WO1999018134A1

WO1999018134A1 - Uv cured coatings containing tertiary amino alcohols

Info

Publication number: WO1999018134A1
Application number: PCT/US1998/019647
Authority: WO
Inventors: Marina D. Hoffman; Nancy F. Farrington
Original assignee: Angus Chemical Company
Priority date: 1997-10-08
Filing date: 1998-09-21
Publication date: 1999-04-15
Also published as: AU9401798A

Abstract

A radiation-curable composition includes photo-polymerizable compounds, such as acrylated epoxies, urethanes and polyesters, and photoinitiators, such as benzophenone with tertiary amino alcohols, such as 2-dimethylamino-1-butanol, as co-initiators. The co-initiator provides improved curing speed, depth of cure or both. Tertiary amino alcohols of the invention are defined by formula (I), where R1 and R2 are methyl, R3 is hydrogen, or C1-C5 alkyl, R4 is C1-C5 alkyl or -CH2OH, and R5 is C1-C5 alkyl substituted with at least one hydroxyl group.

Description

UV CURED COATINGS CONTAINING TERTIARY AMINO ALCOHOLS

BACKGROUND OF THE INVENTION

This invention relates generally to the radiation curing of coatings, inks and overprint varnishes, particularly by ultraviolet (UV) radiation. More particularly, it relates to the improvement of the photoinitiators and co-initiators used to advance the polymerization of such coatings. The invention improves both the extent of polymerization and the speed with which it occurs.

Radiation facilitates the cross-linking of curable compositions by exposing them to ultraviolet (UV) or electron beam (EB) energy. Radiation-curable coatings and inks have gained widespread acceptance because of improved performance. They also have advantages over competing conventional technologies with regard to energy cost and environmental impact. Conventional coatings and inks combine resins with volatile solvents which are removed by evaporation. This consumes energy and releases undesirable volatile organic compounds. In contrast, coatings and inks which are cured by UV or EB radiation eliminate the need for volatile solvents since reactive monomers are used instead. These do not have to be evaporated because they polymerize when exposed to radiation and become part of the cured film. Consequently, the energy consumption is reduced, and the volatile organic emissions are reduced or eliminated. Of the potential sources of radiation, UV and EB are the most commonly used. EB curing requires high voltages to produce electrons which are capable of polymerizing without needing photoinitiators. UV curing requires low energy, typically supplied by mercury vapor lamps, but requires photoinitiators to initiate polymerization. UV curing is often favored over EB curing because of lower installation costs.

Radiation curing involves rapid polymerization of reactive unsaturated compounds. The principal components of UV cured coatings, inks and overprint varnishes are typically acrylated oligomers, multifunctional acrylates, and monofunctional monomers. Photoinitiators are typically alpha cleavage (type I) initiators such as benzoin ethers, benzil ketals, or acetophenones, or hydrogen abstraction (type II) initiators such as benzophenone, thioxanthone, and derivatives thereof. Co-initiators (also called accelerators or synergists) are often used, particularly tertiary amines, and tertiary amino alcohols.

Many patents and literature references could be cited to show the state of the art in the field of radiation curing. Representative of such disclosures with respect to the present invention are the following patents and publications.

U.S. Patent No. 3,772,062 discloses and claims coating compositions comprising various acrylates cured by ultraviolet radiation and using as photoinitiators benzophenone and related ketones with methyl diethanolamine (MDEA).

U.S. Patent No. 3,966,574 discloses the use of certain food grade dyes as photoinitiators and an alkanolamine, particularly MDEA, as an "activator."

U.S. Patent No. 4,054,719 discloses a new photosensitizer, a phenacyl acetate, and a tertiary aliphatic amine used to cure, by ultraviolet radiation, a photopolymerizable composition.

U.S. Patent No. 4,054,721 also discloses a new photosensitizer which is complimented by a tertiary aliphatic amine, exemplified by MDEA.

U.S. Patent No. 4,395,539 discloses a glycol containing a tertiary amine group, which is a component of an aromatic polyester. The polyester is combined with a photopolymerizable compound and a photoinitiator, such as an aromatic ketone.

EP Patent No. 0434 098 A2 discloses a photocurable composition which includes a multifunctional amine as defined therein and an aromatic ketone photoinitiator.

CA 1,224,182 discloses the use of a photoinitiator including a ketone and a hindered amine. Benzophenone and related compounds are listed as suitable ketones, and MDEA and related alkanol amines are listed as suitable hindered amines. German Patent No. DE 4222576 discloses a UV hardened ink formulation which includes at least two amines as accelerators, at least one of which is a tertiary amine.

