阅读说明：本技术 可低温固化、阻燃型粉末涂料用环氧树脂及其制备方法 (Epoxy resin for low-temperature curable flame-retardant powder coating and preparation method thereof ) 是由 王永垒 李海云 江蓉 孙继影 魏文静 殷志康 邹强 于 2019-11-18 设计创作，主要内容包括：本发明属于粉末涂料原料技术领域,具体涉及一种可低温固化、阻燃型粉末涂料用环氧树脂及其制备方法。本发明所提供的可低温固化、阻燃型粉末涂料用环氧树脂,其特征在于,所述的环氧树脂是由以下的主要原料通过聚合反应所制得的：四溴双酚A、2,3-二溴丁二酸、环氧氯丙烷、氢氧化钠、4-溴邻苯二甲酸酐、1,4-二溴-2,3-丁二醇、2,4,6-三氧代-1,3,5-三嗪-1,3,5(2H,4H,6H)-三丙酸、双酚二环甘油醚。本发明采用含阻燃元素溴、氮元素较高的单体作为链段主体,采用双酚二环甘油醚进行环氧封端,保证了本发明所获得的环氧树脂产品环氧基活性较高、可以实现与固化剂2-苯基咪唑制备成粉末涂料后,在低温(130℃/15min)条件下可以发生交联固化,适用于中密度纤维板(MDF)材质。(The invention belongs to the technical field of powder coating raw materials, and particularly relates to an epoxy resin for a low-temperature-curable flame-retardant powder coating and a preparation method thereof. The epoxy resin for the low-temperature-curable flame-retardant powder coating is characterized by being prepared from the following main raw materials through polymerization reaction: tetrabromobisphenol A, 2, 3-dibromo succinic acid, epichlorohydrin, sodium hydroxide, 4-bromophthalic anhydride, 1, 4-dibromo-2, 3-butanediol, 2,4, 6-trioxo-1, 3, 5-triazine-1, 3,5(2H,4H,6H) -tripropionic acid and bisphenol bicyclic glycerol ether. The invention adopts the monomer containing the flame retardant element bromine and the nitrogen with higher content as the chain segment main body, and adopts the bisphenol bicyclic glycerol ether to carry out epoxy end capping, thereby ensuring that the epoxy group activity of the epoxy resin product obtained by the invention is higher, and the epoxy resin product can be crosslinked and cured at low temperature (130 ℃/15min) after being prepared into powder coating with the curing agent 2-phenylimidazole, and is suitable for the material of Medium Density Fiberboard (MDF).)

1. The epoxy resin for the low-temperature-curable flame-retardant powder coating is characterized by being prepared from the following main raw materials in parts by mole through polymerization: tetrabromobisphenol A4-10, 2, 3-dibromosuccinic acid 3-8, epoxy chloropropane 8-18, sodium hydroxide 10-20, 4-bromophthalic anhydride 5-12, 1, 4-dibromo-2, 3-butanediol 6-15, 2,4, 6-trioxo-1, 3, 5-triazine-1, 3,5(2H,4H,6H) -tripropionic acid 5-12, and bisphenol bicyclic glycerol ether 5-10.

2. The epoxy resin for the low-temperature curable, flame-retardant powder coating according to claim 1, wherein a first catalyst of triphenylethylphosphonium bromide and a second catalyst of tetrabutyl titanate are used in the preparation of the epoxy resin.

3. The epoxy resin for the low-temperature curable and flame-retardant powder coating according to claim 2, wherein the amount of the first catalyst, triphenyl ethyl phosphine bromide, is 0.1-0.3% of the total molar amount of the main raw materials; the dosage of the second catalyst tetrabutyl titanate is 0.05-0.15% of the total molar weight of the main raw materials.

