Organic silicon resin as well as preparation method and application thereof

Abstract

The invention relates to an organic silicon resin, which is mainly prepared by carrying out polymerization on dimethyl diethoxy silane, biphenyl p-dimethyl alcohol, diphenyl diethoxy silane, 3, 3, 3-trifluoropropyl methyl dimethoxy silane, triethoxy ethyl silane, neopentyl glycol, 1, 4-succinic acid and the like, and is characterized in that the organic silicon resin is prepared by carrying out polymerization on the dimethyl diethoxy silane, the biphenyl p-dimethyl alcohol, the diphenyl diethoxy silane, the 3, 3, 3-trifluoropropyl methyl dimethoxy silane, the triethoxy ethyl silane, the neopentyl glycol, the 1, 4-succinic acid and the like; a powder coating prepared from the obtained organic silicon resin and a TGIC curing agent can be cured at a low temperature of 150 DEG C / 15 min, and a cured coating film is relatively good in conventional performance, excellent in resistance to high temperature of 350 DEG C for a long time and relatively excellent in scratch resistance and solvent resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of organic silicon resins, and in particular relates to an organic silicon resin and a preparation method thereof, and application of the organic silicon resin in a TGIC powder coating system. Background Art

[0002] Coatings have protective properties for various substrates and additional functional properties, such as flame retardant, high temperature resistance, antistatic, etc. There are many types of coatings, among which powder coatings are solvent-free, 100% solid powder coatings. They are solvent-free, pollution-free, recyclable, environmentally friendly, energy and resource-saving, labor-reducing, and have high mechanical strength of the coating film. They are widely used. At the same time, some high-temperature application fields such as microwave ovens, ovens, and drying rooms have high requirements for the long-lasting high-temperature resistance of powder coatings. In order to improve the high-temperature resistance of the coating film, the common method is to use silicone resin and polyester resin for mixed modification, but the physical mixing modification will bring about the problem of insufficient compatibility, resulting in poor leveling and insufficient uniformity of the coating film. Although there is also a method of introducing silicone segments into polyester resin molecules, polyester resin segments are still the main ones. Since it is difficult to introduce more silicone segments, the long-lasting high-temperature resistance is still insufficient, especially the high-temperature resistance requirement of more than 12 hours under high temperature conditions of 350°C. Because the segments of single silicone resins are too soft, the softening point is generally lower than 60°C and it is difficult to use them in powder coatings. At the same time, since the curing temperature of powder coatings generally needs to reach above 180°C, the high temperature will lead to energy waste on the one hand, and on the other hand, it also has high requirements on the temperature resistance of the substrate. Heat-sensitive substrates are difficult to be coated with powder coatings. How to develop low-temperature curing powder coatings is also a key research direction in the industry.

[0003] In view of the above problems, this scheme starts from the design of molecular structure, makes full use of the advantages of low softening point and high temperature resistance of silicone resin, and uses special monomers for copolymerization; the silicone resin is mainly obtained by polymerization using dimethyldiethoxysilane, biphenyldimethylol, diphenyldiethoxysilane, 3,3,3-trifluoropropylmethyldimethoxysilane, triethoxyethylsilane, neopentyl glycol, 1,4-butanedioic acid, etc. The fluorine element with higher high temperature resistance and hydrophobicity is introduced into the structure of the silicone resin through monomers. Since the single silicone resin chain segment is relatively soft and the softening point is too low, rigid monomers such as biphenyldimethylol and neopentyl glycol and trifunctional triethoxyethylsilane are used to adjust the softening point of the silicone resin. The final softening point of the resin is 86-98℃, and the fluidity is better at 150℃; finally, it can be cured at low temperature with high-purity TGIC curing agent, and the cured coating has good leveling properties and excellent long-term high temperature resistance. Summary of the invention

[0004] The present invention relates to an organic silicon resin, which is prepared from raw materials comprising the following molar compositions:

[0005]

[0006] The raw materials also include catalyst 1, catalyst 2 and antioxidant.

