CN116082611A - A kind of polyester resin containing alkyl ether main chain and powder coating and preparation method thereof - Google Patents

Abstract

The invention discloses a polyester resin containing an alkyl ether main chain, a powder coating and a preparation method thereof. The internal structural unit of the polyester resin contains an alkyl ether main chain; the raw material of the polyester resin consists of the following parts by mass Number of components: aromatic dibasic acid 40-60 parts, diol 30-40 parts, branching agent 0.01-2 parts, acidolysis agent 0-5 parts, esterification catalyst 0.03-0.2 parts, antioxidant 0.01-1.5 parts, curing accelerator 0.01-1 parts. In the present invention, the main chain of alkyl ether is introduced into the polyester resin for powder coatings, and the content of diglycolic acid, a diacid monomer of the structure of the main chain of alkyl ether, is adjusted to realize the reduction of low-temperature curing conditions under the condition of ensuring the storage stability of the coating. Lower melt viscosity, while ensuring that the resin has better thermal stability. The powder coating prepared from this resin achieves low-temperature curing at 130°C.

Description

A kind of polyester resin containing alkyl ether main chain and powder coating and preparation method thereof

technical field

The invention belongs to the field of polyester resin preparation, and in particular relates to a polyester resin containing an alkyl ether main chain and a powder coating prepared based on the resin.

Background technique

Solvent coatings occupy an important position in my country's coatings industry. Compared with traditional solvent-based coatings, powder coatings have the advantages of health and environmental protection, convenient transportation and storage, and less residual odor of coatings. It is considered to be the main trend of coatings development in the future. However, the baking and curing temperature of powder coatings is relatively high, requiring higher investment in energy and equipment, and cannot be applied to heat-sensitive materials such as wood and plastic. The primary condition for powder coatings to achieve low-temperature curing is that the main resin of the coating must be melted and leveled at low temperatures. However, if the melting temperature of the general resin is lowered, the glass transition temperature will also drop significantly, which will affect the storage stability at room temperature.

Improving the flexibility of the polyester molecular chain is the main means to improve the low-temperature melt leveling of the resin, and adipic acid with long aliphatic chains is often used as a comonomer in the synthesis of polyester resins. Adipic acid is a carboxylic acid with an even number of carbon atoms. If it is changed to a carboxylic acid with an odd number of carbon atoms such as glutaric acid, it will make it difficult to stack polymer chains, resulting in a lower melting point of polyester and a sharp drop in crystallinity. Glutaric acid has been used in polyester coatings and adhesives in Chinese patents CN114989725A, CN107353859B and CN101870844A. A small amount of diethylene glycol and tetraethylene glycol are often used in the synthesis of polyester resins as comonomers. It can be seen that the flexibility of ether bonds is better than that of carbon chains. It can be seen from the molecular structure that the carbon atom at the glutaric acid center is replaced by an oxygen atom, and the monomer is diglycolic acid, a carboxylic acid monomer that can take into account both flexibility and crystallinity.

Contents of the invention

The purpose of the present invention is to provide a kind of polyester resin containing alkyl ether main chain and powder coating and preparation method thereof, introduce the main chain of alkyl ether into the polyester resin for powder coating, by regulating and controlling the structural diacid of alkyl ether main chain The content of the monomer diglycolic acid can reduce the melt viscosity under low-temperature curing conditions, and the powder coating prepared from the resin can be cured at 130°C.

To achieve the above object, the present invention adopts the following technical solutions:

A polyester resin containing an alkyl ether main chain, the internal structural unit of the polyester resin contains an alkyl ether main chain structure; the raw material of the polyester resin is composed of the following components in parts by mass: dibasic acid 40-60 parts, 30-40 parts of glycol, 0.01-2 parts of branching agent, 0-5 parts of acidolysis agent, 0.03-0.2 parts of esterification catalyst, 0.01-1.5 parts of antioxidant, 0.01-0.01- parts of curing accelerator 1 serving.

Preferably, the polyester resin is a carboxyl-terminated polyester resin with an acid value in the range of 20-40 mgKOH/g.

Preferably, the dibasic acid is one or a mixture of terephthalic acid and diglycolic acid; when it is a mixture of the two, diglycolic acid accounts for 0- 10%.

Preferably, the dihydric alcohol is neopentyl glycol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,3-butanediol, 2 - A mixture of one or more of methyl-2,4-pentanediol, 2-ethyl-1,3-hexanediol, and 1,4-butanediol.

