Molecule for enhancing hair strength and use thereof

Abstract

The application discloses a molecule for improving hair toughness and application thereof. The molecule for improving hair toughness is a molecule with conjugated double bonds obtained through esterification or acylation reaction of a compound with two hydroxyl groups at two ends, a compound with two amino groups at two ends or a compound with a hydroxyl group at one end and an amino group at the other end and an organic acid or an acid anhydride containing an alpha,beta-carbon-carbon double bond, and the molecule is used to improve hair toughness through Michael addition reaction with sulfydryl in damaged hair. The molecule for improving hair toughness prepared in the application is combined with sulfydryl through a covalent bond, improves the mechanical properties of hair, has relatively good permeability, and can avoid further oxidation of free sulfydryl.

Description

Technical Field

[0001] This invention belongs to the field of hair care products technology, and in particular relates to a molecule that enhances hair strength and its application. Background Technology

[0002] With the increasing demand for hair care, people are washing, perming, dyeing, and styling their hair more frequently. This process often leads to hair lipid degradation, and the breaking and oxidation of disulfide bonds. The breaking of disulfide bonds results in a loss of hair's mechanical strength, reduced water retention, and decreased antioxidant capacity. Research shows that 17% of the amino acids in hair are cysteine. In healthy hair, cysteine ​​residues are bonded together by disulfide bonds to form cystine. However, in damaged hair, disulfide bonds are reduced to thiol groups, which are then oxidized to sulfonate groups, causing the chemical bonds between cysteine ​​residues to break, thus leading to a decline in hair's mechanical properties.

[0003] To address the aforementioned issues, the development of suitable functional molecules for hair care is an urgent market demand. Currently, the most widely used hair-strengthening active ingredients fall into three main categories: (1) forming a film on the hair surface to protect the cuticle and cortex and enhance the hair's water-controlling ability; (2) influencing the mechanical properties of keratin by changing the moisture content and state of the hair; and (3) influencing the mechanical properties of keratin by strengthening the proteins inside the hair or binding to proteins. However, these methods mainly improve tensile properties by strengthening secondary bonds such as hydrogen bonds, salt bonds, and van der Waals forces, which are greatly affected by external environmental factors, and the loss of active ingredients is also quite serious. In contrast, there is a gap in the development of functional active molecules targeting disulfide bonds. Therefore, the development of novel functional molecules to improve hair tensile properties has become a research hotspot. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a molecule for enhancing hair strength and its applications. This invention utilizes compounds with hydroxyl groups at both ends, compounds with amino groups at both ends, or compounds containing a hydroxyl group at one end and an amino group at the other, reacted with an organic acid or anhydride containing an α,β-carbon double bond through esterification or acylation reactions to obtain molecules with conjugated double bonds. These molecules can protect free sulfhydryl groups in hair through Michael addition reactions, thereby enhancing hair strength.

[0005] The technical solution of the present invention is as follows:

[0006] A hair disulfide bond reconnection repair molecule, wherein the hair disulfide bond reconnection repair molecule is obtained by reacting a compound containing hydroxyl and / or amino groups with an organic acid or anhydride; the compound includes compounds with hydroxyl groups at both ends, compounds with amino groups at both ends, or compounds containing a hydroxyl group at one end and an amino group at the other end; the organic acid or anhydride is an organic acid or anhydride containing α,β-carbon-carbon double bonds; the organic acid is bonded to both sides of the compound containing hydroxyl and / or amino groups through ester bonds and amide bonds.

[0007] Furthermore, the polyhydroxy or amino compound is a compound containing two or more esterifying or acylating groups; the esterifying or acylating groups include one or more of phenolic hydroxyl, alcoholic hydroxyl, and primary amino groups.

[0008] Furthermore, the polyhydroxy or amino compound contains a hydrophobic carbon chain with six or more carbon atoms and less than twenty carbon atoms.

[0009] Furthermore, the polyhydroxy or amino compounds include polyols or polyamines.

[0010] Further, the hydroxyl and / or amino-containing compounds include one or more of 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1-aminohexanol, 1-aminoheptanol, 1-aminooctanol, 1-aminononanol, and 1-aminodecanol.

