RADIATION CURABLE ADHESION PROMOTER

Technical Field

This invention relates to a new type of radiation curable adhesion

promoters, which can be applied to coatings, inks and adhesives to improve

adhesion between cured materials and substrates. In particular they can be

applied to radiation curable coatings and adhesives to promote adhesion between

cured materials and substrates.

Background Art

Radiation curable materials (including ultraviolet light curable materials

and electron beam curable materials) have been developed rapidly in the past 20

years. They have been widely used in coatings, inks and adhesives etc since they

provide high productivity, low energy consumption and zero environment

pollution. Radiation curable materials are in general composed of four

ingredients: oligomers, reactive monomers, photoinitiators and additives.

Radiation curable materials are commonly first coated on the substrates, and

cured via radiation resources (ultraviolet light or electron beam). The adhesion

between the substrates and the cured radiation curable materials varies

considerably from system to system. Adhesion promoters are the most common

additives that improve adhesion between cured materials and substrates. The

most common adhesion promoters are alkoxysilanes.

Alkoxysilane adhesion promoters are generally polymerization inactive-can

not participate in polymerization reactions of monomers and oligomers during

curing. As a result, their levels in formulations are considerably limited. The

only commonly used polymerizable alkoxysilane adhesion promoter in industry

is methacryloxypropyl trimethoxysilane. However it contains a certain level of

starting material-allylmethacrylate, which is a volatile and odorous compound.

Therefore its applicability is limited. See Waldman, Silane Coupling Agents

Improving Performance, Modern Paints and Coatings, February, 1996.

On May 2, 1996, WO 96/12749 discloses an oligomer containing

alkoxysilanes and optical fiber coating containing the oligomer. The silane

oligomers are high in molecular weight (500-11000) and a high level of silane

oligomers in the composition is needed (5-99%). Such oligomers are typically

polyurethane materials.

On the other hand, US patent US6391463B1 discloses a new polymerisable

alkoxysilane monomer, which is obtained by hydrosilylation reactions.

Disclosure of Invention

Aiming at above-mentioned shortcomings of current technologies, it is an

object of this invention to provide two easily made and industrialized new

adhesion promoters, which are polymerizable thus can be widely applied to

radiation curable coatings, inks, and adhesives at high contents.

In order to solve above technical problems, this invention provides a

radiation curable adhesion promoter, which is obtained by fast reaction of

alkoxysilane containing isocyanate, with acrylate or methacrylate monomers

containing hydroxy or amino groups, at 40-60 ⁰ C in the presence of dibutyltion

dilaurate catalyst, as shown in Equation 1 :

cat. DBTDL

Equation 1

The second radiation curable adhesion promoter put forward in this

invention was obtained by reaction of acrylate or methacrylate containing

hydroxy or amino groups, with diisocyanate, followed by reaction with

alkoxysilane containing mercapto or amino groups, as shown in Equation 2.

DBTDL

(X= NH, NR, S)

Equation 2

In contrast to current techniques, above two radiation curable adhesion

promoters in this invention due to polymerization activity, are unrestricted in

quantity in their application to coatings, inks, and adhesives. Particularly in

radiation curable coatings, inks and adhesives use of above adhesion promoters

in large quantities can greatly change adhesion power between cured materials

and substrates.

Modes for Carrying Out the Invention

This invention will be further described with the following illustrative

examples:

Example 1

According to Equation 1, 20.5 g of 3-isocyanate propyl trimethylsilane and

0.02 g of dibutyltion dilaurate (DBTDL) were added into a dry and clean reactor,

and 13.0 g of 2-hydroxyethyl methyl methacrylate was added dropwise under

uniform stirring. After complete addition the mixture was kept at 40 ⁰ C for an

hour and the content of isocyanate was below 0.1% obtained by chemical

titration. The resulting light yellow liquid was radiation curable adhesion

promoter A.

Example 2

According to Equation 2, 22.3 g of isophorone diisocyanate (IPDI) and

0.03 g of dibutyltion dilaurate (DBTDL) were added into a dry and clean reactor,

and 17.4 g of 2-hydroxyethyl acrylate was added dropwise under uniform

stirring. After complete addition the mixture was kept at 40 ⁰ C for an hour and

then 19.6 g of 3-mercapto propyl trimethoxysilane was added. After heating to

80 ⁰ C for 12 hours the resulting viscous and colorless liquid was radiation

curable adhesion promoter B. Its viscosity was 34000 cps (60 ⁰ C).

Example 3

According to Equation 2, 22.3 g of isophorone diisocyanate (IPDI) and

0.03 g of dibutyltion dilaurate (DBTDL) were added into a dry and clean reactor,

and 17.4 g of 2-hydroxyethyl methacrylate was added dropwise under uniform

stirring. After complete addition the mixture was kept at 40 ⁰ C for an hour and

then 22.1 g of N-ethyl-3-aminoisobutyl trimethylsilane and 14 g of isobornyl

acrylate.(IBOA) monomer as a dilution agent were added. After agitation at

60 ⁰ C for 1 hour the resulting viscous and yellow liquid was radiation curable

adhesion promoter C. Its viscosity was 8300 cps (25 ⁰ C).

Example 4-Radiation curable adhesive

50% radiation curable adhesion promoter B

47% isobornyl acrylate (IBOA)

3% 1-hydroxycyclohexyl phenyl ketone (Irgacure 184)

Above ingredients were added successively into a reactor. After agitation at

60 ⁰ C for two hours an UV curable adhesive was obtained via filtration. Its

viscosity was 400 cps at 25 ⁰ C. The adhesive can be used in bonding metals and

glass etc with very tight bonding.

Example 5-UV curable ink

45% aromatic polyurethane acrylate oligomer (RMAT 650)

12% hexane-l,6-diol diacrylate (HDDA)

20% trimethlolpropane triacrylate (TMPTA)

15% white color paste (55% titanium dioxide dispersed in TMPTA)

3% 1 -hydroxy cyclohexyl phenyl ketone (Irgacure 184)

1% 2,4,6-trimethylphenol (Irganox 1010)

4% radiation curable adhesion promoter B

Above ingredients were added successively into a reactor. After agitation at

60 ⁰ C for two hours an UV curable ink was obtained via filtration. Its viscosity

was 1720 cps at 25 ⁰ C. This UV curable ink has good bonding to glass, metals,

and some plastics. Other colored inks can be made in a similar way to above.