Release agent for heat transfer printing, release film and preparation method

Abstract

The invention discloses a release agent for heat transfer printing, which is prepared from the following ingredients in parts by mass: 75 to 85 parts of silicone oil main agents, 15 to 25 parts of surface modifiers, 1.3 to 1.7 parts of cross-linking agents, 2.3 to 2.7 parts of catalysts, 0.8 to 1.2 parts of anchoring agents, 0.2 to 0.4 part of silicon dioxide particles and 1380 to 1420 parts of solvents. The surface modifier comprises polymethyl methacrylate and acrylic ester group-containing MQ silicon resin, and the mass ratio of the polymethyl methacrylate to the acrylic ester group-containing MQ silicon resin is 1: (1-2). Through the surface modifier composed of polymethyl methacrylate and acrylate group-containing MQ silicon resin, not only is the transparency of the release film improved, but also the release force of the release film and the adhesive force between the ink layer and the release layer are improved.

Description

Technical Field

[0001] The invention relates to the technical field of release films, and in particular to a release agent for thermal transfer, a release film and a preparation method thereof. Background Art

[0002] Thermal transfer is the process of transferring the pattern or text on the thermal transfer film to the substrate through the action of heat and pressure. The thermal transfer film is a multi-layer functional printing film with a release layer coated with a release agent on the surface of the carrier base film, and the pattern and text are printed on the surface of the release layer and the adhesive is coated on it.

[0003] Silicone oil release agent is a commonly used raw material for release film, but in application, there is a lot of silicon transfer, which leads to oil stains on the surface after printing transfer; the surface energy of the release layer obtained by silicone oil release agent is low, which causes the printed graphics to shrink or fall off, making it unusable.

[0004] Therefore, it is necessary to improve the release agent in the prior art. Summary of the invention

[0005] One of the purposes of the present invention is to overcome the defects existing in the prior art and provide a release agent for thermal transfer, which not only improves the transparency of the release film, but also improves the release force of the release film and the adhesion between the ink layer and the release layer through a surface modifier composed of polymethyl methacrylate and MQ silicone resin containing an acrylate group.

[0006] In order to achieve the above-mentioned process effect, the technical solution of the present invention is: a release agent for thermal transfer, which comprises 75-85 parts of silicone oil main agent, 15-25 parts of surface modifier, 1.3-1.7 parts of cross-linking agent, 2.3-2.7 parts of catalyst, 0.8-1.2 parts of anchoring agent, 0.2-0.4 parts of silica particles, and 1380-1420 parts of solvent in parts by mass; The surface modifier comprises polymethyl methacrylate and MQ silicone resin containing acrylate groups, and the mass ratio of the polymethyl methacrylate and the MQ silicone resin containing acrylate groups is 1:(1-2).

[0007] The preferred technical solution is: the acrylate-containing MQ silicone resin is prepared by tripropylene glycol diacrylate and hydrogen-containing MQ silicone resin under the joint action of a platinum catalyst and an inhibitor; the hydrogen-containing MQ silicone resin is prepared by hydrolysis and condensation of tetraethyl orthosilicate and 1,1,3,3-tetramethyldisiloxane under the catalysis of hydrochloric acid.

[0008] The preferred technical solution is: the molar ratio of the tetraethyl orthosilicate to 1,1,3,3-tetramethyldisiloxane is 1:(0.6-0.7); the molar ratio of the tripropylene glycol diacrylate to the hydrogenated MQ silicone resin is (2-2.5):1.

[0009] The preferred technical solution is: the molecular weight of the polymethyl methacrylate is 80,000-120,000.

[0010] The preferred technical solution is: the particle size of the silicon dioxide particles is 2-3 μm.

[0011] The preferred technical solution is: the silicone oil main agent is Wacker D955, the cross-linking agent is Wacker V60, the anchoring agent is Wacker HF87, and the catalyst is Wacker C05.

[0012] The preferred technical solution is: the solvent includes toluene and butanone in a mass ratio of 1: (2-3).

[0013] The second purpose of the present invention is to overcome the defects in the prior art and provide a release film for thermal transfer, comprising a substrate layer and a release layer, wherein the release layer is obtained by curing the above-mentioned release agent for thermal transfer, and the thickness of the release layer is 1 to 3 μm.

