NO134701B - - Google Patents

Description

The invention relates to a varnish binder which is suitable for curing by electron irradiation, and which consists of 10-80 weight percent vinyl monomers and 20-90 weight percent of an alkenically unsaturated reaction product of a polysiloxane with 3-18 silicon atoms and at least two hydroxy or lower alkoxy groups, and the varnish binder is characterized by the fact that the alkenically unsaturated polysiloxane reaction product is produced by etherifying the polysiloxane with a hydroxyester of an a,3- alkenically unsaturated carboxylic acid.

The preferred hydroxyesters are acrylates and methacrylates.

The binder according to the invention is suitable for the production of paints and varnishes with great weather resistance. Such paints and varnishes can be used as coatings on various objects, e.g. of wood, metals or plastic, and the material can be hardened after application by electron irradiation.

The binder can be used alone or mixed with common ones

pigments and fillers used in ordinary paint.

The polysiloxanes used for the production of the binder have a reactive hydroxyl or lower alkoxy group attached to at least two of the silicon atoms. The term polysiloxane means a compound containing the group:

in that the free valences are linked to a hydrocarbon group, a hydrocarbonoxy group, hydrogen, a hydroxyl group or an oxygen atom which connects the silicon atom with another silicon atom.

For simplicity, the polysiloxanes are hereinafter referred to as "siloxanes".

It is advantageous to use an acyclic siloxane containing 3-18 silicon atoms per molecule with corresponding oxygen bridges. The

A

w^freduced siloxanes can be represented by the general formula:

where'ri is at least 1, and X is (a) a C1 to C8 monovalent hydrocarbon group, preferably a C1 to C4 alkyl group, or (b) a C1 to C0 Q monovalent hydrocarbonoxy group, preferably a C1 ,- to C4„-Alkoxy group, or (c) a hydroxyl group or (d) hydrogen, wherein at least two of the X groups are either (b) or (c) and are separated by a chain of the formula

The cyclic siloxanes which can be used in the indicated material contain at least 3, preferably 6 - 12, and not more than 18, silicon atoms per molecule with corresponding oxygen bridges. The cyclic siloxanes can have one of the following formulas:

T ^ r n • 1

jl. An'£>-Lnun» ' nTOr

n an odd number, at least 3, X = (a) a C^- to Cg-monovalent n'= 2n, and hydrocarbon group, for n"= n stepwise a C-j- to C^-alkyl group, or

(b) a C 1 to C 8 monovalent hydrocarbonoxy group, preferably a C 1 to C 4 alkoxy group, or (c) a hydroxyl group, or (d) hydrogen -

wherein at least two of the X groups are separated by one

in i

X- Si -0- Si -X chain,

■ i

either is (b) or (c).

An example of this is:

An example of this is

An example of this is:

or a condensation dimer, trimer, etc. thereof, formed during the cleavage of water or an alcohol.

An example of this is:

where m is 0 or an integer.

V. X ,Si O „, where

n' nn

n = an even number, at least 8, X = (a) one to Cg monovalent n' = n + 2, and hydrocarbon group, for-n" = 11, 11 + 3, or stepwise one C1 to C^-11 + a multiple of 3 alkyl group, or

(b) one to Cg-monovalent hydrocarbonoxy group, (c) a hydroxyl group, or (d) hydrogen -

wherein at least two of the X groups which are separated by an X-Si-O-Si-X chain,

in i

either is (b) or (c).

Examples of this are:

where m is an integer.

A wide range of methods for producing siloxanes are known. These include controlled hydrolysis of silanes,

polymerization of a low molecular weight siloxane and reaction of silicon tetrachloride with an alcohol. The production of siloxanes and organic resins containing such siloxanes is indicated in the following US patents: 3154597, 3074904, 3044980, 3044979, 3015637, 2996479. ^2973287, 2937230 and 2909549 . ..j: ■ It is also known that hydroxy- and methoxy-functional siloxanes" of this kind can be used in radiation-curable binders, see e.g. Norwegian patent document no. 125,853, Swedish patent document no. 344,182 and US patent document no. 3,437,512. However, the siloxanes are included here as diol building blocks in unsaturated polyesters, together with other diols. In these polyesters, the molecular weight often becomes quite high, which leads to an undesirably high viscosity.

According to this invention, the functional siloxanes are combined with unsaturated acid groups by means of the groups' hydroxy functionality, i.e. by ether ringing, and as these bonds are more stable, an increase is achieved. weather resistance. It is admittedly already known that the etherification principle gives better weather resistance than the esterification principle, see Norwegian patent document no. 133326.

