WO1995011219A1

WO1995011219A1 - Acrylic monomer

Info

Publication number: WO1995011219A1
Application number: PCT/SE1994/000964
Authority: WO
Inventors: Kent SÖRENSEN
Original assignee: Perstorp Ab
Priority date: 1993-10-22
Filing date: 1994-10-14
Publication date: 1995-04-27
Also published as: AU8007994A; SE9303503D0

Abstract

Acrylic monomer based on 2-ethyl-2-butyl-1,3-propanediol ethoxylate, propoxylate, butoxylate and/or phenylethoxylate and/or derivatives thereof. The monomer is primarily intended for radiation curing compositions, whereby constituting 0.1-80 % by weight, of such a composition.

Description

ACRYLIC MONOMER

The present invention relates to an acrylic monomer based on 2-ethyl-2-butyl-1,3-propanediol ethoxylate, propoxylate, butoxylate and/or phenylethoxylate, which acrylic monomer primarily is intended as a component in radiation curing compositions.

Radiation curing compositions are well-known technologies and used in for instance printing inks, paints and lacquers for furniture and packaging materials as well as for adhesives, but can also comprise application areas such as dental

materials. Radiation curing compositions are environmentally suitable and pleasing as they do not contain volatile

solvents. They exhibit furthermore a rapid curing and through hardening when exposed to for instance ultraviolet (UV) light or electron beams (EB). The compositions most often contain one or more oligomers having an unsaturation, normally as acrylate. These oligomers are usually high viscous and are, to obtain applicable viscosities, diluted with various monomers. The monomers are most often acrylic monomers, which monomers are esters of mono, di, tri or polyfunctional alcohols and acrylic and/or methacrylic acid. The most commonly used acrylic monomers normally have an acrylate functionality of 1-4.

In radiation curing compositions used acrylic monomers

include:

- Monofunctional: 2-Ethylhexyl acrylate

2-(2-Ethoxyethoxy)ethyl acrylate

Isobornyl acrylate

Octyl/decyl acrylate

Oxyethoxylated phenol acrylate

- Difunctional: Dipropylene glycol diacrylate

Tripropylene glycol diacrylate 1, 6-Hexanediol diacrylate

Neopentyl glycol diacrylate

- Trifunctional: Pentaerythritol triacrylate

Trimethylolpropane triacrylate

Trimethylolpropane ethoxylate triacrylate Glycerol propoxylate triacrylate

- Tetrafunctional: Pentaerythritol tetracrylate

Pentaerythritol ethoxylate tetracrylate Ditrimethylolpropane tetracrylate

High viscous acrylic monomers having an acrylate functionality of 5 and even higher, such as dipentaerythritol or ethoxylated dipentaerythritol pentacrylate, are also used for specific purposes.

Besides the above exemplified acrylic monomers are acrylates based on for instance cycloaliphatic alcohols such as 1,3-dioxane alcohols and allyl ether alcohols, such as trimethylolpropane allyl ethers, known. Also acrylic monomers of unsubstituted 2-ethyl-2-butyl-1,3-propanediol are known, but due to its skin irritating properties not commonly used

Acrylic monomers are generally highly reactive and as such potentially hazardous being skin and eye irritants and possible sensitizers. The properties in relation to the acrylate functionality can be summarised:

- the lower the acrylate functionality is, the better are the dilution properties and the higher are the skin irritation, toxicity, volatility and odour. -t the higher the acrylate functionality is, the poorer are the dilution properties and the flexibility and the higher are the reactivity, hardness and resistance. Low functional, i.e. mono and difunctional, acrylic monomers must, besides the excellent dilution properties, exhibit low skin irritation and low or no odour to comply with industrial hygienic demands. These properties must, if the monomers are to be utilised properly, be combined with for instance good reactivity, final hardness and resistance. Presently available mono and difunctional acrylic monomers are most often either skin/eye irritating, highly toxic and/or highly volatile or exhibit poor film forming properties such as poor hardness and/or poor resistance. Thus, the Primary Irritation Index (PII), investigated according to the method described by J.H. Draize in "Appraisal of Safety of Chemicals in Foods, Drugs, and Cosmetics", The Association of Food and Drug Officials of the United States, 1959, pages 46-48, for some commonly used mono and difunctional monomers are reported to be in the range of 3-5. Below are some reported PII scores valid for mono and diacrylates listed:

