WO1981000569A1

WO1981000569A1 - A polymerizable water-based composition

Info

Publication number: WO1981000569A1
Application number: PCT/AU1980/000056
Authority: WO
Inventors: K Jones; K Jarrett
Original assignee: Staybond Pty Ltd; K Jones; K Jarrett
Priority date: 1979-08-31
Filing date: 1980-08-29
Publication date: 1981-03-05
Also published as: JPH0379362B2; GB2070047A; DE3049830T1; GB2070047B; DE3049830C2; JPS56501404A

Abstract

Polymerizable compositions based on aqueous monomers. The composition may be an ink or other coating composition, a binding composition or a foaming composition. The invention also discloses related methods of coating, binding and foaming.

Description

The present invention relates to water-based compositions, and methods of operation using the water-based compositions. Whilst initially developed in relation to inks and related printing methods, the composition and method of the invention have been found to be equally efficacious in other coating, and in binding, environments.

Most current coatings and binders consist of compositions which form a film or lattice as the carrier therefor evapor¬ ates. These compositions generally comprise inert dispersed solids or soluble substances of desired properties, which properties are obtained on evaporation. In printing appli¬ cations in particular, these properties (viz. film hardness, gloss, adhesion) must be achieved rapidly in order for the substrate to withstand high substrate velocity through the press. Thus enormous quantities of energy are required to be expended and "fast" organic solvents.are used, thereby introducing fire hazard and pollution problems. ^*

The use of water-based inks as a substitute for solvent- based products is not novel per se. Hitherto, such water- based inks were in the form of dispersion polymers. However, while water-based inks had potential advantages over solvent- based inks - such as cost savings, elimination of fire hazard, reduction in air pollution and more importantly the absence of a hydrocarbon base (hydrocarbons being subject to increas- ing shortages and subsequent price rises) - they also had numerous disadvantages such as difficulties with pigment dispersion, gloss, film thickness, curing time and flow characteristics which difficulties resulted in aqueous inks The present invention relates to water-based compositions, and methods of operation using the water-based compositions. Whilst initially developed in relation to inks and related printing methods, the composition and method of the invention have been found to be equally efficacious in other coating/ and in binding , environments.

Most current coatings and binders consist of compositions which form a film or lattice as the carrier therefor evapor¬ ates. These compositions generally comprise inert dispersed solids or soluble substances of desired properties, which properties are obtained on evaporation. In printing appli¬ cations in particular, these properties (viz. film hardness, gloss, adhesion) must be achieved rapidly in order for the substrate to withstand high substrate velocity through the press. Thus enormous quantities of energy are required to be expended and "fast" organic solvents are used, thereby introducing fire hazard and pollution problems.

The use of water-based inks as a substitute for solvent- based products is not novel per se. Hitherto, such water- based inks were in the form of dispersion polymers. However, while water-based inks had potential advantages over solvent- based inks - such as cost savings, elimination of fire hazard, reduction in air pollution and more importantly the absence of a hydrocarbon base (hydrocarbons being subject to increas- ing shortages and subsequent price rises) - they also had numerous disadvantages such as difficulties with pigment dispersion, gloss, film thickness, curing time and flow characteristics which difficulties resulted in aqueous inks based on dispersion polymers not being attractive.

Against this background, the principal object of the invention is seen as the provision of a water-based ink which obviates the disadvantages inherent in prior art aqueous inks as indicated above (without resurrecting the disadvan¬ tages associated with solvent-based inks) and which, at the same time, is inexpensive, easy to apply, and devoid of toxicity. Further objects include the provision of other water-based coating and binding compositions which (as our research developed) were found to be (i) superior to such compositions of the prior art, and (ii) within the ambit of our inventive concept. These will be elaborated hereafter.

Accordingly, in one broad aspect, the invention provides a polymerizable water-based composition comprising a primary component and an aqueous monomer system, wherein the said system comprises at least one water-soluble or water-miscible (or -dispersible) monomer; the composition being curable by radiation or otherwise.