[0007] Furthermore, catalyst 1 is hydrochloric acid with a mass fraction of 32-35%, and the amount used is 3-4% of the mass of dimethyldiethoxysilane; catalyst 2 is monobutyltin oxide, and the amount used is 0.4-0.7% of the mass of neopentyl glycol.

[0008] Furthermore, the antioxidant is antioxidant 1010, i.e. pentaerythritol tetrakis[methyl-β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], and the amount used is 0.5-0.8% of the mass of neopentyl glycol.

[0009] The method for preparing a silicone resin as described above comprises the following steps:

[0010] A. Add the formulated amount of xylene, dimethyldiethoxysilane, biphenyl-p-dimethanol, diphenyldiethoxysilane and catalyst 1 into a reaction kettle, start stirring and heat to 92-97° C. to carry out polymerization reaction;

[0011] B. Sampling was tested by liquid chromatography. After the reaction of the early polymerization chain segments was basically completed, the temperature was lowered to 82-84°C. Then, 3,3,3-trifluoropropylmethyldimethoxysilane was added to carry out the grafting and chain extension reaction of the fluorinated monomer at 82-84°C.

[0012] C. Sampling is tested by gas chromatography. After the graft polymerization reaction of the fluorinated monomer is basically completed, triethoxyethylsilane is added and the temperature is raised to 95-98°C to carry out a trifunctional chain extension polymerization reaction;

[0013] D. Sampling was tested by gas chromatography. After the trifunctional chain extension polymerization was basically completed, the temperature was raised to 130-135° C., and the formula amount of neopentyl glycol and catalyst 2 were added to carry out hydroxyl end-capping reaction for 1.5-2h; then the temperature was gradually raised to 200-205° C., and the xylene solvent and other unreacted small molecule raw materials were removed during the heating process;

[0014] E. Take samples to detect the softening point of the polymer. When the softening point of the polymer reaches 75-80°C, raise the temperature to 210-215°C, add the formulated amount of antioxidant, and then start the vacuum system to carry out vacuum polycondensation reaction, and simultaneously remove excess unreacted neopentyl glycol by vacuum;

[0015] F. When no obvious substance is evaporated, stop the vacuum system and add the formulated amount of 1,4-succinic acid to carry out carboxyl end-capping reaction. Stop the reaction when the acid value of the polymer reaches 34-40 mgKOH / g, discharge the material while hot, cool the silicone resin, and then crush and granulate it to obtain the silicone resin.

[0016] Furthermore, in step B, when the conversion rate of the freed biphenyl dimethanol reaches more than 95%, it indicates that the reaction of the previous polymerization chain segment is basically completed; in step C, when the conversion rate of the freed 3,3,3-trifluoropropylmethyldimethoxysilane reaches more than 95%, it indicates that the grafting polymerization reaction of the fluorinated monomer is basically completed; in step D, when the conversion rate of the freed triethoxyethylsilane reaches more than 97%, it indicates that the trifunctional chain extension polymerization is basically completed.

[0017] Furthermore, in step D, the temperature is gradually increased to 200-205°C at a heating rate of 25-30°C / h, and the xylene solvent and other unreacted small molecule raw materials are removed during the heating process; in step E, the vacuum degree is controlled at -0.095 to -0.098Mpa; in step F, the silicone resin is cooled with a steel belt with condensed water.

[0018] For example, the above-mentioned method for preparing a silicone resin comprises the following steps:

[0019] A. Add the formulated amount of xylene, dimethyldiethoxysilane, biphenyl-p-dimethanol, diphenyldiethoxysilane and catalyst 1 into a reaction kettle, start stirring and heat to 92-97° C. to carry out polymerization reaction;

[0020] B. Take samples and test them by liquid chromatography. When the conversion rate of free biphenyl-p-dimethanol reaches more than 95%, it means that the reaction of the previous polymerization chain segment is basically completed. Then, cool down to 82-84°C, then add 3,3,3-trifluoropropylmethyldimethoxysilane at 82-84°C to carry out the grafting chain extension reaction of the fluorinated monomer;

[0021] C. Take samples and test them by gas chromatography. When the conversion rate of free 3,3,3-trifluoropropylmethyldimethoxysilane reaches more than 95%, it means that the graft polymerization reaction of the fluorinated monomer is basically completed. At this time, add triethoxyethylsilane and raise the temperature to 95-98°C to carry out trifunctional chain extension polymerization reaction to increase the functionality of the polymer.