- Oxyethoxylated phenol acrylate 3

- 1,6-Hexanediol diacrylate 5

- Dipropylene glycol diacrylate 5

- Tripropylene glycol diacrylate 3

- 2-ethyl-2-butyl-1,3-propanediol acrylates 4-5

From "Appraisal of Safety of Chemicals in Foods, Drugs, and Cosmetics", page 47, the following is quoted:

- "Compounds producing combined averages (primary irritation indexes) of 2 or less are only mildly irritating, whereas those with indexes from 2-5 are moderate irritants, and those with scores above 6 are considered severe irritants".

It can, furthermore, be noted that some acrylate monomers, as for instance neopentyl glycol diacrylate are suspected of being carcinogenic, resulting in a limited or banned use. In the United Kingdom, the Society of British Ink Manufactures Ltd., has issued a list of monomers, which due to for instance a high irritation index or toxicity are voluntarily excluded from use in radiation curing coatings intended for the printing industry. Some of the above listed mono, di, tri, and tetra- functional acrylic monomers are included in this list.

The composition and technology of radiation curing systems and acrylic monomers are further disclosed in i.a. "Chemistry & Technology of UV and EB Formulations for Coatings, Inks and Paints" - Volume 2: "Prepolymers and Reactive Diluents for UV and EB Curable Formulations" by N.S. Allen, M.S. Johnson, P.K.T. Oldring and S. Salim, 1991 Selective Industrial Training Associates Ltd., London, U.K.

According to the present invention above disadvantages using mono and difunctional acrylic monomers have surprisingly been overcome by acrylation of 2-ethyl-2-butyl-1,3-propanediol alkoxylates and excellent dilution properties have been combined with low skin irritation, low volatility, low viscosity and good film forming and mechanical properties.

The acrylic monomer according to the invention is based on 2-ethyl-2-butyl-1,3-propanediol ethoxylate, propoxylate, butoxylate and/or phenylethoxylate and is characterised in the general formula

in which formula i) ' R₁ is HO, HO - (R₃)_n, or

and

or and R₂, is OH, (R₃)_n - OH,

or

wherein R₃ is C₂H₄O, C₃H₆O, C₄H₈O, C₈H₈O or combinations thereof and R₄ is H or CH, and wherein the mean value

for n is 1-24.

It is, besides above disclosed 2-ethyl-2-butyl-1,3-propanediol alkoxylates possible to use derivatives thereof, wherein one or more carbon atoms are alkyl, cycloalkyl, alkenyl and/or aryl substituted, such as 2-ethyl-2-butyl-1,3-propanediol ethoxylate monoallyl ether.

The acrylic monomer according to the invention is prepared in at least two steps, alkoxylation and acrylation. Initially 2-ethyl-2-butyl-1,3-propanediol is ethoxylated, propoxylated, butoxylated and/or phenylethoxylated, which means that ethylene oxide (R₃ = C₂H₄O), propylene oxide (R₃ = C₃H₆O), butylene oxide (R₃ = C₄H₈O) and/or phenylethylene oxide (R₂ = C₈H₈O) is reacted with the diol. A combination such as ethoxylated propoxylate [R₃ = (C₃H₆O)_m(C₂H₄O)_q wherein for instance the mean value

for m is 0.1-5 and the mean value

for q is 1-24] of the diol involves two alkoxylation steps. The first step, in such an embodiment, is propoxylation of the diol and the second step ethoxylation of the propoxylated diol. The product resul ting from the alkoxylation is finally esterified with acrylic and/or methacrylic acid to obtain the acrylic monomer.

Instead of a direct esterification with above acrylic acids, a transesterification using acrylates such as ethylacrylate, butylacrylate and the like and/or corresponding methacrylates, can be employed.