In the foregoing system, a reactive monomer is used which is soluble in a very economical carrier viz. water. The water carrier imparts a fluidic mobility to the compo¬ sition. It is not necessary for this carrier to be removed by evaporation for the composition to attain its desired physical properties. The composition may be cured to a solid polymer, with carrier (or proportion thereof) in situ, by the application of radiation. The radiation may be of any type (.e.g. heat, U.V., I.R., electron beam, gamma and other radiations) which is able to initiate and sustain polymerizatio The expression primary component is defined- by refer¬ ence to the aspects of the invention in which the compositi and related methods, are applied. In its coating aspect, where the composition is applied to a suitable substrate, t component may include pigments, or dyestuffs or like coatin compounds_/ supplemented (or partially or wholly replaced as appropriate) by non-reactive water borne components. In other aspects of the invention, it may be an appropriate filler (the invention having application as a binder for various solids - and also as a foa able preparation) .

The nature and use of the composition for each such purpose along with other contemplated component ingredients, are elaborated in the ensuing description of preferred features of the invention. in its method aspects, the present invention firstly provides a method of coating on a suitable substrate. Broadly this method comprises the steps of applying the above-defined polymerizable water-based composition to a said substrate; and subjecting the so applied composition t curing (e.g. by exposure to heat, U.V., I.R., electron beam gamma or other radiation) , whereby the aqueous monomer syste reacts to form a hydrophobic polymer (the water present being rapidly lost e.g. by being absorbed into the substrat and/or by evaporation) . In a further aspect the invention provides a method of binding or foaming. In this aspect, t method comprises the steps of mixing the aforesaid aqueous monomer system with the appropriate primary component, and catalyst as and if required, and subjecting the resultant

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By controlling the rate and ultimate extent of water release, the resultant coating flexibility can be controlled. Further methods aspects of the invention will be set forth hereafter.

The invention will now be described with reference to the foreshadowed preferred forms thereof. It will be under¬ stood that such details are merely illustrative of the inven¬ tion, and hence are not to be limitatively construed. In its coating aspects, the low viscosity composition, in addition to the aqueous monomer system and the appropriate coating (e.g. pigment, dyestuff et al) component - will invariably contain a said catalyst to promote curing, and may also contain one or more of the said non-reactive water borne components (such as emulsions, dispersed or dissolved resins, polymers, and the like) . The composition will generally be formulated in the light of such factors as the type of coating required and the type of radiation to be employed. For example, when curing is carried out by means of electron beam radiation, a catalyst is not required.

In its binding and foaming aspects, the aqueous monomer system is invariably associated, as required, with filler(s) , plasticizer(s) , catalyst(s) and foaming agent(s) . The filler may be selected from those set forth hereafter. This aspect features a dispersion of solid in mobile fluid, the composition being curable as by radiation or by the use of (e.g.) free radical-producing catalysts.

The especially preferred aqueous monomer system is^' a one-part monomer system; however, a two- or three-part monomer system may also be used. These are described in further detail below.

The water-soluble or -miscible (or -dispersible) monomer may be selected from any conventional monomer.

Examples of such monomers include acrylic and methacrylic acid and derivatives thereof; acrylamide and N-methylol acrylamide and derivatives thereof; modified acrylamide, especially acrylamide modified with aldehydes and the like to ultimately form polymerization-condensation type polymers; and pyrrolid- ones such as vinyl pyrrolidones and mixtures thereof.

The catalysts (mentioned above) are generally conven¬ tional free radical-producing components which are chosen in accordance with the type of radiation (heat, U.V. , et al) , or other curing, to be employed. Their purpose is to initiate and/or increase the rate of reaction. The catalysts may be (e.g.) U.V. photoinitiators or free radical-producing catalysts (either alone or as redox couple) or other type - and, as specific examples, there are mentioned persulphates (e.g. ammonium persulphate), peroxides, AZDN, together with various reducing agents such as sodium bisulphite, sodium formaldehyde sulphoxylate , and zinc formaldehyde sulphoxy- late. The benzildimethylketal compound known as "IRGACURE 651" (a Registered Trade Mark of Ciba-Geigy) is a typically suitable compound for promoting (.the initiating effect of) U.V. radiation. Where curing is effected by electron beam radiation a catalyst is not required. The catalyst may be added simultaneously with the monomer. Alternatively, it may be added subsequently together with other optional conventional additives (such as fillers) , or as prior application to the substrate upon which the composition is subsequently to be applied. The plasticizer, which functions to improve the flex¬ ibility of the cured composition, is preferably a humectant plasticizer. Typical examples are calcium and zinc chloride, sugar, glycerine and glycols; other examples include synthetics such as starch and starch derivatives, polyvinyl alcohol, gum and modified cellulose. The aforesaid non- reactive water borne components, which are exemplified by emulsions or dispersed or dissolved resins or polymers, do not take part in the polymerization reaction. However, they are easily dispersed or dissolved in the compositions and function to improve the end properties.

