CN105085876A - Gel point control method in synthesis technology of polyester for powder coatings - Google Patents

Abstract

The invention discloses a gel point control method in a synthesis technology of polyester for powder coatings. In the process of preparing the polyester through reaction of polybasic acid and polyhydric alcohol, the reaction degree is controlled by determining the hydroxyl value or acid value in real time at the condensation polymerization stage, so that the system is controlled to end the reaction before the gel point, and gel generation is avoided. The gel point control method in the synthesis technology of the polyester for the powder coatings has the advantages that the technology is simple, curing efficiency is high, crosslinking point density is large, and the reaction system can be effectively controlled in real time.

Description

Gelation point control method in a kind of polyester synthetic process used for powder coating

Technical field

The present invention relates to the synthesis field of polyester used for powder coating, particularly relate to the gelation point control method of polycondensation phase in a kind of hyper-branched structure polyester synthetic process used for powder coating.

Background technology

Powder coating be one not containing solvent, 100% solid powdery coating, have solvent-free, pollution-free, recyclable, save the energy and resource, reduce labor intensity and film physical strength high, be a kind of novel material of novel, environmental protection.Widely using in recent years along with powder coating, various functional powders coating products is developed in succession, increases rapidly.But, powder coating main raw material is polyester, the polyester with hyper-branched structure has unique branched molecular structure due to it, without tangling between molecule, and containing a large amount of end group, thus show the excellent properties not available for many line polymers such as high-dissolvability, low-viscosity, high workability, high chemical reactivity.

But, when preparation has the polymkeric substance of branched structure, if adopt A ₂+ B ₃during monomer polymerization, very easily produce gel phenomenon, this gel is chemical gel, heats and add solvent all can not dissolve, and destroys production unit, causes damage, improve production cost.Therefore, during in order to avoid polyfunctionality monomer participation reaction, the appearance of gel phenomenon, improves the quality of hyper-branched polyester product, should find a kind of method that can control gelation point.

Summary of the invention

Gelation point control method in the polyester synthetic process used for powder coating that the object of the invention is the deficiency in order to solve the problems of the technologies described above existence, providing that a kind of technique is simple, curing efficiency is high, crosslink density is large, can control effectively to reaction system in real time.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is, when polyester prepared by polyprotonic acid and polyol reaction, utilizes instant mensuration hydroxyl value or acid number to control level of response in polycondensation phase, thus the hierarchy of control terminates reaction before gelation point, avoids the generation of gel.

Gelation point control method of the present invention is:

Step one, polyprotonic acid and polyvalent alcohol carry out polycondensation under temperature 160-280 degree; Polyprotonic acid is made up of a kind of polyprotonic acid (acid anhydrides) or multiple polyprotonic acid (acid anhydrides), and functionality (f) is equal to or greater than 2; Polyvalent alcohol is made up of a kind of polyvalent alcohol or several polyvalent alcohol, and functionality (f) is equal to or greater than 2;

Step 2, when preparing hydroxyl telechelic polyester, start in reaction and in carrying out, the carrying out of acid number measured: in any time of reaction, 1 ~ 10 gram is sampled in reaction system, join following methylene dichloride, tetrahydrofuran (THF), trichloromethane, acetone, in water solvent or in its mixed solvent, stirring and dissolving, after be transferred in the solution cup of potentiometric titrator, potassium hydroxide-ethanol solution is used to carry out titration, until titration end point, write down the volume of the potassium hydroxide-ethanol solution of consumption, parallel titration twice is to reduce error, the calculating of acid number PAV calculates according to GB/T6743-2008 regulation, use PAV ₀and PAV ₁when representing that reaction starts respectively, react the acid number proceeding to certain moment, when time, reaction stops immediately, and can control polyester polycondensation reaction system and there will not be gel, K is constant, value 0.9 ~ 0.95, average functionality, namely equal system reaction initial time 2 times of number of the carboxyl molecule amount divided by alcohol in system, acid and acid anhydrides,

Step 3, when preparing terminal carboxyl polyester, start in reaction and in carrying out, the carrying out of hydroxyl value measured: in any time of reaction, 1 ~ 10 gram is sampled in reaction system, join adjust pH in mixed solvent extremely neutral, after join the Tetra hydro Phthalic anhydride pyridine solution of concentration known, esterification is carried out at 100 ~ 115 DEG C, after be transferred in the solution cup of potentiometric titrator, excessive Tetra hydro Phthalic anhydride standard solution of sodium hydroxide titration, write down the volume of the standard solution of sodium hydroxide of consumption, parallel titration twice is to reduce error, hydroxyl value is calculated according to GB GB/T12008.3-2009, use OHV ₀and OHV ₁when representing that reaction starts respectively, react the hydroxyl value proceeding to certain moment, when time, reaction stops immediately, can control polyester polycondensation reaction system and there will not be gel, K is constant, value 0.9 ~ 0.95, average functionality, namely equal system reaction initial time 2 times of number of the hydroxyl molecule amount divided by alcohol in system, acid and acid anhydrides.

