CN100432160C - Water-based reaction type hindered amine use, formula and method for in-situ photostabilization of coating layer - Google Patents

Abstract

The invention relates to a formula of a water-based reactive hindered amine (r-HALS) water-based light-curing coating and a method for in-situ light stabilization of the coating. The formula of polymer coating of the present invention is made up of r-HALS, water-based oligomer, diluent, photoinitiator, and other auxiliary agents, and the in-situ photostabilization method of UV-curable polymer water-based coating system comprises a. prepolymerization material homogenization, b. coating, c. vacuum drying, d. UV curing and other steps. Tests show that the coating of the present invention has excellent photoprotective properties for its UV curable polymer coating.

Description

Formulation of water-based reactive hindered amine coating and light stabilization method of coating

Technical field

The invention relates to a photocurable coating formulation of water-based reactive hindered amine and an in-situ photostabilization method of the coating.

Background technique

The UV curing technology of polymer coatings has been paid great attention to once it came out, and the success of this curing process mainly depends on its own advanced nature. Selective chemical transitions from quasi-liquid to solid phases can occur over the range of irradiated wavelengths in solvent-free or high-solids formulations at room temperature. The application field of polymer coating UV curing technology is constantly expanding, used to improve the surface properties of various materials, such as plastics, metals, wood, ceramics, glass, fibers and textiles, etc., especially used in the manufacture of drug release films and biological Application and protection of crafts. And rapidly expanded to the fields of coatings, inks, adhesives, packaging materials, medical treatment, biochemistry, and agriculture. For example, photopolymerization systems used for printing inks can achieve rapid curing in a short time of the order of 10-1 seconds at room temperature.

UV-curing polymer coatings are used to protect various materials from photoaging and to improve the surface properties of these materials. Due to the low mobility of the polymer chain, its cross-linked network structure reduces the cage effect (Cage effect) and chain growth generated by the initiator fragments, so that the cross-linked polymerization system has the ability to resist photooxidation. Due to the needs of environmental protection, more and more people pay more and more attention to the UV-cured water-based coating system, and its proportion in the industry is increasing year by year, and it will be an advantageous product in the future coatings industry. Therefore, research and development (R&D) of light stabilization technology for UV-cured water-based coating systems is imminent.

Hindered Amine Light Stabilizers (Hindered Amine Light Stabilizers, HALS) is a new type of light stabilizer with excellent performance that appeared in the mid-1970s, developed by Sankyo Corporation of Japan. Because hindered amines have many advantages such as no coloring, no pollution to resins, and less dosage, especially the success of light stabilization application technology in polyolefin general resins has greatly promoted the rapid development of HALS. Since >NH or >N-CH ₃ in the hindered amine structure of HALS can be directly transformed into a stable nitroxide radical (>NO·) during the photooxidation process of the material, it becomes an effective quencher for active free radicals, thus making it The light stabilization efficiency is extremely high, generally reaching 3 to 4 times that of traditional light stabilizers. However, high molecular weight (or reactive) hindered amines have many advantages such as resistance to extraction, good thermal stability, low volatility and good compatibility with resins, and have been widely used. Reactive hindered amine (reactive-HALS, r-HALS) was proposed in the 1990s, and its early work mainly focused on the synthesis and characterization of r-HALS, and its polymerization to achieve high molecular weight of HALS , such as light stabilizer PDS. In recent years, the application of r-HALS has become a new hotspot, especially the research on the copolymerization of r-HALS with ethylene and propylene. Through a large number of experiments, the inventors found that r-HALS can be used as a photoactive monomer to directly participate in the ultraviolet light process and play the role of "in situ" photostabilization. The so-called "in situ" means that r-HALS is directly bonded in the curing network of the polymer coating on the one hand, and on the other hand, it means that r-HALS simultaneously produces nitrogen oxides during the process of participating in the photocuring reaction. Free radicals act as photostabilizers. Compared with the traditional hindered amine light stabilization technology, the new light stabilization method of the water-based light curing system recommended by the present invention has obvious innovation.

HALS applied to polymer coating The traditional light stabilization method is to add HALS (small molecule or high molecular weight) as an additive in the light curing formula. The disadvantages of the traditional method are: 1) poor compatibility between HALS and matrix resin; 2) serious losses such as surface migration and volatilization of HALS; 3) poor thermal stability of HALS, which is easily decomposed during processing and loses the function of a stabilizer. 4) Most of the traditional HALS are oil-compatible and difficult to apply to water-based light-curing systems. These disadvantages are especially serious in the application of photocurable polymer coatings. The use of r-HALS can avoid the disadvantages of the above-mentioned traditional methods at the same time, especially in the application of light stabilization of water-based light-curing systems, it can show its superiority.

