Radiation polymerizable compositions

Details Radiation polymerizable compositions Radiation polymerizable compositions

2002-03-27

2004-07-27

Berman, Susan (Department: 1711)

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

Synthetic resins

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

C522S081000, C522S088000, C522S104000, C522S120000, C522S121000, C522S141000, C522S142000, C523S106000, C427S500000, C427S514000

Reexamination Certificate

active

06767933

ABSTRACT:

The present invention relates to radiation polymerisable compositions and in particular to compositions curable with ultraviolet light (UV) or electron beam (EB) radiation or elemental sources such as cobalt with its gamma rays, strontium 90 or caesium 137 and the like.
Radiation polymerisable compositions are used in a range of applications including coatings, inks and films. Radiation polymerisable compositions typically contain acrylate or methacrylate monomer and a prepolymer and when UV curing is to be used a photoinitiator or photosensitiser is required.
Attempts have been made to increase curing efficiency and reduce the need to use photoinitiators by increasing the sensitivity of compositions however in many cases this reduces their stability and also reduces the options available to the end user.
The present invention provides a radiation polymerisable composition comprising:
(A) a donor/acceptor component for forming a charge transfer complex said component being selected from the group consisting of:
(i) a bifunctional compound having an electron donor group and an electron withdrawing group and a polymerisable unsaturated group;
(ii) a mixture of (a) at least one unsaturated compound having an electron donor group and a polymerisable unsaturated moiety; and (b) at least one unsaturated compound having an electron acceptor group and a polymerisable unsaturated group; and
(B) a binder polymer composition.
The binder polymer in contrast to the donor acceptor composition will not interact with the components of the donor/acceptor complex to form a change transfer complex.
In contrast with the donor/acceptor component which has a relatively low molecular weight, typically if no more than about 1100 and has a high proportion of unsaturation to readily form donor accepter charge transfer complexes the binder polymer has a significantly higher molecular weight and low level of residual unsaturation. The molecular weight of the binder polymer is higher than 1100, preferably greater than 2000 or a highly viscous material and most preferably greater than 5000. The binder polymer is typically a solid or a highly viscous material at room temperature though in use in the composition of the invention it will typically be dissolved in the other components. The binder polymer does not readily complex with donors such as triethylene glycol divinyl ether (DVE-3) or acceptor to provide a cured film on its own in the absence of a donor/acceptor complex.
Suitable donor/acceptor complexes for use in the present invention are disclosed in U.S. Pat. No. 5,446,073 by Jonsson et al. We have found that such complexes in the absence of a binder polymer can not be adequately controlled for commercial use. Further their use generally requires newly developed excimer lasers which are not commonly used in current industrial UV curing system.
The compositions of the invention by contrast allow rapid cure and yet allow their use to be controlled to provide useful industrial application in many cases allowing UV curing in the absence of photoinitiators and yet are relatively inexpensive.
The compounds employed to provide the charge transfer complex can be ethylenically unsaturated or acetylenically unsaturated. When the complex is from two or more compounds, typically, the double bond molecular ratio of the electron donating compound to the electron withdrawing compound is about 0.5 to about 2, and more typically about 0.8 to about 1.2 and preferably about 1:1. In contrast the binder polymer has a ratio typically less than 0.5 and preferably no more than 0.3. It will be understood that the double bond ratio of the binder may be different in different donor/acceptor complexes and remain inert with respect to donor/acceptor interaction under the conditions used. The complexes employed for the present invention are stable under normal conditions.
In particular, the compositions do not spontaneously polymerise. The strength of both the donor and acceptor groups are not to the high level that could result in spontaneous polymerisation. Instead they polymerise under the influence of the necessary ultraviolet light or ionising radiation.
The charge transfer complex formed from the donor/acceptor is capable of absorbing light having a wave-length that is longer than the longest wavelength in the spectrum of light absorbed by the individual donor and withdrawing groups used to form said complex. The ultraviolet light is thus absorbed by the charge transfer complex rather than by individual groups or components forming said complex. This difference in absorptivity is sufficient to permit the polymerisation of said complex to proceed by absorbing light.
In the terms of commercial utilisation, the complex typically absorbs light which has a wavelength that is about 10 nanometers longer than the shortest wavelength in the spectrum of light absorbed by the individual donor and withdrawing groups or components. This facilitates tailoring the spectral output from the ultraviolet light source to assure the desired polymerisation.
The complex should, on initial exposure to UV, lead to radicals which can initiate free radical polymerisation. In addition to UV, the polymerisation can also be achieved by the use of ionising radiation such as gamma rays or electrons from an electron beam machine. This process can be achieved to workable radiation doses and in air.
The electron withdrawing and electron donating compounds can be represented by the following formula:
(A)
n
—R and (D)
n
—R, respectively;
wherein “n” is an integer preferably from 1 to 4, “R” is the structural part of the backbone. “A” is the structural fragment imparting acceptor properties to the double bond.
This is selected from the groups outlined in the Jonsson et al Patent (U.S. Pat. No. 5,446,073) and consists of maleic diesters, maleic amide half esters, maleic diamides, maleimides, maleic acid half esters, maleic acid half amides, fumaric acid diesters and monoesters, fumaric diamides, fumaric acid monoesters, fumaric acid monoamides, exomethylene derivatives, itaconic acid derivatives, nitrile derivatives of preceding base resins and the corresponding nitrile and imide derivatives of the previous base resins particularly maleic acid and fumaric acid.
Typical electron withdrawing compounds are maleic anhydride, maleamide, N-methyl maleimide, N-ethyl maleimide, N-phenyl maleamide, dimethyl maleate, diethyl and dimethyl fumarate, adamantane fumarate and fumaric dinitrile. Analogous maleimide, N-methyl maleimide, N-ethyl maleimide, phenyl maleimide and their derivatives can also be used.
Examples include polyethylenically unsaturated polyesters, for example, polyesters from fumaric acid and maleic acid or anhydrides thereof.
“D” is the structural fragment imparting donor properties to the double bond and is selected from the groups outlined below. Examples of component D are provided in the Jonnson et al U.S. Pat. No. 5,446,073 and includes vinyl ethers, alkenyl ethers, substituted cyclopentanes, substituted cyclohexanes, substituted furanes or thiophens, substituted pyrans and thiopyrans, ring substituted styrenes, substituted alkenyl benzenes, substituted alkenyl cyclopentanes and cyclohexenes. In the styrene systems, substituents in the ortho- and para-positions are preferred. Unsaturated vinyl esters like vinyl acetate and its derivatives can also be used.
In addition, polyfunctional, that is, polyunsaturated compounds including those with two, three, four or even more unsaturated groups can likewise be employed.
With respect to the ethers, mono-vinyl ethers and di-vinyl ethers are especially preferred. Examples of mono-vinyl ethers include alkylvinyl ethers typically having a chain length of 1 to 22 carbon atoms. Di-vinyl ethers include di-vinyl ethers of polyols having for example 2 to 6 hydroxyl groups including ethylene glycol, propylene glycol, butylene glycol, 3 methyl propane triol and pentaerythritol.
Examples of some specific electron donating materials are monobutyl 4 vinylbutoxy carbonate, monophenyl 4 vinylbutoxy carbonate, ethyl vinyl d

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