It is also known per se to etherify OH-containing siloxanes with hydroxyethyl methacrylate, see examples 1 and 2 in French patent document no. 1522607. The condensate produced here is, however, copolymerized with acrylamide and other low molecular weight monomers, and the produced lacquers are hardened in the conventional way by burning in. ,

The hydroxyl-containing ester included in the etherification product i used according to the invention is preferably a monohydroxy-i alkyl ester of a monocarboxylic acid. The preferred hydroxyesters are acrylates and methacrylates as they introduce alkenic double bonds between the terminal carbon atoms and are easy to polymerize with relatively small doses of radiation. Examples of such connections are:

2-hydroxyethyl acrylate or methacrylate

2-hydroxypropyl acrylate or methacrylate

2-hydroxybutyl acrylate or methacrylate

2-hydroxyoctyl acrylate or methacrylate

2-hydroxydodecanyl acrylate or methacrylate

2-hydroxy-3-chloropropyl acrylate or methacrylate

2-hydroxy-3-acryloxypropyl acrylate or methacrylate 2-hydroxy-3-methacryloxypropyl acrylate or methacrylate 2-hydroxy-3-allyloxypropyl acrylate or methacrylate 2-hydroxy-3-cinnamylpropyl acrylate or methacrylate 2- hydroxy-3-phenoxypropyl acrylate or methacrylate

2-hydroxy-3-(O-chlorophenoxy)propyl acrylate or methacrylate 2-hydroxy-3-(p-chlorophenoxy)propyl acrylate or methacrylate 2-hydroxy-3-(2,4-dichlorophenoxy)propyl acrylate or -methacrylate 2-hydroxy-3-acetoxypropyl acrylate or -methacrylate 2-hydroxy-3-propionoxypropyl acrylate or -methacrylate 2-hydroxy-3-chloroacetoxypropyl acrylate or -methacrylate 2-hydroxy-3-dichloroacetoxypropyl acrylate or - methacrylate 2-hydroxy-3-trichloroacetoxypropyl acrylate or methacrylate 2-hydroxy-3-benzoxypropyl acrylate or methacrylate 2-hydroxy-3-(o-chlorobenzoxy)propyl acrylate or methacrylate 2-hydroxy-3-(p -chlorobenzoxy)propyl acrylate or methacrylate 2-hydroxy-3-(2,4-dichlorobenzoxy)propyl acrylate or methacrylate 2-hydroxy-3-(3,4-dichlorobenzoxy)propyl acrylate or methacrylate 2-hydroxy -3-(2,4,6-trichlorophenoxy)propyl acrylate or -methacrylate 2-hydroxy-3-(2,4,5-trichlorophenoxy)propyl acrylate or -methacrylate 2-hydroxy-3-(o-chlorophenoxyacetoxy) propyl acrylate or methacrylate 2-hydroxy-3-phenoxyacetoxy propyl acrylate or methacrylate 2-hydroxy-3-(.p-chlorophenoxyacetoxy) propyl acrylate or methacrylate 2-hydroxy-3-( 2,4-dichlorophenoxyacetoxy)propyl acrylate or methacrylate 2-hydroxy-3- (2,4,5-trichlorophenoxyacetoxy)propyl acrylate or methacrylate

2-hydroxy-3-crotonoxypropyl acrylate or methacrylate 2-hydroxy-3-cinnamyloxypropyl acrylate or methacrylate 3-acryloxy-2-hydroxypropyl acrylate or methacrylate 3-allyloxy-2-hydroxypropyl acrylate or methacrylate 3-chloro-2-hydroxypropyl acrylate or methacrylate 3-crotonoxy-2-hydroxypropyl acrylate or methacrylate.

Besides acrylates and methacrylates, cinnamates, crotonates and other unsaturated esters can also be used.

The radiation used for polymerization of the specified coating must have an energy above 5000 electron volts. It can thus have an average energy of 100,000 to 500,000 electron volts. If a beam is used, it should preferably have at least 25,000 electron volts per 25 mm distance between the radiation source and the surface to be cured, if the space is air. However, it may be beneficial to introduce an oxygen-free gas, such as nitrogen or helium, into the space.

The formed covers are preferably cured at a relatively low temperature, usually between 20°C and 70°C. The radiation is used in doses of 0.1-100 Mrad per second, the object with a cover preferably being guided past the beam so that the cover receives a radiation of 0.5-100, preferably 5-15/Mrad. The surface layer is transformed with the help of the silent electron beam into a firmly adhering, wear- and weather-resistant cover.

