Storage method of thiohydracrylic acid, thiohydracrylic acid composition and thiohydracrylic acid ester

Abstract

The invention relates to the technical field of optical materials, in particular to a storage method of thiohydracrylic acid, a thiohydracrylic acid composition and thiohydracrylic acid ester. Specifically, the invention provides a storage method of thiohydracrylic acid, and a polymerization inhibitor is added into thiohydracrylic acid. The polymerization inhibitor is added into the thiohydracrylic acid, so that the content of the thiohydracrylic acid can be ensured to be greater than or equal to 98.0% after the thiohydracrylic acid is placed for 3 months, the esterification rate can be improved in the esterification reaction, and the thiohydracrylic acid carboxylic ester can meet the requirement that the yellow index is less than or equal to 5.0 in the application of optical resin.

Description

Technical Field

[0001] The invention relates to the technical field of optical materials, and in particular to a storage method of mercaptopropionic acid, a mercaptopropionic acid composition and a mercaptopropionic ester. Background Art

[0002] Mercaptopropionic acid is widely used in esterification reactions, such as methyl mercaptopropionate, pentaerythritol tetrakis (3-mercaptopropionate), inositol hexa (mercaptopropionate), trimethylolpropane tris (3-mercaptopropionate), etc. When mercaptopropionic acid is used as a raw material for optical resin, the product color requirement is ≤15Hazen to meet the requirements of optical resin, which places high demands on the color quality of mercaptopropionic acid itself.

[0003] Mercaptopropionic acid itself is unstable. With the influence of storage time and temperature, the thiol and carboxyl groups of mercaptopropionic acid can condense through thioester bonds between molecules to form thioesters, which can be compounds formed by intermolecular bonds of two, three or more molecules. The presence of these thioesters will affect the purity of the product and affect downstream use. As described in patent CN101405261B, when the content of raw material mercaptopropionic acid thioester is greater than 5%, the hue of pentaerythritol mercaptocarboxylate deteriorates, and the viscosity of the polymerizable composition before polymerization with the polyiso(thio)cyanate compound increases, resulting in a deterioration in the hue of the lens or white turbidity.

[0004] The boiling point of thioester after self-polymerization of mercaptopropionic acid is 394°C (101.33Kpa). When the thioester increases, the content of mercaptopropionic acid will decrease accordingly, affecting downstream use. At present, the purification method of mercaptopropionic acid is through secondary distillation, which cannot control the formation of thioester from the source. Summary of the invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a storage method of mercaptopropionic acid, a mercaptopropionic acid composition and a mercaptopropionic ester, and to increase the storage time of mercaptopropionic acid by controlling the generation of thioesters.

[0006] The invention provides application of a polymerization inhibitor in improving the storage stability of mercaptopropionic acid.

[0007] Optionally, the polymerization inhibitor includes one or more of phenolic polymerization inhibitors and quinone polymerization inhibitors.

[0008] The invention provides a storage method for mercaptopropionic acid, wherein a polymerization inhibitor is added to the mercaptopropionic acid.

[0009] Optionally, the addition amount of the polymerization inhibitor is 10 to 600 ppm.

[0010] Optionally, the polymerization inhibitor includes one or more of phenolic polymerization inhibitors and quinone polymerization inhibitors.

[0011] Optionally, the phenolic polymerization inhibitor includes one or more of hydroquinone, p-hydroxyanisole, 2,6-di-tert-butyl-p-cresol, 2,5-di-tert-butylhydroquinone, and 2-tert-butylhydroquinone;

[0012] The quinone inhibitor includes one or more of p-benzoquinone, chlorobenzoquinone and 1,4-naphthoquinone.

[0013] The invention provides a mercaptopropionic acid composition, comprising mercaptopropionic acid and a polymerization inhibitor.

[0014] Optionally, the amount of the polymerization inhibitor added is 10 to 600 ppm;

[0015] The polymerization inhibitor includes one or more of phenolic polymerization inhibitors and quinone polymerization inhibitors.

[0016] The invention provides a mercaptopropionic ester, which is prepared by esterification reaction of the mercaptopropionic acid composition and an alcohol compound.

[0017] The invention provides an optical resin, which is prepared by taking the mercaptopropionic acid ester as a raw material.