[0011] Further, the organic acid includes one or more of acrylic acid, fumaric acid, shikimic acid, maleic acid, methacrylic acid, 2-butenoic acid, and 2-pentenoic acid; the acid anhydride includes one or more of acrylic anhydride, fumaric anhydride, shikimic acid anhydride, maleic anhydride, methacrylic anhydride, 2-butenoic anhydride, and 2-pentenoic anhydride. Furthermore, the hair disulfide bond reconnection repair molecule comprises 1,6-hexanediol diester, 1,6-hexanediol fumarate diester, 1,6-hexanediol shikimate diester, 1,6-hexanediol maleate diester, 1,6-hexanediol methacrylate diester, 1,6-hexanediol 2-butenoic acid diester, 1,6-hexanediol 2-pentenoic acid diester, 1,7-heptanediol diester, 1,7-heptanediol fumarate diester, 1,7-heptanediol shikimate diester, 1,7-heptanediol maleate diester, 1,7-heptanediol methacrylate diester, 1,7-heptanediol 2-butenoic acid diester, 1,7-heptanediol 2-pentenoic acid diester, 1,8-octanediol... Diethyl acrylate, 1,8-octanediol fumarate diester, 1,8-octanediol shikimate diester, 1,8-octanediol maleic acid diester, 1,8-octanediol methacrylate diester, 1,8-octanediol 2-butenoic acid diester, 1,8-octanediol 2-pentenoic acid diester, 1,9-nonanediol acrylate diester, 1,9-nonanediol fumarate diester, 1,9-nonanediol shikimate diester, 1,9-nonanediol maleic acid diester, 1,9-nonanediol methacrylate diester, 1,9-nonanediol 2-butenoic acid diester, 1,9-nonanediol 2-pentenoic acid diester, 1,10-decanediol acrylate diester, 1,10-decanediol fumarate diester, 1,10- Decanediol shikimate diester, 1,10-decanediol maleic acid diester, 1,10-decanediol methacrylate diester, 1,10-decanediol 2-butenoic acid diester, 1,10-decanediol 2-pentenoic acid diester, 1,6-hexanediamine diacrylamide, 1,6-hexanediamine difumaramide, 1,6-hexanediamine dishikimate, 1,6-hexanediamine dimaleic acid amide, 1,6-hexanediamine dimethacrylamide, 1,6-hexanediamine di-2-butenoic acid amide, 1,6-hexanediamine di-2-pentenoic acid amide, 1,7-heptanediamine diacrylamide, 1,7-heptanediamine difumaramide, 1,7-heptanediamine dishikimate, 1,7 -Heptanediamine dimaleamide, 1,7-Heptanediamine dimethacrylamide, 1,7-Heptanediamine di-2-butenoic acid amide, 1,7-Heptanediamine di-2-pentenoic acid amide, 1,8-Octandiamine diacrylamide, 1,8-Octandiamine difumaramide, 1,8-Octandiamine dishikimic acid amide, 1,8-Octandiamine dimaleamide, 1,8-Octandiamine dimethacrylamide, 1,8-Octandiamine di-2-butenoic acid amide, 1,8-Octandiamine di-2-pentenoic acid amide, 1,9-Nonadiamine diacrylamide, 1,9-Nonadiamine difumaramide, 1,9-Nonadiamine dishikimic acid amide, 1,9-Nonadiamine dimaleamide, 1,9-Nonadiamine dimethacrylamide, 1,9-nonadiamine di-2-butenoic acid amide, 1,9-nonadiamine di-2-pentenoic acid amide, 1,10-decanediamine dimethacrylamide, 1,10-decanediamine difumaramide, 1,10-decanediamine dishikimic acid amide, 1,10-decanediamine dimaleic acid amide, 1,10-decanediamine dimethacrylamide, 1,10-decanediamine di-2-butenoic acid amide, 1,10-decanediamine di-2-pentenoic acid amide, 6-acrylamidohexyl acrylate, 6-methylpropenyl Hexyl methacrylate, 6-maleamidohexyl maleate, 6-fumaramidohexyl fumarate, 6-(2-butenamido)2-butenyl hexyl ester, 6-(2-pentenamido)2-pentenyl hexyl ester, 6-shikimidylshikimate, 7-acrylamidoacrylate, 7-methacrylamidomethacrylate, 7-maleamidohexyl maleate, 7-fumaramidohexyl fumarate, 7-(2-butenamido)2-butenyl hexyl ester, 7-(2-pentenamido)2-pentenyl hexyl ester Heptyl acrylate, 7-shikimidoyl shikimate, octyl 8-acrylamidoacrylate, octyl 8-methacrylamidomethacrylate, octyl 8-maleamidomaleic acid, octyl 8-fumaramidofumaric acid, octyl 8-(2-butenamido)2-butenanoic acid, octyl 8-(2-pentenamido)2-pentenanoic acid, octyl 8-shikimidoyl shikimate, octyl 9-acrylamidoacrylate, 9-methacrylamidomethacrylate, octyl 9-maleamidomaleic acid, octyl 9-fumaramidofumaric acid Nonyl maleate, nonyl 9-(2-butenamido)-2-butenonic acid, nonyl 9-(2-pentenamido)-2-pentenonic acid, nonyl 9-shikimidylshikimate, decyl 10-acrylamidoacrylate, decyl 10-methacrylamidomethacrylate, decyl 10-maleamidomaleate, decyl 10-fumaramidofumarate, decyl 10-(2-butenamido)-2-butenonic acid, decyl 10-(2-pentenamido)-2-pentenonic acid, and decyl 10-shikimidylshikimate are selected from one or more of these.