The present inventor has found that certain tertiary amino alcohols provide higher curing speeds, increased depth of curing, or both, as compared with the presently preferred commercial amine co-initiator, methyl diethanol amine (MDEA), as will be shown in the detailed description which follows. Improvements in the depth of cure (DOC) can be beneficial in pigmented or thick coatings or inks. Improved chemical resistance, which is a measure of surface cure, permits increased productivity in coating or printing processes by reducing the exposure time to obtain a cured film. It also allows the formulator to reduce the most expensive component, which is the initiator package.

SUMMARY OF THE INVENTION

In one aspect, the invention is a radiation-curable composition which includes a photopolymerizable formulation comprising oligomers and multifunctional and monofunctional monomers, at least one photoinitiator, and a tertiary amino alcohol having formula

where Ri and R₂ are methyl, R₃ is hydrogen or C_\ - C₅ alkyl , R is - C₅ alkyl or - CH₂OH, and R₅ is C1-C₅ alkyl substituted with at least one hydroxyl group.

In another aspect, the invention is an improved method of radiation curing compositions in the presence of a photoinitiator and a tertiary amine where the tertiary amine is a tertiary amino alcohol having the formula

where Ri and R₂ are methyl, R₃ is hydrogen or C_\ - C₅ alkyl , R is C_\ - C₅ alkyl or -

CH₂OH, and R₅ is Cι-C₅ alkyl substituted with at least one hydroxyl group.

The tertiary amino alcohols of the invention may be used with both type I and type II photoinitiators. In a preferred embodiment, type II photoinitiators are shown to provide increased depth of cure, increased surface cure, or both. Such results permit increased productivity, chemical resistance, and reduced cost in commercial applications of the invention. In one embodiment, the tertiary amino alcohol may be -pre-reacted with a polymer so that it becomes part of the cured film.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Photopolymerizable Compounds Compounds which are useful in connection with the present invention, in general, are ethylenically unsaturated and polymerizable by radiation. In typical commercial practice, such compounds are cured by ultraviolet radiation having wavelengths in the range of about 200-450 nm. As previously discussed, UV cured coatings are typically comprised of acrylated oligomers, multifunctional acrylates, and monofunctional acrylates, although other types of polymerizable compounds may be used. Typically, acrylated oligomers are blended with multifunctional acrylates and monofunctional acrylates to form a UV curable composition. The oligomers and monomers are selected to provide the desired film properties. The most commonly used types of oligomers are acrylated epoxies, acrylated aliphatic and aromatic urethanes, acrylics, and acrylated polyesters. Multifunctional monomers are typically of two types, acrylates and methacrylates. While acrylates cure readily by UV or EB radiation, methacrylates usually require EB energy to initiate polymerization. Examples of multifunctional acrylate monomers include tripropylene glycol diacrylate (TRPGDA), trimethylol propane triacrylate (TMPTA), and the alkoxylated forms of TMPTA, such as TMPTAEO and TMPTAPO. These materials dilute the high viscosity acrylated oligomers and form about 20-60% of the coating formulation.

Trifunctional monomers, such as TMPTA, increase the crosslink density, hardness, and solvent resistance of the coating formulation, while difunctional monomers such as TRPGDA, reduce viscosity, increase flexibility and impact resistance, and improve adhesion. These polymerizable materials are selected and blended to provide cured coatings having the desired balance of properties.

Monofunctional monomers are often chosen as diluents in coatings, inks and overprint varnishes to reduce viscosity, increase flexibility, and enhance adhesion by reducing coating shrinkage during cure. Examples of such monomers are vinyl acetate, vinyl pyrrolidone, phenoxyethylacrylate, and isobornyl acrylate. In addition to the polymerizable compounds just described, the curable formulation of the invention may also include additional polymers and monomers, pigments, fillers, initiators, amines and adjuvants.

More specific examples of suitable radiation-curable compounds useful in the invention are acrylated bisphenol A, diglycidyl ether and derivatives, acrylated epoxy novolacs, acrylated aromatic (TDI- and MDI-based) urethanes, acrylated aliphatic (IPDI-, HMDI-, and HDI-based) urethanes, which can be combined with monomers such as tripropylene glycol diacrylate (TRPGDA), trimethylolpropane triacrylate (TMPTA), and alkoxylated forms of TMPTA, such as TMPTAEO and TMPTAPO.

Photoinitiators And Accelerators Photoinitiators are essential in UV curing. When irradiated, they provide free radicals which initiate polymerization. The mechanisms by which this occurs are described by Oster, G., and Yang, N.L., in Chem. Rev., 68, No. 2, p. 125 (1968). One mechanism involves a photochemically induced homolytic fragmentation (type I) of the excited photoinitiator into free radicals. Examples of materials which respond to the UV radiation in this manner are benzoin ethers, benzyl ketals, and acetophenones and derivatives. Specific commercial examples are isobutyl benzoin ether and hydroxycyclohexylphenyl ketone. Another mechanism involves electron excitation of an initiator from a ground state singlet to an excited triplet followed by electron transfer to a hydrogen atom donor to generate free radicals. Examples of hydrogen abstraction (type II) initiators are benzophenone, thioxanthone, and their related compounds or derivatives, with amines.

