SI26411A - Bio-based resin for the preparation of a two-component polyurethane coating for metals - Google Patents

Abstract

Bio-based resin for the preparation of sustainable two-component polyurethane coatings for metals solves the technical problem of providing a sustainable resin by not containing organic solvents and containing biologically-based building blocks. This resin is also directly useful as a replacement for solvent-free polyester polyols in two-component polyurethane coatings with high solids.

Description

Bio-based resin for the preparation of a two-component polyurethane coating for metals

The field of technology

Obtaining bio-based resins; use of bio-based resins; production of coatings.

Technical problem

The technical problem solved by the invention is the problem of how to provide a sustainable resin without the content of organic solvents and with biologically-based building blocks, which will be suitable for the preparation of a two-component polyurethane coating for metals that meets the requirements of European regulations in the field of emissions of volatile organic substances.

State of the art

Polyester polyols synthesized from bio-based building blocks are not new. This is also true for polyurethane coatings based on such polyols.

EP2226311A1 describes a polyol having a substituent attached via a carbon-carbon single bond to a saturated carbon atom in the hydrocarbonyl group of a fatty acid; where R1 and R2 are esterified residues of aliphatic or cycloaliphatic diols; and from 0 to 15% by weight. esterified residues of at least one C4-C12 anhydride, C4-C12 diacid or C4-C12 lactone.

CN110964172B describes a solvent-free biobased modified polyurethane resin and its use. A solvent-free bio-based modified polyurethane resin is prepared by mixing component A and component B. The present invention uses an aromatic compound reactive with the isocyanate group of an isocyanate to modify a solvent-free bio-based polyurethane resin so that the adhesive strength and resistance to hydrolysis modified polyurethane resins on a biological basis without solvents greatly improve.

CN110396182B describes a polyester resin prepared from bio-based raw materials and a process for its preparation. Sorbitol, 1,3-propylene glycol and polyols and polyacids from biobased pohols were prepared by polymerization, with 7oxabicycloheptane-2,3-dicarboxylic anhydride representing 50 moles of all acids. Isosorbide represents 20-60%, and 1,3-propylene glycol 10-30% of the molar content. The polyester resin of the present invention fully uses bio-based materials, which is environmentally friendly and energy-saving. The combination of 7oxabicycloheptane-2,3-dicarboxylic acid anhydride, a rigid polycyclic dibasic acid, and polycyclic isosorbide makes a product with a high glass transition temperature. Due to the presence of the polycyclic structure, the effect of steric hindrance is very high, and the ester bond, which is easily attacked, is well protected, so that the product has good resistance.

EP3191539B1 describes a polyester resin with a linear or branched structure and free of unsaturated fatty acids, which is hydroxylated or carboxylated based on renewable raw materials, in particular based on a specific bio-based polyol and its use in highly durable coatings based on renewable raw materials, in particular for coating metal foils.

EP3212691B1 describes a process for the preparation of polyester polyols and polyester polyols obtainable by this process.

CN113549199A describes a solvent-resistant bio-based polyester polyol, a polyurethane resin and processes for the preparation of a solvent-resistant bio-based polyester polyol and polyurethane resins. Bio-based polyester polyol is characterized by containing bio-based dihydric alcohol and bio-based dibasic acid, and the molar ratio of dihydric alcohol to dibasic acid is (1.05-1.2).1. According to the synthesis method of solvent-resistant polyurethane polyol, polyurethane resin is produced by a special step-by-step polymerization production process, and the prepared polyurethane resin has excellent solvent resistance and high temperature resistance.

CN110746872A describes the use of a bio-based polyester based polyurethane resin in the preparation of a high strength polyurethane anti-corrosion coating. Polyurethane anti-corrosion coating with high strength consists of component A and component B, which are coordinated with each other. Component A comprises by weight 10-60 parts bio-based polyester polyurethane resin, 10-40 parts anti-rust pigment, 0-2 parts dispersant, 0-50 parts mixed filler, 0-2 parts anti-settling agent, 0-0 .2 parts catalytic promoter, 0-1 part antifoam, 0-1 part leveling agent, and 0-20 parts mixed solvent; component B comprises 5-25 parts by weight of isocyanate hardener. The present invention also describes the process of preparing a polyurethane anti-corrosion coating with high strength. The high-strength polyurethane anti-corrosion coating reduces the evaporation of volatile organic compounds (VOCs), retains some of the properties of solvent-based coatings and can be produced directly using an existing production line.

