Silicone resin prepolymer, modified polyester thereof and preparation methods of silicone resin prepolymer and modified polyester

Abstract

The invention relates to a silicon resin prepolymer, modified polyester thereof and preparation methods of the silicon resin prepolymer and the modified polyester, and belongs to the technical field of organic polymer materials. The preparation method comprises the following steps: carrying out a hydrolysis reaction on long-chain alkyl trialkoxysilane and phenyl chlorosilane under the catalysis of a weak base compound, hydrolyzing the product and oxysilane under the action of a strong base to form an alkoxy-terminated silicon resin prepolymer, and carrying out a catalytic modification reaction on the prepolymer, polyol and binary acid to generate modified polyester. The silicon resin prepolymer can maintain good compatibility and viscosity in polyester modification, so that the modified polyester has excellent impact resistance, weather resistance and water resistance.

Description

Technical Field

[0001] The invention relates to a silicone resin prepolymer, a modified polyester thereof and a preparation method thereof, and belongs to the technical field of organic polymer materials. Background Art

[0002] Compared with general organic resins, silicone resin has excellent thermal oxidation stability and UV resistance, and the coating can maintain stable performance for a long time in outdoor environment. Introducing silicone resin into other synthetic resins will make the resin performance more perfect. There are two methods for modifying synthetic resins with silicone: physical blending (cold blending) and chemical modification (hot blending). In most cases, chemical modification is more effective. The chemical modification method uses chemical bonds to combine two polymers with large polarity differences, which can improve the compatibility of the resin and achieve a uniform dispersion effect at the microscopic level. It can not only retain the mechanical properties, hardness, gloss, adhesion and other properties of organic resins, but also improve the high and low temperature resistance, weather resistance, electrical insulation and other properties of traditional resins, expanding the scope of use.

[0003] According to the type of raw materials, the preparation of organosilicon-modified polyester by chemical copolymerization can be divided into two methods: monomer copolymerization and macromolecular copolymerization. When the macromolecular copolymerization modification is adopted, the organosilicon resin is prone to self-polymerization and the reaction is difficult to control. The monomer copolymerization modification method refers to the reaction of the organosilicon intermediate with polyols and polyols. Although the gelation problem in the resin copolymerization process can be solved to a certain extent, it is still not easy to achieve the ideal coating effect. When the amount of silicone resin is low, the compatibility of the resin system is good, but the improvement of the resin performance is limited; when the silicone resin content is high, although the heat resistance is significantly improved, the gloss, mechanical properties, adhesion, etc. of the coating are seriously reduced. The research on silicone resin modified polyester in the prior art, such as patent CN119306933 A, discloses a new organosilicon modified polyester resin and its preparation method, which is made of monophenyltrichlorosilane, propyltrichlorosilane, medium molecular weight polyester resin, catalyst, organic solvent and other raw materials, and has good heat resistance and weather resistance, but a large amount of solvent is required during preparation, and the product needs to be repeatedly washed with water many times, and the process is not environmentally friendly. Patent CN 103159946B discloses silicone resin modified unsaturated polyester resin, which has a simple process, but the amount of silicone resin used is less than 5%, and the improvement of polyester performance is limited. Summary of the invention

[0004] The purpose of the present invention is to provide a silicone resin prepolymer, a modified polyester thereof and a preparation method thereof in view of the above-mentioned problems in the prior art. The silicone resin prepolymer contains structures such as phenyl, alkylphenyl, and long-chain alkyl, which greatly improves the compatibility with polyester resin. The prepared modified resin has good mechanical properties, high gloss, high and low temperature resistance, weather resistance, water resistance and other excellent properties, and can meet the application requirements of various outdoor environments.

[0005] The technical solution adopted by the present invention is:

[0006] A method for preparing a silicone resin prepolymer comprises the following steps:

[0007] (1) Long-chain alkyltrialkoxysilane CH3(CH2) n -Si(OR)3 and phenyltrichlorosilane PhSiCl3, phenylalkyltrichlorosilane Ph-(CH2) m -SiCl3 is mixed in a molar ratio of 1:1-5:1-3 and reacted at 100°C for 2h under the action of a weak base catalyst;

[0008] (2) After cooling the solution obtained in step (1) to room temperature, drip it into an alkaline catalyst aqueous solution for hydrolysis, and maintain the dripping temperature at 5-20°C. After the dripping is completed, methyltrimethoxysilane CH3Si(OMe)3 or methyltriethoxysilane CH3Si(OEt)3 is added, and the reaction solution is heated to reflux, and the reflux reaction is carried out for 1h-2h. The oil layer is separated, washed with water, and low-boiling substances are removed to obtain a silicone resin prepolymer. The molar ratio of methyltrimethoxysilane CH3Si(OMe)3 or methyltriethoxysilane CH3Si(OEt)3 to the total amount of the three silanes in step (1) is 0.05-0.2:1.