Bimolecular hydrogen abstraction is a typical reaction of aromatic ketones and is limited to the type II photoinitiators. Triplet state excited aromatic ketones do not undergo alpha cleavage reactions, although the first type of photoinitiator does. They can. however, extract a hydrogen atom from a suitable hydrogen donor. Three factors are considered to govern the hydrogen abstraction; the triplet state configuration of the ketone. the triplet state energy of the ketone, and the bond strength of the carbon- hydrogen bond to be broken. In many instances, an efficient co-initiator, such as an amine. is necessary. While amines are known to react via hydrogen abstraction, under certain conditions, they may also initiate polymerization via electron transfer.

Electron transfer processes are common in photochemistry, and a large number of bimolecular photoinitiating systems react via a photoinduced electron transfer process. One of these systems is the aromatic ketone-amine combination. Electron transfer to the excited triplet state produces a radical ion pair, which undergoes a proton transfer from the carbon alpha to nitrogen to the ketyl radical anion. The acidity of the α-protons in amines is enhanced after one electron oxidation of the nitrogen, so that very fast proton transfer efficiently competes with back electron transfer. Type II photoinitiators in common use include benzophenone, 2,4,6- trimethylbenzophenone, 3,3-dimethyl-4-methylbenzophenone, and thioxanthone and derivatives (e.g., 2,4-dimethylthioxanthone and 4-isopropylthioxanthone).

Benzophenone has been the focus of several studies, for example, as discussed in J. Polvm. Sci., A-l, 10:3173 (1972) by M. R. Sandner, C. L. Osborn, and D. J. Trecker.

When exposed to UV light, benzophenone is excited to its singlet state, followed by intersystem crossing to the triplet state. Since alpha cleavage is not likely because the energy is insufficient, free radical species are generated in the presence of a tertiary amine via a charge transfer complex (exiplex). Amines are good hydrogen donors for benzophenone because they have a strong affinity for the long lived benzophenone triplet state. The resulting radical is responsible for the initiation reaction, the benzhydril radical will likely dimerize to a benzpinacol compound.

Initiators are inactivated by oxygen because the aminoalkyl radical can react with oxygen to form a peroxide that can generate another amino radical via hydrogen abstraction. Thus, compositions containing benzophenone-amine initiator systems are usually less sensitive to oxygen inhibition. This oxygen consumption effect makes photopolymerization of a thin film very efficient. The most commonly used amine is n- methyldiethanol amine (MDEA), although other aliphatic and aromatic amines have been used.

Tertiary amines can fill two roles in UV curing by a free radical route. They can scavenge peroxy intermediates formed by the reaction of oxygen with radical sites or, as the aminoalkyl/radicals, they can react with oxygen, thus reducing the retarding effect of oxygen on the cure rate. Possible mechanisms for oxygen scavenging reactions between amines, excited amines, and amine radicals with oxygen have been discussed by many authors, including Dietliker, K. K., "Chemistry And Technology Of UV And EB Formulations For Coatings, Inks, And Paints," 3rd ed., SITA Technology, Ltd., London, UK (1991), pp. 83-86.

The present invention employs tertiary amino alcohols as co-initiators, particularly for type II photoinitiators, although they may be used also with type I photoinitiators. The polymerization is advanced for coatings, inks and overprint varnishes using photoinitiators and tertiary amino alcohols of the invention compared to the previous coatings, inks and overprint varnishes. In particular, the depth of cure, the surface cure, or both are improved with type II photoinitiators, as will be seen in the

Examples below.

The tertiary amino alcohols of the invention are particularly useful with thick or pigmented coatings or inks since they can increase the depth of cure, thus reducing the need to use the more expensive alpha cleavage (type I) photoinitiators, which have been considered to provide superior through cure. The tertiary amino alcohols, in combination with the photoinitiators, also can improve the surface cure. It has been claimed by other workers in the field that hydrogen abstraction initiators (type II) in combination with amines gave improved surface cure, but poorer depth of cure. Amines in general have been used as co-initiators with the type II initiators (e.g., aromatic ketones) to improve surface cure by reducing oxygen inhibition of the polymerization at the surface of the film, as discussed above. Improved surface cure is important because it allows the formulator to decrease the initiator package, which is the most expensive component in a formulation, and still achieve a comparable cure. It also allows the end user to increase line speeds, which would increase productivity and/or reduce costs. The preferred commercial amine co-initiator is N-methyldiethanol amine (MDEA). The Examples below will compare MDEA with tertiary amino alcohols of the present invention. The co-initiator tertiary amino alcohols of the present invention, more specifically, are those defined by the formula

R₅ N C R₃

/ I

^R2 4 where Ri and R₂ are methyl, R₃ is hydrogen or Ci - C₅ alkyl, R is C_t - C₅ alkyl or - CH₂OH, and R₅ is C₁-C₅ alkyl substituted with at least one hydroxyl group.