US2015210807A1 describes a polyurethane which is the reaction product of a polyisocyanate and a polyester, said polyester being formed from a fatty acid dimer, a C2 to C4 diol and a C8 to C16 dicarboxylic acid or a C6 to C12 lactide.

The primary use of the polyols cited above is in industrial organic coatings. Their use is limited by Council Directive 1999/13/EC of 11 March 1999 on the limitation of emissions of volatile organic compounds due to the use of organic solvents in certain activities and plants. One of the practically useful technologies for meeting the requirements of this directive is high-substance solvent coatings. The directive does not prescribe a maximum content of volatile organic substances in the coating, but it follows that in large industrial paint shops, the solvent coating must have an average of at least 72.7% of non-volatile substances during application. This also applies to polyurethane topcoats and single-layer coatings.

Such coatings can otherwise only be prepared on the basis of acrylic polyols, but formulators often decide to also include polyester polyol as a binder in the formulation. Particularly effective for this purpose are low-viscosity solvent-free polyester polyols with a viscosity between 500 and 2000 mPas, preferably up to 1000 mPas, a Tg between -70 and -50 °C and a hydroxyl number between 200 and 350 mgKOH/g. Formulation 1 shows a typical example of such a coating:

1 Domacryl 5485 43.3 75% acrylic polyol solution Helios TBLUS d.o.o. 2 DISPERBYK-2150 4.8 sauce ΒΥΚ-Chemie GmbH 3 Butyl Acetate : methoxypropyl acetal 2:1 1.6 mixture of solvents 4 CLAYTONE AF 1 rheological additive ΒΥΚ-Chemie GmbH 5 Hostaperm Blue B2G- L 0.1 pigment Clariant International Ltd 6 Heucodur Yellow 252 1.7 pigment HEUBACH GmbH 7 Kronos 2064 17.1 pigment KRONOS Worldwide, Inc. 8 Color Black FW 200 0.6 pigment Orion Engineered Carbons GmbH 9 Blanc Fixe Micro Filler 7.7 filler Venator Germany GmbH Grinding for 20 min at 17 m/s 10 Domacryl 5485 8.4 75% acrylic polyol solution Helios TBLUS d.o.o. 11 Domopol 6046 10 solvent-free polyester polyol, hydroxyl number 250290 mgKOH/g, viscosity 750-1000 mPas at 23 °C Helios TBLUS d.o.o. 12 Butyl Acetate : methoxypropyl acetal 2:1 0.8 mixture of solvents 13 Butyl glycol acetate 2 solvent j

14 ΒΥΚ-320 0.4 surface additive ΒΥΚ-Chemie GmbH 15 ΒΥΚ-3760 0.4 surface additive ΒΥΚ-Chemie GmbH 16 K-Cat ΧΚ-672 0.1 catalyst King Industries, Inc. 100 17 DesmodurN 3390 32.5 isocyanate hardener Covestro AG

Butyl Acetate 12.8 Solvent

45.3

Formulation 1, high solids solvent polyurethane coating (Formulation Development Domacryl 5485. New High Solids System, Mathis KuleBa, BYK-Chemie GmbH, Wesel, 2022.)

The use of the described polyester polyols, in addition to increasing the proportion of non-volatile substances at the same viscosity, also makes the coating elastic, since the polyester polyol in question has a lower Tg than the acrylic polyols used.

Description of the new solution

Bio-based resin for the preparation of sustainable two-component polyurethane coatings for metals solves the technical problem of providing a sustainable resin by not containing organic solvents and containing biologically-based building blocks. This resin is also directly useful as a replacement for solvent-free polyester polyols in high solids two-component polyurethane coatings.

