A peroxide-cured silicone pressure-sensitive adhesive and a method for preparing the same

Abstract

The present invention provides a formula of a peroxide-cured organosilicon pressure-sensitive adhesive and a pressure-sensitive adhesive prepared therefrom. By changing the structure of the raw rubber and the cross-linking aid in the formula, the adhesive can maintain good initial adhesion and steel plate adhesion while also having excellent high temperature resistance, and has good commercial application value.

Description

Technical Field

[0001] The invention relates to a peroxide-cured organic silicon pressure-sensitive adhesive and a preparation method thereof, and belongs to the field of adhesive manufacturing. Background Art

[0002] Pressure sensitive adhesive is a kind of material that is dry at room temperature and has dry and permanent adhesiveness. It is mainly used in the form of tape. When using it, it can be firmly adhered to the surface of the substrate by gently pressing it with your fingers or palms, and can be peeled off from the surface of the adherend without residue. Silicone pressure sensitive adhesive not only has good adhesion to the surfaces of metal, paper, glass, fabric, plastic and other substrates like general organic pressure sensitive adhesive, but also has good adhesion to some low surface energy substrates, such as polytetrafluoroethylene, silicone rubber, etc. In addition, silicone pressure sensitive adhesive is the only pressure sensitive adhesive that can be used in the temperature range of -65℃-300℃.

[0003] At present, the silicone pressure-sensitive adhesives on the market can be divided into two categories according to the vulcanization method, one is the peroxide vulcanization type, and the other is the hydrosilylation vulcanization type. As the application scenarios become more and more demanding, higher requirements are placed on the temperature resistance of pressure-sensitive adhesives. Patent CN105038689A provides a method for preparing a solvent-free room temperature cross-linked silicone pressure-sensitive adhesive, which is a condensation vulcanization type pressure-sensitive adhesive, that is, a condensation reaction of hydroxyl raw rubber and silane at room temperature to complete the cross-linking process, which solves the problem of high-temperature vulcanization required in the existing system, thereby limiting its application on some substrates with poor temperature resistance. At the same time, the patent uses dimethyl silicone oil as a diluent to solve the environmental pollution problem caused by the use of benzene solvents as diluents in traditional pressure-sensitive adhesive products. However, this method needs to be placed for 3-14 days to completely cure to obtain a pressure-sensitive adhesive product, and the curing speed is too slow. The existing pressure-sensitive adhesive production line requires it to complete the curing within a few minutes, which is difficult to meet the actual needs of the existing production line. At the same time, using dimethyl silicone oil as a diluent will not participate in the cross-linking reaction in the system, nor will it evaporate from the system, but will exist in the pressure-sensitive adhesive in a free form. The pressure-sensitive adhesive tape made with this will have "silicon transfer" and will often contaminate the substrate protected by the pressure-sensitive adhesive tape, and its practical value is poor. In addition, the pressure-sensitive adhesive prepared by this method has weak temperature resistance and its peel strength at high temperature is significantly reduced.

[0004] Patent CN103614110A provides a method for preparing silicone adhesive for fire-resistant mica tape, which improves the heat resistance of mica tape by changing the structure of silicone resin, a tackifier in pressure-sensitive adhesive. That is, silanes with different structures are used to change the structure of silicone resin, an important component of pressure-sensitive adhesive, thereby improving the heat resistance of the tape. The silicone resin with a special structure used in this method has a complex production process, and the proportion of silicone resin in pressure-sensitive adhesive is relatively large (>30%), which poses a huge challenge in terms of economy. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a new peroxide-cured silicone pressure-sensitive adhesive and a preparation method thereof, which uses a cross-linking auxiliary agent with a special structure, and has excellent high temperature resistance while maintaining good initial adhesion and steel plate adhesion of the pressure-sensitive adhesive, and has good commercial application value.

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

[0007] A peroxide-cured silicone pressure-sensitive adhesive comprises the following raw material components in parts by weight:

[0008]

[0009]

[0010] Preferably, the organic silicone pressure-sensitive adhesive, the hydroxyl raw rubber is selected from the polymer having the structure shown in Formula I:

[0011]

[0012] In the formula, R1 is methyl or phenyl; n=7000-12000, preferably 8000-10000; m=0-1600, preferably 0-800; p=0-40, preferably 1-15.

[0013] The crosslinking aid of the silicone pressure-sensitive adhesive is selected from a polymer having a structure as shown in Formula II:

[0014]

[0015]

[0016] In the formula, x=10-80, preferably 10-30; y=1-10, preferably 2-5.

[0017] The organic silicone pressure-sensitive adhesive, the MQ resin is a methyl MQ resin, and the hydroxyl content is 1-5wt%, and more preferably 2.5-3.5wt%.

[0018] The initiator of the silicone pressure-sensitive adhesive is a peroxide compound, such as benzoyl peroxide (BPO), 2,4-dichlorobenzoyl peroxide (DCBP), tert-butyl perbenzoate (TBPB), di-tert-butyl peroxide (DTBP), 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane (bis-2,5), etc., and benzoyl peroxide (BPO) and 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane (bis-2,5) are further preferred.

[0019] The organic silicone pressure-sensitive adhesive, the solvent is a benzene series, such as toluene, xylene, ethylbenzene, etc., and xylene is more preferred.