Examples of such tertiary amino alcohols include, but are not limited to, 2- dimethylamino-1-butanol (DMAB), 2-dimethylamino-2-ethyl-l,3-propanediol

(DMAEPD), 2-dimethylamino-2-methyl-l-propanol (DMAMP), and 2-dimethylamino-2- methyl-l,3-propanediol (DMAMPD).

The amount of the tertiary amino alcohol used in a UV curable formulation will be in the range of about 1-15 wt.%. Typically, the tertiary amino alcohols will be mixed with the reactive oligomers and monomers, along with the photoinitiator, before curing. Another method of using the tertiary amino alcohols is to pre-react them with a polymer so that they become part of the polymer backbone and, in turn, of the cured coating. The tertiary amino alcohol would be pre-reacted with a radiation curable polymer, then mixed with other reactive compounds, such as acrylates, and then radiation cured.

Testing Procedures

In the tests which are described in the Examples below, photopolymerizable mixtures are formulated with benzophenone (BP) as the photoinitiator and with MDEA and the tertiary amino alcohols of the invention listed above as accelerators. The compositions reported in the Tables refer to the ratio of the acrylated oligomer to the acrylate monomer, but the actual formulas are as follows.

Ebecryl® 3700 (acrylated epoxy) 50g Monomer 50g

Benzophenone 4g

Tertiary amine 2g

Ebecryl® 4827 (acrylated aromatic urethane)80g Monomer 20g

Benzophenone 4g

Tertiary amine 2g

Ebecryl® 8402 (acrylated aliphatic urethane)90g

Monomer 10g

Benzophenone 4g

Tertiary amine 2g

Ebecryl® 1701 (acrylic oligomer) 70g

Monomer 30g

Benzophenone 4g

Tertiary amine 2g

Ebecryl® 40 (acrylated polyester) 100g

Benzophenone 4g

Tertiary amine 2g

The Ebecryl® oligomers are products of UCB Radcure. The depth of cure results were determined in the following manner. After preparing the formulations, they were drawn down on a depth of cure comparator having a channel graduated from 1-125 mils. The film was then cured by passing the coated substrate through a Fusion System LC-6 UV processor equipped with one F300S6, H bulb. 156 cm module. The processor speed was 20 ft./min., which irradiated the coating with 945 mj/cπT. The uncured (liquid) portion of the coating was blotted off with a paper towel, and the polymerized film was measured at its thickest section with a

Mitutoyo digimatic gauge. The thickness of the polymer films were reported as depth of cure (DOC) in thousandths of an inch. This test is one way of determining the efficiency of initiator systems in thick or pigmented coatings.

The surface cure was measured by determining the chemical resistance using the double rub MEK (methyl ethyl ketone) method. The films were drawn down on Leneta N2A charts using a #8 wire rod to give a dry film thickness of 0.3-0.4 mils. The films were irradiated in the UV processor described above using belt speeds of 16 - 100 ft./min. The belt speed used was dependent on the oligomer system used. The cured films were double rubbed with the MEK soaked swabs until the swab broke through the film. The number of rubs required was recorded as an indication of the completeness of the cure. It was assumed that full cure was achieved when 200 double rubs with MEK did not break through the film. Then, the belt speed was increased gradually until 200 double MEK rubs were no longer achieved, and differences between the tertiary amine co-initiators were evident. The data reported reflects the speeds at which differences were evident, but as close as possible to full cure.

Example 1 The acrylated epoxy oligomer (Ebecryl® 3700) was formulated with each of four multifunctional monomers, tripropylene glycol diacrylate (TRPGDA), trimethylolpropane triacrylate (TMPTA), ethoxylated trimethylolpropane triacrylate (TMPTAEO), and propoxylated trimethylolpropane triacrylate (TMPTAPO). Benzophenone (BP) was added to each oligomer/monomer mixture as a photoinitiator and one of the tertiary amino alcohols as a co-initiator. The formulations were applied to the depth of cure comparator and then cured at a belt speed of 20 ft./min., and the depth of cure measured as described above. The averaged results are reported in Table I. Each of four tertiary amino alcohols of the invention were compared with the results obtained with N-methyl diethanolamine (MDEA), which is a preferred commercial co-initiator, used as a control.

