WO2009068865A1

WO2009068865A1 - Novel resins suitable for printing inks and varnishes

Info

Publication number: WO2009068865A1
Application number: PCT/GB2008/003934
Authority: WO
Inventors: Martin John Thompson; Douglas Frederick Pavey; Louis Papaspyrou
Original assignee: Sun Chemical Ltd
Current assignee: Sun Chemical Ltd
Priority date: 2007-11-27
Filing date: 2008-11-25
Publication date: 2009-06-04
Anticipated expiration: 2010-05-27
Also published as: GB2455093A; GB0723219D0

Abstract

A reaction product of rosin modified with an ethylenically unsaturated polybasic acid and a further resin, the modified resin being esterified with a polyol, can be used as the major component of an ink or varnish. The further resin, conventionally a resole, is replaced by a dammar resin, preferably a fossil grade thereof.

Description

NOVEL RESINS SUITABLE FOR PRINTING INKS AND VARNISHES

The present invention relates to novel resins which incorporate dammar batu or similar gums, which can be used for printing inks and varnishes, and which are of particular use for offset printing, although they can also be used, with advantage, in printing inks for printing by other methods.

Oleoresinous varnishes, which are blends or reaction products of drying oils with resins, have been known since at least the early twentieth century [see, for example, "Coating and Ink Resins: A Technological Study" by W. Krumbhaar, published by Reinhold Publishing Corporation in 1947]. The simplest consist merely of an oil cooked with a resin, the reaction product of linseed oil with rosin being an example of this. Over the decades, this simple formulation has been modified and improved, and currently the varnishes used in offset printing inks typically contain a hard resin synthesised from gum rosin, modified with maleic anhydride and a resole, which is then esterified with a polyol, this type of formulation itself having been used for several decades [see, for example, The Printing Ink Manual, 2^nd Edition, edited by F.A. Askew et al., published in 1969 by W Heffer & Sons Ltd., pp 648-655].

The incorporation of a resole into the formulation has brought many advantages, such as the ability to increase the molecular weight of the resin while retaining its solubility. Resoles are prepared from phenol or a derivative thereof, such as an alkylphenol, and formaldehyde. There is however growing concern over the health and safety and environmental acceptability of these reagents. Thus, the alkylphenols are generally endocrine disruptors, t-butylphenol being harmful and corrosive, while formaldehyde is toxic and corrosive and a possible carcinogen. Obviously, every care is taken to ensure that residual reagent is not present in the finished product, and this has not generally been a concern; but these materials do present hazards along the supply chain, and inadvertent release into the environment, with potentially serious consequences, is always a possibility. It would, therefore, be highly desirable to eliminate their use completely.

It has, however, proven difficult to find a material that can replace the resoles, giving equivalent properties to the varnish, but without the health and safety and environmental concerns attaching to the resoles.

We have now surprisingly found that this desideratum can be achieved by the use of dammar resin, preferably of a fossil grade such as dammar batu. Further information on the dammar gums can be found in The Chemistry of Dammar Resin. J.S. Mills and A.E.A. Werner. Journal of the Chemical Society, 1955, pp 3132-3140 and "Printing Ink Technology" by E.A. Apps, published in 1958 by Leonard Hill

(Books) Ltd., pp 44-45, the disclosures of which are incorporated herein by reference.

Thus, the present invention consists in the reaction product of rosin modified with an ethylenically unsaturated polybasic acid and a further resin, the modified resin being esterified with a polyol, characterised in that the further resin is a dammar resin, preferably a fossil grade of dammar gum.

Rosin is a well-known, commercially available material. Chemically, it is mainly a mixture of C20 tricyclic fused-ring, mono-carboxylic acids, typically abietic acid. Various grades of rosin are available and may be used, including wood rosin, gum rosin and tall oil rosin. Rosin may be obtained from a number of countries, including the US, Canada, Portugal, China, Greece, Brazil, Spain and the Scandinavian countries, and there will be minor variations in properties between the different grades and the same grade from different countries. However, these are well known in the art and the skilled person knows well the adjustments that need be made to accommodate the different grades and nationalities of rosin.

