NL1002627C2 - Photosensitive resin composition and this composition comprising lacquer. - Google Patents

Description

Short designation: Photosensitive resin composition and this composition comprising lacquer.

The invention relates to a photosensitive resin composition comprising a photopolymer and a polyester resin.

Such a composition is known, for example, from EP-5 B1-0 130 804. This known composition contains four components, namely a photopolymer of a water-soluble, saponified vinyl acetate polymer with certain styrylpyridinium or styrylquinolinium graft groups, a second polymer component selected from water-dispersible or hydrophobic polymers, for example polyurethane or a polyester resin dispersion, a third component of a photopolymerizable unsaturated compound with at least one ethylenically unsaturated group such as a UV acrylate or an unsaturated polyester, and a photopolymerization initiator as a fourth component. Such a composition can be used in a photosensitive lacquer for printing plates or screens.

According to this publication, in particular, the third component and the accompanying initiator are required to obtain good wet strength after development with water, as well as good chemical resistance of the final coating. This composition has better properties compared to that of photopolymers known from GB-B-2030575.

However, it has been found that the composition known from EP-B-0 130 804, although showing the above-mentioned properties, has a clear drawback. Namely, this composition results in a tacky coating which adheres to the film applied thereto during operation. As a result, part of the lacquer transfers to the film, which damages the lacquer layer. Furthermore, this makes the film, which often has to be stored, unusable for reuse. In order to avoid this drawback, it has already been proposed to sprinkle talcum powder on the applied lacquer layer.

The present invention aims to reduce the tackiness of the photosensitive composition while retaining the good properties of the known composition.

The photosensitive resin composition of the type described in accordance with the invention is characterized in that the composition further comprises a resin component selected from an amino resin and / or phenolic resin.

The composition according to the invention mainly consists of three components, namely a fo-topolymer, a polyester resin and a resin, selected from amino and / or phenolic resin, which cures together with the polyester resin. It has been found that such a base composition can be formulated as a lacquer, which is not tacky, i.e. does not adhere too strongly to the film to be applied later, and which gives good stability. The coating obtained from this composition according to the invention provides improved wet strength, chemical resistance and constant photosensitivity compared to the examples described in GB-B-2 030 575 and EP-B-0 130 804. In addition, the presence of a photoinitiator to improve the photosensitivity, as described in EP-B-0 130 804, is not required, which provides an economic advantage. It is believed that the favorable wet strength properties are obtained by a synergistic interaction between the polyester resin, in particular a thermosetting polyester resin, such as an alkyd resin, and the photopolymer. The thermosetting reaction between the amino resin or phenolic resin, the polyester resin and the photopolymer results in a coating with good chemical resistance and flexibility. The absence of a UV-35 resin, for example an acrylate resin as described in EP-B-0 130 804, results in a reduction of the tackiness.

Examples of photopolymers to be used in the composition according to the invention are those described in British patent GB-B-2 030 575 and European patents EP-B-0 130 804, 0 313 220, 0 313 221 and 0 373 537. All of these publications disclose photopolymers of polyvinyl alcohols or acetates with various graft groups and preparation methods thereof. The preferred photopolymers are those according to GB-B-2 030 575 and EP-B-0 313 220 and 0 313 221, hereinafter referred to as stilbazolium grafted polyvinyl alcohols.

The dry matter content of the preferred photopolymer in the base composition is generally in the range of 5-30%, preferably in the range of 9-17%. When the content is less than 5%, the emulsification is not satisfactory because too little protective colloid (PVA) is present to stabilize the resin phase, which leads to an unstable and sticky lacquer. In addition, at such a low content, insufficient stilbazolium groups for the reaction under the influence of light are present, so that the wet strength is not optimal. If the content exceeds the upper limit of 30%, the composition is relatively expensive and the chemical resistance to printing inks used in a printing process is less.

The polyester resin is preferably a thermosetting polyester resin. Thermosetting polyester resins can be divided into the unsaturated polyesters and the alkyd resins (also called oil-modified polyesters). The latter group is particularly preferred.

