Radiation-curable resin compositions

Details Radiation-curable resin compositions Radiation-curable resin compositions

1999-06-29

2001-06-19

Seidleck, James J. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Compositions to be polymerized by wave energy wherein said...

C522S099000, C522S148000, C522S120000, C522S121000, C526S279000, C528S010000, C528S012000, C528S032000, C528S033000, C528S037000

Reexamination Certificate

active

06248803

ABSTRACT:

This invention relates to radiation-curable resin compositions based on acryl group-bearing organopolysiloxanes, and more particularly, to radiation-curable resin compositions based on acryl group-bearing organopolysiloxanes having a minimized content of non-functional organopolysiloxane and finding use in the coating application as mold release coating agents, protective coating agents, water-repellent coating agents, printing ink, and paint.
BACKGROUND OF THE INVENTION
As silicone compositions curable with ultraviolet radiation and electron beams, organopolysiloxanes containing (meth)acryloxy groups in the molecule are known, and compositions comprising the same in admixture with sensitizers are also known from JP-B 53-36515. However, since the organopolysiloxanes in these compositions have a high content of (meth)acryloxy groups, the cured coatings are so hard that they do not smoothly follow the underlying substrates and are liable to cracking.
JP-A 61-232 and 56-86922 disclose a method for preparing an acrylic functional, UV-curable polysiloxane by adding an acrylic acid to an epoxy group-bearing organopolysiloxane. Since some acrylic acid is left unreacted, the cured coating has poor moisture resistance and electrical properties due to the influence of carboxyl groups left therein. If the amount of acrylic acid blended is reduced, some epoxy groups are left instead. As a result, the surface layer of cured coating is exacerbated in weather resistance and acid resistance by epoxy groups.
As a method of preventing acrylic acid from being left in radiation-curable coating compositions, JP-A 5-309664 discloses to introduce (meth)acryl groups into an organopolysiloxane by effecting dealcoholysis between alkoxysilyl groups and a (meth)acryl group-bearing silanol compound in the presence of a tin catalyst. The (meth)acryl group-bearing silanol compound, however, is difficult to synthesize and expensive from the commercial aspect. The residual tin catalyst is undesirable from the safety aspect.
Other methods known for the preparation of (meth)acryl functional organopolysiloxanes of this type include dehydrochlorination reaction between ≡Si—Cl groups and a hydroxyl group-bearing acrylate compound, dehydrochlorination reaction between a carbinol group-bearing siloxane and acrylic chloride, and hydrosilylation reaction between ≡Si—H groups and allyl (meth)acrylate. These methods suffer from problems such as difficult removal of by-products or hydrochloride salts, and complex reactions including dehydrogenation condensation by side reaction during hydrosilylation and multi-stage reaction. These methods are not regarded as commercially simple and inexpensive.
For improving the compatibility with other acrylic compounds and the transparency of resins, it is known to introduce phenyl groups into silicone compounds. This is conventionally carried out by equilibration using octaphenylcyclotetrasiloxane, with the drawback that much cyclic diphenylsiloxane is left in the synthesized polysiloxane.
SUMMARY OF THE INVENTION
An object of the invention is to provide a radiation-curable resin composition which is based on a radiation-curable acryl group-bearing organopolysiloxane compatible with other (meth)acrylic compounds and which cures into a highly flexible product.
The inventor has found that an organopolysiloxane having acrylic functional groups represented by the following average compositional formula (1):
A
x
R
2
y
SiO
(4-x-y)/2
  (1)
wherein A is —(CH
2
)
m
—OCOCR
1
═CH
2
wherein R
1
is hydrogen or a monovalent hydrocarbon group having 1 to 6 carbon atoms, and m is an integer of 1 to 5, R
2
is independently hydrogen or a monovalent hydrocarbon group having 1 to 10 carbon atoms, x is a number from 0.002 to 1.50, y is a number from 0 to 3.0, and the sum of x and y is from 1.5 to 2.5, which can be obtained by equilibration reaction between a first organopolysiloxane of the following average compositional formula (3):