Contents of the invention

The purpose of the present invention is to provide a reactive hindered amine light stabilizer (r-HALS) as a light stabilizer polymer coating formulation and an in-situ light stabilization method for the polymer coating.

The formula of the UV curing polymer coating system of the present invention comprises the following components:

Component content is wt%

r-HALS 0.5～2.0

Water-based oligomer 70.0～88.0

Thinner 10.0～28.0

Photoinitiator 1.0～3.0

Other additives 0.1～1.0

Where r-HALS is 4-acrylamido-2,2,6,6-tetramethylpiperidine (AATP) or 4-methacrylamido-2,2,6,6-tetramethylpiperidine ( One of MATP); the water-based oligomer is one of polyurethane acrylate water-based resin or epoxy resin acrylate water-based resin; the diluent is water, lower alcohol (such as ethanol) or a mixture of the two; light The initiator is water-soluble, such as 2,2-dimethyl-2-hydroxy-p-ethoxyacetophenone (Darocur2959), or oil-soluble, such as 2,2-dimethyl-2-hydroxybenzene One of ethyl ketone (Darocur1173), 2-hydroxy-2-cyclohexyl acetophenone (Irgacure184), 2,2-dimethoxy-2-phenylacetophenone (Irgacure651); other additives It is a leveling agent, defoamer, etc. The type and amount of addition depends on the specific system formula.

The in-situ photostabilization method of the UV-curable polymer water-based coating of the present invention comprises the following steps:

a. Accurately weigh and mix each component in the aforementioned photocurable polymer coating formula to form a prepolymer, and place it in a dark place overnight for homogenization;

b. Use an applicator to evenly coat the aged prepolymer on the required substrate, with a coating thickness of 5-30 μm;

c. Place the coated substrate in a vacuum oven (or industrial drying oven) at 70-90°C and dry under a vacuum of 10-20mm Hg for 30-60 minutes;

d. Place the coated substrate on a UV curing machine for light curing. The main light source is an ultraviolet lamp with an emission wavelength of 365nm and an effective arc length of 15-20cm. The light intensity at the center of the irradiation is 20 ～25mW/cm ² , curing time 6～15 seconds.

The present invention is based on photopolymerization (homopolymerization, copolymerization and photocuring) kinetic research, with polymer coating (polyurethane acrylate and epoxy resin acrylate water-based resin) as the object, and realized by means of ultraviolet curing technology A new method for in situ light stabilization of polymeric waterborne coating systems. The inventors have proved through a large number of experiments that r-HALS not only directly participates in the photocuring reaction (unsaturated double bonds in the structure), but also >NH or >N- _CH in the r-HALS structure can be oxidized in situ (insitu ) into stable nitroxide free radicals (>NO·), which become an effective quencher for active free radicals and play a role in photostabilization. Since the r-HALS is bonded in the cured network structure of the polymer coating, the volatilization and migration loss of the r-HALS on the surface of the polymer coating is avoided, ensuring the persistence of the light stabilization effect.

The reactive hindered amine of the present invention is a water-soluble light stabilizer, and various components in its formula can be combined freely, that is, several kinds of coating formulas can be obtained in practical application, and the effects are all the same. The intensity and curing time of ultraviolet light in photocuring conditions can be determined according to the specific polymer photocuring system.

In the steps of the in-situ photostabilization method of the UV-curable polymer water-based coating:

a. Accurately weigh each component in the photocurable polymer coating formula and configure the UV-curable reactive prepolymer according to the formula of the above-mentioned polymer water-based coating system, and pay attention to the application of the photoinitiator, that is, the oil-capacity trigger The photoinitiator must be dissolved in the water-based oligomer in advance, and the water-soluble initiator can be directly added to the formula. After adding the photoinitiator, the prepolymer must be mixed evenly and placed in a dark place overnight for homogenization;

b. Use an applicator to evenly coat the aged prepolymer on the required substrate, such as plates and sheets, metal and non-metal materials can be used, such as stainless steel or glass, and the coating thickness is 5 ~30μm;

c. Place the coated substrate in a vacuum oven or an industrial drying oven, and dry it for 30-60 minutes at 70-90°C and a vacuum of 10-20mm Hg;

d. Place the coated substrate on a UV curing machine for light curing. The light source is a 2400W or two 1200W high-pressure mercury lamps, the main emission wavelength is 365nm, and the effective arc length is 20cm. The light intensity at the center is about 20mW/cm ² , the crawler speed is 92cm/min, and the curing time is 6-15 seconds.