Alkyd resins can be prepared, as is known in the art, from three components, namely 1) polybasic alcohols or mixtures thereof, such as for example propylene glycol, ethylene glycol, glycerol, pentaerythritol, polyglycerol, dimethanol propionic acid, sorbitol, mannitol and neopentyl glycol with 2) polyvalent acids, anhydrides or mixtures thereof, such as, for example, trivalent or higher acids, such as citric 1002627 4 acid-malalized unsaturated fatty acids, maleized rosin, trimellitic acid, benzophenone tetracarboxylic acid, divalent acids such as phthalic acid, isophthalic acid, adipic acid, succinic acid, azelaic acid, sebacinic acid and 3) monobasic acid or mixture thereof, such as, for example, saturated or unsaturated fatty acids or oils thereof, such as, for example, coconut, (dehydrated) castor, soy, linseed, pine and sunflower oil . The alkyd resin can be of the oxidatively drying type or of the muffle type.

Examples of alkyd resins which can be used in the composition of the invention are available, inter alia, under the trade names Crodakyd, Uralac, Alftalat, Sacolyd, Novalkyd, Sintal, Jagalyd and Worleekyd. Typically, these alkyd resins are prepared from phthalic anhydride (25-70%) or isophthalic anhydride (10-20%). The oil content (30-80%) is based on a wide variety of fatty acids (eg linseed oil, pine oil, coconut oil, castor oil or synthetic acids). The fatty acids, which contain a non-conjugated unsaturated bond, are particularly preferred. Examples thereof include coconut, castor, grape seed, linseed, palm, safflower, sunflower, soy and pine oils. The oil content is preferably in the range of 30-55%. Furthermore, the hydroxyl content of the alkyd resin is important, which is preferably in the range of 3-7.5%. From the standpoint of stability, alkyd resins with an acid value of less than 25 are advantageously used, although alkyd resins with acid values up to 50 mg KOH / g solid of the alkyd resin have been found to be useful.

The choice of ingredients depends on the intended properties, both for processing and the properties of the final product. The dry matter content of the alkyd resin in the base composition is generally in the range of 20-80%, preferably 40-75%. At a higher content, the chemical resistance is insufficient and, on the other hand, too little amino resin may be present to effect good cross-linking, while at a lower content the flexibility is too low and a brittle layer is formed. The use of alkyd resins containing drying or semi-drying (unsaturated) oils or fatty acids is particularly preferred.

The third component selected from amino resin and / or phenolic resin is preferably an amino resin such as melamine formaldehyde and more preferably a benzoguanamine resin from the viewpoint of shelf life. The amino resin allows the joint curing (drying) of the polyester resin, in particular an alkyd resin, during baking. The third component is generally present in a content (% dry matter of total composition) of 10-70%, preferably 15-50%. The upper limit is determined by the flexibility, while the lower limit is determined by the chemical resistance due to the insufficient presence of amino or phenolic resin for the crosslinking reaction. Suitable amino resins which can be used according to the invention are commercially available under the trade names Luwipal, Beetle, Maprenal, Cymel and Resimene.

The invention further relates to a photosensitive screen printing lacquer, which contains as essential component the photosensitive resin composition according to the invention, in addition to conventional solvents. The photosensitive lacquer according to the invention preferably consists of 35-50% base composition, 40-75% water and 5-15% organic solvent, the best results being achieved with a lacquer consisting of about 45% base composition, 45% water and 10% organic solvent exists.

The solvents suitable for use in the lacquer according to the invention particularly comprise the lower alkyl alcohols and acetates or glycols or mixtures thereof, such as isobutanol, propanol and butyl glycol and preferably butyl acetate, butyl alcohol or a mixture thereof. When using a mixture of organic solvents, the ratio of the various components thereof is not critical and can be determined by the skilled person depending on the specific application requirements.

As already indicated above, the lacquer is used in the printing industry, in particular in screen printing. Here, a layer of the lacquer according to the invention is applied to a screen, for example a cylindrical screen, and dried at a slightly elevated temperature, for example about 35 ° C, for a sufficient period of time, for example on the order of 30 minutes. Of course, the correct drying conditions depend on the nature and quantities of the components in the lacquer and the applied layer thickness. A patterned film is then applied to the dried lacquer, which is exposed, after which the film is removed, and the non-exposed lacquer layer, so that the screen is correctly printed and the actual printing can be started.

The invention will be elucidated hereinbelow with reference to the following examples.

Comparative example 1.

54.5 g of liquid epoxy resin, formed from bisphenol A and epichlorohydrin, were placed in a glass beaker, the contents were heated to 115 ° C and then an amine curing agent was added. The mixture thus obtained was allowed to cool to 50 ° C. In another beaker, 59.4 g of urethane acrylate oligomer (85% 30 in 1,6-hexanediol acrylate) were introduced and heated to 50 ° C, after which 0.6 g of photoinitiator Irgacure 369 (Ciba Gei-gy) was added. The mixtures were combined and kept at 50 ° C until further processing.