4. The process for preparing an epoxy resin for a low-temperature curable, flame-retardant powder coating according to claim 3, comprising the steps of:

(1) tetrabromobisphenol A and 2, 3-dibromo succinic acid are added into a reaction kettle A, then sodium hydroxide solution is added, stirring is carried out, the temperature is increased, and heat preservation reaction is carried out; then adding epoxy chloropropane and a first catalyst, heating and carrying out heat preservation reaction, keeping the temperature and standing for layering after the reaction is stopped, separating out a water phase, and washing with boiling water to obtain epoxy group-terminated epoxy resin;

(2) adding 4-bromophthalic anhydride, 1, 4-dibromo-2, 3-butanediol and a second catalyst into a reaction kettle B, heating for esterification, adding 2,4, 6-trioxo-1, 3, 5-triazine-1, 3,5(2H,4H,6H) -tripropionic acid for carboxyl end capping reaction, stopping reaction after esterification is continued, and cooling;

(3) and adding the epoxy resin material in the reaction kettle A into a reaction kettle B, reacting, adding bisphenol bicyclic glycerol ether epoxy end capping reaction, stopping the reaction, discharging at high temperature while the reaction is hot, cooling the epoxy resin by using a steel belt with condensed water, and crushing and granulating to obtain the epoxy resin for the low-temperature-curable flame-retardant powder coating.

5. The process for preparing an epoxy resin for a low-temperature curable, flame-retardant powder coating according to claim 4, wherein:

(1) adding tetrabromobisphenol A and 2, 3-dibromosuccinic acid into a reaction kettle A, slowly dropwise adding a sodium hydroxide solution with the mass concentration of 48-52%, stirring, completing dropwise adding within 1.5-2.5 h, heating to 60-70 ℃, carrying out heat preservation reaction for 0.8-1.2 h, then adding epoxy chloropropane and a first catalyst, heating to 90-105 ℃, carrying out heat preservation reaction for 2-4 h, testing the epoxy equivalent of a system product, stopping the reaction when the epoxy equivalent is 400-450 g/mol, carrying out heat preservation at 100-110 ℃, standing and layering for 0.3-0.8 h, separating out a water phase, washing for 2-4 times by using boiling water, obtaining epoxy group-terminated epoxy resin, and carrying out heat preservation for later use at 100-105 ℃.

6. The process for preparing an epoxy resin for a low-temperature curable, flame-retardant powder coating according to claim 4, wherein:

(2) adding 4-bromophthalic anhydride, 1, 4-dibromo-2, 3-butanediol and a second catalyst into a reaction kettle B, heating to 150-170 ℃ to perform esterification reaction for 5-10H, adding 2,4, 6-trioxo-1, 3, 5-triazine-1, 3,5(2H,4H,6H) -tripropionic acid to perform carboxyl end capping reaction when the acid value of the system is reduced to be below 5mgKOH/g, continuing the esterification reaction for 1-3H at 150-170 ℃, stopping the reaction when the acid value reaches 120-150 mgKOH/g, and cooling to 100-105 ℃.

7. The process for preparing an epoxy resin for a low-temperature curable, flame-retardant powder coating according to claim 4, wherein:

(3) adding the epoxy resin material reserved in the reaction kettle A into a reaction kettle B, reacting for 1-2 hours at 100-105 ℃, adding bisphenol bicyclic glycerol ether for epoxy capping when the epoxy equivalent of the resin is more than 1200g/mol and the acid value is less than 50mgKOH/g, reacting for 0.5-2 hours at 110-115 ℃, stopping the reaction when the epoxy equivalent reaches 500-600 g/mol, discharging at high temperature while hot, cooling the epoxy resin by using a steel belt with condensed water, and crushing and granulating to obtain the epoxy resin for the low-temperature-curable flame-retardant powder coating.

8. The process for preparing an epoxy resin for a low-temperature curable, flame-retardant powder coating according to claim 4, comprising the steps of:

(1) adding tetrabromobisphenol A and 2, 3-dibromosuccinic acid into a reaction kettle A, slowly dropwise adding a sodium hydroxide solution with the mass concentration of 48-52%, stirring, completing dropwise adding within 1.5-2.5 h, heating to 60-70 ℃, carrying out heat preservation reaction for 0.8-1.2 h, then adding epoxy chloropropane and a first catalyst, heating to 90-105 ℃, carrying out heat preservation reaction for 2-4 h, testing the epoxy equivalent of a system product, stopping the reaction when the epoxy equivalent is 400-450 g/mol, carrying out heat preservation at 100-110 ℃, standing and layering for 0.3-0.8 h, separating out a water phase, washing for 2-4 times by using boiling water to obtain epoxy group-terminated epoxy resin, and carrying out heat preservation at 100-105 ℃ for later use;

