate is mixed with 25 kg of water and 0.03 kg of a surfactant (polyethylene glycol ether) and stirred until the sodium alginate is completely dissolved, then sodium hydroxide is added to adjust the pH value of the solution to 8.5, under the condition that the water bath temperature is 70°C, 0.7 kg of dodecyl glycidyl ether is added dropwise, and refluxed at this temperature for 7.5 hours, after the reaction is completed, the solution is cooled to room temperature and the pH value of the solution is adjusted to 3.5 with acetic acid, washed with acetone, filtered and dried to obtain the modified sodium alginate, wherein the weight ratio of sodium alginate to dodecyl glycidyl ether is 1:0.7, and the weight ratio of sodium alginate to water is 1:25;

[0041] S2. Grind the mixture obtained in step S1 at 60° C. for 20 minutes to obtain a colorant for silicone products with a viscosity of 30,000 mPa·s.

[0042] Example 4

[0043] A method for preparing a colorant for silicone products, which is different from Example 2 in that the weight ratio of modified sodium alginate to sodium dodecyl sulfate is 1:0.8, and the rest is the same as Example 2.

[0044] Example 5

[0045] A method for preparing a colorant for silicone products, which is different from Example 2 in that the weight ratio of modified sodium alginate to sodium dodecyl sulfate is 1:1.2, and the rest is the same as Example 2.

[0046] Example 6

[0047] A method for preparing a colorant for silicone products, which is different from Example 4 in that the amount of raw materials used in the preparation of modified sodium alginate is different, as follows:

[0048] 1 kg of sodium alginate was mixed with 30 kg of water and 0.05 kg of a surfactant (polyethylene glycol ether) and stirred until the sodium alginate was completely dissolved, and then sodium hydroxide was added to adjust the pH value of the solution to 9. Under the condition of a water bath temperature of 75°C, 0.7 kg of dodecyl glycidyl ether was added dropwise, and refluxed at this temperature for 7.5 hours. After the reaction was completed, the solution was cooled to room temperature and the pH value of the solution was adjusted to 3.5 with acetic acid. The solution was washed with acetone, filtered and dried to obtain modified sodium alginate, wherein the weight ratio of sodium alginate to dodecyl glycidyl ether was 1:0.7, and the weight ratio of sodium alginate to water was 1:30. The rest was the same as in Example 2.

[0049] Example 7

[0050] A method for preparing a colorant for silicone products, which is different from Example 4 in that the amount of raw materials used in the preparation of modified sodium alginate is different, as follows:

[0051] 1 kg of sodium alginate was mixed with 35 kg of water and 0.06 kg of surfactant (polyethylene glycol ether) and stirred until the sodium alginate was completely dissolved, and then sodium hydroxide was added to adjust the pH of the solution to 9. Under the condition of a water bath temperature of 75°C, 0.7 kg of dodecyl glycidyl ether was added dropwise, and refluxed at this temperature for 7.5 hours. After the reaction was completed, it was cooled to room temperature and the pH of the solution was adjusted to 3.5 with acetic acid. The solution was washed with acetone, filtered and dried to obtain modified sodium alginate, wherein the weight ratio of sodium alginate to dodecyl glycidyl ether was 1:0.7, and the weight ratio of sodium alginate to water was 1:35.

[0052] Example 8

[0053] A method for preparing a colorant for silicone products, which is different from Example 4 in that the amount of raw materials used in the preparation of modified sodium alginate is different, as follows:

[0054] 1 kg of sodium alginate was mixed with 30 kg of water and 0.05 kg of surfactant (polyethylene glycol ether) and stirred until the sodium alginate was completely dissolved, and then sodium hydroxide was added to adjust the pH of the solution to 9.5. Under the condition of a water bath temperature of 80°C, 1 kg of dodecyl glycidyl ether was added dropwise, and refluxed at this temperature for 8.5 hours. After the reaction was completed, it was cooled to room temperature and the pH of the solution was adjusted to 4.5 with acetic acid. The solution was washed with acetone, filtered and dried to obtain modified sodium alginate, wherein the weight ratio of sodium alginate to dodecyl glycidyl ether was 1:1, and the weight ratio of sodium alginate to water was 1:30.

