A water-based primer composition for printing, and its preparation method and application

Abstract

The present invention discloses a water-based primer composition for printing, a preparation method and an application thereof, which comprises a modified acrylic resin, ethanol and water; the modified acrylic resin is prepared by reacting the following components: (i) selected from the formula (I): #imgabs0#t1 is selected from 1-6, R1 is C 2‑6 Alkyl; (ⅱ) dihydroxystyrene; (ⅲ) selected from the formula (Ⅱ): #imgabs1# is C 2‑10 A linear alkyl group, a diol having a molecular weight of 200-2000; (iv) a polyacid; (v) a diisocyanate; and a molar ratio of components (i), (ii) and (iii) of 1:0.2-0.5:2.0-5.0. The water-based primer composition of the present invention has low film-forming temperature and fast film-forming speed, and the formed film has strong flexibility and weather resistance, is suitable for use on thin film materials, does not substantially yellow during UV curing, and has a dyne value greater than or equal to 45 mN / m, and can be used as a primer for UV inks.

Description

Technical Field

[0001] The present invention relates to the technical field of water-based primers, and in particular to a water-based primer composition for printing, a preparation method thereof, and applications thereof. Background Art

[0002] Solvent-based gravure inks are currently the most commonly used ink for printing thin film materials. While gravure prints produce exquisite products with outstanding color, they are expensive to produce. Furthermore, gravure inks contain large amounts of highly volatile organic solvents, which are toxic and flammable, and therefore not environmentally friendly. As society enters a period of rapid development, low-carbon and environmentally friendly practices have become a trend. A small number of printing houses have begun using UV flexographic printing, combined with environmentally friendly UV inks. However, the use of UV inks on thin film materials has certain limitations. Because UV inks lack solvents and the surface wettability of common plastic films (such as PET, PP, and PE) is poor, direct printing on thin films prevents them from adhering firmly to the surface.

[0003] To address the adhesion issues of UV inks, a common approach is to apply a primer, preferably a green and environmentally friendly water-based primer, to the film to increase the surface tension of the plastic, improve its surface printing properties, and thus enable UV printing on the film. However, the application of water-based primers in film materials also presents significant technical difficulties, primarily manifested in the following: first, slow film formation, which impacts production cycle time; second, high film formation temperature, high energy consumption, and potential impact on the film substrate; and third, the inability to balance weather resistance and flexibility, resulting in a trade-off between weather resistance and flexibility. Summary of the Invention

[0004] The object of the present invention is to overcome one or more deficiencies in the prior art and to provide an improved aqueous primer composition for printing, which has low film-forming temperature, fast film-forming speed, and the formed film has strong flexibility and weather resistance, is suitable for use on thin film materials, does not substantially yellow during UV curing, and has a dyne value greater than or equal to 45 mN / m.

[0005] The present invention also provides a method for preparing the above-mentioned water-based primer composition and its application as a primer for UV ink in the surface printing process of film materials.

[0006] To achieve the above object, the present invention adopts a technical solution: a water-based primer composition for printing, the water-based primer composition comprising a modified acrylic resin, ethanol and water; the modified acrylic resin is prepared by reacting the following components: (i) at least one hydroxy acrylate compound selected from the group consisting of formula (I):

[0007] In formula (I), t1 is selected from 1-6, R1 is C2-6 alkyl;

[0008] (ii) dihydroxystyrene;

[0009] (iii) at least one diol selected from the group consisting of: In formula (II), R2 is C 2-10 A linear alkyl group, wherein the molecular weight of the diol represented by formula (II) is 200-2000;

[0010] (iv) polyacids;

[0011] (v) diisocyanates;

[0012] The molar ratio of component (i), component (ii) and component (iii) is 1:0.2-0.5:2.0-5.0;

[0013] During the preparation process, component (i), component (iii) and component (v) are reacted, an initiator is added, and the reaction is carried out. After the reaction is completed, the initiator is separated, and then component (ii) and component (iv) are added and reacted.

[0014] According to some preferred aspects of the present invention, in formula (I), t1 is 1, 2 or 3, and R1 is ethyl, propyl or butyl.

[0015] According to a specific aspect of the present invention, the hydroxy acrylate compound represented by formula (I) is butyl 2,2-bis(hydroxymethyl)acrylate.