[0012] Furthermore, the hair disulfide bond reconnection repair molecule includes one or more of the following structural formulas:

[0013]

[0014]

[0015]

[0016]

[0017]

[0018] A method for preparing the hair disulfide bond reconnection repair molecule includes the following steps: mixing a polyhydroxy or amino compound, an organic acid, and a solvent, stirring the mixture, filtering, and purifying to obtain the hair disulfide bond reconnection repair molecule; the stirring reaction is carried out at a temperature of 40-60℃ for 1-6 hours.

[0019] Further, the solvent is acetone; the mixture of the hydroxyl or amino compound and the organic acid is referred to as the reactant; the mass ratio of the reactant to acetone is 0.1-0.5:1, preferably 0.2-0.4:1, and most preferably 0.3:1; the molar ratio of the hydroxyl or amino compound to the organic acid or anhydride is 1:2-1:2.5, preferably 1:2-1:2.2.

[0020] A hair disulfide bond reconnection repair molecule for hair strengthening, wherein the method of using the hair disulfide bond reconnection repair molecule for hair strengthening is as follows:

[0021] (1) After mixing the hair disulfide bond reconnection repair molecule with water, stir to dissolve, and then add triethanolamine to adjust the pH value to obtain a hair strengthening agent solution.

[0022] (2) After soaking the damaged hair strands in the hair strengthening agent solution prepared in step (1) and reacting, take them out and air dry them; the reaction temperature is 35℃-50℃, preferably 40℃, and the time is 5-30min.

[0023] In step (1), the mass concentration of hair disulfide bond reconnection repair molecules in the hair strengthening agent solution is ≥0.1%, preferably 0.1-1.0%, most preferably 0.5%, and the pH value is 5-8, preferably 7.

[0024] The present invention also protects the hair strengthening agent solution obtained in step (1) above, wherein the pH value of the hair strengthening agent solution is 5-8.

[0025] The beneficial technical effects of this invention are as follows:

[0026] This invention relates to molecules with multiple α,β-unsaturated ester or α,β-unsaturated amide structures prepared by esterification or acylation of compounds with hydroxyl groups at both ends, compounds with amino groups at both ends, or compounds with a hydroxyl group at one end and an amino group at the other end with organic acids or anhydrides containing α,β-carbon double bonds, and these molecules are used in the field of hair care products.

[0027] This invention utilizes the click reaction between carbon-carbon double bond groups of molecules with multiple α,β-unsaturated ester or α,β-unsaturated amide structures and cysteine ​​thiol groups that damage hair keratin to form CS bonds. This process protects the internal thiol groups of the hair, enhances its strength, and solves the problem of impaired hair mechanical properties caused by disulfide bond damage due to various stresses (including bleaching, perming, dyeing, pollution exposure, UV irradiation, repeated washing, high temperatures, etc.).

[0028] Meanwhile, this invention prepares repair molecules with α-carbonyl carbon-carbon double bonds at both ends by reacting hydroxyl or amino compounds with similar symmetrical structures with organic acids. The repair molecules with approximately symmetrical structures can simultaneously connect keratin at both ends, forming two CS bonds, which can improve the binding rate of organic thiol groups.

[0029] The molecule proposed in this invention enhances hair strength by using covalent bonds to compensate for the loss of covalent bonds caused by the breaking of disulfide bonds, thereby compensating for mechanical damage and improving hair strength, compared to traditional molecules that interact with hair keratin through hydrogen bonds, ionic bonds, and van der Waals forces.

[0030] Furthermore, the molecule proposed in this invention exhibits superior permeability and reactivity tailored to the specific properties of hair. Compared to molecules that typically perform the Michael reaction, the molecule proposed in this invention is notable for possessing a relatively long hydrophobic group, which enhances its hair-penetrating properties. This allows it to easily penetrate the hair cuticle and lipid layer, entering the spaces between keratinocytes to initiate a chemical reaction. Attached Figure Description

[0031] Figure 1 This is the HPLC spectrum of the product molecule in Example 1 of the present invention.