[0018] Compared with the prior art, the present invention provides a storage method for mercaptopropionic acid, wherein a polymerization inhibitor is added to the mercaptopropionic acid. By adding the polymerization inhibitor to the mercaptopropionic acid, the present invention can ensure that the content of mercaptopropionic acid is ≥98.0% after being placed for 3 months, and can improve the esterification rate in the esterification reaction, and mercaptopropionic acid carboxylate can meet the yellow index of ≤5.0 in the application of optical resin. DETAILED DESCRIPTION

[0019] The invention provides application of a polymerization inhibitor in improving the storage stability of mercaptopropionic acid.

[0020] Preferably, the polymerization inhibitor includes one or more of phenolic polymerization inhibitors and quinone polymerization inhibitors.

[0021] Preferably, the phenolic polymerization inhibitor includes one or more of hydroquinone, p-hydroxyanisole, 2,6-di-tert-butyl-p-cresol, 2,5-di-tert-butylhydroquinone, and 2-tert-butylhydroquinone.

[0022] Preferably, the quinone inhibitor includes one or more of p-benzoquinone, tetrachlorobenzoquinone, and 1,4-naphthoquinone.

[0023] In some specific embodiments of the present invention, the polymerization inhibitor is p-hydroxyanisole.

[0024] The invention avoids the formation of thioester by condensing the thioester bond between the thioester group and the carboxyl group of the mercaptopropionic acid molecules, thereby avoiding the generation of the mercaptopropionic acid thioester.

[0025] Based on this, the present invention provides a storage method of mercaptopropionic acid, wherein an inhibitor is added to the mercaptopropionic acid.

[0026] The amount of the polymerization inhibitor added is preferably 10 to 600 ppm, specifically 10 ppm, 20 ppm, 30 ppm, 50 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, or a range value with any of the above values ​​as the upper or lower limit, more preferably 30 to 600 ppm, further preferably 300 to 600 ppm.

[0027] The test results show that excessive addition of polymerization inhibitor will cause the chromaticity of mercaptopropionic acid and its prepared esters to increase. Therefore, it is necessary to control the addition amount of polymerization inhibitor to solve the chromaticity problem of mercaptopropionic acid polymerization and its products.

[0028] As the inhibitor is introduced into the mercaptopropionic acid, the mercaptopropionic acid can be stored more stably and can be stored for 3 months, with the mercaptopropionic acid content still being ≥98.0% and the chromaticity being ≤10.0 Hazen.

[0029] The storage temperature of the mercaptopropionic acid is not particularly limited in the present invention, and is preferably 18 to 50° C. The freezing point of mercaptopropionic acid is 15 to 18° C. When the temperature is lower than the freezing point, mercaptopropionic acid becomes solid and needs to be melted into liquid again when used. To avoid repeated heating of mercaptopropionic acid, the storage temperature is preferably greater than 18° C. The increase in temperature will promote the generation of thioesters, so to avoid the generation of thioesters, the storage temperature is preferably 18 to 50° C., and more preferably 18 to 40° C.

[0030] Preferably, the polymerization inhibitor includes one or more of phenolic polymerization inhibitors and quinone polymerization inhibitors.

[0031] Preferably, the phenolic polymerization inhibitor includes one or more of hydroquinone, p-hydroxyanisole, 2,6-di-tert-butyl-p-cresol, 2,5-di-tert-butylhydroquinone, and 2-tert-butylhydroquinone.

[0032] Preferably, the quinone inhibitor includes one or more of p-benzoquinone, tetrachlorobenzoquinone, and 1,4-naphthoquinone.

[0033] In some specific embodiments of the present invention, the polymerization inhibitor is p-hydroxyanisole.

[0034] p-Hydroxyanisole is a white flake or waxy white crystal with a boiling point of 243°C (101.33Kpa). It is easily soluble in organic solvents such as ethanol, ether, acetone, acetic acid, and ethyl acetate. When p-Hydroxyanisole consumes free radicals, it will become p-benzoquinone. During the use of p-Hydroxyanisole, its inhibition mechanism is that phenols are oxidized into corresponding quinones that combine with free radicals in the chain to inhibit polymerization.

[0035] Quinone inhibitors such as p-benzoquinone can also play an inhibitory role under anaerobic conditions. p-Benzoquinone is a yellow crystal that can be dissolved in alcohol and ether. Benzoquinone compounds have a highly conjugated structure, so they are all colored compounds. Most p-quinones are yellow, and most ortho-quinones are red or orange. Therefore, the more inhibitors are added, the better. When the amount of inhibitor added is 30-600ppm, it can not only inhibit the oxidation of mercaptopropionic acid and protect the product content, but also avoid the problem of increased color of mercaptopropionic acid products. Through research, it is found that when the amount of inhibitor added is 30-600ppm, the color of mercaptopropionic acid is ≤10Hazen, which can meet the application of downstream products.