100 g of the above warm resin phase was then emulsified in a mixture of 48 g of photopolymer LS400 (Toyo Gosei, Japan; a 13% aqueous solution of a polyvinyl derivative consisting of 88% saponified polyvinyl acetate with a polymerization degree of 500, and 1 0 0 v 6 1 7 7 modified with 4.2 mol% styrylpyridinium groups) and 192 g of a 10% aqueous solution of an 88% saponified polyvinyl acetate with a degree of polymerization of 3300. The photo-emulsion thus obtained was then mixed with Diluted water and ethanol and stained using a water-soluble dye.

This photoemulsion was further diluted with water and then applied to a nickel screen for rotary screen printing by dip coating. After drying for 40 minutes at 35 ° C, the still tacky emulsion was treated with talc to obtain a non-stick coating. The screen was then exposed through a photonegative film using a gallium-doped low-pressure mercury lamp and then developed with water. After polymerization for 1 hour at 180 ° C, the coating was no longer sticky. However, the photoemulsion showed poor wet strength and chemical resistance.

The results of this comparative example, as well as of the examples described below, are summarized in Table 1.

Comparative example 2.

In order to reduce the sticking of the dry film, another photoemulsion was prepared as a comparison. Herein, the resin phase was modified by reducing the amount of tacky UV-acrylate oligomer.

68 g of the epoxy resin used in Comparative Example 1 was heated to 115 ° C, to which was added 7 g of amine curing agent. Separately, 29 g of urethane acrylate oligomer and 1 g of photoinitiator Irgacuer-369 were mixed, ie the amount of urethane acrylate oligomer was half that in Comparative Example 1. Combining the two mixtures gave 105 g of a warm resin phase, which was similar to in comparative example 1, the same mixture of photopolymer and polyvinyl alcohol solution was emulsified. The photo-emulsion thus obtained was somewhat less sticky.

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However, the wet strength was extremely poor, and after development with water, the entire photo-emulsion applied to the screen was re-emulsified.

5 Example 1.

A mixture of 150 g of short chain oil alkyd resin (a so-called "short oil alkyd") and 150 g of alkylated benzoguanamine resin was introduced into a glass beaker. This mixture was then heated to 65 ° C with stirring. The alkyd resin is a 65% solution in butyl acetate.

The alkyd resin has a castor oil content of 42% and a maximum acid value of 15 mg KOH per g solid of the resin and a hydroxyl content of 4% (OH equivalent). The benzoguanamine resin, which is described as a non-plasticizing ben-zoguanamine formaldehyde resin, is an 80% solution in n-butanol.

The warm mixture was then emulsified in 200 g of photopolymer (photopolymer SPP H13 from Toyo Gosei (JP); a 13% aqueous solution of a polyvinylalcohol derivative consisting of 88% saponified polyvinyl acetate with a polymerization degree of 1700, modified with 1.3 mol% styrylpyridinium groups) using a high shear mixer.

The emulsion thus obtained was diluted with 80 g of water, neutralized using a 33% aqueous solution of DMEA and colored using 1 g of a water-soluble dye to form a photoemulsion . The photoemulsion had a solids content of 42% and a solvent phase comprising 44% water, 9% butanol and 5% n-butanol.

This emulsion was allowed to stand for 1 week, after which the emulsion was further diluted with water. The resulting lacquer composition was applied to a rotary nickel screen. After drying at 35 ° C for 40 minutes, the non-tacky photoemulsion was exposed through a negative film using a Ga-doped low pressure Hg lamp. The screen was then developed with water and the unexposed coating was readily redispersed, while the lightly cross-linked coating exhibited good wet strength. After polymerization for 1 hour at 180 ° C, the rotary screen was ready for use. The coating exhibited good wet strength and good chemical resistance to a wide variety of chemicals.

Example 2.

Using the same starting materials as in Example 1, 185 alkyd resin was mixed with 125 g of benzoguanamine resin. The mixture was then emulsified in 200 g of photopolymer and processed into a photo-emulsion according to Example 1. The composition of the photo-emulsion thus obtained was as follows: solids content 42%, butyl acetate 11% and n-butanol 4%. The final coating exhibited improved flexibility, however, somewhat at the expense of chemical resistance.