Phenylethylene oxide (styrene oxide) can for specific applications and/or in order to incorporate one or more phenolic rings into the molecule be combined with ethylene oxide,

propylene oxide and/or butylene oxide. Such a combination can for example suitably be performed by either an intermediate reaction step following the addition of ethylene oxide, propylene oxide and/or butylene oxide to the diol, and prior to the acrylation step or through an initial reaction step prior to said addition, in which initial step phenylethylene oxide is added to the diol. In both cases phenylethylene oxide is added in amounts corresponding to the desired final properties.

The following process is suitable for preparation of 2-ethyl-2-butyl-1,3-propanediol ethoxylate, propoxylate, butoxylate and/or phenylethoxylate. The diol is charged in a reaction vessel equipped with a stirrer, temperature control and inlet of inert gas. An alkaline compound, such as potassium hydroxide, is thereafter charged as catalyst. The reaction mixture is heated to 100-160°C and a pressure of 2000-4000 mm Hg is

applied. Ethylene oxide, propylene oxide, butylene oxide and/or phenylethylene oxide (styrene oxide) is then, in an amount resulting in the desired degree of addition, slowly pumped into the reaction vessel. Suitable charging time is about 1 hour followed by a post-reaction during 30 minutes. The product obtained is usually neutralised to pH 6-8 by an addition of for instance sodium hydrogenphosphate together with a small amount of water and a filter aid. The water is, after stirring for about 1 hour at 100-150°C, evaporated by vacuum distillation. The product is finally filtered at 100°C and preferably

stabilised by addition of an antioxidant such as butylhydroxytoluene (BHT).

Instead of above described process, ethylene oxide, propylene oxide, butylene oxide and/or phenylethylene oxide can be replaced by equivalent glycols and/or polyglycols, whereby a conventional etherification is performed.

A suitable process for preparation of an acrylic and/or methacrylic ester of 2-ethyl-2-butyl-1,3-propanediol ethoxylate, propoxylate, butoxylate and/or phenylethoxylate can be disclosed as follows. The diol, the acrylic and/or methacrylic acid and an azeotropic solvent, such as toluene, are charged into a reaction vessel provided with a stirrer, temperature control, air inlet and a cooler connected to a water-trap. The used acrylic acid is charged in excess in relation to desired degree of acrylation and the amount of azeotropic solvent is suitably equal to the subtotal weight of charged raw materials. The reaction mixture is stirred until a clear solution is obtained, a heating to 40-60°C may be necessary. Inhibitors such as

4-methoxyphenol or 2-methyl hydroquinone and nitrobenzene and a catalyst such as a sulphonic acid are added and the reaction mixture is heated to reflux using an air sparge. The reflux is maintained until the desired degree of esterification and formed esterification water is continuously removed azeotropically. When the desired degree of acrylation is obtained, the reaction mixture is cooled to room temperature and neutralised in order to remove the excess of used acrylic acid. The neutralisation is usually carried out to a pH of 7-8, using for instance an aqueous solution of sodium hydroxide. The water/salt phase is removed and the product/toluene phase is then repeatedly washed with water. The water phase is after each washing removed. Active carbon and a filter aid are following the washing added to the product/toluene phase, which phase thereafter is filtered. An antioxidant such as 4-methoxyphenol or 2-methyl hydroquinone, is added to the product/toluene phase and residual toluene is evaporated under vacuum, while maintaining an air sparge.

An acrylation can, as alternative to a direct esterification as above, involve a transesterification using acrylates such as ethylacrylate, butylacrylate and.the like and/or corresponding methacrylates.

Above described acrylation processes are suitable for acrylation of 2-ethyl-2-butyl-1,3-propanediol ethoxylate, propoxylate, butoxylate and/or phenylethoxylate as well as derivatives thereof, but other known processes can of course also be used.

The acrylic monomer obtained according to the invention exhibits a very low skin irritation combined with excellent dilution properties, a high degree of through hardening, a good final hardness and a good flexibility and resistance.

The acrylic monomer according to the invention can favourably be used as a component in radiation curing compositions. The percentage monomer is in such compositions within the range of 0.1-80% by weight, preferably 5-40% by weight. The radiation curing composition can for example be a printing ink, a paint, a lacquer, an adhesive, a dental material or the like. It is, besides radiation curing systems, also possible to use the monomer for compositions cured by means of peroxides or other radical forming initiators as well as for the preparation of latex dispersions.