[0009] In the above method, the long-chain alkyltrialkoxysilane described in step (1) is selected from one or more of octyltrimethoxysilane, octyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, and octadecyltriethoxysilane; the phenylalkyltrichlorosilane is selected from one or more of benzyltrichlorosilane, phenethyltrichlorosilane, phenylpropyltrichlorosilane, and phenylbutyltrichlorosilane; the weak base catalyst is selected from one of triethylamine, imidazole, pyridine, 4-dimethylaminopyridine, and urea. The mass ratio of the weak base catalyst to PhSiCl3 in step (1) is 1:90 to 130.

[0010] The alkaline catalyst described in step (2) is KOH, and the mass ratio of the alkaline catalyst to water is 5-15:100; the molar ratio of methyltrimethoxysilane CH3Si(OMe)3 or methyltriethoxysilane CH3Si(OEt)3 to water in step (2) is 0.05-0.2:2-3.

[0011] A method for preparing silicone prepolymer modified polyester comprises the following steps:

[0012] a. Preparation of silicone prepolymer, the method as described above;

[0013] b. Add silicone resin prepolymer, catalyst and part of polyol into the reaction kettle, heat to no more than 130℃ until all the materials are melted, continue to heat to 180-190℃ and keep warm for 2-3h under nitrogen atmosphere and stirring; reduce the temperature of the reactor to below 130℃, add dibasic acid and remaining polyol, gradually increase the temperature to 220-240℃, keep warm for 3-5h, the material in the kettle gradually becomes transparent, reduce pressure to remove low boiling point, test viscosity and acid value during this period, stop vacuum when acid value is ≤1mg KOH / g, cool down and filter out insoluble matter, and discharge to obtain silicone modified polyester resin.

[0014] The mass ratio of the silicone resin prepolymer to the polyol and the dibasic acid in step b of the above method is 10-60:5-40:5-45, preferably 10:5-15:5-15; the polyol added together with the silicone resin prepolymer accounts for about 30-60% of the total mass of the polyol.

[0015] The polyol is a compound containing two or more hydroxyl groups, selected from one or more of ethylene glycol, propylene glycol, butylene glycol, pentanediol, hexanediol, heptanediol, octanediol, trimethylolpropane, trimethylolethane, and pentaerythritol.

[0016] The dibasic acid refers to a dicarboxyl functional compound or a corresponding acid anhydride, selected from one or more of terephthalic acid, isophthalic acid, phthalic acid, acetic anhydride, phthalic anhydride, and maleic anhydride.

[0017] The catalyst is an organic titanium compound, selected from one or more of tetraisopropyl titanate, tetra-n-butyl titanate, di(acetylacetonato) diisopropyl titanate, and the amount of the catalyst is 0.5% to 1% of the mass of the silicone prepolymer.

[0018] The beneficial effects of the present invention are:

[0019] 1. Preparation of silicone resin prepolymer: Long-chain alkyltrialkoxysilane and organochlorosilane are pre-condensed by weak base compounds to avoid the self-condensation reaction of the silane raw material in the co-hydrolysis stage; the condensate of the two is co-hydrolyzed and condensed under the action of strong base, and the Si-O-Si chain is rearranged and condensed to form a compact siloxane structure terminated with alkoxy groups. The silicone resin with this structure has a low tendency to self-polymerize and can be evenly distributed in the polyester resin. When added in a high proportion of 45 to 60wt%, it can maintain good compatibility.

[0020] 2. The silicone resin prepolymer of the present invention introduces long-chain alkyl [CH3(CH2) n -SiO 1.5 )] and phenylalkyl [Ph-(CH2) m -SiO 1.5 ]T structure, the polyester modified with the synthesized silicone resin prepolymer has moderate glass transition temperature Tg and viscosity and good processing performance.