The abbreviation Mrad means 1000000 Rad, and 1 Rad is the radiation dose that provides absorption of 100 erg of energy per g absorbent, e.g. cover feeder.ialet. The electron source can be a linear electron accelerator which develops a direct current potential of the strength indicated above. In such a device, the electron beams are usually developed by using a hot filament, and they are accelerated through a uniform voltage gradient. The electron beam, which can have a diameter of approx. 3 mm, then spread in a fan shape and passed through a metal window, e.g. of a magnesium-thorium alloy, aluminum, an alloy of! aluminum and a smaller amount of copper or a similar metal, and of a thickness of e.g. 0.08 mm.

The film-forming material must be sufficiently free-flowing to be able to be quickly applied to surfaces in a suitable layer thickness, e.g. at least 0.02 mm. The usual covers usually have a layer thickness of 0.02-0.1 mm, and the viscosity of the cover material should be regulated to achieve such a layer thickness. A suitable viscosity can be achieved with the specified coating material alone, but the viscosity can also be regulated by means of volatile solvents, e.g. toluene or xylene. The term vinyl monomers is used for monomeric compounds containing a terminal group with the formula:

and allyl compounds are not covered by this group. The vinyl monomers can be esters of monohydric alcohols with 1-8 carbon atoms and acrylic acid or methacrylic acid, e.g. ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, octyl acrylate and 2-ethylhexyl acrylate. Alcohols with several carbon atoms, i.e. 9-15 carbon atoms, can also be used in the production of such acrylates and methacrylates. Unsaturated hydrocarbons, e.g. styrene and alkylated styrenes, such as vinyltoluene and α-methylstyrene, can be used alone or together with acrylates and methacrylates. A smaller amount of other vinyl monomers can also be used together with acrylates and methacrylates or vinyl hydrocarbons, such as, for example acrylonitrile, acrylamide, N-methylol-acrylonitrile, vinyl chloride and vinyl acetate.

Example 1

A siloxane unsaturated ester was prepared from the following ingredients in the manner indicated below.

The siloxane and the monomeric methacrylate containing hydroquinone as inhibitor were heated to 100°C in a flask fitted with a Barrett-type still. The titanate catalyst was added and the temperature increased to 150°C during 3 hours while methanol was distilled off. The cooled reaction product had a viscosity of 0.6 stoke at 25°C. 70 parts of the reaction product were mixed with . 30 parts of an equimolar mixture of styrene and methymethacrylate and was applied as a 0.02 mm film to a metal or wood surface. It was then polymerized under the influence of an electron beam. The radiation conditions were:

An excellent varnish coating was achieved.

Example 2

The procedure according to example 1 was repeated, but with the change that the polysiloxane was a methoxylated partial hydrolyzate of monophenyl- and phenylmethylsilanes consisting mainly of dimethyltriphenyltrimethoxytrisiloxane and with the following typical properties:

(This polysiloxane is also used in Norwegian patent document no. 125853, example 3.)

Example 3

A siloxane-containing coating material was prepared with the following components in the manner indicated.

(This polysiloxane is also used in Norwegian patent document no. 125853 and in US patent document no. 3437512, both places example 1). A 3-necked flask fitted with a stirrer, thermometer, nitrogen inlet tube and a Barrett trap was charged with the siloxane, methacrylate, xylene and hydroquinone. The solution was heated under reflux to 138°C over 30 minutes. Nitrogen was bubbled through the reaction mixture throughout the process. The water formed as a by-product was slowly removed and the temperature gradually increased to 146°C. After 5 hours, 8.5 ml of water had been collected, which showed that the reaction was practically complete. The xylene was evaporated under reduced pressure and the product then diluted with methyl methacrylate to a 70% non-volatile content. This solution was applied to surfaces of metal, wood and polymeric materials (ABS-acrylonitrile-butadiene-styrene) to an average layer thickness of 0.025 mm, and the coating was then cured using an electron beam and the same conditions as indicated in Example 1.

Example 4

The procedure according to examples 1-3 was repeated, but with the change that an equivalent amount of 2-hydroxyethyl acrylate was used instead of the hydroxymethyl methacrylate.

Example 5

The procedure according to examples 1-3 was repeated, but with the change that an equivalent amount of 2-hydroxypropyl methacrylate was used instead of the hydroxyethyl methacrylate.