Radiation curing compositions most often comprise one or more oligomers in an amount of 10-80% by weight. Some commonly used oligomers are for instance polyurethane acrylates, polyester acrylates, epoxy acrylates, silicone acrylates and unsaturated polyesters. Radiation curing compositions can, furthermore, comprise one or more, to the acrylic monomer according to the invention, additional mono, di and/or multifunctional acrylic monomers in amounts of 0.1-70% by weight. One or more initiators, for example photoinitiators such as benzoephenones and aromatic keto compounds prepared from benzoephenones such as alkylated and halogen-alkylated benzoephenones are also present. Further suitable photoinitiators are for example antraquinones, benzoines and derivatives thereof, acetophenones, acyloxime esters and benzil ketals. The percentage initiator in a radiation curing composition is normally 0.1-10% by weight. Above described compositions can be cured either by means of ultraviolet light or by means of electron beams, so called UV and EB curing.

The present invention is further explained in connection with enclosed embodiment Examples 1-10 and enclosed Figure 1, which Examples and Figure disclose as follows:

- Example 1: Preparation of 2-ethyl-2-butyl-1,3-propanediol ethoxylate.

- Example 2: Preparation of 2-ethyl-2-butyl-1,3-propanediol propoxylate.

- Examples 3 and 4: Preparation of diacrylates of the products according to Examples 1 and 2.

- Example 5: Determination of skin irritating properties of the diacrylate according to Example 4.

- Examples 6 and 7: Preparation of UV-curing lacquers based on products according to Examples 3 and 4. - Examples 8 - 10: Evaluations of the UV-curing lacquers

according to Example 6 and 7.

The invention is not limited to disclosed embodiments as these can be modified within the true scope of the invention.

EXAMPLE 1

160 g (1 mole) of 2-ethyl-2-butyl-1,3-propanediol and 3.9 g of powdered potassium hydroxide were weighed into a 1 litre laboratory autoclave. The mixture was heated under stirring and nitrogen purge to 120°C. 88 g (2 moles) of ethylene oxide were during one hour, at a temperature of 120°C and a pressure of 2000-4000 mm Hg, pumped into the autoclave. A post-reaction was performed during 30 minutes at 120°C. A vacuum of < 1 mm Hg was thereafter applied, whereby possibly unreacted ethylene oxide and during the reaction formed low molecular glycols were evaporated. The obtained product was neutralised to pH 6-8 with 3% of sodium hydrogenphosphate together with 1.5% of water and 1.5% of a filter aid (Celite), calculated on charged raw materials. The water was after one hour of stirring at 120°C, evaporated during 30 minutes at this temperature and at a vacuum of < 1 mm Hg. Finally, the product was filtered at 100°C.

The obtained product consisted of 2-ethyl-2-butyl-1,3-propanediol diethoxylate having the following characteristics:

Appearance: Clear colourless liquid

Viscosity: 213 mPas at 23°C

Hydroxyl value: 446 mg KOH/g

Ash content (as Na⁺ and K⁺) 294 ppm EXAMPLE 2

Example 1 was repeated with the difference that 116 g (2 moles) of propylene oxide was charged instead of 88 g (2 moles) of ethylene oxide.

The obtained product consisted of 2-ethyl-2-butyl-1,3-propanediol dipropoxylate having the following characteristics:

Appearance: Clear colourless liquid

Viscosity: 316 mPas at 23°C

Hydroxyl value: 401 mg KOH/g

Ash content (as Na⁺ and K⁺) 400 ppm

EXAMPLE 3

248 g (1 mole) of the product obtained in Example 1, 180 g (3 moles) of acrylic acid and 500 ml of toluene were charged in a glass flask equipped with a stirrer, air inlet, a cooler and a water-trap (Dean-Stark). 1600 ppm of 4-methoxyphenol and 200 ppm of nitrobenzene were added as inhibitors and 1.2% of methanesulphonic acid was added as catalyst. The reaction mixture was under an air sparge heated to 120°C, resulting in a reflux. Water formed during the esterification was removed azeotropically. The reflux was maintained until the desired degree of esterification was obtained. The reaction mixture was after 7 hours cooled to room temperature and to remove excess acrylic acid neutralised with a 5% aqueous solution of sodium hydroxide. The water/salt phase containing i.a. sodium acrylate was removed and the product/toluene phase was washed three times with water, which after each washing was removed. 5% of active carbon (0.6-1.5 mm Hydraffin BK) and 2% of a filter aid (Celite) was following the washings added to the product/toluene phase, which thereafter was heated to 90°C. The product/toluene phase was kept at 90°C temperature for 15 minutes, after which time it was cooled to room temperature and filtered. Following the filtration, 200 ppm of 4-methoxyphenol was added and a vacuum of 20 mm Hg was applied. The residual toluene was evaporated at 20 mm Hg and a temperature of max. 40°C, whilst maintaining an air sparge.

The obtained product consisted of 2-ethyl-2-butyl-1,3-propanediol diethoxylate diacrylate having the following characteristics:

Viscosity: 35 mPas at 23°C

Colour according to Gardner: 3-4

EXAMPLE 4

Example 3 was repeated with the difference that 276 g (1 mole) of the product obtained in Example 2 was charged instead 248 g (1 mole) of the product obtained in Example 1.

The obtained product consisted of 2-ethyl-2-butyl-1,3-propanediol dipropoxylate diacrylate having the following characteristics:

Viscosity: 40 mPas at 23°C

Colour according to Gardner: 3-4

EXAMPLE 5

Skin irritation was determined for 2-ethyl-2-butyl-1,3-propanediol dipropoxylate diacrylate obtained according to Example 4. The primary skin irritant effect of 2-ethyl-2-butyl-1,3-propanediol dipropoxylate diacrylate, 100%, was investigated accor ding to the method described by J.H. Draize in "Appraisal of the Safety of Chemicals in Foods, Drugs, and Cosmetics", the Association of Food and Drug Officials of the United States (1959, pp. 46-48). From page 47 the following statement is quoted:

- "Compounds producing combined averages (primary irritation indexes) of 2 or less are only mildly irritating, whereas those with indexes from 2-5 are moderate irritants, and those with scores above 6 are considered severe irritants"

The evaluation was performed by Scantox, Lille Skensved,

Denmark (Danish Accreditation Reg.no. 145) and reported in a Test Report (Lab. No. 14310, dated 14.10.1993) on authorised technical test executed under authorisation granted by the Danish Accreditation Scheme.

The Primary Skin Irritation Index (PII) was determined to 1.5.

The conclusion is that 2-ethyl-2-butyl-1,3-propanediol dipropoxylate diacrylate is only mildly irritating.

EXAMPLE 6

An UV-curing lacquer containing the product obtained in Example 3 was prepared by mixing of below components:

25 parts of acrylic monomer according to Example 3

50 parts of polyester oligomer (Laromer LR 8799, BASF AG, DE)

25 parts of trimethylolpropane triethoxylate triacrylate

4 parts of UV-initiator (Darocure 1173, Firma E. Merck, DE)

Obtained lacquer exhibited a viscosity of 310 mPas at 23°C. EXAMPLE 7

An UV-curing lacquer containing the product obtained in Example 4 was prepared by mixing of below components:

25 parts of acrylic monomer according to Example 4

50 parts of polyester oligomer (Laromer LR 8799, BASF AG, DE)

25 parts of tripropylene glycol diacrylate

4 parts of UV-initiator (Darocure 1173, Firma E. Merck, DE)

Obtained lacquer exhibited a viscosity of 340 mPas at 23°C.

EXAMPLE 8

The lacquers obtained according to Examples 6 and 7 were cured by means of a UV-lamp of 80W/cm and at a belt speed of 20 m/min. The lacquers were coated on glass panels at a filmthickness of 30 ± 5 μm (cured) and were allowed to pass the UV-lamp 1, 2, 4, 8 and 16 times. The samples were after curing conditioned for 24 hours at 23 ± 2°C and at 50 ± 5% relative humidity, whereupon the filmhardness was measured by means of a König pendulum according to Swedish Standard SS 18 41 86, Edition 4.