[0055] Example 9

[0056] A method for preparing a colorant for silicone products, which is different from Example 6 in that the surfactant polyethylene glycol ether is not added in the preparation of the modified sodium alginate, and the rest is the same as Example 6.

[0057] Example 10

[0058] A method for preparing a colorant for silicone products is different from Example 6 in that, in the preparation of modified sodium alginate, the added amount of the surfactant polyethylene glycol ether is 0.02 kg, and the rest is the same as Example 6.

[0059] Embodiment 11

[0060] A method for preparing a colorant for silicone products, which is different from Example 6 in that, in the preparation of modified sodium alginate, the added amount of surfactant polyethylene glycol ether is 0.07 kg, and the rest is the same as Example 6.

[0061] Example 12

[0062] A method for preparing a colorant for silicone products, which is different from Example 6 in that, in the preparation of modified sodium alginate, the amount of water added is 20 kg, and the rest is the same as Example 6.

[0063] Embodiment 13

[0064] A method for preparing a colorant for silicone products, which is different from Example 6 in that, in the preparation of modified sodium alginate, the amount of water added is 40 kg, and the rest is the same as Example 6.

[0065] Embodiment 14

[0066] A method for preparing a colorant for an organosilicon product, which is different from Example 6 in that the inorganic pigment is a modified inorganic pigment, wherein the modification method comprises the following steps:

[0067] (1) 5 kg of inorganic pigment and 30 kg of tetrahydrofuran were mixed, and then stirred and dispersed uniformly at a temperature of 60° C.;

[0068] (2) preparing a monomer mixture, adding 2 kg of acrylic acid, 2 kg of 2-hydroxyethyl methacrylate, 1 kg of a silicon-containing acrylic monomer (triisopropylsilyl acrylate is used in all embodiments of the present application), and 0.1 kg of dibenzoyl peroxide to 0.4 kg of butyl acetate and stirring for 30 min to obtain a monomer mixture, and adding the monomer mixture dropwise to the mixture obtained in step (1) at 60° C. while stirring. After the addition is completed, the mixture is kept warm for reaction for 2 h, and then filtered, washed, and dried at 60° C. to obtain a modified inorganic pigment.

[0069] Embodiment 15

[0070] A method for preparing a colorant for an organosilicon product, which is different from Example 6 in that the inorganic pigment is a modified inorganic pigment, wherein the modification method comprises the following steps:

[0071] (1) 5 kg of inorganic pigment and 40 kg of tetrahydrofuran were mixed, and then stirred and dispersed uniformly at a temperature of 65° C.;

[0072] (2) Prepare a monomer mixture: add 2.1 kg of acrylic acid, 2.6 kg of 2-hydroxyethyl methacrylate, 1.3 kg of silicon-containing acrylic monomer, and 0.12 kg of dibenzoyl peroxide to 0.63 kg of butyl acetate and stir for 30 min to obtain a monomer mixture; add the monomer mixture dropwise to the mixture obtained in step (1) at 65° C. while stirring; after the addition is completed, keep the mixture warm for 2.5 hours, filter it with suction, wash it, and dry it at 65° C. to obtain a modified inorganic pigment.

[0073] Comparative Example 15

[0074] A method for preparing a colorant for silicone products, which is different from Example 15 in that no silicon-containing acrylic monomer is added to the monomer emulsion, and the added amounts of other monomers are: 2.7 kg of acrylic acid, 3.3 kg of 2-hydroxyethyl methacrylate, and the rest are the same as Example 15.