[0032] Figure 2 The structural characteristics of the product molecule in Example 2 of this invention 1 H-NMR spectrum.

[0033] Figure 3 The structural features of the product molecule in Example 3 of this invention 1 H-NMR spectrum.

[0034] Figure 4 The structural characteristics of the product molecule in Example 4 of this invention 1 H-NMR simulated spectrum.

[0035] Figure 5 The structural characteristics of the product molecule in Example 5 of this invention 1 H-NMR simulated spectrum. Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0037] This invention proposes using the Michael reaction to design molecules that enhance hair strength by reconnecting disulfide bonds in damaged hair, thereby improving hair's mechanical properties. Based on the fact that -SH can undergo Michael addition reactions with some molecules having specific C=C bond structures, it is possible to protect -SH and improve hair's mechanical properties.

[0038] Taking 1,6-hexanediamine bismaleamide as an example, the specific reaction route for reconnecting disulfide bonds in damaged hair using the repair molecule of the present invention is shown below:

[0039]

[0040] As can be seen from the above reaction pathway, the repair molecule proposed in this invention can react with the sulfhydryl groups in cysteine ​​residues in damaged hair to form CS bonds. Simultaneously, because the repair molecule proposed in this invention has a symmetrical or near-symmetrical structure containing two reactive groups, it can react with the cysteine ​​residues of two keratin peptide chains, thereby acting as a link between the two keratin peptide bonds. Through this link, the intermolecular forces between keratin peptide chains in the hair strand are strengthened, giving the hair strand the ability to resist external stress, thus resulting in improved hair strength.

[0041] The preparation method of the hair disulfide bond reconnection repair molecule of the present invention includes the following steps: mixing a polyhydroxy or amino compound, an organic acid and a solvent, stirring and reacting, filtering and purifying to obtain the hair disulfide bond reconnection repair molecule.

[0042] In one embodiment of the present invention, the temperature of the stirring reaction is 40°C, 45°C, 50°C, 55°C or 60°C, and the time is 1h, 2h, 3h, 4h, 5h or 6h.

[0043] In one embodiment of the present invention, the solvent is acetone; the mixture of the hydroxyl or amino compound and the organic acid is referred to as the reactant; the mass ratio of the reactant to acetone is 0.1:1, 0.2:1, 0.3:1, 0.4:1 or 0.5:1; the molar ratio of the hydroxyl or amino compound to the organic acid or anhydride is 1:2, 1:2.3, 1:2.2, 1:2.3, 1:2.4 or 1:2.5.

[0044] The hair disulfide bond reconnection repair molecule of this invention is used for hair strengthening, and the method of using the hair disulfide bond reconnection repair molecule for hair strengthening is as follows:

[0045] (1) After mixing the hair disulfide bond reconnection repair molecule with water, stir to dissolve, and then add triethanolamine to adjust the pH value to obtain a hair strengthening agent solution.

[0046] (2) After soaking the damaged hair strands in the hair strengthening agent solution prepared in step (1) and reacting, remove them and let them air dry.

[0047] In step (1), the mass concentration of hair disulfide bond reconnection repair molecules in the hair strengthening agent solution is ≥0.1%. In one embodiment of the present invention, the mass concentration is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.7%, 0.8%, or 1.0%, and the pH value is 5, 6, 7, or 8.

[0048] In one embodiment of the present invention, in step (2), the temperature of the reaction is 35°C, 40°C, 42°C, 45°C or 50°C, and the time is 5 min, 8 min, 10 min, 15 min, 18 min, 20 min, 23 min, 25 min or 30 min.

[0049] The present invention will be further described below through specific embodiments.

[0050] Example 1

[0051] Dimaleyl 1,8-octanediamine was synthesized from 1,8-octanediamine and maleic anhydride. The synthetic route is as follows.

[0052]

[0053] The specific method of synthesis is as follows:

[0054] The reactants maleic anhydride and 1,8-octanediamine were accurately weighed using a balance (specific reaction conditions are shown in Table 1). Acetone was selected as the reaction solvent, and both were added to a three-necked flask. The mixture was stirred at 60°C for 1 hour. The resulting product was purified by recrystallization twice. After the reaction was complete, the solvent was evaporated to obtain a yellow solid. After recrystallization twice, a fine yellow powder was obtained, which is the repair molecule proposed in this invention. The structural characteristic spectrum of this molecule is shown in [Figure 1]. Figure 5 HPLC chromatogram as follows Figure 1 As shown.