[0022] D. Take samples and test them by gas chromatography. When the conversion rate of free triethoxyethylsilane reaches more than 97%, it means that the trifunctional chain extension polymerization is basically completed. At this time, the temperature is raised to 130-135° C., and the formula amount of neopentyl glycol and catalyst 2 are added to carry out hydroxyl end-capping reaction for 1.5-2h; then the temperature is gradually raised to 200-205° C. at a heating rate of 25-30° C. / h, and the xylene solvent and other unreacted small molecule raw materials are removed during the heating process;

[0023] E. Take samples to detect the softening point of the polymer. When the softening point of the polymer reaches 75-80° C., raise the temperature to 210-215° C., add the formulated amount of antioxidant, and then start the vacuum system. The vacuum degree is controlled at -0.095 to -0.098 MPa to carry out vacuum polycondensation reaction, and simultaneously remove excess unreacted neopentyl glycol by vacuum;

[0024] F. When no obvious substance is evaporated (less than 1 drop within 30 seconds), stop the vacuum system and add the formulated amount of 1,4-succinic acid to carry out carboxyl end-capping reaction. When the acid value of the polymer reaches 34-40 mgKOH / g, stop the reaction, discharge the material while hot, and cool the silicone resin with a steel belt with condensed water, then crush and granulate it to obtain the silicone resin.

[0025] The obtained product has the appearance of colorless and transparent particles, an acid value of 34-40 mgKOH / g, and a softening point of 86-98°C.

[0026] The present invention also relates to the use of the above-mentioned organosilicon resin or the organosilicon resin obtained by the preparation method in a TGIC powder coating system.

[0027] In addition to the above-mentioned silicone resin and TGIC, the formula may also include titanium dioxide, barium sulfate, brightener, leveling agent, benzoin, etc. as needed; the materials are mixed according to the powder coating formula, extruded, tableted, and crushed by a twin-screw extruder, and then the tablets are crushed and sieved (such as 160-180 mesh) to form a powder coating. The powder coating is sprayed on the surface-treated tinplate substrate with an electrostatic spray gun, and cured (for example, at 150°C / 15min) to obtain a coating.

[0028] Beneficial Effects

[0029] This scheme starts from the design of molecular structure, makes full use of the advantages of low softening point and high temperature resistance of silicone resin, and adopts special monomers for copolymerization; the synthesis of the silicone resin first uses dimethyldiethoxysilane, biphenyl dimethanol, and diphenyldiethoxysilane to synthesize the preliminary polymerization chain segment, and then introduces the fluorine-containing monomer 3,3,3-trifluoropropylmethyldimethoxysilane for grafting reaction, and after the grafting reaction is completed, it is subjected to chain extension polymerization reaction with trifunctional triethoxyethylsilane, and then an excess of neopentyl glycol is used for hydroxyl end-capping, and finally 1,4-succinic acid is used for carboxyl end-capping polymerization to obtain the product. Fluorine elements with stronger high temperature resistance and hydrophobicity are introduced into the silicone resin structure through monomers. Since the individual silicone resin segments are relatively soft and have a low softening point, rigid monomers such as biphenyl dimethanol and neopentyl glycol and trifunctional triethoxyethyl silane are used to adjust the softening point of the silicone resin. The final softening point of the resin is 86-98°C, and the fluidity is better at 150°C. Finally, low-temperature curing can be achieved with high-purity TGIC curing agent, and the cured coating has good leveling properties and excellent long-term high temperature resistance.

[0030] The present invention has been described in detail above, but the above embodiments are only illustrative in nature and are not intended to limit the present invention. In addition, this article is not limited by any theory described in the above prior art or invention content or the following examples. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with examples. It should be noted that the following examples are provided for illustrative purposes only and do not constitute a limitation on the scope of protection claimed for the present invention.