For the avoidance of doubt, the term "rosin", as used herein, refers to rosin from any source, including tall oil rosin, gum rosin and wood rosin, or country. The term "rosin" also includes treated rosin, which may have been treated, for example, by disproportionation and/or hydrogenation reactions. The term "rosin" also includes dimerised rosin. These materials are all well known in the art, as is their use in coating compositions, such as printing inks and varnishes. Rosin is typically characterized by its acid number, and rosins having acid numbers ranging from about 160 to about 180 mg KOH/ gram are preferred for use in the present invention.

The ethylenically unsaturated polybasic acid or derivative thereof is a compound capable of undergoing a Diels-Alder reaction with the rosin. Such compounds are well known in the art and any commonly used in the art may equally be used in the present invention. Examples of suitable ethylenically unsaturated polybasic acids include: maleic acid, fumaric acid and itaconic acid (methylenesuccinic acid), of which maleic acid is preferred. In place of the acids themselves, appropriate reactive derivatives of the acids, such as the anhydrides or reactive esters, e.g. methyl and ethyl esters, may be used.

Examples of suitable polyols include ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylene glycol, glycerol, 2,2-propanediol, polyethylene glycol, polypropylene glycol, polybutylene glycol, trimethylolpropane, di-trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, trimethylolethane, trimethylolpropane, mannitol and sorbitol, of which pentaerythritol is preferred.

Dammar is the name given to a group of resins obtained from trees of the Dipterocarpaceae family. Fresh dammar gum is obtained directly from the trees. However, this invention preferably uses the fossil grades of dammar, which are commonly said to be obtained from the ground, but are actually obtained from the region of the roots of the trees. Several types of so-called semi-fossil dammars are known, such as Daging, Batu, Sengai and Hitam, and any of these may be used in the present invention. However, the preferred dammar resins used are dammar batu. Surprisingly, these grades of dammar gum can act as a direct replacement for the resole resins and have the advantage of eliminating from use such unpleasant materials as the alkylphenols and formaldehyde. Moreover, being a natural product, this can be expected to be much more readily acceptable to today's increasingly discerning consumer. The fossil grades of these gums are derived from fresh gums by natural processes, which can be replicated synthetically, and so the terms "fossil" and "semi- fossil" cover such grades of gum whether derived by natural or synthetic processes. The preferred order of reaction is rosin plus polybasic acid, then add the dammar gum and finally add the polyol. Since the first of these reactions has an optimum reaction temperature lower than that of the second and third reactions and the second reaction has an optimum reaction temperature lower than that of the third reaction, this reaction order allows the reactions to be carried out, as is preferred, as a one pot reaction (i.e. without intermediate isolation or purification of intermediate products) and without unnecessary cooling or heating, by steadily raising the temperature as the reactions proceed. However, since the dammar gum is a straight replacement for the resole used in the prior art, any order of reaction used in the prior art may equally be used here.

Although not essential, the reaction may be carried out in the presence of a solvent, if desired. If used, a hydrocarbon, such as xylene, may be used as the solvent. However, in most cases, a solvent will not be needed, and is therefore best avoided.

The temperature at which the reactions are carried out is not critical to of the present invention. In general, the reactions are carried out at temperatures within the range from 180 to 270°C. However, as noted above, the reactions are preferably carried out at steadily increasing temperatures, as is well known in the art. By way of example, the reaction of the rosin with the polybasic acid may take place at a temperature in the range from 180 to 190°C; the reaction of this product with the dammar gum may take place at a temperature from 200 to 250⁰C; and the reaction with the polyol may take place at a temperature in the range from 250 to 27O⁰C.

In general, the final reaction, that with the polyol, is carried out until the desired acid value, preferably from 15 to 50 mg KOH/ gram, more preferably from 15 to 30 mg KOH/ gram, is achieved.