[0016] According to some preferred aspects of the present invention, R2 is n-propyl, n-butyl, n-pentyl or n-hexyl.

[0017] According to some preferred aspects of the present invention, the dihydroxystyrene is 3,4-dihydroxystyrene.

[0018] In some embodiments of the present invention, the polyacid is a dibasic acid and / or an acid anhydride. The dibasic acid is phthalic acid, isophthalic acid, etc., and the anhydride is phthalic anhydride, etc.

[0019] According to a specific aspect of the present invention, the dibasic acid is composed of phthalic acid and isophthalic acid in a molar ratio of 1:0.2-0.4.

[0020] In some embodiments of the present invention, the diisocyanate is a combination of one or more selected from toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), and lysine diisocyanate (LDI).

[0021] According to some preferred aspects of the present invention, the ratio of the total molar amount of component (i), component (ii) and component (iii) to the molar amount of component (iv) and component (v) is 1:0.5-0.8:0.2-0.6.

[0022] According to some preferred aspects of the present invention, the method for preparing the modified acrylic resin includes:

[0023] (1) reacting component (i), component (iii) and component (v) at 80-90 degrees Celsius to produce a first intermediate;

[0024] (2) heating to 100-140 degrees Celsius, adding an initiator, and reacting under a protective atmosphere to generate a second intermediate;

[0025] (3) After separating the initiator, add component (ii) and component (iv) to the second intermediate, and carry out polycondensation reaction at 180-220 degrees Celsius to generate the modified acrylic resin.

[0026] In some embodiments of the present invention, in step (2), the initiator is azobisisobutyronitrile.

[0027] In some embodiments of the present invention, the components (i), (ii) and (iii) are all dehydrated before being added.

[0028] According to some preferred aspects of the present invention, based on 100% of the total amount of the ethanol and the water, the ethanol accounts for 1%-5%, and the water accounts for 95%-99%.

[0029] In the present invention, a small amount of ethanol is added to the water-based primer composition, which has the following main effects: (1) the water-based primer contains water for diluting the resin particles, and ethanol is a volatile liquid that can promote the volatilization of water in the film layer, thereby achieving the effect of accelerating drying; (2) after ethanol is added to the water-based primer, its volatility can promote the close arrangement of the resin particles to form a glossy film layer, thereby improving the gloss of the film layer; (3) adding an appropriate amount of ethanol can reduce the adhesion between the internal particles without destroying the properties of the base layer, thereby achieving the effect of reducing the viscosity of the water-based primer.

[0030] In some embodiments of the present invention, the solid content of the aqueous primer composition is 10%-40%.

[0031] Another technical solution provided by the present invention is a method for preparing the above-mentioned aqueous primer composition for printing, which comprises: mixing modified acrylic resin, ethanol and water, and controlling the solid content to be 10%-40%.

[0032] Another technical solution provided by the present invention is the use of the above-mentioned aqueous primer composition for printing as a primer for UV ink in the surface printing process of a film material.

[0033] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0034] The present invention addresses the problems of slow film-forming speed and high film-forming temperature in the prior art water-based primers, and the inability to achieve both weather resistance and flexibility. The present invention innovatively provides an improved modified acrylic resin and applies it to a water-based primer composition. A hydroxyl acrylate compound represented by formula (I) is introduced into the modified acrylic resin. On the one hand, the hydroxyl group of the modified acrylic resin can react with diisocyanate to form a polyurethane structure. On the other hand, the terminal acrylate group of the modified acrylic resin can initiate polymerization to form an acrylic resin. This allows the overall structure to contain both carbamate and acrylate groups, and thus achieves the properties of both polyurethane and acrylic resin, such as wear resistance, heat resistance, low-temperature resistance, adhesion, flexibility, and high peel strength.

[0035] At the same time, the diol represented by formula (II) is further combined to introduce a longer linear flexible chain segment into the system to increase the flexibility of the film after formation;

[0036] By adding dihydroxystyrene and polyacid to the system, a specific alkyd resin structure can be formed in the system, which improves the mechanical properties of the film-forming material. The introduction of benzene rings is also beneficial to improving weather resistance.