[0032] Unless otherwise specified, the raw materials, reagents, methods, etc. used in the examples are conventional raw materials, reagents, methods in the art.

[0033] Preparation Example 1

[0034] An organic silicon resin is prepared from raw materials comprising the following molar compositions:

[0035]

[0036] Catalyst 1 is hydrochloric acid with a mass fraction of 35%, and the dosage is 4% of the mass of dimethyldiethoxysilane; Catalyst 2 is monobutyltin oxide, and the dosage is 0.7% of the mass of neopentyl glycol; and the antioxidant is antioxidant 1010, and the dosage is 0.8% of the mass of neopentyl glycol.

[0037] The preparation method comprises the following steps:

[0038] A. Add the formulated amount of xylene, dimethyldiethoxysilane, biphenyl-p-dimethanol, diphenyldiethoxysilane and catalyst 1 into a reaction kettle, start stirring and heat to 92° C. to carry out polymerization reaction;

[0039] B. Take samples and test them by liquid chromatography. When the conversion rate of free biphenyl-p-dimethanol reaches more than 95%, it means that the reaction of the previous polymerization chain segment is basically completed. Then, cool down to 82°C, and then add 3,3,3-trifluoropropylmethyldimethoxysilane to carry out the grafting and chain extension reaction of the fluorinated monomer at 82°C;

[0040] C. Take samples and test them by gas chromatography. When the conversion rate of free 3,3,3-trifluoropropylmethyldimethoxysilane reaches more than 95%, it means that the graft polymerization reaction of the fluorinated monomer is basically completed. At this time, add triethoxyethylsilane and raise the temperature to 95°C to carry out trifunctional chain extension polymerization reaction to increase the functionality of the polymer.

[0041] D. Sampling was tested by gas chromatography. When the conversion rate of free triethoxyethylsilane reached 97% or more, it indicated that the trifunctional chain extension polymerization was basically completed. At this time, the temperature was raised to 130° C., and the formula amount of neopentyl glycol and catalyst 2 were added to carry out hydroxyl end-capping reaction for 2 hours; then the temperature was gradually raised to 200° C. at a heating rate of 25° C. / h, and the xylene solvent and other unreacted small molecule raw materials were removed during the heating process;

[0042] E. Take samples to detect the softening point of the polymer. When the softening point of the polymer reaches 75-80° C., raise the temperature to 210° C., add the formulated amount of antioxidant, and then start the vacuum system. The vacuum degree is controlled at -0.095 to -0.098 MPa to perform vacuum polycondensation reaction, and simultaneously remove excess unreacted neopentyl glycol by vacuum;

[0043] F. When no obvious substance is evaporated (less than 1 drop within 30 seconds), stop the vacuum system and add the formulated amount of 1,4-succinic acid to carry out carboxyl end-capping reaction. When the acid value of the polymer reaches the expected value, stop the reaction, discharge the material while hot, and cool the silicone resin with a steel belt with condensed water, then crush and granulate it to obtain the silicone resin.

[0044] The obtained product has the appearance of colorless and transparent particles, an acid value of 39 mgKOH / g, and a softening point of 88°C.

[0045] Preparation Example 2

[0046] An organic silicon resin is prepared from raw materials comprising the following molar compositions:

[0047]

[0048] Catalyst 1 is hydrochloric acid with a mass fraction of 32%, and the dosage is 4% of the mass of dimethyldiethoxysilane; Catalyst 2 is monobutyltin oxide, and the dosage is 0.7% of the mass of neopentyl glycol; and the antioxidant is antioxidant 1010, and the dosage is 0.8% of the mass of neopentyl glycol.

[0049] The preparation method is the same as that of Preparation Example 1.

[0050] The obtained product has the appearance of colorless and transparent particles, an acid value of 36 mgKOH / g, and a softening point of 93°C.

[0051] Preparation Example 3

[0052] An organic silicon resin is prepared from raw materials comprising the following molar compositions:

[0053]

[0054] Catalyst 1 is hydrochloric acid with a mass fraction of 35%, and the amount used is 3% of the mass of dimethyldiethoxysilane; Catalyst 2 is monobutyltin oxide, and the amount used is 0.5% of the mass of neopentyl glycol; and the antioxidant is antioxidant 1010, and the amount used is 0.6% of the mass of neopentyl glycol.