[0014] The third object of the present invention is to overcome the defects existing in the prior art and provide a method for preparing a release film for thermal transfer, comprising the following steps: S1: preparing a release agent coating liquid and configuring a substrate layer; S2: applying the release agent coating liquid to the surface of the substrate layer, and curing to obtain a release film semi-finished product having a release layer; S3: Curing the semi-finished release film to obtain a release film for thermal transfer; The aging temperature in S3 is 58-62°C.

[0015] The preferred technical solution is: the curing temperatures in S2 are set to 90±5°C, 115±5°C, 130±5°C, 140±5°C, 145±5°C, and 120±5°C in sequence.

[0016] The advantages and beneficial effects of the present invention are: The release agent for thermal transfer uses a surface modifier composed of polymethyl methacrylate and MQ silicone resin containing an acrylate group, which not only improves the transparency of the release film, but also improves the release force of the release film and the adhesion between the ink layer and the release layer; the contact area between the ink layer and the release layer is increased by silicon dioxide, further improving the adhesion between the two. DETAILED DESCRIPTION

[0017] The specific implementation of the present invention is further described below in conjunction with the examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention, and cannot be used to limit the protection scope of the present invention.

[0018] Release agent It includes silicone oil main agent, surface modifier, cross-linking agent, catalyst, anchoring agent, silica particles and solvent.

[0019] The main silicone oil is the main formula material, which affects the release force performance of the release layer and the stability and flatness of the coating. Furthermore, the main silicone oil is methyl vinyl silicone oil, which has extremely low surface energy and can provide excellent release effect; it has high thermal stability and is not easy to decompose or deteriorate in high temperature environment; by adjusting the molecular weight and cross-linking degree, the hardness and elasticity of the release coating based on methyl vinyl silicone oil can be changed to adapt to different application scenarios; it has low viscosity and is easy to be evenly coated on the surface of the substrate to form a continuous and smooth film.

[0020] Silica particles form tiny bumps or depressions in the release agent coating, thereby increasing the microscopic roughness of the surface, which helps to improve the spreadability and adhesion of the ink on it, while reducing the surface energy to maintain good release performance. By adjusting the particle size and addition amount of silica, the release force is made more stable and easy to control.

[0021] Adding too much cross-linking agent increases the cross-linking density, but leads to a decrease in release force and surface energy, resulting in shrinkage of the ink pattern; adding too little cross-linking agent causes the release film to not fully cure and cannot be used. Adding too much anchoring agent causes a decrease in reaction rate; adding too little anchoring agent results in poor adhesion between the release layer and the substrate layer. Furthermore, the catalyst is a platinum catalyst, and adding too much catalyst results in high product cost, short life of the slurry, and accelerated aging of the release film, resulting in unstable release force of the release film; adding too little catalyst causes the product to fail to cure normally.

[0022] Toluene has low polarity and similar solubility parameters to polymethyl methacrylate, which is conducive to the dissolution of polymethyl methacrylate and improves the coating thickness and uniformity of the coating solution. Too much butanone will produce shrinkage holes; too little butanone will slow down the volatilization rate and have a negative impact on the surface flatness of the release layer.

[0023] Surface modifiers include polymethyl methacrylate and MQ silicone resin containing acrylate groups. Among them, polymethyl methacrylate increases the surface energy of the release layer because of the ester groups with high polarity in its molecules. The addition of silicon dioxide easily leads to reduced transparency and increased haze of the release film. Polymethyl methacrylate has good transparency and improves the optical properties of the release film. MQ silicone resin containing acrylate groups improves the compatibility between polymethyl methacrylate and the silicone oil main agent because it contains acrylate segments and siloxane segments; the acrylate segments participate in the cross-linking of the silicone oil main agent, increase the cross-linking density, and improve the high temperature resistance of the release film.

[0024] In order to obtain a release layer with better flexibility and surface smoothness, the molecular weight of polymethyl methacrylate (PMMA) is further 80000~120000. If the molecular weight of PMMA is too high, the viscosity will increase, which will easily lead to poor fluidity during coating, making it difficult to form a thin coating, and the surface energy of the release layer will be reduced; if the molecular weight of PMMA is too low, although the viscosity is low and it is easy to coat, the surface energy will increase, which is not conducive to the peeling of the release film.