(2) adding 4-bromophthalic anhydride, 1, 4-dibromo-2, 3-butanediol and a second catalyst into a reaction kettle B, heating to 150-170 ℃ to perform esterification reaction for 5-10H, adding 2,4, 6-trioxo-1, 3, 5-triazine-1, 3,5(2H,4H,6H) -tripropionic acid to perform carboxyl end capping reaction when the acid value of the system is reduced to be below 5mgKOH/g, continuing the esterification reaction for 1-3H at 150-170 ℃, stopping the reaction when the acid value reaches 120-150 mgKOH/g, and cooling to 100-105 ℃;

(3) adding the epoxy resin material reserved in the reaction kettle A into a reaction kettle B, reacting for 1-2 hours at 100-105 ℃, adding bisphenol bicyclic glycerol ether for epoxy capping when the epoxy equivalent of the resin is more than 1200g/mol and the acid value is less than 50mgKOH/g, reacting for 0.5-2 hours at 110-115 ℃, stopping the reaction when the epoxy equivalent reaches 500-600 g/mol, discharging at high temperature while hot, cooling the epoxy resin by using a steel belt with condensed water, and crushing and granulating to obtain the epoxy resin for the low-temperature-curable flame-retardant powder coating;

the mol parts of the raw materials are as follows:

tetrabromobisphenol A4-10, 2, 3-dibromosuccinic acid 3-8, epoxy chloropropane 8-18, sodium hydroxide 10-20, 4-bromophthalic anhydride 5-12, 1, 4-dibromo-2, 3-butanediol 6-15, 2,4, 6-trioxo-1, 3, 5-triazine-1, 3,5(2H,4H,6H) -tripropionic acid 5-12, and bisphenol bicyclic glycerol ether 5-10.

9. The epoxy resin for low-temperature curable, flame-retardant powder coating prepared according to the process of claim 3, wherein the epoxy resin obtained has an epoxy equivalent weight of 500 to 600g/mol and a softening point of 82 to 92 ℃.

Technical Field

The invention belongs to the technical field of powder coating raw materials, and particularly relates to an epoxy resin for a low-temperature-curable flame-retardant powder coating and a preparation method thereof.

Background

The common E-12 epoxy resin is obtained by directly reacting bisphenol A and epoxy chloropropane under the action of alkali, is commonly used for coating outdoor powder coating systems such as cabinets, refrigerators and the like, and has the comprehensive advantages of strong solvent resistance, good adhesive force and the like.

As for the resin used for the powder coating, the following patent documents are disclosed:

CN104371499A discloses an epoxy resin composite material for powder coating, which is characterized by being prepared from the following raw materials in parts by weight: 45-55 parts of dicyclopentadiene phenol epoxy resin, 1.2-3.1 parts of zinc naphthenate, 1-3 parts of low-calcium fly ash, 2-3 parts of tungsten disulfide, 6-8 parts of white factice, 4-7 parts of triethylene tetramine, 20-30 parts of o-tolyl glycidyl ether, 8-12 parts of tricresyl phosphate, 10-13 parts of dicyclopentadiene, 11-14 parts of isobutanol, 2.1-3.2 parts of trimethylolpropane, 9-11 parts of diphenylmethane diisocyanate, 8-13 parts of propylene glycol methyl ether acetate and 4-7 parts of an auxiliary agent; the auxiliary agent is prepared from the following raw materials in parts by weight: 0.6-0.9 part of imidazoline, 0.7-1.2 part of 2-mercaptobenzothiazole, 5-7 parts of benzoic acid, 14-16 parts of ethylene glycol butyl ether, 4-7 parts of linseed oil, 0.8-1.3 parts of calcium stearate, 0.4-0.8 part of sodium octaborate, 2-3 parts of locust bean gum, 8-10 parts of dioctyl sebacate, 1-2 parts of nano titanium dioxide and 3-5 parts of coconut oil fatty acid diethanolamide, and the preparation method comprises the following steps: grinding the nano titanium dioxide, the imidazoline, the linseed oil and the sodium octaborate for 10-20 minutes, dispersing the ground nano titanium dioxide, the imidazoline, the linseed oil and the sodium octaborate in ethylene glycol monobutyl ether by ultrasonic waves, adding the benzoic acid, the calcium stearate and the locust bean gum, stirring for 30-40 minutes, heating to 160-180 ℃, preserving the heat for 3-5 hours, cooling a reaction product to 85-98 ℃, adding the dioctyl sebacate, the coconut oil fatty acid diethanolamide and other residual components, and stirring for 1-2 hours to obtain the catalyst.