Example 6

The procedure according to examples 1-3 was repeated, but with the change that an equivalent amount of 2-hydroxybutyl acrylate was used instead of the hydroxyethyl methacrylate.

" Example 7

The procedure according to examples 1-3 was repeated, but with the change that an equivalent amount of 2-hydroxyoctyl acrylate was used instead of the hydroxyethyl methacrylate.

Example 8

The procedure according to examples 1-3 was repeated, but with the change that an equivalent amount of 2-hydroxydodecanyl methacrylate was used instead of the hydroxyethyl methacrylate.

Example 9

The procedure according to examples 1-3 was repeated, but with the change that an equivalent amount of 3-chloro-2-hydroxypropyl acrylate was used instead of the hydroxyethyl methacrylate.

#■ Example 10

The procedure according to examples 1-3 was repeated, but with the change that an equivalent amount of 3-acryloxy-2-hydroxypropyl methacrylate was used instead of the hydroxyethyl methacrylate.

example 11

The procedure according to examples 1-3 was repeated, but with the change that an equivalent amount of 3-crotonoxy-2-hydroxypropyl acrylate was used instead of the hydroxyethyl methacrylate.

Example 12

The procedure according to examples 1-3 was repeated, but with the change that an equivalent amount of 3-acryloxy-2-hydroxypropylcinnamate was used instead of the hydroxyethyl methacrylate.

Example 13

The procedure according to examples 1-3 was repeated, but with the change that an equivalent amount of 3-acryloxy-2-hydroxypropylcrotonate was used instead of the hydroxyethyl methacrylate.

Example 14

The procedure according to example 1 was repeated, but with the change that the reagents were distributed in such a way that a reaction mixture consisting of 412 parts by weight of the polysiloxane, 195 parts by weight of the hydroxyethyl methacrylate and 0.2 parts by weight of hydroquinone was obtained.

Example 15

The procedure according to example 1 was repeated, but with the change that the reagents were distributed so that a reaction mixture consisting of 206 parts by weight of polysiloxane, 65 parts by weight of hydroxyethyl methacrylate and 0.1 part by weight of hydroquinone was obtained.

Example 16

The procedure according to example 1 was repeated, but with the change that the polysiloxane used was dimethyltriphenyltrimethoxytrisiloxane.

Example 17

The procedure according to example 1 was repeated, but with the change that the polysiloxane used was dipropoxytetramethyl-cyclotrisiloxane.

^^ example

The procedure according to example 1 was repeated, but with the change that the polysiloxane used was dibutoxytetramethyl-..disiloxane.

Example 19

The procedure according to example 1 was repeated, but with the change that the polysiloxane used was pentamethyltrimethoxytrisiloxane.

Example 2 0

A pigmented paint was prepared by first mixing 75 parts by weight of siloxane plus unsaturated ester from Example 3 with 150 parts by weight of titanium dioxide pigment and 20 parts by weight of methyl methacrylate. The mixture was ground by shaking with the same weight of glass balls in a regular shaker for 30 minutes. The premix was diluted with an additional 75 parts by weight of siloxane plus unsaturated ester. The paint was applied to an aluminum plate by spreading with a stick wrapped with wire. The paint was cured in a nitrogen atmosphere with an electron beam of 275 kV and 25 milliamperes at a dose of 20-25 Mrad. The applied paint had a thickness of 0.05 mm and a gloss of 100 measured with a Gardner 60° gloss meter. The plate was mounted in a weather resistance measuring device equipped with 2 ball arcs. After irradiation for 1216 hours, the paint had a 60° gloss of 95 and showed no chalking.

The weather resistance measuring device is an instrument used for determining the weather resistance at accelerated speed. In this case, the light from the carbon arcs was used to emit ultra-violet and visible light of high intensity. Water was also sprayed on the cover during part of the irradiation.

Example 21

The procedure according to example 1 was repeated, but with the change that the hardening was carried out with an irradiation of 17 5000" volts, the object being placed 7.5 mm from the radiation source, and at 400,000 volts at a distance of 250 mm<*> in both cases in a nitrogen atmosphere containing small amounts of carbon dioxide.

Claims (1)

Varnish binder which is suitable for curing by electron irradiation, and which consists of 10-80 weight percent vinyl monomers and 20-90 weight percent of an alkenically unsaturated reaction product of a polysiloxane with 3-18 silicon atoms and at least two hydroxy or lower alkoxy groups, characterized in that the alkenic unsaturated polysiloxane reaction product is prepared by etherifying the polysiloxane with a hydroxyester of an α,3-alkenic unsaturated carboxylic acid.