[0075] Example 16

[0076] A method for preparing a colorant for an organosilicon product, which is different from Example 6 in that the inorganic pigment is a modified inorganic pigment, wherein the modification method comprises the following steps:

[0077] (1) 5 kg of inorganic pigment and 50 kg of tetrahydrofuran were mixed, and then stirred and dispersed uniformly at a temperature of 70° C.;

[0078] (2) Prepare a monomer mixture: add 2.2 kg of acrylic acid, 3.3 kg of 2-hydroxyethyl methacrylate, 1.5 kg of silicon-containing acrylic monomer, and 0.14 kg of dibenzoyl peroxide to 0.88 kg of butyl acetate and stir for 30 min to obtain a monomer mixture; add the monomer mixture dropwise to the mixture obtained in step (1) at 70° C. while stirring; after the addition is completed, keep the mixture warm for 2.5 hours, filter it with suction, wash it, and dry it at 70° C. to obtain a modified inorganic pigment.

[0079] Comparative Example 16

[0080] A method for preparing a colorant for silicone products, which is different from Example 16 in that an equal amount of ethyl acrylate is used instead of acrylic acid, and the rest is the same as Example 16.

[0081] Comparative Example 1

[0082] A method for preparing a colorant for silicone products, which is different from Example 2 in that unmodified sodium alginate is used, and the rest is the same as Example 2.

[0083] Comparative Example 2

[0084] A method for preparing a colorant for silicone products, which is different from Example 14 in that unmodified sodium alginate is used, and the rest is the same as Example 14.

[0085] Comparative Example 3

[0086] A method for preparing a colorant for silicone products is different from Example 2 in that only sodium dodecyl sulfate is used as a dispersant, and the rest is the same as Example 2.

[0087] Comparative Example 4

[0088] A method for preparing a colorant for silicone products is different from Example 2 in that only modified sodium alginate is used as the dispersant, and the rest is the same as Example 2.

[0089] Comparative Example 5

[0090] A method for preparing a colorant for silicone products, which is different from Example 2 in that silicone oil is not added in step S2, and the colorant for silicone products is obtained by directly stirring and mixing at a temperature of 55° C. for 25 minutes, and the rest is the same as Example 2.

[0091] Performance Testing

[0092] The colorants obtained in the above examples and comparative examples were tested for stability and migration resistance. The test results are shown in Table 1.

[0093] The stability test includes aggregation degree test, sedimentation stability and instability index test, specifically: the aggregation degree test is as follows: the colorant obtained in the above embodiment or comparative example is diluted to 30 mL with ethanol, and then placed in an environment with a temperature of 25°C and a pH of 7 for 2 hours, and the average particle size before and after placement is measured, which are expressed as d0 and dT, respectively, and the calculation formula is ST = (dT-d0) / d0×100%;

[0094] The sedimentation stability test is specifically as follows: the colorant obtained in the above embodiment or comparative example is diluted to 30 mL with ethanol, and stored at 25°C for 72 hours. The absorbance of the supernatant before and after storage at 500 nm is measured by a UV-visible spectrophotometer, which are expressed as A0 and A1, respectively, and the calculation formula is: R = A1 / A0 × 100%;

[0095] The stability index (TSI) was determined by placing the colorant obtained in the above examples or comparative examples in a special bottle of the analyzer, and measuring the scattering signal to evaluate its stability. The scanning frequency was 1 time / h. The TSI calculation formula was:

[0096]

[0097] The test of migration resistance is as follows: 2g of the organosilicon colorant obtained in the above embodiment or comparative example, 50g of α,ω-dihydroxypolysiloxane, 50g of nano calcium carbonate, 4g of tetrabutyl ketoxime silane, and 0.1g of dibutyltin dilaurate are mixed evenly, and the mixed slurry is coated on a black card with a 200μm coating preparation device. After film formation at room temperature, it is placed in a constant temperature box at 105℃±2℃ and dried until completely dry, the rubber is peeled off, and the black card is observed to see if there is any migrated pigment.

[0098] Table 1 Colorant performance test results

[0099]

[0100]

[0101] Note: The reference substance is 5 kg of inorganic pigment dispersed in 4 kg of ethanol.