For the purposes of this description, a bio-based resin particularly (including and not limited to) a resin that derives at least 80%, preferably 90%, even more preferably 99%, or some or all of its constituent monomers from biological sources.

The invention relates in particular to a sustainable bio-based resin that does not contain organic solvents for use in two-component polyurethane coatings for metals.

The invention also relates to a bio-based resin, wherein the building blocks of said bio-based resin are bio-renewable, preferably more than 95% bio-renewable, even more preferably 100% bio-renewable, wherein the acid number is from 3 to 20 mgKOH/g, hydroxyl number is from 200 to 350 mgKOH/g, glass transition temperature from -70 C to -50 C, viscosity at 23 °C from 500 to 2000 mPas, number average molar mass from 500 to 2000 and weight average molar mass from 1000 to 5000.

The purpose of the invention is to provide a sustainable bio-based resin, on the basis of which it will be possible to prepare a sustainable two-component polyurethane coating for metals. The bio-based resin comprises 25 to 75% by weight of diacids and 25 to 75% by weight of polyalcohols and does not comprise fatty acids. According to the invention, the production process of bio-based resin with the previously described characteristics is also provided.

Known bio-based resin production approaches do not provide the preparation of a polyester polyol without the use of organic solvents with a viscosity between 500 and 2000 mPas, preferably up to 1000 mPas, a Tg between -70 and -50 °C and a hydroxyl number between 200 and 350 mgKOH/g.

EP2226311A1 focuses on the preparation of the resin without the use of fatty acid solvents, but its application is more directed to the use of the resin as an adhesive agent in laminates. CN110964172B presents the preparation of polyurethane resin without the use of solvents for the application of improving the adhesion and hydrolytic resistance of artificial leather.

CN110396182B assumes the preparation of bio-based polyester for application in the coating of cans, and at the same time they also represent a higher numerical average of molar masses (15000-45000) and a higher glass transition temperature (80-120 °C).

EP3191539B1 describes the preparation of a bio-based polyester for use in the coating of metal foils and in the production of powder coatings. The presented resin expresses a lower hydroxyl number (10-150), a higher glass transition temperature (10-50 °C).

ΕΡ3212691 BI presents the preparation of polyester polyols for use in polyurethane foam applications. Several resin examples are presented, but all indicate a lower acid number (up to 1 mgKOH/g) and a higher viscosity (10000 mPas at 25 °C). CN113549199A presents a bio-based polyester polyol resistant to solvents, while presenting a lower acid number (0.8 mgKOH/g) and a lower hydroxyl number (36-116 mgKOH/g).

CN110746872A represents polyurethane resin based on bio-based polyester obtained from vegetable oil (soybean oil). US2015210807A1 describes the preparation of polyurethane resin as a reaction product of polyester and polyisocyanate, whereby fatty acids are also used to prepare polyester, and the prepared coating is application-oriented to wood coatings and improvement of adhesion properties.

The invention relates to a bio-based resin, which is a linear saturated polyester and is used alone or in combination with an acrylic resin, in two-component polyurethane coatings with very good UV resistance.

The bio-based resin comprises:

• 25 to 75% by weight of diacids and • 25 to 75% by weight of polyalcohols.

Wherein the diacids are selected from the group consisting especially, but not exclusively, of sebacic acid, succinic acid, azelaic acid, adipic acid.

Polyalcohols are selected from the group consisting especially, but not exclusively, of neopentyl glycol, trimethylol propane, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerol.

Specifically, it is a bio-based resin that does not contain organic solvents.

Furthermore, it is a bio-based resin, where the proportion of bio-renewable components is at least 80%, preferably 90%, even more preferably 99%, in relation to the entire bio-based resin. The bio-renewable share is proven in a state-of-the-art manner, preferably either by measurements of the 14C isotope (e.g. according to the ASTM 6866 method) and/or via a mass balance certification system (e.g. ISCC+ certificate) and/or via other recognized methods and certificates, which take into account sustainability aspects, including recycled materials.