[0037] In particular, the modified acrylic resin of the present invention still retains the double bond structure on the styrene benzene ring, which can participate in the photocuring process of the UV ink set on the film layer of the water-based primer later. In particular, the double bond structure on the benzene ring is uniformly dispersed throughout the resin structure. This means that when it participates in the photocuring process of the UV ink, it is equivalent to establishing an additional chemical connection relationship between the film layer formed by the water-based primer and the UV-curing film layer in addition to the adhesion relationship, thereby greatly improving the adhesion strength of the UV film layer on the film. DETAILED DESCRIPTION

[0038] The above scheme is further described below in conjunction with specific examples; it should be understood that these examples are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following examples; the implementation conditions adopted in the examples can be further adjusted according to specific requirements, and the implementation conditions not specified are generally the conditions in routine experiments.

[0039] Unless otherwise specified in the following examples, all raw materials were purchased from commercial sources or prepared by conventional methods in the art.

[0040] In the following, polytetrahydrofuran diol was purchased from Sigma-Aldrich and had an average molecular weight of about 1000.

[0041] Example 1

[0042] This example provides a water-based primer composition for printing and a preparation method thereof. Calculated by weight percentage, the water-based primer composition for printing includes 30% modified acrylic resin, 2.1% ethanol and 67.9% water: the raw materials of the modified acrylic resin include 188 parts of 2,2-bis(hydroxymethyl)butyl acrylate, 54.5 parts of 3,4-dihydroxystyrene, 2000 parts of polytetramethylene glycol, 235.2 parts of phthalic acid, 47 parts of isophthalic acid, 285.6 parts of hexamethylene diisocyanate, and 25 parts of azobisisobutyronitrile.

[0043] The preparation method of the aqueous primer composition for printing comprises:

[0044] The method comprises the following steps: dehydrating a formulated amount of butyl 2,2-bis(hydroxymethyl)acrylate, polytetrahydrofuran diol, and 3,4-dihydroxystyrene under vacuum heating conditions until the moisture content is less than 0.1‰; adding the dehydrated butyl 2,2-bis(hydroxymethyl)acrylate, polytetrahydrofuran diol, and hexamethylene diisocyanate into a reaction kettle, stirring and reacting at 83±2° C. for 3 hours at a stirring speed of 100 rpm under nitrogen protection; heating the kettle to 115±5° C. after the reaction, adding azobisisobutyronitrile, and reacting the mixture for 4 hours under nitrogen protection; separating the azobisisobutyronitrile after the reaction, adding 3,4-dihydroxystyrene, phthalic acid, and isophthalic acid, and carrying out a polycondensation reaction at 195±5° C. for 3 hours to generate a modified acrylic resin; then adding ethanol and water to control the solid content to 30%, mixing and stirring, and preparing a water-based primer composition for printing.

[0045] Example 2

[0046] This example provides a water-based primer composition for printing and a preparation method thereof. The water-based primer composition for printing comprises, by weight, 30% modified acrylic resin, 2.1% ethanol, and 67.9% water. The raw materials for the modified acrylic resin include 282 parts of butyl 2,2-bis(hydroxymethyl)acrylate, 68 parts of 3,4-dihydroxystyrene, 4500 parts of polytetramethylene glycol, 498 parts of phthalic acid, 149.4 parts of isophthalic acid, 436.8 parts of hexamethylene diisocyanate, and 40 parts of azobisisobutyronitrile. The preparation method for the water-based primer composition for printing is the same as that of Example 1.

[0047] Example 3

[0048] This example provides a water-based primer composition for printing and a preparation method thereof. The composition comprises, by weight, 30% modified acrylic resin, 2.1% ethanol, and 67.9% water. The raw materials for the modified acrylic resin include 188 parts of butyl 2,2-bis(hydroxymethyl)acrylate, 40.8 parts of 3,4-dihydroxystyrene, 3000 parts of polytetramethylene glycol, 255 parts of phthalic acid, 102 parts of isophthalic acid, 361.2 parts of hexamethylene diisocyanate, and 30 parts of azobisisobutyronitrile. The preparation method for the water-based primer composition for printing is the same as in Example 1.

[0049] Comparative Example 1

[0050] This example is substantially the same as Example 1, except that 2,2-bis(hydroxymethyl)butyl acrylate is not added and is replaced by an equimolar amount of polytetrahydrofuran diol.