As Table I shows, all the coatings made with TRPGDA performed better (i.e., the depth of cure was greater) with the tertiary amino alcohols of the invention than with MDEA. Coatings made with TMPTA showed that the depth of cure with DMAB and DMAMPD was the same as with MDEA, while DMAEPD and DMAMP gave an increase in the depth of cure. With coatings made with TMPTAEO and TMPTAPO, DMAB, DMAEPD, and DMAMP produced a greater depth of cure than MDEA, while DMAMPD was equivalent to MDEA.

Example 2

The experiment of Example 1 was repeated using a different oligomer, Ebecryl® 8402, an acrylated aliphatic urethane. The results are reported in Table II. As Table II shows, for coatings containing TRPGDA and TMPTA, two of the tertiary amino alcohols (DMAB and DMAMP) provided greater depth of cure than coatings containing MDEA. The coating containing DMAEPD was equivalent to that containing MDEA, while DMAMPD was slightly worse. For coatings including the monomer TMPTAEO, only those containing DMAB gave a greater depth of cure, while with the coatings made with the monomer TMPTAPO, all of the tertiary amino alcohols of the invention showed greater depth of cure than those made with MDEA.

Example 3

The experiment of Example 1 was repeated again using another oligomer Ebecryl® 4827, an acrylated aromatic urethane. The results are reported in Table III.

As Table III shows, coatings containing the multifunctional monomers TRPGDA, TMPTA, and TMPTAEO, all had a greater depth of cure when each of the tertiary amino alcohols DMAB, DMAEPD, DMAMP, and DMAMPD were used as co-initiators with benzophenone (BP). When the monomer TMPTAPO was used, however, only the coating containing DMAB provided a greater depth of cure. DMAEPD was equivalent to MDEA, while DMAMP and DMAMPD provided a lower depth of cure. Example 4

The experiment of Example 1 was repeated using still another oligomer.

Ebecryl® 1701, an acrylic oligomer. The results are reported in Table IV.

As Table IV shows, when the oligomer was formulated with the monomer TRPGDA, the tertiary amino alcohols DMAB and DMAEPD gave a greater depth of cure than did MDEA, but DMAMP and DMAMPD provided a lower depth of cure. For coatings containing the monomers TMPTA, TMPTAEO, and TMPTAPO, however, all the tertiary amino alcohols of the invention provided a greater depth of cure than MDEA, with the exception of the combination of TMPTAEO and DMAMPD, which was equivalent to TMPTAEO and MDEA.

Example 5

The acrylated polyester. Ebecryl® 40, was formulated without monomers, but with the same five benzophenone/tertiary amino alcohol initiator systems used in Examples 1-4.

As Table V shows, DMAB and DMAMP amines provided a greater depth of cure than the control, MDEA. DMAEPD provided the same depth of cure and DMAMPD somewhat poorer depth of cure.

Example 6

An acrylated epoxy oligomer, Ebecryl® 3700, was formulated with each of the four acrylated monomers and each of the five tertiary amino alcohols used in the previous experiments. The films were cured at various belt speeds and then tested using the double rub (with MEK) method previously described. The speed of the UV processor was adjusted to provide a full cure, i.e., 200 double MEK rubs, and then the belt speed was increased by 10 ft./min. to determine differences between tertiary amines. The results are reported in Table VI.

In the formulation containing TRPGDA, the initiator packages BP/DMAB and

BP/DMAMPD showed improved surface cure when compared to BP MDEA. In the other mixtures containing TMPTA, TMPTAEO, and TMPTAPO, each of the four tertiary amino alcohols demonstrated improved surface cure compared to the BP/MDEA control. Example 7

An acrylated aliphatic urethane oligomer, Ebecryl® 8402, was formulated with each of the four monomers and each of the five tertiary amino alcohols as in Example 6. The coated films were cured and tested as in Example 6. In this test, the slowest speed available on the UV processor was used, since the oligomer is inherently slow curing. A full cure (i.e., 200 double MEK rubs) was not achieved, but some differences were apparent. The results are reported in Table VII.

In the formulation containing TRPGDA, all the tertiary amino alcohols provided slightly inferior surface cure than the control (MDEA). Improvements were observed, however, in the other three monomer formulations. In the TMPTA containing mixture, the BP/DMAB and BP/DMAMPD initiator packages showed improved surface cure when compared to BP MDEA. The other two tertiary amino alcohols resulted in inferior surface curing compared to the control. In the system containing TMPTAEO, all of the tertiary amino alcohols improved the surface cure. With TMPTAPO, the BP/DMAB and BP/DMAEPD improved the surface cure while the BP/DMAMP and BP/DMAMPD did not. Example 8

An acrylated aromatic urethane oligomer, Ebecryl® 4827, was formulated as in Example 6 and tested in the same manner. The results are reported in Table VIII. The speed of the UV processor was adjusted in a similar manner as in Example VI. except that for formulations containing TMPTAPO, the lowest speed was used as in Example 7.

