Silica gel surface digital printing pretreatment process

Abstract

The invention discloses a silica gel surface digital printing pretreatment process which comprises the following steps: 1, compounding a transparent silica gel film with a PET release film to form a composite base material; 2, coating silica gel oil for improving the surface energy of the transparent silica gel film on the surface of the composite base material, and then baking until the surface is dry; the silica gel oil comprises the following components in percentage by mass: 30%-50% of silicone rubber, 15%-30% of modified polyurethane, 20%-40% of a diluent and 1%-2% of a catalyst, thirdly, corona treatment is conducted on the surface of the silica gel treated in the second step, the corona power ranges from 800 W to 1200 W, and the silica gel is coated with polyethyleneimine prime coating liquid; the silica gel surface of the pre-treated composite base material can be digitally printed by using traditional printing equipment, and printing ink can uniformly and firmly exist on the silica gel surface.

Description

Technical Field

[0001] The present invention relates to the technical field of silicone digital printing, and particularly relates to a pretreatment process for digital printing on the surface of silicone rubber. Background Art

[0002] Silicone digital printing technology is an advanced manufacturing method that combines digital printing technology with the characteristics of silicone materials. As a printing substrate, silicone materials have characteristics such as softness, elasticity, smooth surface, and low surface energy (usually less than 25 mN / m). During the digital printing process, due to the low surface energy of silicone materials, the interfacial bonding strength between the ink and the silicone material is low, resulting in difficult firm adhesion of the ink, uneven printing, and easy peeling.

[0003] Moreover, for traditional printing equipment, such as HP inkjet printers or laser printers, they are mainly used for printing on rigid or semi-rigid substrates such as paper and plastic films; the flexibility and elasticity of silicone materials are significantly in conflict with the default working mode of traditional printing equipment, making it difficult to be directly compatible. The inks used in traditional printing equipment have a small viscosity, and due to the low surface energy of silicone materials, inks with a large viscosity are required for printing, so traditional printing equipment is difficult to be applied to the digital printing production of silicone materials.

[0004] In view of this, the present invention proposes a pretreatment process for digital printing on the surface of silicone rubber to solve the above problems. Summary of the Invention

[0005] In order to overcome the above technical deficiencies, the present invention provides a pretreatment process for digital printing on the surface of silicone rubber. After pretreatment, the silicone surface of the composite substrate can be digitally printed using traditional printing equipment, and the printing ink can uniformly and firmly adhere to the silicone surface.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A pretreatment process for digital printing on the surface of silicone rubber, comprising the following steps:

[0008] Step 1: Composite a transparent silicone film with a PET release film to form a composite substrate;

[0009] Step 2: Coat a silicone oil for increasing the surface energy of the transparent silicone film on the surface of the composite substrate, and then bake it until the surface is dry; the silicone oil comprises the following components in mass fractions: 30% - 50% silicone rubber, 15% - 30% modified polyurethane, 20% - 40% diluent, 1% - 2% catalyst;

[0010] Step 3: Corona treat the surface of the silicone rubber processed in Step 2 with a corona power of 800 - 1200 W, and coat with a polyethyleneimine primer solution; the processed composite substrate is used for digital printing patterns.

[0011] Preferably, the catalyst in the silicone oil is methyl disiloxane.

[0012] Preferably, the thickness of the silicone oil is 0.002 - 0.005 mm.

[0013] Preferably, the mass fraction of polyethyleneimine in the primer solution is 20% - 30%.

[0014] Preferably, the PET release film includes a PET film with a thickness of 0.01 - 0.2 mm and a release coating applied on the PET film.

[0015] Preferably, the thickness of the transparent silicone rubber film is 0.1 - 0.2 mm.

[0016] Preferably, the baking temperature of the silicone oil in Step 2 is 70 - 90 °C.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] 1. In the present invention, by coating silicone oil on the transparent silicone rubber film, the modified polyurethane in the silicone oil has polar groups such as urethane groups, which can enhance the interfacial adhesion force of the silicone surface. The silicone rubber in the silicone oil has Si - O bonds, which can adsorb polar molecules or polar groups, facilitating the uniform spreading of the ink.

[0019] 2. The present invention also generates polar groups on the silicone surface through corona treatment, and the Si - O bonds of the silicone rubber can adsorb these polar groups, increasing the surface energy of the silicone interface, further facilitating the wetting and spreading of the ink; the polyethyleneimine primer solution binds to the ink resin through hydrogen bonds and covalent bonds of the amine groups, enabling the ink to firmly adhere to the silicone surface.

[0020] 3. The present invention combines the transparent silicone rubber film with the PET release film to form a composite substrate, which is compatible with most digital printing devices, especially HP digital printing devices. The PET release film can provide rigid support to the transparent silicone rubber film during the printing process, avoiding pattern deviation caused by silicone deformation during printing. And the PET release film is convenient for subsequent transfer or demolding of the finished product. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic structural diagram of a silicone rubber label prepared using Example 1 of the present invention;

[0022] Figure 2 is a schematic diagram of a physical silicone rubber label prepared using Example 1 of the present invention;

[0023] The implementation, functional features, and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with embodiments. Specific Embodiments

[0024] The following further details the features of the present invention and other related features through embodiments for the understanding of those skilled in the same industry:

[0025] An embodiment of the present invention provides a pretreatment process for digital printing on the surface of silicone rubber, including the following steps:

[0026] Step 1: Composite a transparent silicone rubber film with a PET release film to form a composite substrate;

[0027] Step 2: Coat silicone oil for increasing the surface energy of the transparent silicone rubber film on the surface of the composite substrate, and then bake it until the surface is dry; the silicone oil includes the following components by mass fraction: 30% - 50% silicone rubber, 15% - 30% modified polyurethane, 20% - 40% diluent, 1% - 2% catalyst;

[0028] Step 3: Perform corona treatment on the silicone rubber surface treated in Step 2, with a corona power of 800 - 1200 W, and coat a polyethyleneimine primer solution; the treated composite substrate is used for digital printing patterns.