The method in the patent literature cannot realize low-temperature curing, has no obvious flame retardant property, and cannot meet the application in the coating field with requirements on low-temperature curing and flame retardant property.

Therefore, the invention needs to overcome the defects and invent an epoxy resin for low-temperature curable flame-retardant powder coating.

Disclosure of Invention

In order to solve the technical problems, the invention provides a flame retardant with excellent flame retardant property and combustion property of B₁The epoxy resin for the flame-retardant powder coating capable of being cured at low temperature can be cured at low temperature, contains flame-retardant bromine and nitrogen, and has high flame-retardant performance;

the invention also provides a preparation method of the epoxy resin.

Specifically, tetrabromobisphenol A, 2, 3-dibromosuccinic acid, epoxy chloropropane, sodium hydroxide, 4-bromophthalic anhydride, 1, 4-dibromo-2, 3-butanediol, 2,4, 6-trioxo-1, 3, 5-triazine-1, 3,5(2H,4H,6H) -tripropionic acid, bisphenol bicyclic glycerol ether and the like are mainly used as raw materials for polymerization, so that the epoxy resin for the flame-retardant powder coating capable of being cured at low temperature is obtained;

the epoxy resin product obtained by the invention has higher epoxy group activity, can be crosslinked and cured at low temperature (130 ℃/15min) after being prepared into powder coating with curing agent 2-phenylimidazole, is suitable for Medium Density Fiberboard (MDF) materials, and has excellent curing film-forming property. Meanwhile, the epoxy resin chain segment contains a high content of flame-retardant element bromine, so that the flame-retardant property is excellent, and the flame-retardant grade can reach B₁More than grade.

The epoxy resin for the low-temperature curable flame-retardant powder coating is characterized by being prepared from the following main raw materials in parts by mole through polymerization: 4-10 parts of tetrabromobisphenol A, 3-8 parts of 2, 3-dibromo-succinic acid, 8-18 parts of epoxy chloropropane, 10-20 parts of sodium hydroxide, 5-12 parts of 4-bromophthalic anhydride, 6-15 parts of 1, 4-dibromo-2, 3-butanediol, 5-12 parts of 2,4, 6-trioxo-1, 3, 5-triazine-1, 3,5(2H,4H,6H) -tripropionic acid and 5-10 parts of bisphenol bicyclic glycerol ether.

In the preparation process of the epoxy resin, a first catalyst of triphenyl ethyl phosphonium bromide and a second catalyst of tetrabutyl titanate are adopted.

The dosage of the first catalyst triphenyl ethyl phosphonium bromide is 0.1-0.3% of the total molar amount of the raw materials; the amount of the second catalyst tetrabutyl titanate is 0.05-0.15% of the total molar amount of the raw materials.

The preparation method of the epoxy resin for the low-temperature-curable flame-retardant powder coating comprises the following steps:

(1) tetrabromobisphenol A and 2, 3-dibromo succinic acid are added into a reaction kettle A, then sodium hydroxide solution is added, stirring is carried out, the temperature is increased, and heat preservation reaction is carried out; then adding epoxy chloropropane and a first catalyst, heating and carrying out heat preservation reaction, keeping the temperature and standing for layering after the reaction is stopped, separating out a water phase, and washing with boiling water to obtain epoxy group-terminated epoxy resin;

(2) adding 4-bromophthalic anhydride, 1, 4-dibromo-2, 3-butanediol and a second catalyst into a reaction kettle B, heating for esterification, adding 2,4, 6-trioxo-1, 3, 5-triazine-1, 3,5(2H,4H,6H) -tripropionic acid for carboxyl end capping reaction, stopping reaction after esterification is continued, and cooling;

(3) and adding the epoxy resin material in the reaction kettle A into a reaction kettle B, reacting, adding bisphenol bicyclic glycerol ether epoxy end capping reaction, stopping the reaction, discharging at high temperature while the reaction is hot, cooling the epoxy resin by using a steel belt with condensed water, and crushing and granulating to obtain the epoxy resin for the low-temperature-curable flame-retardant powder coating.