[0021] 3. The preparation method of the present invention does not use organic solvents, has low consumption and is environmentally friendly. The prepared modified polyester resin changes color slightly without cracking after being subjected to a high temperature of 250°C×24h, Td10%≥400°C, has an adhesion level of 0, has excellent impact resistance, weather resistance, and water resistance, and has broad application prospects in the field of temperature-resistant powder coatings. DETAILED DESCRIPTION

[0022] The following is further described in conjunction with specific embodiments.

[0023] Example 1

[0024] A method for preparing silicone prepolymer modified polyester comprises the following steps:

[0025] a. Preparation of silicone prepolymer: 234.4g octyl trimethoxysilane CH3(CH2)7-Si(OMe)3 and 6g triethylamine catalyst were added to the reaction bottle, and a mixture of 634.5g phenyl trichlorosilane PhSiCl3 and 119.5g phenyl ethyl trichlorosilane Ph-(CH2)2-SiCl3 was added dropwise. After the addition was completed, the temperature was raised to 100°C for reaction for 2h; then the reaction solution was cooled to room temperature, and a strong alkaline solution composed of 23g KOH and 194.4g water was added dropwise for hydrolysis, and the solution was dropped in 3h. After the addition was completed, 27.2g methyl trimethoxysilane CH3Si(OMe)3 was added, and the temperature was raised to reflux the reaction solution for about 2h; after the reaction was completed, the water layer was separated, the oil layer was washed with water until neutral, dried, and the low-boiling substances were removed under reduced pressure at 80°C to obtain a silicone prepolymer with a methoxy mass percentage of 18.5%.

[0026] b. Take 290g silicone resin prepolymer, 84g neopentyl glycol, 13.4g trimethylolpropane, and 0.8g tetrabutyl titanate and add them to the reactor. Raise the temperature to no more than 130℃ until all the materials are melted. Pass nitrogen and start stirring. Continue to raise the temperature to 180℃ and keep it warm for 2.5h. The small molecules generated by polycondensation will be evaporated by reaction. Lower the temperature of the reactor to below 130℃, add 200g terephthalic acid and 92.8g neopentyl glycol, gradually raise the temperature to 230℃ and keep it warm. After about 4h, the materials in the reactor gradually become transparent, reduce the pressure to remove low boiling, test the viscosity and acid value during this period, stop the vacuum when the acid value is ≤1mg KOH / g, cool down and filter out the insoluble matter, and the material can be obtained by discharging the silicone modified polyester resin. The obtained modified resin has a hydroxyl value of 51.2mg KOH / g; a melt viscosity of 2350mpa·s; and a glass transition temperature Tg of 56.8℃. The performance indicators of the resin after high-temperature curing at 220℃×30min are shown in Table 1.

[0027] Example 2

[0028] A method for preparing silicone prepolymer modified polyester comprises the following steps:

[0029] a. Preparation of silicone prepolymer is the same as step a of Example 1;

[0030] b. Take 400g of the prepared silicone resin prepolymer, and prepare the organosilicon-modified polyester resin according to the raw materials and process of step b of Example 1. The obtained modified resin has a hydroxyl value of 54.8mg KOH / g, a melt viscosity of 2020mpa·s, and a glass transition temperature Tg of 50.6°C. The performance indicators of the cured resin are shown in Table 1.

[0031] Example 3

[0032] A method for preparing silicone prepolymer modified polyester comprises the following steps:

[0033] a. Preparation of silicone prepolymer is the same as step a of Example 1;

[0034] b. Take 480g of the prepared silicone resin prepolymer, and prepare the organosilicon-modified polyester resin according to the raw materials and process of step b of Example 1. The obtained modified resin has a hydroxyl value of 56.4mg KOH / g, a melt viscosity of 1910mpa·s, and a glass transition temperature Tg of 48.2°C. The performance indicators of the cured resin are shown in Table 1.

[0035] Example 4

[0036] A method for preparing silicone prepolymer modified polyester comprises the following steps:

[0037] The amount of water used for hydrolysis in the synthesis of the silicone resin prepolymer in step a of Example 1 was adjusted to 225.4 g, and the remaining steps of Example 1 were followed to prepare the organosilicon-modified polyester resin. The mass percentage of methoxyl groups in the silicone resin prepolymer was 15.2%; the obtained modified resin had a hydroxyl value of 48.5 mg KOH / g; a melt viscosity of 2560 mPa·s; and a glass transition temperature Tg of 59.0°C. The performance indicators of the cured resin are shown in Table 1.