[0055] Yield Calculation: The reaction product was titrated with acid value. The acid value was calculated first, and then the yield was calculated based on the acid value. The specific method was as follows: Approximately 1.0 g of the sample was accurately weighed into a 250 ml Erlenmeyer flask, 25 ml of neutral ethanol was added, and the mixture was shaken well. Five drops of phenolphthalein indicator were added, and the solution was titrated with 0.1 mol / L standard KOH solution until it turned pink. The acid value and yield were calculated using the following formulas:

[0056]

[0057] In the formula: V is the volume of KOH standard concentration consumed in the titration, mL; c is the concentration of KOH standard solution, mol / L; m is the sample mass, g; 56.11 is the molar mass of KOH, g / mol.

[0058] Yield (%) = (Acid value at the beginning of the reaction - Acid value at the end of the reaction) * 100% / (Acid value at the beginning of the reaction - Theoretical acid value at the end of the reaction)

[0059] The yields of the products obtained in Example 1 are shown in Table 1.

[0060] Examples 2-5

[0061] Examples 2-5 describe the reactions of different polyhydroxy or amino compounds with different organic acids or their anhydrides to obtain molecule protectants (specific raw materials, contents, and reaction conditions are shown in Table 1). The synthetic routes for Examples 2-4 are as follows:

[0062] Example 2

[0063]

[0064] Example 3

[0065]

[0066] Example 4

[0067]

[0068] The polyhydroxy or polyamino compounds (denoted as B) in the examples were reacted with organic acids (or anhydrides) (denoted as A) in different types, molar ratios, reaction times, and reaction temperatures to obtain Examples 2-5. The yields were calculated using the method of Example 1. The specific conditions and yields of Examples 2-5 and Comparative Examples 1-5 are shown in Table 1. The structural characteristic spectra of the products obtained in Examples 2-3 are shown below. Figure 2-3 As shown. Figure 4-5 The simulated spectra of the product molecules in Examples 4-5 are shown in sequence. As can be seen from Examples 1-3 and the preliminary experiments, the simulated spectra are the same as the actual measured spectra for the products of this application.

[0069] Comparative Examples 1-5

[0070] In Table 1, the polyhydroxy or polyamino compounds (denoted as B) in the comparative examples were varied with different types of organic acids (or anhydrides) (denoted as A), different molar ratios, reaction times, and reaction temperatures to obtain Comparative Examples 1-5. The yields were calculated using the same method as in Example 1. The specific conditions and yields of Comparative Examples 1-5 are shown in Table 1.

[0071] Table 1 Synthesis parameters and yields of the examples and comparative examples

[0072] Reactant A Reactant B <![CDATA[Raw material ratio / n A : n B > Reaction time / h Reaction temperature / ℃ Yield / % Example 1 Maleic anhydride 1,8-Octandiamine 2.5:1 1 60 77.53 Example 2 acrylic acid 1,8-Octanediol 2.5:1 5 20 81.25 Example 3 methacrylic acid 1-Hydroxyoctylamine 2:1 2 40 76.72 Example 4 Maleic acid 1,10-Decanediol 2:1 3 50 82.11 Example 5 Maleic anhydride 1,8-Octandiamine 2.15:1 6 30 81.73 Comparative Example 1 Maleic anhydride 1,8-Octanediol 1:1 1 60 2.71 Comparative Example 2 Maleic anhydride Lauryl alcohol 2.15:1 2 50 - Comparative Example 3 Maleic acid 1,4-Butanediamine 2.15:1 6 40 76.74 Comparative Example 4 fumaric acid 1,8-Octanediol 2.15:1 0.5 20 5.12 Comparative Example 5 methacrylic acid 1,8-Octandiamine 2.15:1 10 80 -

[0073] As can be seen from the table above, Examples 1-5 all exhibited good yields of the target product. Comparative Example 1 reduced the proportion of raw materials and decreased the amount of organic acid, resulting in a significantly lower yield of the target product. Comparative Example 2 used lauryl alcohol, which does not meet the requirements of this invention; lauryl alcohol has only one hydroxyl group, and after esterification, it has only one functional group. Subsequent application examples show that this product cannot improve hair strength. Comparative Example 3 used 1,4-butanediamine, which does not meet the requirements of this invention, lacking a long hydrophobic carbon chain. Subsequent application examples also show that this product has a poor effect on improving hair strength because the product molecule is too hydrophilic, hindering its penetration into the hair. Therefore, it is evident that the requirement of this invention that "the above-mentioned polyhydroxy or amino compounds have a structural characteristic of containing a hydrophobic carbon chain of six or more carbons and less than twenty carbons" is crucial for achieving the expected improvement in hair strength. Comparative Example 4 had a short reaction time and low reaction temperature, which is outside the conditions proposed in this invention, resulting in a very low yield. Comparative Example 5 had an excessively long reaction time and excessively high reaction temperature, which were outside the conditions proposed in this invention. The acid value of the final product was difficult to test, and the product had poor flowability. Analysis suggested that polyamide substances were formed, indicating that high temperature or long reaction time is detrimental to product formation.