In the printing ink applications, where the coating weight is very low, oxygen inhibition can be a performance problem. In one optional form of the invention, we overcome the problem by externally applying nitrogen to the printed substrate. Alternatively we may add to the system chemicals which form in situ carbon dioxide or nitrogen during poly¬ merization, such chemicals being for example latent CO-, producing alkali (e.g. basic carbonate for an acidic form¬ ulation) . In two-part monomeric systems, acid-base reactants may be used, such as hydrochloric acid and basic carbonate (e.g. sodium bicarbonate or ammonium carbonate) . In the one-part monomeric system, a basic carbonate alone may be used. The monomer system during reaction turns acid and thus subsequently reacts with the carbonate alkali to ultimately form C0₂.

Amplifying in respect of the monomeric systems, a three-part system may comprise a first water-soluble or 5 -miscible (or-dispersible) monomer part, a second part including plasticizer (e.g. a low-cost carbohydrate plasti¬ cizer) , an acid and a free-radical catalyst, and a third part comprising a plasticizer, a C0₂ inclusive alkali and a reducing redox couple. The three parts may be mixed and,

10 when so mixed, foaming and polymerization take place.

A two-part monomer system may have one part including a water-soluble or -miscible (or -dispersible) monomer, a plasticizer (e.g. a carbohydrate plasticizer) , a CO., inclusive alkali and a U.V. catalyst, and a second part consisting of

L5 carbohydrate plasticizer solution, and acid (the parts may be alternatively constituted as indicated in the detailed examples below) . When such parts are mixed and cured (e.g. by exposure to U.V. light) , polymerization, with formation of C0₂ gas, takes place. The gas so formed produces foaming

20 and oxygen is sparged.

With two- and three-part systems, foaming commences immediately the components are combined, whereas the poly¬ merization reaction takes longer - and thus the formed C0₂ bubbles are prematurely released. These systems are there¬ fore not as suitable for printing (or other) thin film applications as a one-part monomer system - which is especially preferred. Such a system may comprise a water- soluble or -miscible (or -dispersible) monomer, a latent

G ∑FI .„~~V7ΪPO~~ , C0₂ producing alkali, a humectant plasticizer and^' a U.V. catalyst. Upon exposure to a U.V. light source, polymer¬ ization commences, wherein an acidic environment is produced which in turn reacts with the alkali to form.C0₂. Prior to gassing commencing, polymerization occurs and formed gas is entrapped in a viscous polymer mucilage.

As indicated above, the coating component may be a dyestuff or pigment. These terms encompass water-soluble dyestuffs, aqueous pigment dispersions, and such materials as clays (e.g. china clay) and whiting. Other additivies - such as surfactant(s) (to aid dispersion), plasticizers (as indicated above) and viscosity controllers - may also be present as required.

Of those specifically mentioned heretofore, the especially preferred water-soluble or -dispersible monomers are acrylamide or N-methylol derivatives thereof. The con¬ ventional method for producing acrylamide is by hydrating acrylonitrile in the presence of sulphuric acid and water at 100 C, thus forming acrylamide sulphate and subsequently removing the sulphate and recovering pure acrylamide. In the present invention, the acrylamide may be produced by reacting acrylonitrile in the presence of hydrochloric acid to produce acrylamide chloride. By further addition of calcium hydroxide, calcium chloride is formed. The production of calcium chloride in this way is a convenient and inexpensive means of eliminating an otherwise unwanted by-product.

Acrylamide monomer as such (without further modification) is suitable as the water-soluble or dispersible monomer. However, modification of the acrylamide to the N-methylol derivatives adds even greater latitude to the formulation. The reaction of acrylamide with various aldehydes will form the corresponding methylol products and then .upon polymeriz ation the condensation reaction occurs simultaneously.