20 Example 3.

Using the same starting materials as in Example 1, 115 g of alkyd resin were mixed with 150 g of benzo-guanamine resin. The mixture was then emulsified in 345 g of photopolymer. The final coating showed good wet strength, reasonable flexibility and good chemical resistance.

Example 4.

Using the same starting materials as in the previous examples, 163 g of the alkyd resin was mixed with 132 g of the benzoguanamine resin and then emulsified in 273 g of the photopolymer. The photoemulsion had moderate wet strength, good chemical resistance to solvents and acids, and reasonable flexibility.

35

Example 5.

In this example, 150 g of short chain oil alkyd resin (42% coconut oil, 30% phthalic anhydride 1002627 10 dride, acid value <10, solids content 80% in isopropanol) were mixed with 150 g of the above benzoguanamine resin to 75 ° C C heated. The warm mixture was emulsified in 200 g of photopolymer SPP H13. This photo-emulsion showed good wet strength as well as good chemical resistance.

Example 6.

The same warm mixture of alkyd resin and benzoguanami-10 resin as in Example 5 was emulsified in 200 g of photopolymer SPP S10 (also available from Toyo Gosei (JP)). This photopolymer is an 11% aqueous solution of a polyvinyl derivative, consisting of 88% saponified polyvinyl acetate with a polymerization degree of 2300, modified with 1.1 mol% styrylpyridinium groups. The results obtained were comparable to those of Example 5.

Example 7.

The same warm mixture of alkyd resin and benzoguanami resin as in Example 5 was emulsified in 200 g of photopolymer SPP S13 (also available from Toyo Gosei (JP)). This photopolymer is an 11% aqueous solution of a polyvinyl derivative, consisting of 88% saponified polyvinyl acetate with a polymerization degree of 2300, modified with 1.37 mole% styrylpyridinium groups. The results obtained using this photopolymer were similar to those of Examples 5 and 6.

30 Example 8.

In this example, 117 g long oil chain length alkyd resin (83% mixed acids, 13% phthalic anhydride, acid value <7, solids content 99%) were mixed with 145 g benzoguanamine resin. This premix was heated to 75 ° C and then in 200 g photopolymer SPP

H13 emulsified. The presence of this long oil chain length alkyd resin improved the flexibility of the final coating obtained.

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Example 9.

150 G short chain oil alkyd resin (35% special acids, 25% phthalic anhydride, acid value <10, hydroxy content 4.4%, solid content 80% in isobutyl 5-acetate) was mixed with 150 g benzoguanamine resin, then heated and with 200 g of photopolymer SPP H13 emulsified. This resulted in a photo-emulsion with excellent chemical resistance to bases, but at the expense of wet strength and chemical resistance to solvents.

Example 10.

197 g of alkyd resin (50% non-drying oil, acid value <50, solids content 75% in n-butanol / butyl glycol) were mixed with 84 g of benzoguanamine resin, then heated and emulsified in 200 g of photopolymer SPP H13. The result was a photo-emulsion with excellent flexibility, wet strength and very good chemical resistance.

20

Example 11.

206 g of the same alkyd resin as in Example 10 were mixed with 67 g of benzoguanamine resin (esterified with methanol, solids content 75% in isobutanol), heated and then emulsified in 200 g of photopolymer SPP H13. This gave an excellent balance of properties.

Example 12.

Example 11 was repeated except that 209 g of alkyd-30 resin was mixed with 89 g of benzoguanamine resin. The results obtained with this photoemulsion were similar to those of Example 11, except that the chemical resistance to bases was somewhat less.

35 Example 13.

Example 11 was repeated using 180 g of alkyd resin and 120 g of benzoguanamine resin. Again, the same favorable properties were obtained, except that the flexibility and chemical resistance to bases was somewhat less.

Example 14.

In this example, a polyester resin (65% in methoxypropyl acetate) was used instead of an alkyd resin. 255 g of polyester resin was mixed with 55 g of the benzoguanamine resin used in Example 11, heated and then the warm mixture was emulsified in 200 g of SPP H13. The photoemulsion was only slightly tacky, had reasonable wet strength and good chemical resistance to acids. The resistance to solvents and especially to bases was less.

15 Example 15.

Example 14 was repeated using 237 g of a highly reactive saturated polyester resin (acid value <18, solids content 85% in isobutyl acetate). The same results as in Example 14 were obtained. However, the chemical resistance to solvents was somewhat worse.

Table 1 below summarizes the results of the above comparative examples and examples.