[0074] Applied research: Enhancing the resilience of damaged hair

[0075] Given that disulfide bonds in hair break during UV irradiation or perming, generating free thiol groups, which further damage hair structure and reduce hair strength, the repair molecule prepared in this invention can protect thiol groups, forming CS bonds and improving hair strength. To explore the optimal conditions for the product molecule to protect free thiol groups, different experiments were designed to treat damaged hair strands. Healthy hair strands were provided by Shanghai Canyu Co., Ltd., model Natural black Chinese / 27cm x 1g, free 25cm; damaged hair strands were obtained by incubating healthy hair strands with a 6% thioglycolic acid aqueous solution for 3 hours.

[0076] Application Example 1 (corresponding to the product of Example 1):

[0077] Hair was treated using 1,8-octanediamine maleate prepared in Example 1. The principle is that 1,8-octanediamine maleate forms a CS bond with free thiol groups, thereby binding the free thiol groups and linking them to the keratin peptide chain. The reaction route is as follows:

[0078]

[0079] The specific method is as follows:

[0080] (1) Dimaleic 1,8-octanediamine was prepared and purified according to the method in Example 1;

[0081] (2) Take a 150ml beaker, add 0.5g of dimaleidoyl 1,8-octanediamine and 99.5g of deionized water, stir to dissolve, add an appropriate amount of triethanolamine to adjust the pH to 7.0, and obtain a 0.5wt% hair strengthening agent solution.

[0082] (3) Accurately weigh 0.5g of damaged hair strands and soak them in hair strengthening agent solution. Set the reaction temperature to 40℃ and the reaction time to 15min. Take them out and let them dry to obtain the treated hair strands.

[0083] Application Example 2: (Same as Application Example 1, except that in Application Example 1, the pH was changed from 7 to 8, the reaction temperature was changed to 35℃, the reaction time was changed to 30 min, and the concentration of the hair strengthening agent was changed to 1 wt%)

[0084] (1) Dimaleic 1,8-octanediamine was prepared and purified according to the method in Example 1;

[0085] (2) Take a 150ml beaker, add 1g of dimaleido-1,8-octanediamine and 99g of deionized water, stir to dissolve, add an appropriate amount of triethanolamine to adjust the pH to 8.0, and obtain a 1wt% hair strengthening agent solution.

[0086] (3) Accurately weigh 0.5g of damaged hair strands and soak them in hair strengthening agent solution. Set the reaction temperature to 35℃ and the reaction time to 30min. Take them out and let them dry to obtain the treated hair strands.

[0087] Application Example 3 (The product of Example 2 was changed, the pH was changed from 7 to 5, the reaction temperature was changed to 50°C, the reaction time was changed to 15 min, and the hair strengthening agent dosage was changed to 0.5 wt%)

[0088] (1) 1,8-octanediol diester was prepared and purified according to the method in Example 2;

[0089] (2) Take a 150ml beaker, add 0.5g of 1,8-octanediol acrylate diester and 99.5g of deionized water, stir to dissolve, add an appropriate amount of triethanolamine to adjust the pH to 5.0, and obtain a 0.5wt% hair strengthening agent solution.

[0090] (3) Accurately weigh 0.5g of damaged hair strands and soak them in hair strengthening agent solution. Set the reaction temperature to 50℃ and the reaction time to 15min. Take them out and let them dry to obtain the treated hair strands.

[0091] Comparative Application Example 1: (Same as Application Example 1, except that the pH was adjusted from 7 to 4 in Application Example 1)

[0092] (1) Dimaleic 1,8-octanediamine was prepared and purified according to the method in Example 1;

[0093] (2) Take a 150ml beaker, add 0.5g of dimaleido-1,8-octanediamine and 99.5g of deionized water, stir to dissolve, do not add triethanolamine to adjust the pH, the pH is about 4.0, and obtain a hair strengthening agent solution with a concentration of 0.5wt%.

[0094] (3) Accurately weigh 0.5g of damaged hair strands and soak them in hair strengthening agent solution. Set the reaction temperature to 40℃ and the reaction time to 15min. Take them out and let them dry to obtain the treated hair strands.