[0029] In some embodiments, the catalyst in the silicone oil is methyl disiloxane, which is used to quickly form a stable coating during the surface drying stage of the silicone oil.

[0030] In some embodiments, the thickness of the silicone oil is 0.002 - 0.005 mm.

[0031] In some embodiments, the mass fraction of polyethyleneimine in the primer solution is 20% - 30%.

[0032] In some embodiments, the PET release film includes a PET film with a thickness of 0.01 - 0.2 mm and a release coating coated on the PET film. The present invention composites a transparent silicone rubber film with a PET release film to form a composite substrate, which can provide rigid support for the transparent silicone rubber film during the printing process and avoid pattern deviation caused by silicone deformation during printing. The PET release film can also facilitate subsequent transfer or demolding of the finished product.

[0033] In some embodiments, the thickness of the transparent silicone rubber film is 0.1 - 0.2 mm.

[0034] In some embodiments, the diluent is an oily solvent that is well compatible with silicone rubber and modified polyurethane.

[0035] In some embodiments, the baking temperature of the silicone oil in Step 2 is 70 - 90 °C.

[0036] Example 1, as Figure 1 shown, the present invention provides a silicone printed label, and its preparation method includes the following steps:

[0037] Step 1: A roll of transparent silicone film (3) with a thickness of 0.2 mm is laminated on a PET release film to form a composite substrate. The PET release film includes a PET film (1) with a thickness of 0.01 - 0.2 mm and a release coating (2) coated on the PET film.

[0038] Step 2: Use a coater to coat a silicone oil (4) with a thickness of 0.002 - 0.005 mm on the glue surface of the composite substrate, and then bake it at 80 °C until the surface is dry. The silicone oil (4) includes the following components by mass fraction: 40% silicone rubber, 20% modified polyurethane, 38% solvent oil, and 2% methyl disiloxane.

[0039] Step 3: Corona treat the silicone surface after the treatment in Step 2 with a corona power of 1000 W, and coat a polyethyleneimine primer solution (5); the mass fraction of polyethyleneimine in the primer solution is 25%.

[0040] Step 4: Use a HP Latex printing press to print four-color and white inks on the surface of the composite substrate to form a pattern (6).

[0041] Comparative Example 1 provides a silicone printed label, and its preparation method includes Step 1 and Step 4 of Example 1.

[0042] Comparative Example 2 provides a silicone printed label, and its preparation method includes Step 1, Step 3, and Step 4 of Example 1.

[0043] Performance Test

[0044] I. Ink adhesion test: After pasting with 3M tape, quickly peel off the silicone printed label and observe the ink peeling area.

[0045] II. Before Step 4, use a dyne pen to test the surface energy of the composite substrate surface.

[0046] III. Use an optical microscope to observe the ink spreading situation.

[0047] Table 1 Performance test results of Example 1 and Comparative Examples 1 - 2

[0048] Project Ink shedding ratio Grade (0 - 5B) Silicone surface energy (mN / m) Ink spreading condition Example 1 <5％ 5B (no shedding) 58 Ink droplets spread evenly Comparative Example 1 >92％ 0B (complete shedding) 23 Ink droplets shrink into island shape Comparative Example 2 Approximately 40% 2B - 3B 32 Uneven spreading in some areas

[0049] It can be seen from the test results that after the surface pretreatment of the silicone surface in the present invention, the surface energy of the silicone can be significantly improved, enabling the subsequent digital printing ink to spread evenly on the silicone surface, and the digital printing ink can firmly adhere to the silicone surface.

[0050] The above are only the preferred embodiments of the present invention, and thus do not limit the patent scope of the present invention. Any equivalent structural transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall similarly be included within the patent protection scope of the present invention.

Claims

1. A pre-treatment process for digital printing on the surface of silica gel, characterized in that, It includes the following steps: Step 1: Compound a transparent silicone film with a PET release film to form a composite substrate; Step 2: Coat silicone oil for improving the surface energy of the transparent silicone film on the surface of the composite substrate, and then bake it until the surface is dry; the silicone oil includes the following components by mass fraction: 30% - 50% silicone rubber, 15% - 30% modified polyurethane, 20% - 40% diluent, 1% - 2% catalyst; Step 3: Perform corona treatment on the silicone surface after the treatment in Step 2, with a corona power of 800 - 1200 W, and coat a polyethyleneimine primer solution; the treated composite substrate is used for digital printing patterns.

2. The pre-treatment process for digital printing on the surface of silica gel according to claim 1, characterized in that, The catalyst in the silicone oil is methyl disiloxane.

3. A silica gel surface digital printing pre-treatment process according to claim 1, characterized in that: The thickness of the silicone oil is 0.002 - 0.005 mm.

4. A pre-treatment process for digital printing on the surface of silica gel according to claim 1, characterized in that, The mass fraction of polyethyleneimine in the primer solution is 20% - 30%.

5. A pre-treatment process for digital printing on the surface of silica gel according to claim 1, characterized in that, The PET release film includes a PET film with a thickness of 0.01 - 0.2 mm and a release coating coated on the PET film.

6. The pre-treatment process for digital printing on the surface of silica gel according to claim 1, characterized in that, The thickness of the transparent silicone film is 0.1 - 0.2 mm.

7. A pre-treatment process for digital printing on the surface of silica gel according to claim 1, characterized in that, The baking temperature of the silicone oil in Step 2 is 70 - 90 °C.

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