NL1002628C2 - 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 vinyl acetate polymer with certain styrylpyridinium or styrylquinolinium graft groups, a second polymer component selected from water-dispersible or hydrophobic polymers such as polyurethane or a polyester resin dispersion, a third component of a photopolymerizable unsaturated compound with at least one ethylenically unsaturated group, for example, 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 associated initiator are required to obtain a good wet strength after development with water, as well as a 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 30 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.

1002628 2

The present invention aims to reduce the tackiness of the photosensitive composition, while at least retaining the other good properties.

The photosensitive resin composition of the type described according to the invention is characterized in that the polyester resin is an alkyd resin.

Surprisingly, it has been found that the choice of an alkyd resin with a photopolymer improves the tackiness property. It is believed that this favorable property is due, inter alia, to the replacement of the third component from the above-described known composition, in particular the UV acrylate, by alkyd resin. The coating obtained from such a composition has, in addition to the improved tackiness property, good wet strength, stability, chemical resistance and photosensitivity, which are at least equal to that of the known compositions. As is usual, the composition may contain a photoinitiator. However, its presence is not required, which can provide an economic advantage.

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 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%, insufficient emulsification takes place because too little protective colloid is present, which gives rise 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%, then the composition is relatively expensive and the chemical resistance to printing inks used in a printing process is less.

Alkyd resins (also called carbon black modified polyesters) 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-value acids, such as citric acid maleized unsaturated fatty acids, maleized rosin, trimellitic acid, benzophenone tetracarboxylic acid, such as phthalic acid, isophthalic acid, adipic acid, succinic acid, azelaic acid, sebacic 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, soya , linseed, pine and sunflower oil. The alkyd resin can be of the oxidatively drying type or of the stoving type.

Examples of alkyd resins which can be used in the composition of the invention are, inter alia, available 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 especially 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.

In addition to the alkyd resin, for example, other resins compatible therewith, such as those described in the aforementioned European patent EP-B1-0 130 804, can be used in the composition according to the invention. A particular stability-favorable combination of resins consists of alkyd resin with amino-30 resin and / or phenolic resin, the amino resin being most preferred.

Amino resins are well known per se in the coating sector. Examples thereof are melamine formaldehyde resin and (single) benzoguanamine resin, the latter being particularly preferred 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. Suitable amino resins, 1002628, which can be used according to the invention, are commercially available under the trade names Luwipal, Beetle, Maprenal, Cymel and Resimene.

If one or more other resins are present in the composition according to the invention in addition to the alkyd resin, the dry matter content thereof generally amounts to 10-70% of the total composition, preferably 15-50%. In the case of an amino resin, the upper limit is determined by the flexibility, while the lower limit is determined by the chemical resistance.

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 20.

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. The correct drying conditions are of course 1002628 6 dependent 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, as well as the non-exposed lacquer layer, so that the screen is provided with the correct printing pattern and the actual printing can be started.

The invention will be explained below with reference to the following examples.

10

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 hardener was added. The mixture thus obtained was allowed to cool to 50 ° C. 59.4 g of urethane acrylate oligomer (85% in 1,6-hexanediol acrylate) was introduced into another beaker and heated to 50 ° C, after which 0.6 g of photoinitiator Irgacure 369 (Ciba Gei-20 gy) was added. The mixtures were combined and kept at 50 ° C until further processing.

100 g of the above warm resin phase were 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 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 30,3300. The photo-emulsion thus obtained was then diluted with water and ethanol and using a water-soluble dye colored.

This photoemulsion was further diluted with water and then dipped on a nickel rotary screen screen for rotary screen printing. After drying at 35 ° C for 40 minutes, the still tacky emulsion was treated with talc to obtain a non-stick coating. The screen was then exposed through a photo-negative 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.

10

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 decreasing 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 7 g of amine curing agent was added. Separately, 29 g of urethane acrylate oligomer and 1 g of photoinitiator Irgacu-20 re 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 is similar to that of in comparative example 1, the same mixture of photopolymer 25 and polyvinyl alcohol solution was emulsified. The photo-emulsion thus obtained was somewhat less sticky. However, the wet strength was extremely poor, and after development with water, the entire photo-emulsion applied to the screen was re-emulsified.

30

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 10 to 8 δ the resin and a hydroxyl content of 4% (OH equivalent). The benzoguanamine resin, which is described as a non-plasticizing benzoguanamine 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 polyvinyl alcohol derivative consisting of 88% saponified polyvinyl acetate with a polymerization degree of 1700, modified 10 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 photo-emulsion. 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-25 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 10026X8 9. 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, which is somewhat detrimental to chemical resistance.