Detailed ways

Example 1:

The in-situ photostabilized UV-curable polymer waterborne coating system was prepared according to the following formula:

Component Content is wt%

4-acrylamido-2,2,6,6-tetramethylpiperidine (AATP) 2.0

Polyurethane acrylate water-based resin 86.0

Mixed diluent (ethanol: water = 1:4) 10.0

Photoinitiator 2959 1.5

Leveling agent 0.5

Accurately weigh each component in the above-mentioned photocurable polymer coating formulation, and formulate a UV-curable reactive prepolymer. The prepolymer must be mixed evenly, and placed in a dark place for overnight homogenization; the aged prepolymer is evenly coated on the PVC sheet with an applicator, the coating thickness is 20μm, and the A-528 thickness gauge is used to (produced by Guilin Measuring Tool Factory, with a sensitivity of 10 ^-2 mm) to measure the coating thickness of the sample; the PVC sheet coated with the coating is placed in a vacuum oven, and dried for 40 minutes at 80 ° C under a vacuum of 10 mm Hg; The dried PVC substrate is placed on a UV curing machine for light curing. The light source is a 2400W high-pressure mercury lamp, the main emission wavelength is 365nm, the effective arc length is 20cm, and the light intensity at the center of the irradiation is 20mW/ cm ² or so, the crawler speed is 92cm/min, and the curing time is about 8 seconds. The polymer coating prepared by the above method was subjected to 4000 hours of artificial accelerated photo-oxidation test according to relevant industry standards, and the results have shown that the UV-curable polymer coating has excellent light protection performance.

Example 2:

The in-situ photostabilized UV-curable polymer waterborne coating system was prepared according to the following formula:

Component Content is wt%

4-methacrylamido-2,2,6,6-tetramethylpiperidine (MATP) 1.0

Epoxy resin acrylate water-based resin 70.5

Mixed diluent (ethanol: water = 1:4) 25.0

Photoinduced 2959 2.5

Leveling agent 1.0

Accurately weigh each component of the above formula to prepare a reactive prepolymer cured by ultraviolet light. The prepolymer must be mixed evenly, and placed in a dark place for overnight homogenization; the aged prepolymer is evenly coated on the PVC sheet with an applicator, the coating thickness is 20μm, and the A-528 thickness gauge is used to (produced by Guilin Measuring Tool Factory, with a sensitivity of 10 ^-2 mm) to measure the coating thickness of the sample; place the coated PVC sheet in a vacuum oven at 80°C and dry for 40 minutes under a vacuum of 10 mm Hg; The dried PVC substrate is placed on a UV curing machine for light curing. The light source is a 2400W high-pressure mercury lamp, the main emission wavelength is 365nm, the effective arc length is 20cm, and the light intensity at the center of the irradiation is 20mW/cm ² or so, the crawler speed is 92cm/min, and the curing time is 15 seconds. The polymer coating prepared by the above method was subjected to 4000 hours of artificial accelerated photooxidation test according to relevant industry standards, and the results have shown that the UV curable polymer coating has excellent light protection performance.

Example 3:

The in-situ photostabilized UV-curable polymer waterborne coating system was prepared according to the following formula:

Component Content is wt%

4-acrylamido-2,2,6,6-tetramethylpiperidine (AATP) 2.0

Epoxy resin acrylate water-based resin 86.0

Mixed diluent (ethanol: water = 1:4) 10.0

Photoinitiator 651 1.5

Leveling agent 0.5

Accurately weigh each component in the above-mentioned photocurable polymer coating formula to prepare a reactive prepolymer for ultraviolet light curing. Since the photoinitiator 651 is oil-soluble, it needs to be dissolved in the epoxy resin first, and then the water-based pre-polymerization mixture is configured. The prepolymer must be mixed evenly, and placed in a dark place for overnight homogenization; the aged prepolymer is evenly coated on the epoxy resin substrate with an applicator, the thickness of the coating is 20 μm, and it is measured with A-528 Thickness meter (produced by Guilin Measuring Tool Factory, with a sensitivity of 10 ^-2 mm) to measure the coating thickness of the sample; place the coated epoxy resin substrate in a vacuum oven, and dry it at 80 °C under a vacuum of 10 mmHg for 55 Minutes; place the dried epoxy resin substrate on a UV curing machine for light curing, the light source is a 2400W high-pressure mercury lamp, the main emission wavelength is 365nm, the effective arc length is 20cm, and the center of the irradiation The light intensity is about 20mW/cm ² , the crawler speed is 92cm/min, and the curing time is 6 seconds. The polymer coating prepared by the above method was subjected to 4000 hours of artificial accelerated photooxidation test according to relevant industry standards, and the results have shown that the UV curable polymer coating has excellent light protection performance.