Preferably, the preparation method of the epoxy resin for the low-temperature curable flame-retardant powder coating comprises the following steps:

(1) adding tetrabromobisphenol A and 2, 3-dibromosuccinic acid into a reaction kettle A, slowly dropwise adding a sodium hydroxide solution with the mass concentration of 50%, stirring, completing dropwise adding within 1.5-2.5 h, heating to 60-70 ℃, carrying out heat preservation reaction for 0.8-1.2 h, then adding epoxy chloropropane and a first catalyst, heating to 90-105 ℃, carrying out heat preservation reaction for 2-4 h, testing the epoxy equivalent of a system product, stopping the reaction when the epoxy equivalent is 400-450 g/mol, carrying out heat preservation at 100-110 ℃, standing and layering for 0.3-0.8 h, washing for 2-4 times by using boiling water after a water phase is separated out, thus obtaining epoxy group-terminated epoxy resin, and carrying out heat preservation at 100-105 ℃ for later use;

(2) adding 4-bromophthalic anhydride, 1, 4-dibromo-2, 3-butanediol and a second catalyst into a reaction kettle B, heating to 150-170 ℃ to perform esterification reaction for 5-10H, adding 2,4, 6-trioxo-1, 3, 5-triazine-1, 3,5(2H,4H,6H) -tripropionic acid to perform carboxyl end capping reaction when the acid value of the system is reduced to be below 5mgKOH/g, continuing the esterification reaction for 1-3H at 150-170 ℃, stopping the reaction when the acid value reaches 120-150 mgKOH/g, and cooling to 100-105 ℃;

(3) adding the epoxy resin material reserved in the reaction kettle A into a reaction kettle B, reacting for 1-2 hours at 100-105 ℃, adding bisphenol bicyclic glycerol ether for epoxy capping when the epoxy equivalent of the resin is more than 1200g/mol and the acid value is less than 50mgKOH/g, reacting for 0.5-2 hours at 110-115 ℃, stopping the reaction when the epoxy equivalent reaches 500-600 g/mol, discharging at high temperature while hot, cooling the epoxy resin by using a steel belt with condensed water, and crushing and granulating to obtain the epoxy resin for the low-temperature-curable flame-retardant powder coating;

the mol parts of the raw materials are as follows:

4-10 parts of tetrabromobisphenol A, 3-8 parts of 2, 3-dibromo-succinic acid, 8-18 parts of epoxy chloropropane, 10-20 parts of sodium hydroxide, 5-12 parts of 4-bromophthalic anhydride, 6-15 parts of 1, 4-dibromo-2, 3-butanediol, 5-12 parts of 2,4, 6-trioxo-1, 3, 5-triazine-1, 3,5(2H,4H,6H) -tripropionic acid and 5-10 parts of bisphenol bicyclic glycerol ether.

The epoxy resin for the low-temperature-curable flame-retardant powder coating prepared by the method has the epoxy equivalent of 500-600 g/mol and the softening point of 82-92 ℃.

The scheme of the invention is that monomers with high flame-retardant elements of bromine and nitrogen such as tetrabromobisphenol A, 2, 3-dibromo succinic acid, epoxy chloropropane, sodium hydroxide, 4-bromophthalic anhydride, 1, 4-dibromo-2, 3-butanediol, 2,4, 6-trioxo-1, 3, 5-triazine-1, 3,5(2H,4H,6H) -tripropionic acid are used as chain segment main bodies, and bisphenol bicyclic glycerol ether is used for epoxy end capping, so that the epoxy resin product obtained by the invention has high epoxy group activity, can be crosslinked and cured at low temperature (130 ℃/15min) after being prepared into powder coating with curing agent 2-phenylimidazole, and is suitable for medium-density fiberboard (MDF) materials.

2, 3-dibromo succinic acid and tetrabromobisphenol A are simultaneously reacted with epoxy chloropropane to prepare epoxy resin, so that the obtained epoxy resin has softer chain segment, the softening point is reduced, and the excellent leveling property of a coating film after low-temperature curing can be ensured;

2,4, 6-trioxo-1, 3, 5-triazine-1, 3,5(2H,4H,6H) -tripropionic acid is adopted to participate in the reaction, so that high-functionality epoxy resin and a high-crosslinking-density coating film can be obtained, and excellent impact resistance, adhesive force performance and solvent resistance are realized.

Meanwhile, the epoxy resin chain segment contains a high-content flame-retardant element bromine, so that the flame-retardant property is excellent, and the combustion property can reach B₁More than grade.

Detailed Description

In order that those skilled in the art will better understand the present invention, the inventors will further describe the present invention by the following examples and comparative examples.