[0036] The invention also provides a mercaptopropionic acid composition, comprising mercaptopropionic acid and a polymerization inhibitor.

[0037] The amount of the polymerization inhibitor added is preferably 10 to 600 ppm, specifically 10 ppm, 20 ppm, 30 ppm, 50 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, or a range value with any of the above values ​​as the upper or lower limit, more preferably 30 to 600 ppm, further preferably 300 to 600 ppm.

[0038] Preferably, the polymerization inhibitor includes one or more of phenolic polymerization inhibitors and quinone polymerization inhibitors.

[0039] Preferably, the phenolic polymerization inhibitor includes one or more of hydroquinone, p-hydroxyanisole, 2,6-di-tert-butyl-p-cresol, 2,5-di-tert-butylhydroquinone, and 2-tert-butylhydroquinone.

[0040] Preferably, the quinone inhibitor includes one or more of p-benzoquinone, tetrachlorobenzoquinone, and 1,4-naphthoquinone.

[0041] In some specific embodiments of the present invention, the polymerization inhibitor is p-hydroxyanisole.

[0042] After the mercaptopropionic acid composition is stored for 3 months, the mercaptopropionic acid content thereof can still be ≥98.0% and the chromaticity ≤10.0 Hazen.

[0043] The invention provides a mercaptopropionic ester, which is prepared by esterification reaction of the mercaptopropionic acid composition and an alcohol compound.

[0044] The present invention has no special limitation on the alcohol compound, which may be an alcohol compound for preparing mercaptopropionic acid ester, and may be a monohydric alcohol, a dihydric alcohol or a polyhydric alcohol.

[0045] The monohydric alcohol is preferably a C1-C10 monohydric alcohol, including but not limited to methanol, ethanol, etc.; the dihydric alcohol is preferably a C2-C10 dihydric alcohol, including but not limited to ethylene glycol, etc.; the polyhydric alcohol is preferably a 3-6-hydric alcohol, such as one or more of a C3-C15 trihydric alcohol, a C4-C20 tetrahydric alcohol, a C5-C20 pentahydric alcohol or a C6-C20 hexahydric alcohol, including but not limited to one or more of 1,3-propylene glycol, trimethylolpropane, pentaerythritol, sorbitol, etc.

[0046] The present invention does not specifically limit the specific synthesis method of the mercaptopropionic ester, and it can be a method well known to those skilled in the art. For example, referring to the esterification reaction in "Basic Organic Chemistry", mercaptopropionic acid and an alcohol compound are added to a four-necked flask equipped with a mechanical stirrer, a thermometer, a reflux condenser and a water separator, and a catalyst and a water-carrying agent are added to carry out an esterification reaction.

[0047] In order to increase the esterification reaction rate, preferably, an esterification catalyst and a water-carrying agent are added to promote the reaction.

[0048] The present invention has no particular limitation on the esterification catalyst, which can be a catalyst suitable for esterification reaction well known to those skilled in the art, preferably one or more of hydrochloric acid, sulfuric acid, phosphoric acid, p-toluenesulfonic acid, methanesulfonic acid and trifluoroacetic acid.

[0049] The present invention has no special limitation on the amount of the esterification catalyst added, and it can be a general catalytic amount. Preferably, the molar amount of the catalyst is 0.1% to 5% of the molar amount of mercaptopropionic acid.

[0050] The present invention has no special limitation on the water-carrying agent, and can be a water-carrying agent suitable for esterification reaction well known to those skilled in the art. The water-carrying agent is preferably one or more of toluene, xylene, dichloroethylene, chloroform, cyclohexane, n-hexane and chlorobenzene.

[0051] The temperature of the esterification reaction is preferably 80 to 90° C., and the time of the esterification reaction is preferably 8 to 20 hours.

[0052] After the reaction is completed, the system is cooled, the liquid is separated, and the product is washed with water, and then the low-boiling substances are removed under reduced pressure to obtain mercaptopropionic acid ester.

[0053] The mercaptopropionic acid ester prepared by the invention can be used for preparing optical materials.

[0054] The optical material includes but is not limited to optical resin.