The following results were obtained:

Pendulum hardness, König seconds

Lacquer according to

Number of passages Example 6 Example 7

1 62 50

2 73 71

4 91 84

8 118 108

16 143 139 EXAMPLE 9

The lacquers obtained according to Examples 6 and 7 were coated, cured and conditioned as in Example 8.

The resistance to liquids after 8 passages under the UV-lamp was evaluated according to Swedish Standard SS 839118, Edition 2, which fully complies with ISO 4211-1979. The evaluation scale according to the Standard is 0 - 5, wherein 5 is best.

The following results were obtained:

Evaluation

Lacquer according to

Example 6 Example 7

Acetone, 2 minutes 5 5

NaOH, 1% (aq), 24 hours 5 5

Water, 24 hours 5 5

EXAMPLE 10

The lacquers obtained according to Examples 6 and 7 were coated on aluminium panels at a filmthickness of 35 ± 5 μm (cured) and cured and conditioned as in Example 8.

The impact resistance and the flexibility were determined after 8 passages under the UV-lamp.

The impact resistance was determined by means of a Gardner Impact Tester and the flexibility by means of a conical mandrel (mandrel bending test) as disclosed in the Swedish Standard SS 18 41 77, Edition 3. The following results were obtained:

Lacquer according to Example 6 Example 7

Impact resistance 8 inch-lbs 7 inch-lbs

Flexibility 3.2 mm 3.5 mm

Claims

1. Acrylic monomer c h a r a c t e r i s e d i n, the

general formula

in which formula i) R₁ is HO, HO - (R₃)_n, or

and

or

ii) and R₂ is OH, (R₃)_n - OH,

or

wherein

R₃ is an alkyl group of formula C₂H₄O, C₃H₆O or C₄H₈O or an alkylaryl group of formula C₈H₈O or combinations thereof and

R₄ is H or CH₃ and wherein the mean value n for n is 1-24.

2. Acrylic monomer according to claim 1 c h a r a c t e r i s e d i n, that R₃ is C₂H₄O and the mean value

for n is 2-8.

3. Acrylic monomer according to claim 1 c h a r a c t e r i s e d i n, that R₃ is C₃H₆O and the mean value

for n is 2-6.

4. Acrylic monomer according to claim 1 c h a r a c t e r i s e d i n, that R₃ is (C₃H₆O)m (C₂H₄O)q wherein the mean value m for m is 0.1-5, preferably 0.5-2, and the mean value q for q is 1-24.

5. Acrylic monomer according to claim 1 c h a r a c t e r i s e d i n, that the monomer is a mono or diacrylate or methacrylate of 2-ethyl-2-butyl-1, 3-propanediol ethoxylate, 2-ethyl-2-butyl-1, 3-propanediol propoxylate, 2-ethyl- 2-butyl-1, 3-propanediol butoxylate, 2-ethyl-2-butyl-1, 3-propanediol phenylethoxylate or a derivative thereof wherein one or more carbon atoms are alkyl, cycloalkyl, alkenyl and/or aryl substituted.

6. Acrylic monomer according to claim l or 5 c h a r a c t e r i s e d i n, that the monomer is 2-ethyl-2-butyl-1,3- propanediol diethoxylate diacrylate.

7. Acrylic monomer according to claim 1 or 5 c h a r a c t e r i s e d i n, that the monomer is 2-ethyl-2-butyl-1,3- propanediol dipropoxylate diacrylate.

8. Acrylic monomer according to claim 1 or 5 c h a r a c t e r i s e d i n, that the monomer is 2-ethyl-2-butyl-1,3- propanediol ethoxylate monoallyl ether monoacrylate.

9. Acrylic monomer according to any of the claims 1 - 8 c h a r a c t e r i s e d i n, that the acrylic monomer constitutes 0.1-80% by weight, preferably 5-40% by weight, of a radiation curing composition composition.

10. Acrylic monomer according to claim 9 c h a r a c t e r i s e d i n, that the radiation curing composition consists of a paint, a lacquer, a printing ink, an adhesive or a dental material.