[0025] Preparation of MQ silicone resin containing acrylate: Tetraethyl orthosilicate (TEOS) and 1,1,3,3-tetramethyldisiloxane (TMDSO) are mixed in a mixed solvent of water and ethanol at a molar ratio of 1: (0.6~0.7), and hydrolyzed and condensed under the catalysis of hydrochloric acid. The reaction temperature is room temperature 25°C and the reaction time is 2.5h to obtain hydrogenated MQ silicone resin. Take tripropylene glycol diacrylate (TPGDA) and hydrogenated MQ silicone resin at a molar ratio of (2~2.5):1, and first mix tripropylene glycol diacrylate with an anticoagulant, a platinum catalyst and isopropanol. After heating to 65°C, add dropwise the hydrogenated MQ silicone resin dissolved in isopropanol for 1~1.5h, and then keep warm for reaction for 1.5h. After the reaction is completed, purify and distill under reduced pressure to obtain the product.

[0026] Among them, the amount of mixed solvent added is 35% of the total mass of ethyl orthosilicate and 1,1,3,3-tetramethyldisiloxane. The mass fraction of hydrochloric acid is 40%, and the amount of hydrochloric acid added is 9% of the total mass of ethyl orthosilicate and 1,1,3,3-tetramethyldisiloxane. Too little addition of hydrochloric acid can easily lead to excessive molecular weight of hydrogen-containing MQ silicone resin, reduced hydrogen content, which is not conducive to the grafting of acrylate groups; too much addition of hydrochloric acid can easily lead to aggravated dehydrogenation reaction, increased viscosity of the reaction liquid, and reduced hydrogen content. The anticoagulant is p-hydroxyanisole, and the amount added is 0.15% of the total mass of tripropylene glycol diacrylate and hydrogen-containing MQ silicone resin. The amount of isopropanol added is 50% of the total mass of tripropylene glycol diacrylate and hydrogen-containing MQ silicone resin. The amount of platinum catalyst added is 0.2% of the total mass of tripropylene glycol diacrylate and hydrogen-containing MQ silicone resin.

[0027] The synthetic raw material composition of the MQ silicone resin sample containing acrylate is: Sample 1: Through the above preparation method, ethyl orthosilicate and 1,1,3,3-tetramethyldisiloxane are mixed in a molar ratio of 1:0.65, and hydrolyzed and condensed under the catalysis of hydrochloric acid to obtain hydrogen-containing MQ silicone resin; tripropylene glycol diacrylate and hydrogen-containing MQ silicone resin are mixed in a molar ratio of 2.2:1 under the joint action of platinum catalyst and inhibitor.

[0028] Sample 2: Through the above preparation method, ethyl orthosilicate and 1,1,3,3-tetramethyldisiloxane are mixed in a molar ratio of 1:0.5, and hydrolyzed and condensed under the catalysis of hydrochloric acid to obtain hydrogen-containing MQ silicone resin; tripropylene glycol diacrylate and hydrogen-containing MQ silicone resin are mixed in a molar ratio of 2.2:1 under the joint action of platinum catalyst and inhibitor.

[0029] Sample 3: Through the above preparation method, ethyl orthosilicate and 1,1,3,3-tetramethyldisiloxane are mixed in a molar ratio of 1:0.65, and hydrolyzed and condensed under the catalysis of hydrochloric acid to obtain hydrogen-containing MQ silicone resin; tripropylene glycol diacrylate and hydrogen-containing MQ silicone resin are mixed in a molar ratio of 1.5:1 under the joint action of platinum catalyst and inhibitor.

[0030] Example 1

[0031] The release film for thermal transfer includes a substrate layer and a release layer. The release layer is made by curing the release agent for thermal transfer. The release agent for thermal transfer includes 80 parts of silicone oil main agent (Wacker D955), 20 parts of surface modifier, 1.5 parts of cross-linking agent (V60), 2.5 parts of catalyst (C05), 1 part of anchoring agent (HF87), 0.3 parts of silica particles (KMP-590), and 1400 parts of solvent in terms of weight. Among them, the surface modifier includes polymethyl methacrylate and MQ silicone resin containing acrylate groups. The mass ratio of polymethyl methacrylate and MQ silicone resin containing acrylate groups is 1:1.6. The MQ silicone resin containing acrylate groups is sample 1. The solvent is toluene and butanone in a mass ratio of 1:2.5.