[0055] Based on this, the present invention provides an optical resin prepared using the above-mentioned mercaptopropionic acid ester as a raw material.

[0056] The present invention has no particular limitation on the method for preparing the optical resin, and the method may be a method for preparing an optical resin well known to those skilled in the art.

[0057] For example, the following method is used for preparation:

[0058] The above-mentioned mercaptopropionic acid ester is used as a raw material, and then a mixture of toluene diisocyanate, dimethyltin dichloride, butoxyethyl acid phosphate and di(butoxyethyl acid phosphate) is fully stirred and mixed at room temperature. The obtained mixture is then decompressed and degassed to obtain a uniform monomer mixture. The monomer mixture is injected into a molding die including a pair of glass molds and a resin gasket. The wall thickness and diameter of the plastic lens are set, and the molding die is assembled.

[0059] After the monomer mixture is injected into a molding mold, it is heated and polymerized to obtain an optical resin lens.

[0060] The heating polymerization is preferably carried out by heating from 20°C to 120°C and heating at 120°C for 3 to 6 hours.

[0061] Preferably, the time for raising the temperature from 20°C to 120°C is 10 to 20 hours.

[0062] Under the influence of environmental factors such as ultraviolet radiation, the internal molecular chains and molecular structures of polymer materials such as resin plastics will change, and the changes reflected on the surface of the material are yellowing. The yellowness index is usually used to characterize the degree of yellowing of the material, and the yellowness index meter is used to measure the scope and trend of yellowing.

[0063] The yellowness index (YI) is used to characterize the degree of yellowing (yellowing) of colorless, transparent, translucent or nearly white polymer materials.

[0064] Expression method: YI = 100 (C x XC z Z) / Y

[0065] X, Y, and Z are tristimulus values, and Cx and Cz values ​​can be found in relevant ASTM standard materials.

[0066] The yellowness index can be positive or negative. The larger the yellowness index, the yellower the sample.

[0067] The present invention adopts Vista spectrophotometer to characterize yellow index YIE313. Firstly, a circular flat lens with a wall thickness of 5 mm and a diameter of 75 mm is manufactured. Then, Vista spectrophotometer is used to measure the spectrum range of 400 nm to 700 nm. The yellow index YI≤5.0 is qualified.

[0068] In some specific embodiments of the present invention, pentaerythritol tetrakis (3-mercaptopropionate) is prepared using mercaptopropionic acid and pentaerythritol, the product chromaticity is ≤15 Hazen, and is used to prepare optical resin, and the obtained optical lens has a yellow index of ≤5.0.

[0069] In order to further illustrate the present invention, the following is a detailed description in conjunction with the embodiments. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the invention.

[0070] All raw materials of the present invention have no particular limitation on their sources, and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0071] In the following examples, the content of mercaptopropionic acid was analyzed by the following method: Agilent 1260 Infinity II liquid chromatography system was used, 0.01MH3PO4 / acetonitrile (40 / 60) aqueous solution was used as the mobile phase, the column temperature was 40°C, the flow rate of the mobile phase was 0.95 ml / min, and the wavelength was 230 nm, the content of mercaptopropionic acid and mercaptopropionic acid self-polymer was analyzed. The total area sum of the two was 100%.

[0072] The chromaticity of mercaptopropionic acid and mercaptopropionic acid esters was measured using a UV752 ultraviolet-visible spectrophotometer.

[0073] Examples 1-5

[0074] The mercaptopropionic acid provided by Yifeng New Materials Co., Ltd. was used for analysis by Agilent 1260 Infinity II liquid chromatography. The content of mercaptopropionic acid was 99.5%, and the content of mercaptopropionic acid thioester was 0.5%. The color of mercaptopropionic acid was measured by UV752 ultraviolet-visible spectrophotometer, and the color was 3.7 Hazen.

[0075] Different types of inhibitors and different contents of inhibitors were added to mercaptopropionic acid, and the contents and chromaticity were measured after the mixture was placed at 18°C-40°C for 3 months.

[0076] The mercaptopropionic acid to which the polymerization inhibitor was added was used as a raw material to synthesize the mercaptopropionic acid ester, and the mercaptopropionic acid ester was placed at 18°C-40°C for 3 months and then the content and colorimetry were analyzed. The example of the stability verification of mercaptopropionic acid is shown in Table 1 below:

[0077] Table 1

[0078]

[0079]

[0080] Comparative Example 1

[0081] No polymerization inhibitor was added to the mercaptopropionic acid, and the remaining operations were the same as those in Example 1-5.