Polyprotonic acid wherein in step one is made up of a kind of polyprotonic acid (acid anhydrides) in terephthalic acid, m-phthalic acid, phthalic acid, toxilic acid, succsinic acid, sebacic acid, suberic acid, fumaric acid, pentanedioic acid, propanedioic acid, m-phthalic acid, nonane diacid, dimethylol propionic acid, maleic anhydride, succinyl oxide, trimellitic acid 1,2-anhydride, polyacrylic acid, polymethyl acrylic acid or multiple polyprotonic acid (acid anhydrides).

Polyvalent alcohol wherein in step one is by ethylene glycol, 1,2-propylene glycol, 1, a kind of polyvalent alcohol of ammediol, BDO, neopentyl glycol, hexylene glycol, glycol ether, hexanetriol, glycerine, Glycerol dimer, triglycerin, TriMethylolPropane(TMP), trimethylolethane, tetramethylolmethane, Dipentaerythritol, Polyglycerine, tetrahydroxybutane, Xylitol, maltose alcohol, mannitol, polyvinyl alcohol or several polyvalent alcohol composition.

Wherein preparing in hydroxyl telechelic polyester process, in system, hydroxy number needs are excessive, and the polyprotonic acid functionality in system is greater than 2.

Wherein preparing in terminal carboxyl polyester process, in system, carboxyl number needs are excessive, and the functionality polyols in system is greater than 2.

The present invention is directed to existing when preparation has the polymkeric substance of branched structure, if adopt A ₂+ B ₃the defect of gel phenomenon is easily there is during monomer polymerization, analyze polyfunctional monomer and participate in the mechanism that reaction generates gel, can find: no matter be adjustment temperature, monomer adds the condition such as speed, monomer add-on, generate in the polycondensation of ester at multi-functional carboxylic acid and multi-functional alcohol and all can occur gelatin phenomenon, therefore, as long as control level of response well below gelation point, the gelatin phenomenon in polycondensation of polyester so just can be avoided; Meanwhile, the end group of the hyper-branched polyester of preparation contains more carboxyl or hydroxyl, and this correspondence prepares powder coating, and reflecting point during baking-curing increases, and can improve curing efficiency and crosslink density.

The polyester prepared by the present invention is the low-molecular-weight polyester with hyper-branched structure, and end group is hydroxyl or carboxyl, and molecular weight ranges is at 2000 ~ 5000g/mol.

Embodiment

Specific embodiment is below to set forth the present invention further.Should be understood that these embodiments are only not used in for illustration of the present invention to limit the scope of the invention.In addition should be understood that those skilled in the art can make various changes or modifications the present invention after having read content disclosed by the invention, but these equivalent forms are equally within the scope of rights protection of the presently claimed invention.

Embodiment 1

In reaction vessel, add terephthalic acid 1mol (mole, amount of substance), trimellitic acid 1,2-anhydride 1mol, ethylene glycol 2.6mol, a small amount of catalyzer, mix, sample 0.7 gram, carry out titration with the potassium hydroxide-ethanol solution of 0.1mol/L, test acid number according to GB GB/T6743-2008, calculate PAV ₀be 540 ± 5mg/g, be then heated to 130 DEG C of esterifications, be heated to 210 DEG C subsequently, under vacuum tightness 10kPa, carry out polycondensation that 3 as a child sampling detecting acid numbers calculate PAV ₁be 200 ± 5mg/g.Calculate:

$1-\frac{{\mathrm{PAV}}_1}{{\mathrm{PAV}}_0}=1-\frac{200}{540}=1-0.370=0.630$

$\frac{2K}{\stackrel{\‾}{f}}=\frac{2\×0.95}{\frac{1\×2+1\×3}{1+1+2.6}}=0.874$

relational expression is set up, now stopped reaction, system thickness, and gel-free generates, can smooth flow blowing, test mean polymerisation degree 3-4.

Embodiment 2

In reaction vessel, add terephthalic acid 1mol (mole, amount of substance), trimellitic acid 1,2-anhydride 1mol, ethylene glycol 2.6mol, a small amount of catalyzer, mix, sample 0.7 gram, carry out titration with the potassium hydroxide-ethanol solution of 0.1mol/L, test acid number according to GB GB/T6743-2008, calculate PAV ₀be 540 ± 5mg/g, be then heated to 140 DEG C of esterifications, be heated to 210 DEG C subsequently, under vacuum tightness 75kPa, carry out polycondensation that 3 as a child sampling detecting acid numbers calculate PAV ₁be 108 ± 5mg/g.Calculate:

$1-\frac{{\mathrm{PAV}}_1}{{\mathrm{PAV}}_0}=1-\frac{108}{540}=1-0.2=0.8$

$\frac{2K}{\stackrel{\‾}{f}}=\frac{2\×0.95}{\frac{1\×2+1\×3}{1+1+2.6}}=0.874$

relational expression is set up, now stopped reaction, system thickness, and gel-free generates, can smooth flow blowing, test mean polymerisation degree 7-8.