[0032] The preparation method of the release film for thermal transfer comprises the following steps: S1: preparing a release agent coating liquid and configuring a substrate layer; S2: Coat the release agent coating liquid on the surface of the substrate layer using an M120 micro-concave roller at a coating speed of 40 m / min; cure in an oven with 6 sections, each section being 4 meters long, to obtain a release film semi-finished product with a release layer, with a coating dry weight of 0.3 g / m 2 The curing temperatures are set to 90°C, 115°C, 130°C, 140°C, 145°C, and 120°C in sequence, wherein the thickness of the release layer is 2 μm.

[0033] S3: Curing the semi-finished release film at a temperature of 60° C. for 24 hours to obtain a release film for thermal transfer.

[0034] Example 2

[0035] Example 2 is based on Example 1, except that, by weight, the thermal transfer release agent includes 85 parts of silicone oil main agent (Wacker D955), 15 parts of surface modifier, 1.5 parts of crosslinking agent (V60), 2.5 parts of catalyst (C05), 1 part of anchoring agent (HF87), 0.3 parts of silica particles (KMP-590), and 1400 parts of solvent. The composition and preparation method remain unchanged.

[0036] Example 3

[0037] Example 3 is based on Example 1, except that the MQ silicone resin containing acrylate groups is sample 2, and the composition ratio and preparation method remain unchanged.

[0038] Example 4

[0039] Example 4 is based on Example 1, except that the MQ silicone resin containing acrylate groups is sample 3, and the composition ratio and preparation method remain unchanged.

[0040] Example 5

[0041] Example 5 is based on Example 1, except that the surface modifier comprises polymethyl methacrylate and MQ silicone resin containing acrylate groups, and the mass ratio of polymethyl methacrylate to MQ silicone resin containing acrylate groups is 1:1.

[0042] Comparative Example 1 Comparative Example 1 is based on Example 1, except that the surface modifier only includes polymethyl methacrylate, and the other compositions remain unchanged.

[0043] Comparative Example 2 Comparative Example 2 is based on Example 1, except that the surface modifier only includes MQ silicone resin containing acrylate groups, and the other compositions remain unchanged.

[0044] Performance Test: (1) Silicon weight: Use X-ray fluorescence spectrometer to test silicon weight; (2) Peel force: Tensile test was performed after 20 minutes of lamination using Nitto 31B tape (the force value detected at a peeling speed of 300 mm / min at an angle of 180°); (3) Residual bonding rate: Use Nitto 31B tape to test the residual bonding rate; (4) Aging resistance: After laminating Tesa, place it in an environment of 70°C for 24 hours, then take it out, cool it for 2 hours, and test the peeling force; (5) Surface roughness: Tester: Japan Keyence VR-6000.

[0045] (6) Adhesion: A 30μm ink layer is provided on the release layer surface of the release film. A vertical line is drawn on the surface of the ink layer at intervals of 1mm*1mm, and the adhesion between the ink layer and the release layer is judged based on the extension of the scratch. The adhesion is graded as follows: the grades are divided into 0~4 grades, where 0 means that small pieces of ink peel off at the cut and intersection, and the actual damage in the grid area is less than 5%; 1 means that the area of ​​the cut and intersection edge peeling is 5~15%; 2 means that the cut and intersection edge peeling is partial or large-scale peeling, and the peeling area is 16~35%; 3 means partial square peeling, and the peeling area is 36~65%; 4 means that the peeling area is greater than 65%. The lower the adhesion grade, the better the adhesion of the ink layer on the release layer.

[0046] The measurement results of the embodiments and comparative examples are shown in the table below:

[0047] Compared with Example 1, Example 3 has a reduced content of 1,1,3,3-tetramethyldisiloxane in the synthesis of the hydrogenated MQ silicone resin, which leads to a reduced hydrogen content of the hydrogenated MQ silicone resin, thereby reducing the addition reaction with tripropylene glycol diacrylate, thereby reducing the acrylate group content, which has a negative effect on the release force, has a negative effect on the crosslinking density of the release agent, and thus has a negative effect on the aging resistance, is also not conducive to the compatibility of polymethyl methacrylate and the silicone oil main agent, leads to increased roughness, and uneven concave-convex microstructure on the surface of the release layer, which has a negative effect on the adhesion between the ink layer and the release layer.