In the formulation containing TRPGDA, all the BP/tertiary amino alcohol packages improved the surface cure of the films, except for BP/DMAMP, when compared to the BP/MDEA control. In the formulations containing TMPTA and TMPTAPO, all the BP/tertiary amino alcohol packages of the present invention improved the surface cure. For the TMPTAEO formulations, all of the BP/tertiary amino alcohol packages improved surface cure, except for the BP/DMAB combination.

Example 9

An acrylic oligomer, Ebecryl® 1701, was formulated and tested as in Example 6. The speed of the UV processor was adjusted as in Example 6, except for the formulation containing TRPGDA for which 200 MEK double rubs were never achieved. It was cured at the slowest possible speed, but differences in surface cure were found. The results are reported in Table IX.

In the system containing TRPGDA, all the BP/tertiary amino alcohol packages showed improved surface cure compared to the BP/MDEA control. In the TMPTA formulation, only BP/DMAB and BP/DMAEPD improved surface cure, while the

BP/DMAMP and BP/DMAMPD were inferior to BP/MDEA. For the TMPTAEO and

TMPTAPO formulations, all of the BP/tertiary amino alcohol combinations gave poorer surface cure compared to the control.

Example 10

An acrylated polyester oligomer, Ebecryl® 40, was formulated and tested as in Example 6, except that no multifunctional monomers were used. The results are reported in Table X.

All of the BP/tertiary amino alcohol initiator packages provided improved surface cure compared to the BP/MDEA control.

TABLE I

Depth of Cure (inches x 1000) Ebecryl® 370050/50* Acrylated Epoxy

Ratio of oligomer/monomer.

Actual thickness/percentage of improvement over MDEA. TABLE II

Depth of Cure (inches x 1000) Ebecryl® 8402 90/10* Acrylated Aliphatic Urethane

Ratio of oligomer/monomer.

Actual thickness/percentage of improvement over MDEA.

TABLE III Depth of Cure (inches x 1000) Ebecryl® 4827 80/20* Acrylated Aromatic Urethane

Ratio of oligomer/monomer.

Actual thickness/percentage of improvement over MDEA. TABLE IV

Depth of Cure (inches x 1000) Ebecryl® 1701 70/30* Acrylated Oligomer

Ratio of oligomer/monomer.

Actual thickness/percentage of improvement over MDEA.

TABLE V

Depth of Cure (inches x 1000) Ebecryl® 40

Acrylated Polyester

* Actual thickness/percentage of improvement over MDEA. TABLE VI

Ratio of oligomer/monomer.

Actual chemical resistance/percentage of improvement over MDEA.

TABLE VII

* Ratio of oligomer/monomer.

** Actual chemical resistance/percentage of improvement over MDEA. TABLE VIII

Ratio of oligomer/monomer.

Actual chemical resistance/percentage of improvement over MDEA

TABLE IX

Ratio of oligomer/monomer.

Actual chemical resistance/percentage of improvement over MDEA.

N/A = Not Available. TABLE X

Actual thickness/percentage of improvement over MDEA.

It may be concluded from the results shown in the preceding Tables that DMAB

(2-dimethylamino 1-butanol) provides improved depth of cure compared with the other tertiary amino alcohols, including the preferred commercial MDEA (n-methyldiethanol amine) which has been used as a comparative control. DMAEPD (2-dimethylamino-2- ethyl-1,3 propanediol) and DMAMP (2-dimethylamino-2-methyl-l-propanol) also showed significantly improved depth of cure compared to MDEA, especially in the acrylated epoxy, acrylated aromatic urethane and acrylic oligomer systems. These results indicate that these tertiary amino alcohols would be very useful for thick or pigmented coatings or inks, since the need for more expensive alpha cleavage (type I) initiators would be reduced or eliminated, since such initiators are used to obtain through cure. Another conclusion that may be drawn from the above Examples is that DMAB,

MAEPD and DMAMPD (2-dimethylamino-2-rnethyl-l,3 propanediol) are able to provide significant improvements in surface cure compared to the MDEA control. Improved surface cure allows the formulator flexibility to decrease the initiator package while retaining adequate cure. It also allows the user to increase line speeds, providing increases in productivity and/or reducing costs.

It can also be concluded that DMAB and DMAEPD can be incorporated in a formulation when good depth of cure and surface cure are both sought. Present initiators are not able to provide both benefits.

Claims

WHAT IS CLAIMED IS:

1. In a method of radiation curing coating compositions in the presence of a photoinitiator and a tertiary amine, the improvement comprising using as the tertiary amine a tertiary amino alcohol having the formula

R₅

where Ri and R₂ are methyl,

R is hydrogen or C₁-C₅ alkyl, R is C,-C₅ alkyl or -CH₂OH, and R₅ is C1-C5 alkyl substituted with at least one hydroxyl group.