Example 3.

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

15

Example 4.

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

Example 5.

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

Example 6.

The same warm mixture of alkyd resin and benzoguanamine 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 1002628 of a polyvinyl derivative, consisting of 88% saponified polyvinyl acetate with a polymerization degree of 2300, modified with 1.1 mol% styryl pyridinium groups. The results obtained were comparable to those of Example 5.

Example 7.

The same warm mixture of alkyd resin and benzoguanamine resin as in Example 5 was emulsified in 200 g of photopolymer SPP 10 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 comparable to those of Examples 5 and 6.

Example 8.

In this example, 117 g of long chain oil alkyd resin (83% mixed acids, 13% phthalic anhydride, acid value <7, solids content 99%) were mixed with 145 g of benzoguanamine resin. This premix was heated to 75 ° C and then emulsified in 200 g of photopolymer SPP H13. The presence of this long chain oil alkyd resin improved the flexibility of the finally obtained coating.

Example 9.

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

t r> o 0 β 2 8 11

Example 10.

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

10 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.

15 This gave an excellent balance of properties.

Example 12.

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

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.

30

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

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Table 1. Results.

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

Compare very - bad

Compare 2 poor 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 ++ ++ ++ + + ++ = excellent; + good; +/- «sufficient; - / + = insufficient; - = bad; - = very bad.

25

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.

1002628

Claims (11)

1. C 2 6 2 8 characterized in that the organic solvent is selected from the group consisting of alcohols, acetates, glycols and mixtures thereof. Photosensitive resin composition comprising a photopolymer and a polyester resin, characterized in that the polyester resin is an alkyd resin. The photosensitive resin composition according to claim 1, characterized in that the photopolymer is a stilvazol-grafted polyvinyl alcohol. 3. A composition according to claim 1 or 2, characterized in that the alkyd resin is selected from an oxidatively drying alkyd resin and / or a stoving alkyd resin. Composition according to any one of claims 1 to 3, characterized in that the composition comprises 5-30% photopolymer, 20-80% alkyd resin and optionally 10-70% other resins, the percentages being expressed as a percentage of dry matter of the total composition. 5. Composition according to any one of the preceding claims 1-4, characterized in that the other resins are selected from amino and / or phenolic resin. 6. A composition according to any one of the preceding claims 4 or 5, characterized in that the composition comprises 40-75% alkyd resin, 15-50% amino resin and 9-17% photopolymer. Composition according to claim 5 or 6, characterized in that the amino resin is benzoguanamine resin. 30 Photosensitive lacquer for screen printing, characterized in that the lacquer comprises 35-50% of the photosensitive composition according to any one of claims 1-7, as well as 40-75% water and 5-15% organic solvent. 35 The photosensitive lacquer according to claim 8, having the Photosensitive lacquer according to claim 8 or 9, characterized in that the lacquer contains about 45% of the base composition according to any one of claims 1-7, about 45% water and about 10% organic solvent. Screen printing stencil, comprising a support with a photosensitive film of the photosensitive lacquer as claimed in any one of claims 8-10. 1 ö 0 - 6 Z 8 COOPERATION TREATY (PUI) REPORT ON NEWNESS RESEARCH OF INTERNATIONAL TYPE OF IDENTIFICATION OF THE NATIONAL APPLICATION Characteristic of the applicant or of the gemacnogoe 955176 / JV / nbr Close application No '. - Indianngseatjm 1002628 March 15, 1996 Inaugurate priority saun Applicant (Name) STORK SCREENS B.V. Daum of wet reconciliation for an undercut of ntemaaaiai type By the Insanoe for miameaaiaiai Research (ISA) on wet reconciliation for the undercut of remaeonaaiai type toaganand nr. SN 27293 NL I. CLASSIFICATION OF THE SUBJECT (at eepaamg of united land daasAcaaoemb. All dateiteeeoeymb. tasks) According to eg mamaoonaie canificaee (IPC) Int. Cl.G 03 F 7/038, G 03 F 7/12 II. RESEARCHED FIELDS OF OE TECHNOLOGY ____Onoerzocffle minimum documentation_ Classification system Classificationsvoolen _ Int. Cl.6 G 03 F Onaerzoenta other documents than minimum doumenaoa, insofar as such documents are mentioned by means of an argument and other III. ί? NO INVESTIGATION MAY BE FOR CERTAIN CONCLUSIONS (Comments on Supplemental Oad) j (J | IV. I 1 LACK OF UNITY OF INVENTION (Comments on Supplementary Lad) | = orm PC7 / 1SA / 201UIC6: 9fti