[0048] In Example 4 compared with Example 1, the content of tripropylene glycol diacrylate in the acrylate-containing MQ silicone resin is reduced, which promotes the addition reaction of the hydrogen-containing MQ silicone resin and tripropylene glycol diacrylate, resulting in a decrease in the double bond content in tripropylene glycol diacrylate, and an obvious dehydrogenation reaction in the hydrogen-containing MQ silicone resin. The viscosity-increasing effect in the release agent is reduced, which has a negative impact on the release force, and also leads to a decrease in the crosslinking density of the release agent, which has a negative impact on the aging resistance and the adhesion between the ink layer and the release layer.

[0049] Compared with Example 1, the transparency of the release film of Example 5 is increased and the haze is reduced.

[0050] Compared with Example 1, the cross-linking density of the release agent in Comparative Example 2 is large. Although the aging resistance is improved, the polar groups are encapsulated in the polymer, the surface energy is reduced, and thus the release force and the adhesion between the ink layer and the release layer are negatively affected.

[0051] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A release agent for thermal transfer, characterized in that: By mass, it includes 75-85 parts of silicone oil main agent, 15-25 parts of surface modifier, 1.3-1.7 parts of cross-linking agent, 2.3-2.7 parts of catalyst, 0.8-1.2 parts of anchoring agent, 0.2-0.4 parts of silica particles, and 1380-1420 parts of solvent; The surface modifier comprises polymethyl methacrylate and MQ silicone resin containing acrylate groups, and the mass ratio of the polymethyl methacrylate and the MQ silicone resin containing acrylate groups is 1:(1-2).

2. The release agent for thermal transfer according to claim 1, characterized in that: The acrylate-containing MQ silicone resin is prepared by reacting tripropylene glycol diacrylate and hydrogen-containing MQ silicone resin under the combined action of a platinum catalyst and a polymerization inhibitor; the hydrogen-containing MQ silicone resin is prepared by hydrolysis and condensation of ethyl orthosilicate and 1,1,3,3-tetramethyldisiloxane under the catalysis of hydrochloric acid.

3. The release agent for thermal transfer according to claim 2, characterized in that: The molar ratio of the tetraethyl orthosilicate to 1,1,3,3-tetramethyldisiloxane is 1:(0.6-0.7); the molar ratio of the tripropylene glycol diacrylate to the hydrogenated MQ silicone resin is (2-2.5):

1.

4. The release agent for thermal transfer according to claim 1, characterized in that: The molecular weight of the polymethyl methacrylate is 80,000-120,000.

5. The release agent for thermal transfer according to claim 1, characterized in that: The particle size of the silicon dioxide particles is 2-3 μm.

6. The release agent for thermal transfer according to claim 1, characterized in that: The silicone oil main agent is Wacker D955, the crosslinking agent is Wacker V60, the anchoring agent is Wacker HF87, and the catalyst is Wacker C05.

7. The release agent for thermal transfer according to claim 1, characterized in that: The solvent includes toluene and butanone in a mass ratio of 1:(2-3).

8. A release film for thermal transfer, characterized in that: The invention comprises a substrate layer and a release layer, wherein the release layer is obtained by curing the release agent for thermal transfer according to any one of claims 1 to 7, and the thickness of the release layer is 1 to 3 μm.

9. A method for preparing a release film for thermal transfer, characterized in that: The following steps are involved: S1: preparing a release agent coating liquid and configuring a substrate layer; S2: applying the release agent coating liquid to the surface of the substrate layer, and curing to obtain a release film semi-finished product having a release layer; S3: Curing the semi-finished release film to obtain a release film for thermal transfer; The aging temperature in S3 is 58-62°C.

10. The method for preparing a release film for thermal transfer according to claim 9, characterized in that: The curing temperatures in S2 are set to 90±5°C, 115±5°C, 130±5°C, 140±5°C, 145±5°C, and 120±5°C in sequence.

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