The production process of the bio-based resin according to the invention is carried out according to a process that includes the following steps:

• in step 1, a mixture of diacids and polyalcohols is prepared in the reactor vessel, whereby the contents of the reactor vessel are heated to a temperature between 150 and 250 °C, and the polymerization of the components in the reaction vessel is further initiated by heating to the temperature;

• in step 2, the course of the reaction is monitored by measuring the acid number and viscosity, and after the reaction is finished, the resin is cooled to room temperature.

The sustainable concept of bio-based resin is expressed by the reduction of emissions of volatile organic solvents, since the resin does not contain organic solvents; and the use of building blocks from renewable sources. The latter applies to all the mentioned building blocks. To calculate the share of renewable resources, the results of analytical measurements of the carbon 14 isotope ( ¹⁴ C) and declarations of monomer producers regarding the biological share according to the principle of Bio-Mass-Balance (BMB) are used.

The bio-based resin thus prepared is used in the formulation of a two-component polyurethane coating for metals.

In the embodiment, it can be a bio-based resin, in the embodiment it is a polyester polyol, the building blocks of which are bio-renewable, preferably 100% bio-renewable, with an acid number of 3 to 20 mgKOH/g, a hydroxyl number of 200 up to 350 mgKOH/g, glass transition temperature from -70 °C to -50 °C, viscosity at 23 °C from 500 to 2000 mPa.s, number average molar masses from 500 to 2000 and weight average molar masses from 1000 to 5000.

In the embodiment, it is a bio-based resin, whereby the share of bio-renewable components is essential, preferably 100%, in relation to the entire bio-based resin. To calculate the share of renewable resources, the results of analytical measurements of the carbon 14 (C) isotope, such as ASTM D6866, and the declarations of monomer producers regarding the biological share according to the principle of Bio-Mass-Balance (BMB) are used.

In an embodiment, it can further be a polyester polyol, whereby the mentioned polyalcohols are selected from the group formed in particular by neopentyl glycol, trimethylol propane, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6 -hexanediol, glycerol and the like.

In an embodiment, it can further be a polyester polyol, wherein said diacids are selected from the group formed especially, but not exclusively, by sebacic acid, succinic acid, azelaic acid, adipic acid and the like.

In an embodiment, it can further be a bio-based resin, for the synthesis of which at least two diacids selected from the group formed by, in particular, but not exclusively, sebacic acid, succinic acid, azelaic acid, adipic acid and the like were used.

In the embodiment, it can also be a bio-based resin, for the synthesis of which sebacic acid and succinic acid were used in a ratio of 1:9 to 9:1.

The bio-based resin manufacturing process according to the embodiment may include the following steps:

in step 1, a mixture of acids and alcohols is prepared in the reactor vessel, whereby the contents of the reactor vessel are heated to a temperature of 150 °C to 250 °C, whereby further heating to the temperature initiates the polymerization of the components in the reaction vessel; in step 2, the course of the reaction is monitored by measuring the acid number and viscosity, and after the reaction is finished, the resin is cooled to room temperature.

According to the embodiment, a coating produced using the bio-based resin of the embodiment as the sole polyol or a mixture of the bio-based resin of the embodiment and one or more other polyols is performed.

Several examples are shown below for better understanding.

Example 1

The acquisition of bio-based resin for the preparation of sustainable coatings for metals was carried out in a manner that will be described below. A glass reaction vessel with a volume of 51 was used, equipped with a condenser for the elimination of reaction water. 2220 g of succinic acid, 1388 g of neopentyl glycol and 1069 g of 1,3-propanediol were initially introduced into the reaction vessel. Then the reaction vessel was heated to a temperature of 210 C. After 1 hour and 50 minutes, the acid number of the mixture in the reactor was 9.7 mgKOH/g and the zone-plate viscosity of the mixture in the reactor was 306 mPa.s. This was followed by cooling to room temperature. The content of dry matter in the thus obtained polymer solution was 100% by mass, the viscosity at 23 °C was 2340 mPa.s, the acid number was 9.7 mgKOH/g, the hydroxyl number was 248 mgKOH/g, the color was 0 .1 Gardner and Tg was -49.7 °C. The number average molar mass was 611, and the weight average molar mass was 1153.