Example 4:

The in-situ photostabilized UV-curable polymer waterborne coating system was prepared according to the following formula:

Component Content is wt%

4-methacrylamido-2,2,6,6-tetramethylpiperidine (MATP) 1.0

Polyurethane acrylate water-based resin 75.6

Mixed diluent (ethanol: water = 1:2) 20.0

Photoinduced 2.5

Leveling agent 1.0

Accurately weigh each component in the above-mentioned photocurable polymer coating formula to prepare a reactive prepolymer for ultraviolet light curing. Since the photoinitiator 1173 is oil-soluble, it needs to be dissolved in the polyurethane resin first, and then the water-based pre-polymerization mixture is configured. The prepolymer must be mixed evenly, and placed in a dark place for overnight homogenization; the aged prepolymer is evenly coated on the stainless steel with an applicator, the coating thickness is 20 μm, and the A-528 thickness gauge (Guilin Measuring tool factory, sensitivity is 10 ^-2 mm) to measure the coating thickness of the sample; place the coated stainless steel substrate in a vacuum oven, and dry it for 30 minutes at 80°C under a vacuum of 10mm Hg; The finished stainless steel substrate is placed on a UV curing machine for photocuring. The light source is a 2400W high-pressure mercury lamp, the main emission wavelength is 365nm, the effective arc length is 20cm, and the light intensity at the center of the irradiation is 20mW/cm ² Around, the crawler speed is 92cm/min, and the curing time is 10 seconds. The polymer coating prepared by the above method was subjected to 4000 hours of artificial accelerated photooxidation test according to relevant industry standards, and the results have shown that the UV curable polymer coating has excellent light protection performance.

The above are several examples of various combinations in the formulation of the present invention. Other combinations can achieve the same effect, and the formulation and curing method of the present invention are not limited thereto.

The present invention adopts a novel series of water-soluble reactive hindered amine light stabilizers (r-HALS) as the light stabilizer, and utilizes the optical differential thermal analysis method (DPC) to study its photopolymerization (homopolymerization, copolymerization and photocuring) kinetics , to ensure that it has a reactive function and a quenching function. The polymer water-based coating system realizes the in situ chemical transformation from hindered amine (>NH,>N—CH ₃ ) to stable nitroxide free radical (>NO·) during the UV curing molding process. Through indoor artificial accelerated ultraviolet aging experiments on polymer coatings, the characterization parameters during the photooxidation process, such as yellowness index (Yellowness Index, YI), carbonyl index (Carboxyl Value, CV), gloss, haze, etc. Real-time monitoring confirmed that the water-soluble r-HALS has an excellent long-lasting photoprotective effect on UV-curable polymer waterborne coating systems.

Claims (2)

1. the prescription of a UV curable polymer coating system, its component and content are as follows:

Component content is wt%

r-HALS 0.5～2.0

Water-based oligopolymer 70.0～88.0

Thinner 10.0～28.0

Light trigger 1.0～3.0

Other auxiliary agents 0.1～1.0

Wherein r-HALS is a 4-acrylamido-2,2,6,6-tetramethyl piperidine or 4-methacryloyl amido-2,2,6, a kind of in the 6-tetramethyl piperidine; The water-based oligopolymer is a kind of in polyurethane acrylic ester water resin or the Resins, epoxy acrylic ester aquosity resin; Thinner is water, lower alcohol or the proportioning mixture of the two; Light trigger is 2,2-dimethyl-2-hydroxyl-paraethoxyacetophenone, 2,2-dimethyl-2-hydroxy acetophenone, 2-hydroxyl-2-cyclohexyl methyl phenyl ketone, 2, a kind of in 2-dimethoxy-2-phenyl methyl phenyl ketone; Other auxiliary agents are flow agent or defoamer.

2. the photostabilization in-situ method of a UV curable polymer aqueous coating system may further comprise the steps:

A. each component in claim 1 prescription is accurately weighed and mix the formation prepolymer, be placed on the dark place homogenizing of spending the night;

B. the prepolymer that ageing is good is uniformly coated on the needed base material coat-thickness 5～30 μ m with applicator;

The base material that c. will apply coating is placed on vacuum drying oven or industrially drying case, and at 70～90 ℃, drying is 30～60 minutes under the vacuum tightness of 10～20mm Hg;

D. the base material that drying is handled carries out photocuring, and light source is that main emission wavelength is 365nm, and real arcs length is the UV-lamp of 15～20cm, and the light intensity of irradiation central position is 20～25mW/cm ², 6～15 seconds of set time.