Preferably, the branching agent is a mixture of one or more of trimethylolpropane, trimethylolethane, 1,2,5-pentanetriol and pentaerythritol.

Preferably, the acidolysis agent is a mixture of one or more of isophthalic acid, adipic acid, trimellitic anhydride and maleic anhydride.

Preferably, the esterification catalyst is a mixture of one or more of dibutyltin oxide, tributyltin oxide, dihydroxybutyltin chloride, stannous oxalate, and monobutyltin oxide.

Preferably, the antioxidant is tris(2,4-di-tert-butylphenyl)phosphite, tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol A mixture of one or more of stearyl esters and β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

Preferably, the curing accelerator is triphenylphosphine, triphenylethylphosphine bromide; Tetraethylammonium bromide, tetrabutylammonium bromide, tetrabutylammonium chloride, dibutyltin dilaurate A mixture of one or more.

Preferably, the solid-liquid transition point temperature of the polyester resin is <75.6°C.

A preparation method of a polyester resin containing an alkyl ether main chain, comprising the following steps:

(1) under nitrogen atmosphere, add dihydric alcohol, branching agent, esterification catalyst, a part of antioxidant into the reactor;

(2) heating, then adding aromatic dibasic acid, stirring evenly;

(3) Heating to start the reaction, then heat up, and keep warm until the reaction system is clarified;

(4) reduce reaction system temperature;

(5) add acidolysis agent, then heat up, keep warm, continue to react;

(6) Sampling and analyzing the acid value and viscosity. After reaching the qualified index, add the curing accelerator and the remaining antioxidant, and discharge after stirring.

Preferably, in the step (2), the temperature is raised to 130°C.

Preferably, in the step (3), the temperature is raised to 180°C to start the reaction, and then the temperature is raised to 250°C at a rate of 10-15°C/h. At this temperature, the temperature is kept until the reaction system becomes clear.

Preferably, in the step (4), when the acid value (AV) of the sampling test reaches 5-20 mgKOH/g, reduce the temperature of the reaction system to 220°C.

Preferably, in the step (5), the temperature is then raised to 240° C., and after being kept for 2 hours, the reaction is continued for 2 to 4 hours at a vacuum degree of -0.09 to -0.099 Mpa.

Preferably, in the step (6), the acid value and viscosity are sampled and analyzed, wherein: the acid value is controlled at 20-40mg KOH/g, and the viscosity is controlled at 10-40pa.s at 200°C. After the index is qualified, add solidification The accelerator and the remaining antioxidant are discharged after stirring for 0.5h.

A powder coating, the raw material of the powder coating is composed of the following components by weight: 50-60 parts of polyester resin containing alkyl ether main chain, 2-4.5 parts of triglycidyl isocyanurate, 10 parts of titanium dioxide -18 parts, 8-16 parts of barium sulfate, 1-2 parts of leveling agent, 0.5-1 part of brightening agent, 0.2-0.6 parts of benzoin.

Preferably, the leveling agent is GLP503/588 type leveling agent, the brightening agent is accelerator BLC701, and the benzoin is benzoethanolone.

A method for preparing powder coatings, comprising the following steps: mixing raw materials in a mixer, extruding them into sheets through a twin-screw extruder at a temperature of 110° C., grinding them into powder with a mill, and finally The powder coating was obtained after being screened through a 200-mesh sieve; the powder coating was sprayed on a sample plate by an electrostatic spray gun, and was cured by an oven at 130°C for 20 minutes.

Beneficial effect: the resin raw material of the present invention adopts dibasic acid, dibasic alcohol, branching agent, acidolysis agent, esterification catalyst, antioxidant and curing accelerator. By adjusting the content of diglycolic acid monomer in the dibasic acid, the temperature of the solid-liquid transition point is <75.6°C. The powder coating prepared by the resin of the present invention can be cured at a low temperature of 130° C., and has good storage stability and excellent paint film leveling property.

Description of drawings

Fig. 1 is the ¹ H-NMR spectrogram of the polyester prepared in Example 3 of the present invention;

Figure 2a and 2b are the rheological cooling curves of the polyesters prepared by Examples 1 and 6 of the present invention

Detailed ways

The present invention will be further described below in conjunction with embodiment.