Embodiment 3

In reaction vessel, add terephthalic acid 1mol (mole, amount of substance), trimellitic acid 1,2-anhydride 1mol, ethylene glycol 2.6mol, a small amount of catalyzer, mix, sample 0.7 gram, carry out titration with the potassium hydroxide-ethanol solution of 0.1mol/L, test acid number according to GB GB/T6743-2008, calculate PAV ₀be 540 ± 5mg/g, be then heated to 140 DEG C of esterifications, be heated to 210 DEG C subsequently, under vacuum tightness 90kPa, carry out polycondensation that 2 as a child sampling detecting acid numbers calculate PAV ₁be 80 ± 2mg/g.Calculate:

$1-\frac{{\mathrm{PAV}}_1}{{\mathrm{PAV}}_0}=1-\frac{80}{540}=1-0.148=0.852$

$\frac{2K}{\stackrel{\‾}{f}}=\frac{2\×0.95}{\frac{1\×2+1\×3}{1+1+2.6}}=0.874$

relational expression is set up, now stopped reaction, system thickness, and gel-free generates, can smooth flow blowing, test mean polymerisation degree 13-15.

Claims (3)

1. the gelation point control method in polyester synthetic process used for powder coating, is characterized in that: step one, polyprotonic acid and polyvalent alcohol carry out polycondensation under temperature 160-280 degree, polyprotonic acid is made up of a kind of polyprotonic acid (acid anhydrides) or multiple polyprotonic acid (acid anhydrides), and functionality (f) is equal to or greater than 2, polyvalent alcohol is made up of a kind of polyvalent alcohol or several polyvalent alcohol, and functionality (f) is equal to or greater than 2, step 2, when preparing hydroxyl telechelic polyester, start in reaction and in carrying out, the carrying out of acid number measured: in any time of reaction, 1 ~ 10 gram is sampled in reaction system, join following methylene dichloride, tetrahydrofuran (THF), trichloromethane, acetone, in water solvent or in its mixed solvent, stirring and dissolving, after be transferred in the solution cup of potentiometric titrator, potassium hydroxide-ethanol solution is used to carry out titration, until titration end point, write down the volume of the potassium hydroxide-ethanol solution of consumption, parallel titration twice is to reduce error, the calculating of acid number PAV calculates according to GB/T6743-2008 regulation, use PAV ₀and PAV ₁when representing that reaction starts respectively, react the acid number proceeding to certain moment, when time, reaction stops immediately, and can control polyester polycondensation reaction system and there will not be gel, K is constant, value 0.9 ~ 0.95, average functionality, namely equal system reaction initial time 2 times of number of the carboxyl molecule amount divided by alcohol in system, acid and acid anhydrides, step 3, when preparing terminal carboxyl polyester, start in reaction and in carrying out, the carrying out of hydroxyl value measured: in any time of reaction, 1 ~ 10 gram is sampled in reaction system, join adjust pH in mixed solvent extremely neutral, after join the Tetra hydro Phthalic anhydride pyridine solution of concentration known, esterification is carried out at 100 ~ 115 DEG C, after be transferred in the solution cup of potentiometric titrator, excessive Tetra hydro Phthalic anhydride standard solution of sodium hydroxide titration, write down the volume of the standard solution of sodium hydroxide of consumption, parallel titration twice is to reduce error, hydroxyl value is calculated according to GB GB/T12008.3-2009, use OHV ₀and OHV ₁when representing that reaction starts respectively, react the hydroxyl value proceeding to certain moment, when time, reaction stops immediately, can control polyester polycondensation reaction system and there will not be gel, K is constant, value 0.9 ~ 0.95, average functionality, namely equal system reaction initial time 2 times of number of the hydroxyl molecule amount divided by alcohol in system, acid and acid anhydrides.

2. the gelation point control method in a kind of polyester synthetic process used for powder coating according to claim 1, is characterized in that: polyprotonic acid is made up of a kind of polyprotonic acid (acid anhydrides) in terephthalic acid, m-phthalic acid, phthalic acid, toxilic acid, succsinic acid, sebacic acid, suberic acid, fumaric acid, pentanedioic acid, propanedioic acid, m-phthalic acid, nonane diacid, dimethylol propionic acid, maleic anhydride, succinyl oxide, trimellitic acid 1,2-anhydride, polyacrylic acid, polymethyl acrylic acid or multiple polyprotonic acid (acid anhydrides).

3. the gelation point control method in a kind of polyester synthetic process used for powder coating according to claim 1, it is characterized in that: polyvalent alcohol is by ethylene glycol, 1,2-propylene glycol, 1, a kind of polyvalent alcohol of ammediol, BDO, neopentyl glycol, hexylene glycol, glycol ether, hexanetriol, glycerine, Glycerol dimer, triglycerin, TriMethylolPropane(TMP), trimethylolethane, tetramethylolmethane, Dipentaerythritol, Polyglycerine, tetrahydroxybutane, Xylitol, maltose alcohol, mannitol, polyvinyl alcohol or several polyvalent alcohol composition.