[0038] Example 5

[0039] A method for preparing silicone prepolymer modified polyester comprises the following steps:

[0040] In the synthesis of silicone prepolymer in step a of Example 1, 234.4 g of octyl trimethoxy silane was replaced with 346.3 g of hexadecyl methyl trimethoxy silane CH3(CH2) 15-Si(OMe)3; 119.5g phenylethyltrichlorosilane was replaced with 133.5g phenylbutyltrichlorosilane Ph-(CH2)4-SiCl3, and the remaining raw materials and processes were in accordance with the reaction steps of Example 1 to prepare an organosilicon-modified polyester resin. The mass percentage of methoxyl groups in the silicone resin prepolymer was 13.1%; the hydroxyl value of the obtained modified resin was 50.8mg KOH / g; softening point; melt viscosity was 2110mpa·s; and glass transition temperature Tg was 52.4℃. The performance indicators of the cured resin are shown in Table 1.

[0041] Example 6

[0042] A method for preparing silicone prepolymer modified polyester comprises the following steps:

[0043] a. Preparation of silicone prepolymer: 328.2g of octyltrimethoxysilane CH3(CH2)7-Si(OMe)3 and 6g of triethylamine catalyst were added to the reaction bottle, and a mixture of 592.2g of phenyltrichlorosilane PhSiCl3 and 71.7g of phenylethyltrichlorosilane Ph-(CH2)2-SiCl3 was added dropwise. After the addition was completed, the temperature was raised to 100°C for reaction for 2h; then the reaction solution was cooled to room temperature, and a strong alkaline solution composed of 23g KOH and 156.2g water was added dropwise for hydrolysis, and the solution was dropped in 3h. After the addition was completed, 40.8g of methyltrimethoxysilane CH3Si(OMe)3 was added, and the temperature was raised to reflux the reaction solution for about 2h; after the reaction was completed, the water layer was separated, the oil layer was washed with water until neutral, dried, and the low-boiling substances were removed under reduced pressure at 80°C to obtain the silicone prepolymer. The silicone prepolymer has a methoxy mass percentage of 19.6%.

[0044] b. Take 290g silicone resin prepolymer, 84g neopentyl glycol, 13.4g trimethylolpropane, and 0.8g tetrabutyl titanate and add them to the reactor. Raise the temperature to no more than 130℃ until all the materials are melted. Pass nitrogen and start stirring. Continue to raise the temperature to 180℃ and keep it warm for 2.5h. The small molecules generated by polycondensation will be evaporated by reaction. Lower the temperature of the reactor to below 130℃, add 200g terephthalic acid and 92.8g neopentyl glycol, gradually raise the temperature to 230℃ and keep it warm. After about 4h, the material in the reactor gradually becomes transparent, and the low boiling point is removed by decompression. During this period, the viscosity and acid value are tested. When the acid value is ≤1mg KOH / g, stop the vacuum, cool down and filter out the insoluble matter, and the silicone modified polyester resin can be obtained by discharging the material.

[0045] The obtained modified resin has a hydroxyl value of 47.5 mg KOH / g, a softening point, a melt viscosity of 1860 mPa·s, and a glass transition temperature Tg of 47.8° C. The performance indicators of the cured resin are shown in Table 1.

[0046] Among the above indicators, the acid value is tested according to GB / T6743-2008; the hydroxyl value is tested according to GB / T12008.3-2009; the glass transition temperature Tg is tested according to GB / T19466.2-2004; and the melt viscosity is tested according to GB / T9751.1-2008, and the test temperature is 200°C.

[0047] In the performance test, the hardness is tested according to GB / T6739-2022; the impact resistance is tested according to GB / T1732-2020, and the mass of the hammer is 1kg; the adhesion is tested according to GB / T 9286-1998; heat resistance 250℃×24h; thermal stability is tested by thermogravimetric analyzer, N2 atmosphere, heating rate 10℃ / min, and the corresponding temperatures Td5%, Td10%, Td20% are recorded when the weight loss is 5%, 10%, and 20%; gloss retention: gloss is measured according to GB / T 8807-1988, baked in a muffle furnace at 360℃ for 5h, and the gloss retention rate of the sample before and after baking is calculated. The weather resistance test was carried out according to [xenon lamp 200h, 250℃×24h high temperature] for 5 cycles; the water resistance test was carried out according to GB / T9274-1988, and the samples were immersed in salt water (5% NaCl aqueous solution) for 6 months at room temperature to observe the changes in the appearance of the samples.