[0055] The preparation method is the same as that of Preparation Example 1.

[0056] The obtained product has the appearance of colorless and transparent particles, an acid value of 37 mgKOH / g, and a softening point of 91°C.

[0057] Preparation Example 4

[0058] An organic silicon resin is prepared from raw materials comprising the following molar compositions:

[0059]

[0060] Catalyst 1 is 35% hydrochloric acid, and its dosage is 4% of the mass of dimethyldiethoxysilane; Catalyst 2 is monobutyltin oxide, and its dosage is 0.7% of the mass of neopentyl glycol; Antioxidant is antioxidant 1010, and its dosage is 0.5% of the mass of neopentyl glycol.

[0061] The preparation method is the same as that of Preparation Example 1.

[0062] The obtained product has the appearance of colorless and transparent particles, an acid value of 38 mgKOH / g, and a softening point of 95°C.

[0063] Comparative Preparation Example 1: The polyester resin of Example B of CN201910838016.2 was used as Comparative Example 1;

[0064] Comparative Preparation Example 2: The other conditions are the same as those of Comparative Preparation Example 1, except that the curing conditions are changed from 150°C / 15min to 200°C / 10min.

[0065] Examples 1-4 and Comparative Examples 1 and 2

[0066] The resins or reaction conditions corresponding to the above-mentioned Examples 1-4 or Comparative Examples 1 and 2 are used to obtain the powder coating. The existing powder coating formula is as follows in parts by weight:

[0067]

[0068] The resin is the silicone resin used in Examples 1-4 of the present invention and the polyester resin used in Comparative Examples 1-2, and the TGIC is a high-purity electronic-grade TGIC product, model JF-77B, purchased from Huangshan Jinfeng Industrial Co., Ltd.

[0069] Preparation of coating: Mix all materials according to the above powder coating formula, extrude, tablet and crush with a twin-screw extruder, and then crush and sieve the tablets (160-180 mesh) to make powder coating. The powder coating is sprayed on the surface treated tinplate substrate with an electrostatic spray gun, and cured at 150℃ / 15min to obtain the coating.

[0070] Coating index testing is based on: GB / T 21776-2008 "Guide to Testing Standards for Powder Coatings and Their Coatings". The scratch resistance test standard is based on the method of GB / T9727-88 "Paint and Varnish Scratch Test", with a load mass of 220 grams. The conventional solvent resistance is tested by the drip method, and 5 drops of test solvent are added to the coating surface at room temperature. After 6 hours, the coating surface is observed for discoloration and bubbling (if the solvent evaporates, add more solvent at the original drip position in time).

[0071] Table 1 Coating properties of examples and comparative examples

[0072]

[0073] As can be seen from Table 1, the silicone resin prepared by the specific raw material combination adopted in the present invention is used in powder coatings. After low-temperature curing at 150°C / 15min, the coating has good impact resistance and gloss. In particular, the coating prepared by the silicone resin has excellent high temperature resistance, with basically no obvious change at 350°C / 12h, and excellent scratch resistance, with almost no scratches. This is because the silicone resin itself has excellent wear resistance and scratch resistance. In addition, the silicone resin has excellent solvent resistance, and the coating has no obvious change after being exposed to solvents such as acetone and toluene for 8h.

[0074] Comparative Example 1 uses a polyester resin containing an organic silicon segment, which has certain high temperature resistance. However, since the polyester resin cannot achieve low-temperature curing of 150°C / 15min, the coating film is not completely cured, resulting in poor impact resistance, gloss, high temperature resistance, scratch resistance, and solvent resistance. Comparative Example 2 increases the curing temperature to 200°C, which can achieve full curing, and has good impact resistance and gloss, but is still significantly insufficient when resistant to a high temperature of 350°C / 12h, and exhibits obvious yellowing. It is also significantly inferior to the product of the present invention in terms of scratch resistance and solvent resistance.