Example 1

Polyester resin O-0, under a nitrogen atmosphere, 245 grams of neopentyl glycol, 40 grams of ethylene glycol, 10 grams of trimethylolpropane, 1 gram of catalyst monobutyltin oxide and 1 gram of triphenyl phosphite Add it into the reactor and heat up to 130°C. Then add 442 grams of terephthalic acid and stir evenly. Heat up to 250°C. Under this reaction condition, keep warm until the reaction system is clear, then lower the temperature of the reaction system to 220°C, add 50 grams of isophthalic acid, then raise the temperature to 240°C, keep it warm for 2 hours, and conduct vacuum polycondensation for 3 hours . Sampling and analysis of acid value and viscosity, the acid value is 22.9mg KOH/g, the viscosity is 27.3pa.s (200°C, 78.5rad/s), the indicators are qualified, and the antioxidant tris(2,4-di-tert-butyl 2 grams of phenyl) phosphite and 1 gram of pentaerythritol tetrapropionate were discharged after stirring for half an hour. The solid-liquid transition point measured by a rheometer was 75.6°C.

Example 2

Polyester resin O-2, under a nitrogen atmosphere, 245 grams of neopentyl glycol, 40 grams of ethylene glycol, 10 grams of trimethylolpropane, 1 gram of catalyst monobutyltin oxide and 1 gram of triphenyl phosphite Add it into the reactor and heat up to 130°C. Then add 433 grams of terephthalic acid and 7 grams of diglycolic acid, and stir well. Heat up to 250°C, keep warm until the reaction system is clear, then lower the temperature of the reaction system to 220°C, add 50 grams of isophthalic acid, then raise the temperature to 240°C, keep the temperature for 1 hour, and conduct vacuum polycondensation for 1 hour. Sampling and analysis of acid value and viscosity, the acid value is 30.2mg KOH/g, the viscosity is 21.1pa.s (200°C, 78.5rad/s), the indicators are qualified, and the antioxidant tris(2,4-di-tert-butyl 1 gram of phenyl) phosphite, 2 grams of pentaerythritol tetrapropionate, discharge after stirring for half an hour. The solid-liquid transition point measured by a rheometer was 73.8°C.

Example 3

Polyester resin O-4, under nitrogen atmosphere, 245 grams of neopentyl glycol, 40 grams of ethylene glycol, 10 grams of trimethylolpropane, 1 gram of catalyst monobutyltin oxide and 1 gram of triphenyl phosphite Add it into the reactor and heat up to 130°C. Then add 424 grams of terephthalic acid and 14 grams of diglycolic acid, and stir well. Heat up to 250°C, keep warm until the reaction system is clear, then reduce the temperature of the reaction system to 220°C, add 50 grams of isophthalic acid, then raise the temperature to 240°C, keep it warm for 1 hour, and conduct vacuum polycondensation for 1 hour. Sampling and analysis of acid value and viscosity, the acid value is 34.4mg KOH/g, the viscosity is 21.4pa.s (200°C, 78.5rad/s), the indicators are qualified, and the antioxidant tris(2,4-di-tert-butyl 1 gram of phenyl) phosphite, 2 grams of pentaerythritol tetrapropionate, discharge after stirring for half an hour. The solid-liquid transition point measured by a rheometer was 70.4°C.

Example 4

Polyester resin O-6, 245 grams of neopentyl glycol, 40 grams of ethylene glycol, 10 grams of trimethylolpropane, 1 gram of catalyst monobutyltin oxide and 1 gram of triphenyl phosphite were mixed under nitrogen atmosphere Add it into the reactor and heat up to 130°C. Then add 415 grams of terephthalic acid and 21 grams of diglycolic acid, and stir well. Heat up to 250°C, keep warm until the reaction system is clear, then reduce the temperature of the reaction system to 220°C, add 50 grams of isophthalic acid, then raise the temperature to 240°C, keep it warm for 1 hour, and conduct vacuum polycondensation for 1 hour. Sampling and analysis of acid value and viscosity, the acid value is 22.1mg KOH/g, the viscosity is 16.70pa.s (200℃, 78.5rad/s), the index is qualified, and the antioxidant tris(2,4-di-tert-butyl 1 gram of phenyl) phosphite, 2 grams of pentaerythritol tetrapropionate, discharge after stirring for half an hour. The solid-liquid transition point measured by a rheometer is 67.8°C.