[0048] Table 1 Properties of modified polyester resin

[0049]

[0050]

[0051] It can be seen from Table 1 that the modified polyester resin of the present invention has no cracking phenomenon after high-temperature aging and weather resistance testing at 250° C.×24 h, and has excellent mechanical and heat resistance properties compared with existing materials.

[0052] Although the above describes typical embodiments of the present invention, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A method for preparing a silicone resin prepolymer, characterized in that: The steps include: (1) Long-chain alkyltrialkoxysilane CH3(CH2) n -Si(OR)3 and phenyltrichlorosilane PhSiCl3, phenylalkyltrichlorosilane Ph-(CH2) m -SiCl3 is mixed in a molar ratio of 1:1-5:1-3 and reacted at 100°C for 2h under the action of a weak base catalyst; (2) After cooling the solution obtained in step (1) to room temperature, drip it into an alkaline catalyst aqueous solution for hydrolysis, and maintain the dripping temperature at 5-20°C. After the dripping is completed, methyltrimethoxysilane CH3Si(OMe)3 or methyltriethoxysilane CH3Si(OEt)3 is added, and the reaction solution is heated to reflux, and the reflux reaction is carried out for 1h-2h. The oil layer is separated, washed with water, and low-boiling substances are removed to obtain a silicone resin prepolymer. The molar ratio of methyltrimethoxysilane CH3Si(OMe)3 or methyltriethoxysilane CH3Si(OEt)3 to the total amount of the three silanes in step (1) is 0.05-0.2:

1.

2. The method for preparing a silicone resin prepolymer according to claim 1, characterized in that: The long-chain alkyltrialkoxysilane described in step (1) is selected from one or more of octyltrimethoxysilane, octyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, and octadecyltriethoxysilane; the phenylalkyltrichlorosilane is selected from one or more of benzyltrichlorosilane, phenethyltrichlorosilane, phenylpropyltrichlorosilane, and phenylbutyltrichlorosilane.

3. The method for preparing a silicone resin prepolymer according to claim 1, characterized in that: The weak base catalyst described in step (1) is selected from one of triethylamine, imidazole, pyridine, 4-dimethylaminopyridine and urea, and the mass ratio of the weak base catalyst to PhSiCl3 is 1:90-130.

4. The method for preparing a silicone resin prepolymer according to claim 1, characterized in that: The alkaline catalyst described in step (2) is KOH, and the mass ratio of the alkaline catalyst to water is 5-15:100; the molar ratio of methyltrimethoxysilane CH3Si(OMe)3 or methyltriethoxysilane CH3Si(OEt)3 to water is 0.05-0.2:2-3.

5. The silicone resin prepolymer prepared by the method described in any one of claims 1 to 4.

6. A method for preparing silicone prepolymer modified polyester, characterized in that: The steps include: a. preparing a silicone resin prepolymer by the method according to any one of claims 1 to 4; b. Add silicone resin prepolymer, catalyst and part of polyol into the reaction kettle, heat to no more than 130℃ until all the materials are melted, continue to heat to 180-190℃ and keep warm for 2-3h under nitrogen atmosphere and stirring; reduce the temperature of the reactor to below 130℃, add dibasic acid and remaining polyol, gradually increase the temperature to 220-240℃, keep warm for 3-5h, the material in the kettle gradually becomes transparent, reduce pressure to remove low boiling point, test viscosity and acid value during this period, stop vacuum when acid value is ≤1mg KOH / g, cool down and filter out insoluble matter, and discharge to obtain silicone modified polyester resin.

7. The method for preparing silicone prepolymer modified polyester according to claim 6, characterized in that: The mass ratio of the silicone resin prepolymer to the polyol and the dibasic acid in step b is 10-60:5-40:5-45, and the polyol added together with the silicone resin prepolymer accounts for about 30-60% of the total mass of the polyol.

8. The method for preparing silicone prepolymer modified polyester according to claim 7, characterized in that: The mass ratio of the silicone resin prepolymer to the polyol and the dibasic acid described in step b is 10:5-15:5-15.

9. The method for preparing silicone prepolymer modified polyester according to claim 6, characterized in that: The catalyst is an organic titanium compound, selected from one or more of tetraisopropyl titanate, tetra-n-butyl titanate, di(acetylacetonato) diisopropyl titanate, and the amount of the catalyst is 0.5% to 1% of the mass of the silicone prepolymer.

10. Silicone resin prepolymer modified polyester prepared by the method according to any one of claims 6 to 9.

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