Formaldehyde (in the form of paraformaldehyde) is the parti ularly preferred reactant. The percentage solids is not critical.

Turning to the other (non-ink) water-based compositio foreshadowed heretofore, the prior art problems have again been overcome. Thus, in the field of paper and board sizin the principal problem encountered with the use of prior art acrylic emulsions was in the difficulty in removing the residual carrier, which resulted in the use of considerable energy during the drying operation. This problem is obviat by the present invention. Where the compositions of the invention are used as alternative coating compositions, suc compositions may be applied to a substrate using convention techniques and cured using such methods as described above. Typical substrates includepaper, board, wood, metal masonry glass, cloth synthetic surfaces and the like.

In binding applications of the invention, the compo¬ sitions may contain conventional solid carriers (fillers) a primary component. As solid carriers there may be mentione (ground) natural minerals, such as clays, talc, chalk, kaol quartz, diatomaceous earth and the like and (ground) synthe minerals such as alumina and silicates and the like. There may also be mentioned (crushed and fractionated) natural ro

_OMP _Vrt> IP such as marble, calcite pumice and the like as well as (granules of) organic materials such as solid synthetic poly¬ mers (e.g. polyethylene) , sawdust and vegetable fibres and organic pulp such as paper pulp and the like. 5 The water-soluble or -miscible (or -dispersible) monomer acts as a binder for such solid carriers. In one such embodiment of the present invention, methylol acrylamide together with a heat induced free radical catalyst acts as a binder for sand and/or marble chips. When moulded into a 0 desired shape and cured by means of heat, e.g. hot platen press, heated rollers, oven dielectric, and the like, such composition cures through a polymerization condensation type reaction to form hard, dimensionally stable imitation brick. Sawdust and/or paper may be substituted for the sand and 5 marble and marble chips and the resulting composition cured by means as described above.

In the above-mentioned cases, the advantage of the process lies in the considerable energy savings resulting from the polymerization reaction which is exothermic. 0 The above-mentioned carrier(s) can, of course, be augmented. Thus, plasticizer(s) , stabilizer(s) , dyestuff(s) and the like may also be added.

In the foaming applications of the invention, the com¬ position may be based on water-soluble monomer, plasticizer(s) 5 and foaming agent(s) . The water-soluble monomer may be in the form of a two-part monomeric system, the parts (including monomer, plasticizer, catalyst et al) being as constituted heretofore or as specifically exemplified in the subsequent examples. Alternatively, a three-part system may comprise a first monomer part, a second part incorporating a plasti¬ cizer, an acid and a free radical catalyst, and a third par incorporating plasticizer, C0₂ inclusive alkali and reducin redox couple. The components may be formulated to equal volume and mixed - with resultant simultaneous foaming and polymerization. The foam composition thus produced (where air may act as a filler material) has use, inter alia, in insulation environments and as a protective coating for animals.

The invention will now be described, in greater detai with reference to specific working examples. The examples illustrate all aspects of the invention. Unless specifical indicated to the contrary, parts are by weight. Where implementation of the examples has involved the use of conventional proprietary compositions - which, in the art, are obtainable under, and normally identified by, trade or like names - these compositions have been so identified and in conjunction therewith, have been identified, (as far as possible), by reference to their general chemical con¬ stitution. Similarly, where known commercial equipment is used Ce.g. as the source of radiation in the specific examples) , such equipment is identified in the manner in which it is known in the art.

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V. Example 1

This example illustrates a three-part monomer system. The first part comprises 100 parts by weight of N-methylol acrylamide -(.60%) (hereinafter sometimes referred to, for convenience, simply as N.M.A.). The second part was formed from.50 parts by weight water, 45 parts by weight sugar, 3.5 parts by weight hydrochloric acid and 1.5 parts by weight ammonium .persulphate and a third part from 50 parts by weight water, 45 parts by weight sugar, 1.5 parts by weight sodium formaldehyde sulphox late, and 3.5 parts by weight sodium bicarbonate. The three parts were mixed together in equal proportions. Example 2