[0095] Comparative Example 2: (Same as Application Example 1, except that excess triethanolamine was added to adjust the pH to 11 in Application Example 1)

[0096] (1) Dimaleic 1,8-octanediamine was prepared and purified according to the method in Example 1;

[0097] (2) Take a 150ml beaker, add 0.5g of dimaleidoyl 1,8-octanediamine and 99.5g of deionized water, stir to dissolve, add an appropriate amount of triethanolamine to adjust the pH to 11.0, and obtain a 0.5wt% hair strengthening agent solution.

[0098] (3) Accurately weigh 0.5g of damaged hair strands and soak them in hair strengthening agent solution. Set the reaction temperature to 40℃ and the reaction time to 15min. Take them out and let them dry to obtain the treated hair strands.

[0099] Comparative Example 3: (Same as Application Example 1, except that the reaction was carried out at room temperature in Application Example 1, and the reaction time was shortened to 5 minutes)

[0100] (1) Dimaleic 1,8-octanediamine was prepared and purified according to the method in Example 1;

[0101] (2) Take a 150ml beaker, add 0.5g of dimaleido-1,8-octanediamine and 99.5g of deionized water, stir to dissolve, add an appropriate amount of triethanolamine to adjust the pH to about 7.0, and obtain a hair strengthening agent solution with a concentration of 0.5wt%.

[0102] (3) Accurately weigh 0.5g of damaged hair strands and soak them in hair strengthening agent solution. React at room temperature for 5 minutes. Remove and air dry to obtain the treated hair strands.

[0103] Comparative Example 4: (Same as Application Example 1, except that the amount of hair strengthening agent added in Application Example 1 is changed to 0.01% wt)

[0104] (1) Dimaleic 1,8-octanediamine was prepared and purified according to the method in Example 1;

[0105] (2) Take a 150ml beaker, add 0.01g of dimaleidoyl 1,8-octanediamine and 99.99g of deionized water, stir to dissolve, add an appropriate amount of triethanolamine to adjust the pH to about 7.0, and obtain a hair strengthening agent solution with a concentration of 0.01wt%.

[0106] (3) Accurately weigh 0.5g of damaged hair strands and soak them in hair strengthening agent solution. Set the reaction temperature to 40℃ and the reaction time to 15min. Take them out and let them dry to obtain the treated hair strands.

[0107] Comparative Example 5 (corresponding to the product of Comparative Example 2):

[0108] Using lauryl maleate prepared in Comparative Example 2:

[0109] (1) Lauryl maleate was prepared and purified according to the method of Comparative Example 2;

[0110] (2) Take a 150ml beaker, add 0.5g lauryl maleate and 99.5g deionized water, stir to dissolve, add an appropriate amount of triethanolamine to adjust pH=7.0, and obtain a 0.5wt% hair strengthening agent solution.

[0111] (3) Accurately weigh 0.5g of damaged hair strands and soak them in hair strengthening agent solution. Set the reaction temperature to 40℃ and the reaction time to 15min. Take them out and let them dry to obtain the treated hair strands.

[0112] Comparative Example 6 (compared to the product of Comparative Example 3):

[0113] The 1,4-butanediamine bismaleic acid amide prepared in Comparative Example 3 was used to strengthen damaged hair strands. The specific method is as follows:

[0114] (1) Dimaleic 1,4-butanediamine was prepared and purified according to the method of Comparative Example 3;

[0115] (2) Take a 150ml beaker, add 0.5g of 1,4-butanediamine and 99.5g of deionized water, stir to dissolve, add an appropriate amount of triethanolamine to adjust the pH to 7.0, and obtain a 0.5wt% hair strengthening agent solution.

[0116] (3) Accurately weigh 0.5g of damaged hair strands and soak them in hair strengthening agent solution. Set the reaction temperature to 40℃ and the reaction time to 15min. Take them out and let them dry to obtain the treated hair strands.

[0117] Test example:

[0118] (1) Detection of free thiol content:

[0119] The Ellman method was used to quantify free thiol groups in different hair strands. The principle of the Ellman method is as follows: Free thiol groups react with excess 5,5'-dithiobis(2-nitrobenzoic acid) (DNTB) at room temperature to form a colored substance that absorbs ultraviolet light at 412 nm (Emol = 13600). According to the Lambert-Beer law, A = Emol·C·L, where L = 1, the actual concentration of thiol groups can be determined by measuring the absorbance (A).

[0120] The specific procedure is as follows: Approximately 20 mg of hair sample was accurately measured and immersed in 1.0 mL of a reaction buffer consisting of 8 M urea, 10 mM DTNB, 3 mM EDTA, and 0.2 M Tris-HCl, at pH 8.0. The sample was incubated under nitrogen for 15 min. Then, it was centrifuged at 9000 rpm for 10 min to obtain the supernatant, and its absorbance was read at 412 nm using a UV spectrophotometer. Three replication experiments were performed for each data point. The thiol content was calculated using the following equation:

[0121] Thiol content (μmol*g) -1 = A*V / (13600*m)*100%.