[0051] Comparative Example 2

[0052] This example is substantially the same as Example 1, except that polytetrahydrofuran diol is not added and is replaced by an equimolar amount of 2,2-bis(hydroxymethyl)butyl acrylate.

[0053] Performance Testing

[0054] The water-based primer compositions prepared in Examples 1-3 and Comparative Examples 1-2 were evenly applied to a PP film and dried naturally at room temperature. The following performance tests were performed on the resulting coating films:

[0055] 1. Conduct adhesion test according to GB / T 9286-1998 "Scratch test for paint and varnish films";

[0056] 2. Conduct pencil hardness test according to GB / T 6739-2006 “Paints and varnishes - determination of film hardness by pencil method”;

[0057] 3. Surface tension test was carried out according to GB / T 14216-2008 "Plastic films and sheets - Determination of wetting tension";

[0058] 4. Determine the surface drying time and actual drying time according to the method in GB / T1728-2020 "Determination of Drying Time of Paint Film and Putty Film";

[0059] 5. Water resistance test: Place the PP film coated with a water-based primer in 80°C water to evaluate whether it has any warping or peeling phenomenon.

[0060] The specific results are shown in Table 1.

[0061] Table 1

[0062]

[0063] At the same time, practice shows that after the water-based primer composition of the present invention is applied to a PP film, a 30 cm tape (3M) is taken to cover it and smoothed to remove bubbles. After leaving it for 10 seconds, it is quickly and vigorously torn off at an angle of 45 to 90 degrees without de-inking and the die-cut edge film cannot be peeled off.

[0064] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

[0065] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

Claims

1. A water-based primer composition for printing, characterized in that The water-based primer composition comprises a modified acrylic resin, ethanol and water; the modified acrylic resin is prepared by reacting the following components: (i) at least one hydroxy acrylate compound selected from the group consisting of: In formula (I), t1 is selected from 1-6, R1 is C 2-6 alkyl; (ii) dihydroxystyrene; (iii) at least one diol selected from the group consisting of: In formula (II), R2 is C 2-10 A linear alkyl group, wherein the molecular weight of the diol represented by formula (II) is 200-2000; (iv) polyacids; (v) diisocyanates; The molar ratio of component (i), component (ii) and component (iii) is 1:0.2-0.5:2.0-5.0; the molar ratio of the total molar amount of component (i), component (ii) and component (iii) to the molar amount of component (iv) and component (v) is 1:0.5-0.8:0.2-0.6; The embodiment of preparing the modified acrylic resin includes: (1) reacting component (i), component (iii) and component (v) at 80-90 degrees Celsius to produce a first intermediate; (2) Heating to 100-140 degrees Celsius, adding an initiator, and reacting under a protective atmosphere to generate a second intermediate; (3) After separating the initiator, adding component (ii) and component (iv) to the second intermediate, and carrying out a polycondensation reaction at 180-220 degrees Celsius to produce the modified acrylic resin; The initiator is azobisisobutyronitrile.

2. The aqueous primer composition for printing according to claim 1, characterized in that In formula (I), t1 is 1, 2 or 3, and R1 is ethyl, propyl or butyl.

3. The aqueous primer composition for printing according to claim 1, characterized in that R2 is n-propyl, n-butyl, n-pentyl or n-hexyl.

4. The aqueous primer composition for printing according to claim 1, characterized in that The dihydroxystyrene is 3,4-dihydroxystyrene; and / or the polyacid is a dibasic acid and / or an acid anhydride; and / or the diisocyanate is a combination of one or more selected from toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate.

5. The aqueous primer composition for printing according to claim 1, characterized in that The components (i), (ii) and (iii) are all dehydrated before being added.

6. The aqueous primer composition for printing according to claim 1, characterized in that Based on 100% of the total amount of the ethanol and the water, the ethanol accounts for 1%-5%, and the water accounts for 95%-99%; and / or the solid content of the aqueous primer composition is 10%-40%.

7. A method for preparing a water-based primer composition for printing according to any one of claims 1 to 6, characterized in that: The preparation method comprises: uniformly mixing modified acrylic resin, ethanol and water, and controlling the solid content to be 10%-40%.

8. Use of the aqueous primer composition for printing according to any one of claims 1 to 6 as a primer for UV ink in a surface printing process of a film material.

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