This example illustrates a two-part monomer system. The first part was produced by mixing 37.5 parts by weight water, 52 parts by weight calcium chloride, 2 parts by weight hydrochloric acid, 8 parts by weight acetone co-solvent, and 0.5 parts by weight of the catalyst known as "IRGACURE 651" Csee.heretofore) . The second part was produced by 87 parts by weight 60% N.M.A. , 5 parts by weight ammonium hydroxide and 8 parts by weight ammonium carbonate and the two parts mixed together. Example 3

This example further illustrates a two-part monomer system. The first part was formed by mixing 66 parts by weight 60% N.M.A. , 28 parts by weight 50% sugar/water solution 0.3 parts by weight "IRGACURE 651" and 5.7 parts by weight of sodium bicarbonate. The second part was produced by

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. • r.„ W "VIUPCOKJ « mixing 90 parts by weight 50% sugar/water solution, 9 parts by weight acetone, 0.3 parts by weight "IRGACURE 651" and 0.7 parts by weight acetic acid. The two parts were then mixed together. Examples 4-7

These examples illustrate several one-part monomeric systems. For convenience, the systems are presented in tabular form.

In the following examples, the compositions and relat methods of the invention are illustrated. As elsewhere, parts are by weight. Examples 8 to 13 illustrate the print ing and other coating aspects of the invention, whilst ⁵ Examples 14 and 15 illustrate the binding and foaming aspec Example 8

Gravure ink (black) : cured by U.V. radiation. Composition: 60% N-methylolacrylamide (water-soluble monomer) 52.0

10 Primal 1-94 (alkali soluble polymer emulsion) 40.0

Continex N326 (carbon black pigment) 5.0 aqueous ammonia 1.0

Irgacure 651 (photoinitiator catalyst) 2.0

The Primal 1-94 is neutralized with aqueous ammonia,

^•*--> and then added slowly, with stirring, to the N.M.A. solutio A transparent solution results. The pigment and photo- initiator catalyst are dispersed into this medium, using a bead mill, at a temperature less than 40°C. Printing, on a paper substrate, is effected using a rotogravure

20 press. As indicated above, curing is by U.V. radiation

(U.V. Curing Unit (H type bulb) of Fusion Systems Corp.) . Example 9

Flexographic ink (black) for reclaimed paper: cured by U.V. radiation.

25 Composition:

60% N-methylolacrylamide (water-soluble monomer) 50.0 P.V.P. K-30 (viscosity controller) 0.5 alkanate 3SN5 (surfactant) 0.05 Continex N326 (carbon black pigment) 7.45 water 40.0

Irgacure 651 (photoinitiator catalyst) 2.0

The P.V.P. K-30 (polyvinylpyrrolidone) is dissolved in the N.M.A. solution, and the surfactant and water are then added. The pigment and photoinitiator catalyst are dispersed as in Example 8. Printing upon the paper sub¬ strate is effected with a flexographic press. U.V. curing is carried out as in Example 8. Example 10

Clear coating for printed paper: cured by U.V. radiation. Composition: 60% N-methylolacrylamide (water-soluble monomer) 30.0 Primal HA-16 (polymer emulsion) 30.0

Irgacure 651 (photoinitiator catalyst) 1.0 acetone 5.0 water 34.0

The polymer emulsion is stirred into the N.M.A. solution and water is added. The photoinitiator catalyst is dissolved in the acetone, following which the dissolved catalyst is slowly added to the N.M.A. solution with high speed mixing. Coating is effected per medium of a roll coater with doctor blade. Radiation is carried out as in Examples 8 and 9. Example 11

Transparent coating for clay coated paper: cured by electron beam radiation. Composition:

60% N-methylolacrylamide (water-soluble monomer) 50.0 33% Platamid M1255 (water-soluble copolyamide resin) 48.0 Eriosin blue dye 2.0 The polyamide and N.M.A. solutions are mixed, and the dye is dissolved therein. Coating is effected as in Example 10. Electrom bean radiation is carried out using a 250kV electron accelerator. Example 12 Clay coating for paper: cured by U.V. radiation.