Example 2

The acquisition of bio-based resin for the preparation of sustainable coatings for metals was carried out in a manner that will be described below. A glass reaction vessel with a volume of 51 was used, equipped with a condenser for the elimination of reaction water. 2553 g of sebacic acid, 1074 g of neopentyl glycol and 827 g of 1,3-propanediol were initially introduced into the reaction vessel. The reaction vessel was then heated to a temperature of 210 °C. After 2 hours and 45 minutes, the acid number of the reactor mixture was 10.3 mgKOH/g and the zone-plate viscosity of the reactor mixture was 161 mPa.s. This was followed by cooling to room temperature. After cooling, the resin crystallized. The content of dry matter in the thus obtained polymer solution was 100% by mass, the viscosity at 23 °C was 2700 mPa.s, the acid number was 10.3 mgKOH/g, the hydroxyl number was 250 mgKOH/g, the color was 12 .0 Gardner and Tg was -66.2 °C. The number average molar mass was 4762 and the weight average molar mass was 50619.

Example 3

The acquisition of bio-based resin for the preparation of sustainable coatings for metals was carried out in a manner that will be described below. A glass reaction vessel with a volume of 51 was used, equipped with a condenser for the elimination of reaction water. 1470 g of sebacic acid, 858 g of succinic acid, 1240 g of neopentyl glycol and 955 g of 1,3-propanediol were initially introduced into the reaction vessel. The reaction vessel was then heated to a temperature of 210 °C. After 2 hours and 45 minutes, the acid number of the reactor mixture was 10.2 mgKOH/g and the zone-plate viscosity of the reactor mixture was 179 mPa.s. This was followed by cooling to room temperature. The content of dry matter in the thus obtained polymer solution was 100% by mass, the viscosity at 23 °C was 960 mPa.s, the acid number was 10.2 mgKOH/g, the hydroxyl number was 280 mgKOH/g, the color was 0 .2 Gardner and Tg was -64.7°C. The number average molar mass was 552, and the weight average molar mass was 1046.

Example 4

Two-component polyurethane coating prepared according to Formulation 1. The coating is called Coating A.

Example 5

Two-component polyurethane coating prepared analogously to Formulation 1, except that item 11 Domopol 6046 was replaced with the resin from Example 3. The coating is called Coating B.

Coating A and Coating B were applied to steel test plates with ELECRON LB-280 (Kansai Paint Co.,Ltd) cataphoresis pre-applied.

The properties of Coating A and Coating B are shown in the Tables

Property The method Coating A Coating B Non-volatile fraction substances ISO 3251 125 °C 1 h 82.4 82.5 Density at 23 °C ISO 2811 (kg/L) 1.27 1.27

Viscosity at 20 0.01 s' ¹ (Belt) 16,26 16.77 °C, rheometer 25 PP lOOs' ¹ (Belt) 8.03 8.35 sensor lOOOs' ¹ (Belt) 4.77 5.16

Table 1, physical properties of the polyol components of Coating A and Coating B.

Property The method Coating A Coating B System thickness ISO 9514, doubled viscosity, 23 °C (min) 120 120 Drying ISO 9117-4 st. 1 17 min 22 min ISO 9117-4 st. 2 5 h 14 min 5 h 14 min ISO 9117-4 st. 3 6 h 3 min 6 h 3 min ------------------------------------ --------------- --------- ISO 9117-4 st. 4 9 h 11 min 9 h 46 min

Table 2, reactivity and curing of Coating A and Coating B.

Property The method Coating A Coating B Thickness movie dry ISO 2808 (pm) 82.5 ±2.1 82.1 ±3.0 Konig hardness ISO 1522 after 24 h 77 77 ISO 1522 after 48 h 110 107 ISO 1522 after 72 h 131 121 ------- -------- ------------- ISO 1522 after 7d 150 141

Table 3, hardness development of Coating A and Coating B.