100-527 13

Table 1. Results.

Pre-Adhesive Wet Chemical Resistance Flexibility Strength Against 1 Lity Solvent Acids Bases 5 Agents

Compare very - bad

Compare 2 bad I sufficient + ++ ++ + +/- 10 2 dry +/- + +/- - +/- 3 dry + ++ ++ +/- + / _ 4 dry +/- ++ + + - +/- 5 sufficient + +/- ++ +/- +/- 6 sufficient + + ++ +/- +/- 15 7 sufficient ++ + ++ +/- + / ~ 8 dry - ++ + - + 9 dry +/- +/- + ++ + / ~ 10 dry ++ ++ ++ + ++ II dry ++ ++ ++ ++ ++ 20 12 dry ++ ++ ++ + ++ 13 dry ++ ++ ++ + + 14 sufficient +/- +/- ++ 15 sufficient +/- +/- ++ - 25 ++ * excellent; + = good; +/- = sufficient; - / + = insufficient; - = bad; - = very bad.

1: Solvents tested were acetone, butyl acetate, cyclohexane, ethanol and xylene.

Acids tested were 5% acetic acid and 5% sulfuric acid.

Base tested was 5% sodium hydroxide.

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Claims (12)

Photosensitive resin composition comprising a photopolymer and a polyester resin, characterized in that the composition further comprises a resin component selected from an amino resin and / or phenolic resin. 5 The photosensitive resin composition according to claim 1, characterized in that the photopolymer is a stilvazol-grafted polyvinyl alcohol. Composition according to claim 1 or 2, characterized in that the polyester resin is a thermosetting polyester. Composition according to any one of claims 1 to 3, characterized in that the polyester resin is an alkyd resin. 5. Composition according to any one of the preceding claims 1-4, characterized in that the composition comprises 20-80% alkyd resin, 10-70% amino resin and 5-30% photopolymer, the percentages being expressed as percent dry matter of the total composition. Composition according to claim 5, characterized in that the composition comprises 40-75% alkyd resin, 15-50% amino resin 25 and 9-17% photopolymer. Composition according to any one of claims 1 to 6, characterized in that the alkyd resin is selected from an oxidatively drying alkyd resin and / or a stoving alkyd resin. 30 Composition according to any one of claims 1 to 7, characterized in that the amino resin is benzoguanamine resin. Photosensitive lacquer for screen printing, characterized in that the lacquer comprises 35-50% of the photosensitive composition according to any one of claims 1-8, as well as 1002627 40-75% water and 5-15% organic solvent. Photosensitive lacquer according to claim 9, characterized in that the organic solvent is selected from the group consisting of alcohols, acetates, glycols and mixtures thereof. Photosensitive lacquer according to claim 9 or 10, characterized in that the lacquer contains about 45% of the base composition according to any one of claims 1-8, about 45% water and about 10% organic solvent. 12. Screen printing stencil, comprising a support with a photosensitive film of the photosensitive lacquer according to any one of claims 9-11. 1002527 wniNbii τν bnrMiiuw v cnunnu \ r w · / REPORT ON NEWNESS RESEARCH OF INTERNATIONAL TYPE II DISTRIBUTION OF OE NATIONAL APPLICATION Identifier of the applicant ol of d · gemacnegoe 955116 / JV / nbr Ne oen to application no. inoienngsoaajm 1002627 March 15, 1996 Invited for Jianguaum Applicant (Name) STORK SCREENS B.V. 3aum of net request for a search of mtemaaaiai type By the insMaM for miemaionaei Unsearch (ISA) to net request for a search of nnmoonoon type © e known nr SN 27292 NL. CLASSIFICATION OF THE SUBJECT (at © e patong of vertcful lande datoftcaoat. Specify all ctatoficaoetym boats) tolgora de mamauraie aatoicaM (IPC) Int. Cl. 6: G 03 F 7/038, G 03 F 7/12. FIELDS OF TECHNIQUE INVESTIGATED Onqerzoefwe minimum documentation Classification system I Classificanesvmoolon Int. Cl.6 G 03 F rerouted anoere oocumena »can ae minimum Oocumenaee insofar as such Oocumanan m Oe onoerzocna prayers qn taken! ! NO RESEARCH OPPORTUNITY FOR CERTAIN CONCLUSIONS (Comments on Pollution Path)! LACK OF UNITY OF INVENTION (Comment on Complementary Load) I = -—-: _ j form PCT.1SA / '201iai C6 1984