Example 5

Polyester resin O-8, under nitrogen atmosphere, 245 grams of neopentyl glycol, 40 grams of ethylene glycol, 10 grams of trimethylolpropane, 1 gram of catalyst monobutyltin oxide and 1 gram of triphenyl phosphite Add it into the reactor and heat up to 130°C. Then add 406 grams of terephthalic acid and 28 grams of diglycolic acid, and stir well. Heat up to 250°C, keep warm until the reaction system is clear, then lower the temperature of the reaction system to 220°C, add 50 grams of isophthalic acid, then raise the temperature to 240°C, keep the temperature for 1 hour, and conduct vacuum polycondensation for 1 hour. Sampling and analysis of acid value and viscosity, the acid value is 31.1mg KOH/g, the viscosity is 14.30pa.s (200°C, 78.5rad/s), the indicators are qualified, and the antioxidant tris(2,4-di-tert-butyl 1 gram of phenyl) phosphite, 2 grams of pentaerythritol tetrapropionate, discharge after stirring for half an hour. The solid-liquid transition point measured by a rheometer is 65.1°C.

Example 6

Polyester resin O-10, 245 g of neopentyl glycol, 40 g of ethylene glycol, 10 g of trimethylolpropane, 1 g of catalyst monobutyltin oxide, and 1 g of triphenyl phosphite were mixed under a nitrogen atmosphere. Add it into the reactor and heat up to 130°C. Then add 398 grams of terephthalic acid and 35 grams of diglycolic acid, and stir well. Heat up to 250°C, keep warm until the reaction system is clear, then lower the temperature of the reaction system to 220°C, add 50 grams of isophthalic acid, then raise the temperature to 240°C, keep the temperature for 1 hour, and conduct vacuum polycondensation for 1 hour. Sampling and analysis of acid value and viscosity, the acid value is 26.6mg KOH/g, the viscosity is 10.2pa.s (200°C, 78.5rad/s), the indicators are qualified, and the antioxidant tris(2,4-di-tert-butyl 1 gram of phenyl) phosphite, 2 grams of pentaerythritol tetrapropionate, discharge after stirring for half an hour. The solid-liquid transition point measured by a rheometer was 63.9°C.

This embodiment illustrates, along with the increase of diglycolic acid monomer consumption, the solid-liquid transition point of polyester resin continues to decline, and the rotational viscosity also presents a downward trend, but when the consumption exceeds 10% (mol) carboxylic acid total amount, resin Storage stability of formulated powder coatings with risk of caking.

The performance of the polyester resin synthesized by the method of the present invention can be reflected by the performance of the powder coating made. 50-60 parts of polyester resin synthesized by the above-mentioned embodiment 1-6, respectively with 2-4.5 parts of triglycidyl isocyanurate; 10-20 parts of titanium dioxide; 8-20 parts of barium sulfate; leveling agent 1- 2 parts; brightening agent 0.5-1 part; benzoin 0.2-0.6 part. Weigh it according to the ratio in Table 1, mix it well, melt and extrude it into a sheet through a twin-screw extruder under the condition of 110°C, then grind it into powder with a mill, and finally pass through a 200-mesh sieve to make it powder coating. The powder coating was sprayed on the surface-treated (phosphating) metal plate with an electrostatic spray gun, cured at 130°C/20min, and then various performance tests were performed. The performance test results are shown in Table 1.

Comparative example 7 is the existing product DM7101 of Jiangsu Dameirui New Material Co., Ltd., and its product index is an acid value of 32.8mg KOH/g and a viscosity of 51pa.s (200°C).

Table 1

Fig. 1 is the ¹ H-NMR spectrum of the polyester prepared in Example 3 of the present invention. The chemical shift of 4.20 is the hydrogen on the CH ₂ of diglycolic acid, and 4.27 is the hydrogen on the CH ₂ of neopentyl glycol, indicating that diglycolic acid is synthesized into the polymer, which proves that the synthesis process is effective and reliable. Figures 2a and 2b are the rheological cooling curves of the polyesters prepared in Examples 1 and 6 of the present invention, and the intersection point of the storage modulus and the loss modulus is the solid-liquid transition point. The introduction of the alkyl ether main chain lowers the transition point temperature. The polyester resin has good fluidity, can promote full contact of curing groups, increase the speed of curing reaction, improve the wetting performance of the resin matrix to pigments and fillers, and improve the leveling performance of the coating.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also possible. It should be regarded as the protection scope of the present invention.