[0082] Example 6 Preparation of pentaerythritol tetrakis (3-mercaptopropionic acid) ester

[0083] The mercaptopropionic acid after being placed for 3 months in the above embodiment is used as a raw material to prepare mercaptopropionic ester, and the synthesis process is as follows:

[0084] Into a 1000ml four-necked flask equipped with a mechanical stirrer, a thermometer, a reflux condenser and a water separator, 4.2mol of mercaptopropionic acid and 1.0mol of pentaerythritol which had been placed for 3 months in Examples 1-5 and Comparative Example 1 were respectively added, 6.5g of a 70% aqueous solution of methanesulfonic acid and 310g of cyclohexane as a water-carrying agent were added, the temperature was controlled at 80-90°C and refluxed for reaction for 11 hours, then the temperature was lowered, the liquids were separated and washed with water, and the product was decompressed to remove low-boiling substances to obtain pentaerythritol tetrakis(3-mercaptopropionic acid) ester.

[0085] The esterification rate and chromaticity of the prepared pentaerythritol tetrakis (3-mercaptopropionic acid) ester were tested, and the results are shown in Table 2.

[0086] Example 7 Preparation of optical resin

[0087] 43.9 g of pentaerythritol tetrakis (3-mercaptopropionic acid) ester prepared in Example 6 was used as a raw material, and then mixed with 50.7 g of toluene diisocyanate, 0.02 g of dimethyltin dichloride, and 0.30 g of a mixture of butoxyethyl acid phosphate and di(butoxyethyl acid phosphate) (mass ratio 1:1) and stirred at room temperature. The obtained mixture was then deaerated under reduced pressure at 500 Pa to obtain a uniform monomer mixture. The above monomer mixture was injected into a molding die comprising a pair of glass molds and a resin gasket. In addition, the above pair of glass molds used a mold with an upper mold curvature of 600 mm and a lower mold curvature of 120 mm, and the molding die was assembled in such a way that the center wall thickness of the plastic lens became 5 mm and the diameter became 75 mm.

[0088] After the monomer mixture was injected into the molding die, the temperature was raised from 20°C to 120°C over 15 hours, polymerized at 120°C for 4 hours, cooled, and the plastic lens was taken out from the molding die to obtain an optical resin lens. The evaluation results are shown in Table 2.

[0089] Table 2

[0090]

[0091] By adding 30ppm-600ppm of inhibitor to mercaptopropionic acid, the content of the product can be guaranteed to be ≥98.0% after being placed for 3 months, and the esterification rate can be increased in the esterification reaction. Mercaptopropionic acid carboxylate can meet the yellowness index of ≤5.0 in optical resin applications.

[0092] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. Application of inhibitors in improving the storage stability of mercaptopropionic acid.

2. The use according to claim 1, characterized in that: The polymerization inhibitor includes one or more of phenolic polymerization inhibitors and quinone polymerization inhibitors.

3. A storage method for mercaptopropionic acid, characterized in that: A polymerization inhibitor is added into the mercaptopropionic acid.

4. The storage method according to claim 3, characterized in that: The addition amount of the polymerization inhibitor is 10 to 600 ppm.

5. The storage method according to claim 3, characterized in that: The polymerization inhibitor includes one or more of phenolic polymerization inhibitors and quinone polymerization inhibitors.

6. The storage method according to claim 5, characterized in that: The phenolic polymerization inhibitor includes one or more of hydroquinone, p-hydroxyanisole, 2,6-di-tert-butyl-p-cresol, 2,5-di-tert-butyl-hydroquinone, and 2-tert-butyl-hydroquinone; The quinone inhibitor includes one or more of p-benzoquinone, chlorobenzoquinone and 1,4-naphthoquinone.

7. A mercaptopropionic acid composition comprising mercaptopropionic acid and a polymerization inhibitor.

8. The mercaptopropionic acid composition according to claim 7, characterized in that The addition amount of the polymerization inhibitor is 10 to 600 ppm; The polymerization inhibitor includes one or more of phenolic polymerization inhibitors and quinone polymerization inhibitors.

9. A mercaptopropionic ester prepared by esterifying the mercaptopropionic acid composition according to any one of claims 7 to 8 with an alcohol compound.

10. An optical resin prepared using the mercaptopropionic acid ester according to claim 9 as a raw material.

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