A
a
R
2
b
SiO
(4-a-b)/2
  (3)
wherein A and R
2
are as defined above, a is an integer from 1 to 3, b is an integer from 0 to 2, and the sum of a and b is from 1 to 3, and a second organopolysiloxane of the following average compositional formula (4):
R
3
c
R
4
d
SiO
(4-c-d)/2
  (4)
wherein R
3
is hydrogen or a monovalent saturated hydrocarbon group having 1 to 6 carbon atoms, R
4
is independently a monovalent hydrocarbon group having 1 to 10 carbon atoms, c is an integer from 0 to 3, d is an integer from 0 to 3, and the sum of c and d is from 1 to 3, has a reduced content of siloxane components non-bondable with acryl functional groups and is fully compatible with other acrylic compounds. This is especially true with an organopolysiloxane having an acryl group at either end represented by the following average compositional formula (2):
wherein R
1
, R
2
and m are as defined above, and n is an integer of 100 to 1,000, which can be obtained by equilibration reaction between an organopolysiloxane dimer having an acryl group at either end represented by the following average compositional formula (5):
wherein R
1
, R
2
, and m are as defined above, and at least one of cyclic organopolysiloxanes of the following average compositional formulae (6) and (7):
wherein R
3
and R
4
are as defined above, each of p and q is an integer from 3 to 8. A resin composition having blended therein the acryl group-bearing organopolysiloxane compound defined above is successful in improving a gel fraction, which has never been achieved with conventional silicone-bearing acrylic resins, while maintaining physical properties inherent to silicone including a low Young's modulus, high elongation and high rupture strength.
DETAILED DESCRIPTION OF THE INVENTION
In one aspect, the invention provides a radiation-curable resin composition comprising (A) an organopolysiloxane having at least one acrylic functional group, preferably an acryl functional group at either end, and (B) a photopolymerization initiator. Upon exposure to radiation, the composition cures into a product having a gel fraction of at least 85% by weight, preferably 85 to 97% by weight, more preferably 90 to 97% by weight.
The term “gel fraction” used herein is determined by extracting a cured resin with 2-butanone for 12 hours by Soxhlet extraction method, vacuum drying the residual resin at 100° C. for 2 hours, measuring the weight of the dry resin, and dividing it by the weight of the initial resin. A cured resin having a low gel fraction is undesirably reduced in strength. A gel fraction of at least 85% by weight ensures that a resin undergoes minimized changes of elongation and strength with the lapse of time.
The organopolysiloxane (A) providing a gel fraction in the above range is preferably an organopolysiloxane having acryl functional groups represented by the following average compositional formula (1), more preferably an organopolysiloxane having an acryl group at either end represented by the following average compositional formula (2).
A
x
R
2
y
SiO
(4-x-y)/2
  (1)
In the formulae, A is —(CH
2
)
m
—OCOCR
1
═CH
2
wherein R
1
is hydrogen or a monovalent hydrocarbon group having 1 to 6 carbon atoms, and m is an integer of 1 to 5, R
2
is hydrogen or a monovalent hydrocarbon group having 1 to 10 carbon atoms, the R
2
groups may be identical or different, letter x is a number having a value of 0.002 to 1.50, y is a number having a value of 0 to 3.0, and the sum of x and y is from 1.5 to 2.5 (i.e., 1.5≦x+y≦2.5), and n is an integer of 100 to 1,000.
Herein, R
1
is hydrogen or a monovalent hydrocarbon group, typically alkyl, having 1 to 6 carbon atoms, preferably hydrogen or methyl. Most desirably R
1
is a hydrogen atom from the standpoint of a reaction rate during radiation curing.
R
2
is hydrogen or a monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably straight, branched or cyclic alkyl groups of 1 to 10 carbon atoms, especially 1 to 6 carbon atoms, aryl groups of 6 to 10 carbon atoms, and aralkyl groups of 7 to 10

Affiliated with

Also associated with

Rating

Radiation-curable resin compositions does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Radiation-curable resin compositions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Radiation-curable resin compositions will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2483852