Claims (10)

1. A polyester resin containing an alkyl ether main chain, characterized in that: the internal structural unit of the polyester resin contains an alkyl ether main chain; the raw material of the polyester resin consists of the following components in parts by mass: Composition: 40-60 parts of dibasic acid, 30-40 parts of diol, 0.01-2 parts of branching agent, 0-5 parts of acidolysis agent, 0.03-0.2 parts of esterification catalyst, 0.01-1.5 parts of antioxidant , 0.01-1 part of curing accelerator. 2 . The polyester resin containing an alkyl ether main chain according to claim 1 , wherein the polyester resin is a carboxyl-terminated polyester resin with an acid value in the range of 20-40 mgKOH/g. 3. the polyester resin containing alkyl ether main chain according to claim 1, is characterized in that: described dibasic acid is one or both mixtures in terephthalic acid and diglycolic acid; When it is a mixture of the two, diglycolic acid accounts for 0-10% of the total amount of polyacids; The dihydric alcohol is neopentyl glycol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,3-butanediol, 2-methyl - A mixture of one or more of 2,4-pentanediol, 2-ethyl-1,3-hexanediol, and 1,4-butanediol. 4. the polyester resin containing alkyl ether main chain according to claim 1, is characterized in that: The branching agent is a mixture of one or more of trimethylolpropane, trimethylolethane, 1,2,5-pentanetriol, and pentaerythritol; The acidolysis agent is a mixture of one or more of isophthalic acid, adipic acid, trimellitic anhydride and maleic anhydride; The esterification catalyst is a mixture of one or more of dibutyltin oxide, tributyltin oxide, dihydroxybutyltin chloride, stannous oxalate, and monobutyltin oxide; The antioxidant is three (2,4-di-tert-butylphenyl) phosphite, tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester, β - a mixture of one or more octadecyl (3,5-di-tert-butyl-4-hydroxyphenyl) propionate; The curing accelerator is triphenylphosphine, triphenylethylphosphine bromide; tetraethylammonium bromide, tetrabutylammonium bromide, tetrabutylammonium chloride, a kind of dibutyltin dilaurate or Various mixes. 5. The polyester resin containing an alkyl ether main chain according to claim 1, characterized in that: the solid-liquid transition point temperature of the polyester resin is <75.6°C. 6. a kind of preparation method of the polyester resin containing alkyl ether main chain as claimed in claim 1, is characterized in that: comprise the following steps: (1) under nitrogen atmosphere, add dihydric alcohol, branching agent, esterification catalyst, a part of antioxidant into the reactor; (2) heating, then adding dibasic acid, stirring evenly; (3) Heating to start the reaction, then heat up, and keep warm until the reaction system is clarified; (4) reduce reaction system temperature; (5) add acidolysis agent, then heat up, keep warm, continue to react; (6) Sampling and analyzing the acid value and viscosity. After reaching the qualified index, add the curing accelerator and the remaining antioxidant, and discharge after stirring. 7. the preparation method of the polyester resin containing alkyl ether main chain according to claim 6, is characterized in that: In the step (2), the temperature is raised to 130° C.; In the step (3), heat up to 180°C to start the reaction, then heat up to 250°C at a rate of 10-15°C/h, and keep warm until the reaction system is clear at this temperature; In the step (4), when the acid value (AV) of sampling detection reaches 5-20mgKOH/g, reduce the temperature of the reaction system to 220°C; In the step (5), the temperature is then raised to 240° C., and after being kept for 2 hours, the reaction is continued for 2 to 4 hours under the condition that the degree of vacuum is -0.09～-0.099Mpa; In the step (6), take samples to analyze the acid value and viscosity, wherein: the acid value is controlled at 20-40mg KOH/g, and the viscosity is controlled at 10-40pa.s at 200°C. After the index is qualified, add the curing accelerator and The remaining antioxidant was discharged after stirring for 0.5h. 8. A powder coating based on the polyester resin containing the alkyl ether main chain according to claim 1, characterized in that: the raw material of the powder coating is made up of the following components by weight: 50-60 parts of polyester resin, 2-4.5 parts of triglycidyl isocyanurate, 10-18 parts of titanium dioxide, 8-16 parts of barium sulfate, 1-2 parts of leveling agent, 0.5-1 part of brightening agent, benzoin 0.2-0.6 parts. 9. The powder coating according to claim 8, characterized in that: the leveling agent is GLP503/588 type leveling agent, the brightening agent is accelerator BLC701, and benzoin is benzophenone. 10. A method for preparing the powder coating according to claim 8, characterized in that: comprising the following steps: after mixing the raw materials in a mixer, melt extruding them into Then use a mill to grind it into powder, and finally pass through a 200-mesh sieve to obtain the powder coating; spray the powder coating on the sample plate with an electrostatic spray gun, and keep it in an oven at 130°C for 20 minutes to cure and form.

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