The proportions of the various reagents may vary widely, as is known for the comparable resole-based resins. However, in general, we prefer from 30 to 80%, more preferably from 45 to 60%, by weight of rosin; from 1 to 10%, more preferably from 4 to 6%, by weight of polybasic acid; from 10 to 40%, more preferably from 25 to 35%, by weight of dammar gum; and from 5 to 20%, more preferably from 7 to 15%, of polyol. The resulting resins may be used for the formulation of various coating compositions, particularly inks and varnishes, as a direct replacement for the known resole-based resins.

Thus, the present invention also provides a coating composition comprising a resin of the present invention and a solvent therefor, and optionally a colorant, such as a pigment or dye.

The invention further provides a coating method in which a substrate is coated with a coating composition of the present invention.

The solvent may be any such material used in the prior art. However, a drying oil, such as linseed oil, tung oil, poppy seed oil, perilla oil or walnut oil, is preferred. However, in some instances, those formulations which are rich in semi-drying oils may have sufficient drying potential to exclude the need for a drying oil.

Examples of other solvents include the alkyl esters of semi-drying oils such as soya, rapeseed, sunflower, peanut, sesame and safflower oil, preferably the methyl esters (e.g. methyl soyate), including also those solvents derived from mixed vegetable esters solvents (e.g. of rapeseed, soya and palm ), which may include small proportions ofnon drying oils.

Other solvents which may be used include a mineral oil distillate preferably having a boiling range within the limits 200°C - 320°C, and toluene.

Where the composition of the present invention is to be used as an ink, it will include a pigment or dye. There is no restriction on the nature of these, and any such material commonly used in the prior art may equally be used here.

The coating compositions of the present invention are especially suited for varnishes and inks, especially printing inks, including lithographic inks and especially inks for use in offset litho printing. These typically comprise, as additional components to those referred to above, one or more of stabilisers, plasticisers, pigments, waxes, slip aids, levelling aids, adhesion promoters, surfactants and fillers, for example as described in "Printing Ink Manual", fourth edition, Leach R. H. et al (eds.), Van Nostrand Reinhold, Wokingham, (1988), the disclosure of which is incorporated herein by reference.

The invention is further illustrated by the following non-limiting Examples.

EXAMPLE 1

Dammar Hard resin - typical formulation

Components:

Chinese Gum Rosm 54.6%

Maleic Anhydride 5.5%

Dammar Batu 30.0%

Pentaerythritol 9.75%

Calcium Oxide 0.11%

Magnesium oxide 0.04%

Total 100.0%

A manufacturing loss of 5% by weight is expected.

The resin was manufactured by heating the gum rosin to 180°C under an atmosphere of inert gas (nitrogen) and then reacting it via a Diels Alder reaction with the maleic anhydride. The temperature was raised to 200°C, and dammar batu was added portionwise. After ¹A hour at 200°C, the temperature is raised to 210°C, and pentaerythritol was added. Esterification was carried out at 260°C until an acid value below 30mg KOH/ gram was achieved.

EXAMPLES 2 TO 6

Dammar hard resin formulations and properties

A variety of dammar-based resins were prepared, following the procedure described in Example 1, but changing the relative amounts of the components and the target acid value. The materials used are summarised in the following Table 1. Table 1

* Weight average molecular weight by gel permeation chromatography (GPC) T Number average molecular weight ϊ Dispersability index = ratio of Mw to Mn GPC conditions:

Viscotek VEl 122 pump flowing at lml/min THF Gynkotek GTl 03 degasser

Kontron 360 autosampler

Polymer labs columns; 2 x mixed bed C

Polymer lab polystyrene standards - 100OK, 500K, 165K, 7OK, 2OK, 10K, 5K, 2K and 0.6K

Viscotek 250 Dual detector which includes refractive index and viscometry.

Samples prepared at 1% in THF, filtered and injected at lOOμl.