2. A method of Claim 1, wherein said tertiary amino alcohol is 2-dimethylamino-l- butanol (DMAB).

3. A method of Claim 1, wherein said tertiary amino alcohol is 2-dimethylamino-2- ethyl-l,3-propanediol (DMAEPD).

4. A method of Claim 1, wherein said tertiary amino alcohol is 2-dimethylamino-2- methyl-1-propanol (DMAMP).

5. A method of Claim 1, wherein said tertiary amino alcohol is 2-dimethylamino-2- methyl- 1,3 -propanediol (DMAMPD).

6. A method of Claim 1, wherein said photoinitiator is a hydrogen abstraction (type II) photoinitiator.

7. A method of Claim 6, wherein said photoinitiator is selected from the group consisting of benzophenone, thioxanthone and derivatives thereof.

8. A method of Claim 1, wherein said composition is cured by ultraviolet radiation.

9. A method of Claim 1, wherein said composition comprises at least one oligomer selected from the group consisting of acrylated epoxy, acrylated aliphatic urethane, acrylated aromatic urethane, acrylated polyester, and acrylic oligomers.

10. A method of Claim 9 wherein said composition further comprises a multifunctional monomer.

11. A method of Claim 10. wherein said multifunctional monomer is selected from the group consisting of tripropylene glycol diacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate. and propoxylated trimethylolpropane triacrylate.

12. A method of Claim 1, wherein said tertiary amino alcohol comprises about 1-15 wt.% of said composition.

13. A method of improving surface cure in the radiation curing of coating compositions comprising photoinitiators and tertiary amines, by using as said tertiary amine a tertiary amino alcohol having the formula

R₅

N- R

R^ 4 where Ri and R are methyl, R₃ is hydrogen or -C₅ alkyl, R₄ is C1-C₅ alkyl or -CH₂OH, and

R₅ is C1-C₅ alkyl substituted with at least one hydroxyl group.

14. A method of Claim 13, wherein said tertiary amino alcohol is 2-dimethylamino-l- butanol (DMAB).

15. A method of Claim 13, wherein said tertiary amino alcohol is 2-dimethylamino-2- ethyl-l,3-propanediol (DMAEPD).

16. A method of Claim 13, wherein said tertiary amino alcohol is 2-dimethylamino-2- methyl- 1 -propanol (DMAMP) .

17. A method of Claim 13, wherein said tertiary amino alcohol is 2-dimethylamino-2- methyl-l,3-propanediol (DMAMPD).

18. A method of Claim 13, wherein said photoinitiator is a hydrogen abstraction (type II) photoinitiator.

19. A method of Claim 13, wherein said composition is cured by ultraviolet radiation.

20. A method of Claim 13, wherein said composition comprises at least one oligomer selected from the group consisting of acrylated epoxy, acrylated aliphatic urethane, acrylated aromatic urethane, acrylated polyester, and acrylic oligomers.

21. A method of Claim 13, wherein said composition further comprises a multifunctional monomer.

22. A method of Claim 21, wherein said multifunctional monomer is selected from the group consisting of tripropylene glycol diacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, and propoxylated trimethylolpropane triacrylate.

23. A method of Claim 13, wherein said tertiary amino alcohol comprises about 1-15 wt. of said coating composition.

24. A method of improving depth of cure in the radiation curing of coating compositions comprising photoinitiators and tertiary amines, by using as said tertiary amine a tertiary amino alcohol having the formula

R₅

V N C I R₃

/ I

^R2 R, where R_\ and R₂ are methyl, R₃ is hydrogen or C₁-C₅ alkyl, R₄ is C ₁ -C₅ alkyl or -CH₂OH, and

R is C₁-C₅ alkyl substituted with at least one hydroxyl group

25. A method of Claim 24, wherein said tertiary amino alcohol is 2-dimethylamino-l- butanol (DMAB).

26. A method of Claim 24, wherein said tertiary amino alcohol is 2-dimethylamino-2- ethyl- 1.3 -propanediol (DMAEPD).

27. A method of Claim 24, wherein said tertiary amino alcohol is 2-dimefhylamino-2- methyl-1-propanol (DMAMP).

28. A method of Claim 24, wherein said tertiary amino alcohol is 2-dimethylamino-2- methyl-l,3-propanediol (DMAMPD).

29. A method of Claim 24, wherein said photoinitiator is a hydrogen abstraction (type II) photoinitiator.

30. A method of Claim 24, wherein said composition is cured by ultraviolet radiation.

31. A method of Claim 24, wherein said composition comprises at least one oligomer selected from the group consisting of acrylated epoxy, acrylated aliphatic urethane, acrylated aromatic urethane, acrylated polyester, and acrylic oligomers.