[0102] From the table above we can see that:

[0103] The aggregation degree and instability index of the colorant obtained in the examples of the present application are much lower than those in the reference, and the sedimentation stability is much higher than that in the reference. It can be seen that the colorant obtained in the examples of the present application has good dispersion stability, and the migration resistance of the colorant obtained in the examples of the present application is better than the migration resistance of the inorganic pigment in the reference.

[0104] In Examples 1-3 of the present application, as the content of inorganic pigments, silicone oils and dispersants increases, the aggregation degree and instability index of the colorants obtained in Examples 1-3 decrease, and the sedimentation stability shows an increasing trend. However, when the dosage reaches the dosage of Example 3, the stability performance no longer increases. It can be seen that when the inorganic pigments, silicone oils and dispersants are within the scope of the present application, the stability performance of the colorant can be effectively guaranteed.

[0105] Compared with Example 2, as the proportion of sodium dodecyl sulfate in the dispersant increases, the stability of the colorant obtained in Example 4-5 is improved compared with Example 2. However, when the weight ratio of modified sodium alginate to sodium dodecyl sulfate reaches 1:1.2, the stability of the dispersant obtained in Example 5 no longer increases. It can be seen that when the ratio of sodium dodecyl sulfate to modified sodium alginate is within the scope of the present application, the colorant can be guaranteed to have good dispersibility and avoid agglomeration of the organic colorant during use.

[0106] Compared with Example 4, when the content of water and surfactant in the modified sodium alginate is increased compared with that in Example 4, the aggregation degree and instability index of the colorant obtained in Examples 6-7 are reduced, and the sedimentation stability is improved. However, it can be seen from Example 7 that after the content of water and surfactant is further increased compared with that in Example 6, its various properties do not show further improvement. It can be seen that when the water content is within the range specified in the present application, the dispersion effect of modified sodium alginate on inorganic pigments can be effectively improved.

[0107] Compared with Example 6, when the surfactant polyethylene glycol ether is lacking in the preparation process of the modified sodium alginate, the aggregation degree, instability index and sedimentation stability of the colorant obtained in Example 9 are worse than those in Example 6, indicating that the addition of surfactant can improve the grafting efficiency between dodecyl glycidyl ether and sodium alginate, thereby helping to improve the dispersion performance of modified sodium alginate for inorganic pigments.

[0108] Compared with Example 6, when the amount of surfactant is lower or higher than the limit of the present application, the aggregation degree, instability index and sedimentation stability of the colorant obtained in Examples 10-11 are worse than those in Example 6, indicating that when the amount of surfactant is within the range specified in the present application, the stability of the colorant can be guaranteed.

[0109] Compared with Example 6, when the amount of water in the preparation of modified sodium alginate is less than 25 kg or greater than 35 kg, the aggregation degree, instability index and sedimentation stability of the colorant obtained in Examples 12-13 are worse than those in Example 6. The possible reason is that when the amount of water is small, the amount of grafting of sodium alginate and dodecyl glycidyl ether is small, and the yield is low. When the water content is high, dodecyl glycidyl ether is easy to aggregate together and is not easy to undergo grafting reaction with sodium alginate, which also leads to low yield and poor dispersion performance of the colorant finally obtained.

[0110] Compared with Example 6, when the inorganic pigments are modified, the modified inorganic pigments and the modified sodium alginate can be used together to effectively improve the dispersion performance of the inorganic pigments, reduce the probability of aggregation of the inorganic pigments, and thus improve the dispersion stability of the inorganic pigments.

[0111] Compared with Example 15, when the silicon-containing acrylic monomer is lacking in the monomer mixture, the stability of the colorant in Comparative Example 15 is reduced compared with Example 15. Compared with Example 16, when an equal amount of ethyl acrylate is used to replace acrylic acid, the stability of the colorant obtained in Comparative Example 16 is reduced compared with Example 16. It can be seen that the combination of acrylic acid, 2-hydroxyethyl methacrylate and silicon-containing acrylic monomer can achieve effective coating of inorganic pigments, thereby improving the dispersion stability of inorganic pigments.