EXAMPLE 7

Varnish formulation

Dammar hard resin 45.3%

Linseed oil (alkali refined) 12.4%

Methyl Soyate (Cargill) 19.3%

Soybean Oil (alkali refined) 22.7%

Anti oxidant (BHT Sigma Aldrich) 0.3%

Total 100.0% The resin, linseed oil, methyl soyate and soybean oil were heated to 180°C until mixed. The antioxidant was then added as a 5% by weight solution in methyl soyate, and the temperature was raised to 185°C. The varnish was held at 185°C until the heptane tolerance was 35-40 mis.

EXAMPLE 8

Varnish properties

The properties of the varnishes prepared as described in Example 7 are shown in the following Table 2. Table 2

EXAMPLE 9

An offset ink was prepared using a varnish prepared as described in Example 7, with the resin of Example 1.

Components:

Varnish 55.0% Cyan pigment 26.0%

Antioxidant (the same as that in Example 1.0% 2)

Hydrocarbon distillate (aromatic content 3.5% -1%; bp range 240°-270°C)

Additives and driers 12.5%

Total 100.0

The properties of this ink were compared to a standard cyan heatset ink and to a standard sheetfed offset ink. The properties are shown in the following Table 3. Table 3

The Example 9 ink was found to have drying properties similar to the standard inks to which it was compared.

Claims

CLAIMS:

1. A reaction product of rosin modified with an ethylenically unsaturated polybasic acid and a further resin, the modified resin being esterified with a polyol, characterised in that the further resin is a dammar resin.

2. A product according to Claim 1, in which the further resin is a fossil grade of dammar.

3. A product according to Claim 2, in which the further resin is a semi-fossil grade of dammar.

4. A product according to Claim 3, in which the dammar is Daging, Batu, Sengai or Hitam.

5. A product according to Claim 4, in which the dammar is dammar batu.

6. A product according to any one of the preceding Claims, in which the rosin has an acid number ranging from about 160 to about 180 mg KOH/ gram.

7. A product according to any one of the preceding Claims, in which the ethylenically unsaturated polybasic acid is: maleic acid, fumaric acid or itaconic acid or a reactive derivative thereof.

8. A product according to Claim 7, in which the ethylenically unsaturated polybasic acid is maleic acid.

9. A product according to any one of the preceding Claims, in which the polyol is ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, Methylene glycol, tetraethylene glycol, trimethylene glycol, glycerol, 2,2-propanediol, polyethylene glycol, polypropylene glycol, polybutylene glycol, trimethylolpropane, di- trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, trimethylolethane, trimethylolpropane, mannitol or sorbitol.

10. A product according to Claim 9, in which the polyol is pentaerythritol.

11. A product according to any one of the preceding Claims, having an acid value of from 15 to 50 mg KOH/ gram, more preferably from 15 to 30 mg KOH/ gram.

12. A product according to any one of the preceding Claims, comprising: from 30 to 80% by weight of rosin; from 1 to 10% by weight of polybasic acid; from 10 to 40% by weight of dammar gum; and from 5 to 20% of polyol.

13. A product according to Claim 12, comprising: from 45 to 60% by weight of rosin; from 4 to 6% by weight of polybasic acid; from 25 to 35% by weight of dammar gum; and from 7 to 15% of polyol.

14. A coating composition comprising a resin according to any one of the preceding Claims and a solvent therefor.

15. A composition according to Claim 14, in the form of a varnish.

16. A composition according to Claim 14, in the form of an ink, additionally comprising a pigment or dye.

17. A composition according to any one of Claims 14 to 16, in which the solvent comprises a drying oil, preferably linseed oil, tung oil, poppy seed oil, perilla oil or walnut oil.

18. A composition according to any one of Claims 14 to 17, in which the solvent comprises an alkyl ester of a semi-drying oil.

19. A composition according to Claim 18, in which the semi-drying oil is soya, rapeseed, sunflower, peanut, sesame or safflower oil, preferably the methyl ester thereof.

20. A composition according to any one of Claims 14 to 16, in which the solvent comprises a mineral oil distillate of boiling range within the limits 200⁰C - 320°C.

21. A composition according to any one of Claims 14 to 16, in which the solvent is toluene.