Property Method Coating A Coating B Dry film thickness ISO 2808 (pm) 82.5 ±2.1 82.1 ±3.0 Buchholz hardness ISO 2815 1.2 mm 1.2 mm Impact resistance ISO 6272-2 (kgcm) 71 73

Elasticity with penetration of a spherical mandrel ISO 1520 (mm) 8.8 8.7 Shine on ISO 2813 20 ° 87.5 87.9 Shine on ISO 2813 60° 93.2 93.2 A difference of nuance ISO/CIE 11664-4 0.07

Table 4, dry film properties of Coating A and Coating B.

Property The method Coating A Coating B A difference of nuance ISO/CIE 11664-4 0.27 0.20 Retaining the shine ISO 2813 20 ⁰ (%) 0.72 0.71 Retaining the shine ISO 2813 60 °(%) 0.92 0.91

Table 5, change in gloss and shade of Coating A and Coating B after 1000 h of aging according to ISO 16474-3 method C, cycle 4 (UV-B).

Claims (15)

1. Bio-based resin, which includes, in relation to the total mass, each amount of bio-based resin 25 to 75% by mass of bio-based diacids, and 25 to 75% by mass of bio-based polyalcohols. 2. Bio-based resin according to claim 1 for the preparation of a two-component polyurethane coating for metals, especially sustainable. 3. Bio-based resin according to any one of the preceding claims, wherein the building blocks of said bio-based resin are bio-renewable, preferably more than 95% bio-renewable, even more preferably 100% bio-renewable, wherein the acid number is from 3 to 20 mgKOH /g, hydroxyl number from 200 to 350 mgKOH/g, glass transition temperature from -70 °C to -50 °C, viscosity at 23 °C from 500 to 2000 mPas, number average molar masses from 500 to 2000 and weight average molar masses range from 1000 to 5000. 4. Bio-based resin according to any one of the preceding claims, wherein said diacids are selected from the group consisting in particular of sebacic acid, succinic acid, azelaic acid, adipic acid and the like. 5. Bio-based resin according to any one of the previous claims, for the synthesis of which at least two diacids selected from the group consisting in particular of sebacic acid, succinic acid, azelaic acid, adipic acid were used. 6. Bio-based resin according to any of the preceding claims, for the synthesis of which sebacic acid, succinic acid were used in a ratio of 1:9 to 9:1. 7. Bio-based resin according to any one of the preceding claims, wherein said polyalcohols are selected from the group consisting in particular of neopentyl glycol, trimethylol propane, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1 ,6hexanediol, glycerol. 8. Bio-based resin according to any of the preceding claims, wherein the proportion of bio-renewable components is more than 95%, preferably 100%, with respect to the entire bio-based resin, whereby the results of analytical measurements are used to calculate the proportion of renewable resources isotope of carbon 14 (14C), such as ASTM D6866, and declarations of monomer producers regarding the biological fraction according to the principle of bio mass balance (BMB). 9. Bio-based resin according to any one of the preceding claims, wherein the acid number is from 3 to 20 mgKOH/g. 10. Bio-based resin according to any one of the preceding claims, wherein the viscosity at 23 °C is from 500 to 2000 mPas. 11. Bio-based resin according to any one of the preceding claims, wherein the hydroxyl number is from 200 to 350 mgKOH/g. 12. The bio-based resin according to any one of the preceding claims, wherein the number average molar masses are from 500 to 2000 and the weight average molar masses are from 1000 to 5000. 13. Bio-based resin according to any one of the preceding claims, wherein the glass transition temperature is from -70°C to -50°C. 14. A process for producing a bio-based resin according to any of the preceding claims, comprising the following steps: in step 1, a mixture of acids and alcohols is prepared in the reactor vessel, whereby the contents of the reactor vessel are heated to a temperature of 150 °C to 250 °C, whereby the polymerization of the components in the reaction vessel is further initiated by heating to the temperature; in step 2, the course of the reaction is monitored by measuring the acid number and viscosity, and after the reaction is finished, the resin is cooled to room temperature. 15. A coating produced using the resin of claims 1-13 as the sole polyol or a mixture of the resin of claims 1-13 and one or more other polyols.