[0122] In the formula: A is the absorbance value, V is the volume of the reaction buffer (1 ml here), and m is the precise mass of the hair sample in mg.

[0123] The free thiol content after different sample treatments is shown in Table 2 below.

[0124] Table 2. Thiol content and protection rate of different hair strands

[0125] Thiol content (μmol / g) Protection rate Healthy hair tie 0.217 - Damaged hair strands 62.67 - Application Example 1 1.67 97.34％ Application Example 2 10.85 83.56％ Application Example 3 2.97 95.26％ Application Comparative Example 1 41.45 33.86％ Application Comparative Example 2 32.46 48.20％ Application Comparative Example 3 37.25 40.56％ Application Comparative Example 4 48.57 22.50％ Application Comparative Example 5 1.77 97.18％ Application Comparative Example 6 58.94 59.52％

[0126] The above experimental results indicate that Comparative Examples 1-4 showed poor protection against thiol groups, while the application examples generally performed better. Comparative Example 5 also showed good protection against thiol groups, but subsequent studies found that it could not achieve hair strengthening effects due to its lack of a similar symmetrical structure. Furthermore, Comparative Example 6 showed some protection against thiol groups, but it was significantly weaker than the application examples. This is because the molecules manufactured in Comparative Example 3 were too hydrophilic, hindering penetration into the hair surface and thus resulting in a slightly weaker protective effect against thiol groups.

[0127] (2) Tensile property test (i.e., hair strength test):

[0128] Tensile properties were tested on hair bundles treated with the different methods described above. The specific testing methods are as follows: The diameter of the hair strands was measured using an SN-1200W high-definition camera, specifically by averaging the diameters at three points in the middle section. Thirty hair strands with diameter differences within 10 μm from each of the 15 different treated hair bundles were then tested for single fiber strength using a fiber strength tester. The tensile strength of the control group and each sample group was calculated and compared using the following formula:

[0129] σ=F b / S o

[0130] In the formula: σ is the tensile strength, F b The maximum force that the specimen withstands when it breaks, S o This represents the original cross-sectional area of ​​the sample. Furthermore, the average elastic modulus of the yarn is calculated from the elastic modulus region of the tensile curve.

[0131] The results of the hair tensile strength test are shown in Table 3 below.

[0132] Table 3 Comparison of hair stretching properties

[0133]

[0134] The elastic modulus of the hair in the test samples is shown in Table 4 below.

[0135] Table 4 Comparison of Hair Elastic Modulus

[0136]

[0137] The above results show that Application Examples 1-3 significantly improve hair strength (the greater the maximum tensile strength, the stronger the hair; the greater the elastic modulus, the tougher the hair), while Application Example 5 has virtually no effect, indicating that it does not conform to the molecular structure characteristics proposed in this invention (multiple esterifiable / acylated groups) and therefore cannot achieve this effect. Application Examples 1-4 also failed to improve hair strength, proving that the specific conditions of the application method proposed in this invention have practical significance. Application Example 6 showed a poor effect in improving hair strength, indicating that it does not conform to the molecular structure characteristics proposed in this invention (possessing hydrophobic carbon chains) and therefore has a poor effect in improving hair strength.

[0138] The above description is merely a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and variations that are directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included within the protection scope of the present invention.

Claims

1. Use of a hair disulfide bond rejoining repair molecule in a hair strengthening agent, characterized in that: The reactants maleic anhydride and 1,8-octanediamine are weighed, and acetone is used as a reaction solvent, and the mixture is stirred at 60°C for 1h. The obtained product is purified by recrystallization twice. After the reaction is completed, the solvent is evaporated to obtain a yellow solid, and the yellow fine powder is obtained after recrystallization twice. A hair disulfide bond reconnection repair molecule dimaleic acid 1,8-octanediamine is obtained. The method for using the hair disulfide bond reconnection repair molecule in a hair strengthening agent is as follows: 0.5g of the dimaleic acid 1,8-octanediamine, 99.5g of deionized water, stirring and dissolving, adding triethanolamine to adjust pH=7.0, and obtaining a 0.5wt% concentration of a hair strengthening agent solution; after the damaged hair bundle is soaked in the hair strengthening agent solution and reacted, it is taken out and dried; wherein the reaction temperature is 40°C, and the reaction time is 15 min.

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