[0112] Compared with Example 2, when unmodified sodium alginate or only sodium dodecyl sulfate is used as a dispersant or only modified sodium alginate is used as a dispersant or silicone oil is lacking in the colorant raw material, the dispersion stability of the colorant obtained in Comparative Examples 1-5 is reduced. It can be seen that the combined use of modified sodium alginate, silicone oil and sodium dodecyl sulfate in the present application can effectively improve the dispersion stability of inorganic pigments.

[0113] Compared with Comparative Examples 1-2, Example 14 has the best dispersion stability. It can be seen that after sodium alginate is modified and matched with sodium dodecyl sulfate, and the pigment surface is modified, the two modification methods work together to further improve the dispersion stability of the inorganic pigment.

[0114] The embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A colorant for silicone products, characterized in that: The colorant is composed of the following raw materials in parts by weight: 40-60 parts of inorganic pigment, 30-50 parts of silicone oil, and 2-7 parts of dispersant; the dispersant includes modified sodium alginate and sodium dodecyl sulfate in a weight ratio of 1: (0.5-1.2); The modified sodium alginate is obtained by the following preparation method: sodium alginate is mixed with water and a surfactant and stirred until the sodium alginate is completely dissolved, then a base is added to adjust the pH value of the solution to 8.5-9.5, dodecyl glycidyl ether is added dropwise under the condition of a water bath temperature of 70-80° C., and refluxed at this temperature for 7.5-8.5 hours, after the reaction is completed, the solution is cooled and adjusted to a pH value of 3.5-4.5 with an organic acid, washed with acetone, filtered, and dried to obtain the modified sodium alginate; The inorganic pigment is modified, and the modification method comprises the following steps: mixing the inorganic pigment and tetrahydrofuran, and then stirring and dispersing them uniformly at a temperature of 60-70° C., and then adding a monomer mixture, stirring while adding dropwise, reacting for 2-3 hours after the addition is completed, and then filtering, washing, and drying at 60-70° C. to obtain a modified inorganic pigment, wherein the raw materials of the monomer mixture include acrylic acid, 2-hydroxyethyl methacrylate, a silicon-containing acrylic monomer, butyl acetate, and an initiator; The weight ratio of sodium alginate to dodecyl glycidyl ether is 1:(0.7-1); The weight ratio of acrylic acid, 2-hydroxyethyl methacrylate, silicon-containing acrylic monomer, and butyl acetate is 1: (1-1.5): (0.5-0.7): (0.2-0.4); The weight ratio of the total amount of acrylic acid, 2-hydroxyethyl methacrylate, and silicon-containing acrylic monomer to the inorganic pigment is (1-1.5):

1.

2. A colorant for silicone products according to claim 1, characterized in that: The weight ratio of the sodium alginate to water is 1:(25-35).

3. A colorant for silicone products according to claim 1, characterized in that: The added amount of the surfactant is 3-6% of the weight of the sodium alginate.

4. The colorant for silicone products according to claim 1, characterized in that: The surfactant is polyethylene glycol ether.

5. The colorant for silicone products according to claim 1, characterized in that: The added amount of the initiator is 2% of the total amount of acrylic acid, 2-hydroxyethyl methacrylate and silicon-containing acrylic monomer, and the initiator is dibenzoyl peroxide.

6. The colorant for silicone products according to claim 1, characterized in that: The weight ratio of the inorganic pigment to tetrahydrofuran is 1:(6-10).

7. A method for preparing a colorant for silicone products according to any one of claims 1 to 6, characterized in that: The steps include: S1. Add inorganic pigment and dispersant into silicone oil and stir to mix; S2. Grind the mixture obtained in step S1 at a temperature of 50-60° C. for 20-30 minutes to obtain a colorant for silicone products having a viscosity of 25000-30000 mPa·s.

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