[0075] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents, without departing from the spirit and essence of the claims of the present invention; and these modifications or replacements are still within the scope defined by the claims of the present invention.

Claims

1. A silicone resin, characterized in that: The raw materials comprising the following molar compositions: The raw materials also include catalyst 1, catalyst 2 and antioxidant.

2. An organic silicone resin as claimed in claim 1, further characterized in that catalyst 1 is hydrochloric acid with a mass fraction of 32-35%, and the amount used is 3-4% of the mass of dimethyldiethoxysilane; catalyst 2 is monobutyltin oxide, and the amount used is 0.4-0.7% of the mass of neopentyl glycol.

3. The organosilicon resin according to claim 1 or 2, further characterized in that the antioxidant is antioxidant 1010, and the amount used is 0.5-0.8% of the mass of neopentyl glycol.

4. A method for preparing an organosilicon resin according to any one of claims 1 to 3, characterized in that: The following steps are involved: A. Add the formulated amount of xylene, dimethyldiethoxysilane, biphenyl-p-dimethanol, diphenyldiethoxysilane and catalyst 1 into a reaction kettle, start stirring and heat to 92-97° C. to carry out polymerization reaction; B. Sampling was tested by liquid chromatography. After the reaction of the early polymerization chain segments was basically completed, the temperature was lowered to 82-84°C. Then, 3,3,3-trifluoropropylmethyldimethoxysilane was added and the grafting and chain extension reaction of the fluorinated monomer was carried out at 82-84°C. C. Sampling was tested by gas chromatography. After the graft polymerization reaction of the fluorinated monomer was basically completed, triethoxyethylsilane was added and the temperature was raised to 95-98°C for trifunctional chain extension polymerization reaction; D. Sampling was detected by gas chromatography. After the trifunctional chain extension polymerization was basically completed, the temperature was raised to 130-135° C., and the formula amount of neopentyl glycol and catalyst 2 were added to carry out hydroxyl end-capping reaction for 1.5-2 hours; then the temperature was gradually raised to 200-205° C., and the xylene solvent and other unreacted small molecule raw materials were removed during the heating process; E. Take samples to detect the softening point of the polymer. When the softening point of the polymer reaches 75-80°C, raise the temperature to 210-215°C, add the formulated amount of antioxidant, and then start the vacuum system to carry out vacuum polycondensation reaction, and simultaneously remove excess unreacted neopentyl glycol by vacuum; F. When no obvious substance is evaporated, stop the vacuum system and add the formulated amount of 1,4-succinic acid to carry out carboxyl end-capping reaction. When the acid value of the polymer reaches 34-40 mgKOH / g, stop the reaction, discharge the material while hot, cool the silicone resin, and then crush and granulate it to obtain.

5. A method for preparing a silicone resin as claimed in claim 4, further characterized in that, in step B, when the conversion rate of biphenyl dimethanol to be freed reaches more than 95%, it indicates that the reaction of the previous polymerization chain segment is basically completed; in step C, when the conversion rate of 3,3,3-trifluoropropylmethyldimethoxysilane to be freed reaches more than 95%, it indicates that the graft polymerization reaction of the fluorine-containing monomer is basically completed; in step D, when the conversion rate of triethoxyethylsilane to be freed reaches more than 97%, it indicates that the trifunctional chain extension polymerization is basically completed.

6. A method for preparing an organosilicon resin as claimed in claim 4 or 5, further characterized in that in step D, the temperature is gradually increased to 200-205°C at a heating rate of 25-30°C / h, and the xylene solvent and other unreacted small molecule raw materials are removed during the heating process.

7. A method for preparing an organosilicon resin as claimed in claim 4 or 5, further characterized in that in step E, the vacuum degree is controlled at -0.095 to -0.098 MPa.

8. A method for preparing an organosilicon resin as claimed in claim 4 or 5, further characterized in that in step F, the organosilicon resin is cooled by a steel belt with condensed water.

9. Use of the organosilicon resin according to claims 1-3 or the organosilicon resin obtained by the preparation method according to claims 4-8 in a TGIC powder coating system.

Images