Composition:

60% N-methylolacrylamide (water-soluble monomer) 48.0 Eckalite clay 50.0

Irgacure 651 2.0 The photoinitiator catalyst is dispersed in N.M.A. solution, using a bead or sand mill. Thereafter, the clay is dispersed in a similar manner. Coating is carried out as in Examples 10 and 11 (alternatively, the doctor blade can be substituted by an air knife) . U.V. radiation is carr out as in Examples 8 to 10. Example 13

Glazing upon ceramic tiles: cured by U.V. radiation. Composition: 60% N-methylolacrylamide (water-soluble monomer) 35.0 powdered red glazing glass (pigment) 40.0

Sandoray 1000 (photoinitiator catalyst) 1.0 acetone 4.0 water 10.0 The N.M.A. solution is diluted with water, the photo¬ initiator catalyst is dissolved in acetone, and the former is added to the latter with vigorous mixing. Into the resultant medium, the glazing compound is dispersed (with continued vigorous mixing) . Silk screen printing is effected, and the U.V. radiation is performed as above. Example 14 (see Example 2)

Foaming mix: cured by U.V. radiation. Composition: Part A: 60% N-methylolacrylamide 87.0 aqueous ammonia 5.0 ammonium carbonate 8.0

Part B: water 37.5 calcium chloride 52.0 hydrochloric acid (10M) 2.0 acetone 8.0

Irgacure 651 0.5

In relation to Part A, the aqueous ammonia and N.M.A. solution are mixed, and the ammonium carbonate is dissolved therein. In relation to Part B, the calcium chloride plasti¬ cizer is dissolved in water, hydrochloric acid is added, the photoinitiator catalyst is dissolved in acetone, and the solutions are mixed with rapid stirring. Foaming commences when the two parts are mixed together. Radiation may be effected by direct sunlight. Example 15

Artificial brick: heat cured. Composition:

6.^Q% N-methylolacrylamide 20.0 ammonium persulphate - 0.1 sand filler 79.9 The ammonium persulphate catalyst is dissolved in the N.M.A. solution, following which the filler is dispersed therein. Production is carried out by continuous extrusion into an oven at 110°C for five minutes. Radiation is effected thermally (from the oven) . In conclusion, it is reiterated that the preceding performance details, of the ink and other compositions and the printing and other methods, are not to be limitatively construed. Thus the individually specified examples (of the components and monomers) may be replaced by functional equivalents, the effect of oxygen inhibition need not be countered, and so on. As long as the basic inventive criteria - predicated upon the novel application of water- soluble monomers in novel compositions and related methods - are observed, matters falling therewithin may be varied in accordance with situational requirements.

Claims

Claims :

1. A polymerizable water-based composition comprising a primary component and an aqueous monomer system wherein the said system comprises at least one water-soluble or water-miscible or water-dispersible monomer, the composition being curable by radiation or otherwise.

2. A composition as claimed in claim 1 wherein the aqueous monomer system is a one-part system.

3. A composition as claimed in claim 1 or 2 wherein the monomer is acrylamide or the N-methylol derivative thereof.

4. A composition as claimed in any one of the preceding claims wherein curing is effected, in the presence of a photoinitiator catalyst, by U.V. radiation.

5. A composition as claimed in any one of claims ,1 to 3 wherein curing is effected by electron beam radiation.

6. A composition as claimed in any one of the preceding claims wherein such composition is a coating composition which is adapted to be applied to a substrate.

7. A composition as claimed in claim 6 wherein the primary component comprises a dyestuff or pigment.

8. A composition as claimed in any one of claims 1 to 5 wherein such composition is a binding composition, and the primary component comprises at least one appropriate filler.

9. A composition as claimed in any one of claims 1 to 5 wherein such composition is a foaming composition and the primary component comprises at least one plasticizer.

10. A water-based composition substantially as herein described with reference to any one of the foregoing specific examples thereof.

11. A method of coating upon a suitable substrate which comprises the steps of applying, to a said substrate, a composition as claimed in claim 6 or 7, and subjecting the so-applied composition to curing whereby the aqueous monome system is polymerized.

12. A method as claimed in claim 11 wherein the substrate is selected from paper, board, wood, metal masonry, glass, and cloth synthetic surfaces.

13. A method which comprises the steps of mixing the monomer system with a said primary component, as appropriat and subjecting the resultant mix to curing whereby the said system is polymerized.

14. A method substantially as herein described with refer to any one of the foregoing specific examples thereof.

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