32. A method of Claim 24, wherein said composition further comprises a multifunctional monomer.

33. A method of Claim 32, wherein said multifunctional monomer is selected from the group consisting of tripropylene glycol diacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, and propoxylated trimethylolpropane triacrylate.

34. A method of Claim 24, wherein said tertiary amino alcohol comprises about 1-15 wt.% of said coating composition.

35. A radiation-curable composition comprising:

(a) at least one photopolymerizable compound selected from the group consisting of oligomers, multifunctional monomers, and monofunctional monomers; (b) at least one photoinitiator; and

(c) a tertiary amino alcohol having the formula

R₅

N- C- R,

/

R^

R4 where Ri and R₂ are methyl, R is hydrogen or -C5 alkyl, R₄ is C ₁ -C₅ alkyl or -CH₂OH, and

R₅ is C₁-C₅ alkyl substituted with at least one hydroxyl group.

36. A composition of Claim 35 wherein said tertiary amino alcohol is 2- dimethylamino-1-butanol (DMAB).

37. A composition of Claim 35, wherein said tertiary amino alcohol is 2- dimethylamino-2-ethyl-l,3-propanediol (DMAEPD).

38. A composition of Claim 35, wherein said tertiary amino alcohol is 2- dimethylamino-2-methyl- 1 -propanol (DMAMP) .

39. A composition of Claim 35, wherein said tertiary amino alcohol is 2- dimethylamino-2-methyl- 1 ,3-propanediol (DMAMPD).

40. A composition of Claim 35, wherein said composition is curable by ultraviolet radiation.

41. A composition of Claim 35, wherein said oligomers are selected from the group consisting of acrylated epoxy, acrylated aliphatic urethane, acrylated aromatic urethane, acrylated polyester, and acrylic oligomers.

42. The composition of Claim 41 , wherein said multifunctional monomers are selected from the group consisting of tripropylene glycol diacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, and propoxylated trimethylolpropane triacrylate.

43. The composition of Claim 35, wherein said tertiary amino alcohol of (c) comprises about 1-15 wt.% of said composition.

44. The composition of Claim 35, wherein said photoinitiator is a hydrogen abstraction (type II) photoinitiator.

45. The composition of Claim 44, wherein said photoinitiator is selected from the group consisting of benzophenone, thioxanthane and derivatives thereof.

46. A method of improving both depth of cure and surface cure in the radiation curing of coating compositions comprising photoinitiators and tertiary amines, by using as said tertiary amine a tertiary amino alcohol having the formula

R₅

V N C i R₃

^R2 , where Ri and R? are methyl,

R₃ is hydrogen or C₁-C₅ alkyl, R₄ is C╬╣-C₅ alkyl or -CH₂OH, and R₅ is C₁-C₅ alkyl substituted with at least one hydroxyl group.

47. A method of Claim 46, wherein said tertiary amino alcohol is 2-dimethylamino- 1- butanol (DMAB).

48. A method of Claim 46, wherein said tertiary amino alcohol is 2-dimethylamino-2- ethyl-1.3-propanediol (DMAEPD).

49. A method of Claim 46, wherein said composition is cured by ultraviolet radiation.

50. A method of Claim 46, wherein said photoinitiator is a hydrogen abstraction (type

II) photoinitiator.

51. A method of Claim 46, wherein said composition comprises at least one oligomer selected from the group consisting of acrylated epoxy, acrylated aliphatic urethane, acrylated aromatic urethane, acrylated polyester, and acrylic oligomers.

52. A method of Claim 51 , wherein said composition further comprises a multifunctional monomer.

53. A method of Claim 52, wherein said multifunctional monomer is selected from the group consisting of tripropylene glycol diacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, and propoxylated trimethylolpropane triacrylate.

54. A method of Claim 46, wherein said tertiary amino alcohol comprises about 1-15 wt. of said composition.

55. A method of radiation curing coating compositions comprising (a) reacting a radiation curable polymer with a tertiary amino alcohol having the formula

R₅

V N C I R₃

where R_\ and R are methyl, R₃ is hydrogen or C╬╣-C₅ alkyl, R₄ is C,-C₅ alkyl or -CH₂OH, and

R₅ is C╬╣-C₅ alkyl substituted with at least one hydroxyl group;

(b) mixing the product of step (a) with additional radiation curable compounds and a photoinitiator;

(c) radiation curing of the product of step (b).

56. A method of Claim 55, wherein said radiation curable compounds are acrylated.

57. A method of Claim 55, wherein said photoinitiator is a type II initiator.

58. A method of Claim 55, wherein said compositions are cured by UV radiation.