[0020] The preparation process of the organic silicone pressure-sensitive adhesive is as follows: hydroxyl raw rubber, MQ resin and solvent are mixed evenly, and then an acidic or alkaline catalyst is added, and reflux reaction is carried out for 4-6 hours. During this period, the generated water is continuously removed from the system through a water separator, and then the temperature is reduced to obtain a solution.

[0021] The curing process of the organic silicone pressure-sensitive adhesive is as follows: the above solution, cross-linking aid and initiator are mixed evenly, applied on a polyimide or polyester film, placed in an oven, vulcanized at 70-80°C for 2-3 minutes, and then heated to 170-180°C for vulcanization for 8-10 minutes.

[0022] Preferably, the acidic catalyst can be selected from benzoic acid, cation exchange resin, acid clay, etc., preferably benzoic acid. The amount added is 0.05-0.2wt%, preferably 0.1-0.15wt%.

[0023] The alkaline catalyst may be lithium hydroxide, sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, etc., preferably sodium hydroxide. The added mass is 5-100 ppm, preferably 10-30 ppm.

[0024] The traditional peroxide vulcanization system uses the free radicals generated on the initiator to trigger the methyl groups on the silicon to undergo a free radical crosslinking reaction, and the crosslinking points are randomly distributed. That is, increasing the amount of initiator can increase the crosslinking density, improve the cohesive strength of the system, improve the high temperature resistance, and prevent residual glue from occurring at high temperatures. The present invention adopts a new formula system and uses a crosslinking aid with a special structure to make the crosslinking points non-randomly distributed, thereby producing a "concentrated crosslinking" effect. While increasing the crosslinking density and cohesive strength, the elasticity of the body will not be greatly affected. That is, the prepared pressure-sensitive adhesive can maintain good initial adhesion and steel plate adhesion of the pressure-sensitive adhesive while also having excellent high temperature resistance. DETAILED DESCRIPTION

[0025] The present invention is further described in detail with reference to the following examples, but the scope of the present invention is not limited to these examples.

[0026] <Raw material source information>

[0027] Hydroxylated raw rubber-1, molecular weight 600,000, hydroxyl terminated, side chain containing vinyl, vinyl content 0.17%, R1 is methyl, volatile content ≤1%, Shenzhen Jipeng Silicon Fluoride Materials Co., Ltd.;

[0028] Hydroxylated raw rubber-2, molecular weight 600,000, hydroxyl terminated, R1 is methyl, side chain does not contain vinyl, volatile content ≤1%, Shenzhen Jipeng Silicon Fluoride Materials Co., Ltd.;

[0029] Crosslinking aid-1: The structure is Formula II in the claim, wherein x=28, y=1, and it is homemade. The preparation method is as follows:

[0030] In a 5L glass reactor, add 43.2g tetrakis(dimethylvinylsiloxy)silane (0.1mol), 941.9g octamethylcyclotetrasiloxane (3.2mol), 55.5g methylphenylcyclosiloxane (0.1mol), 1.0g trifluoromethanesulfonic acid (0.1wt%), then heat to 50°C and react for 4h. Cool to room temperature, add 10.4g calcium carbonate, react for 2h, then filter to obtain a crude product. Then remove volatiles at 150°C and 1kPa for 2h to obtain 915.6g of product with a yield of 88%.

[0031] Its structure was identified by NMR, and the result was:

[0032] 1 H NMR (400MHz, CDCl3): [d,ppm]=0.13(-SiCH3,684H), 5.17-5.42(-SiCH=CH2-,3H), 7.19(-SiC6H5,8H), 7.28(-SiC6H5,8H), 7.46(-SiC6H5,4H).

[0033] Crosslinking aid-2: The structure is Formula II in the claim, wherein x=52, y=3, and it is homemade. The preparation method is as follows:

[0034] In a 5L glass reactor, add 43.2g tetrakis(dimethylvinylsiloxy)silane (0.1mol), 1.75kg octamethylcyclotetrasiloxane (5.9mol), 163.47g methylphenylcyclosiloxane (0.3mol), 2.0g trifluoromethanesulfonic acid (0.1wt%), then heat to 50°C and react for 4h. Cool to room temperature, add 19.6g calcium carbonate, react for 2h, then filter to obtain a crude product. Then remove volatiles at 150°C and 1kPa for 2h to obtain 1.72kg of product with a yield of 88%.

[0035] Its structure was identified by NMR, and the result was:

[0036] 1H NMR (400MHz, CDCl3): [d, ppm] = 0.13 (-SiCH3, 1284H), 5.17-5.42 (-SiCH = CH2-, 3H), 7.19 (-SiC6H5, 24H), 7.28 (-SiC6H5, 24H), 7.46 (-SiC6H5, 12H).

[0037] Vinyl silane: vinyl trimethoxy silane, >98%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0038] Vinyl silicone oil: Vinyl-terminated silicone oil, viscosity 50 cp, RH-V395, purchased from Ningbo Runhe High-tech Materials Technology Co., Ltd.

[0039] Initiator: benzoyl peroxide (BPO), 2,5-dimethyl-2,5-di-tert-butyl peroxyhexane (bis-2,5), 93%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0040] MQ resin: hydroxyl content 3wt%, molecular weight Mw=20256, homemade. The preparation method refers to patent CN114230795A, the specific method is as follows:

[0041] At 10°C, in reactor A, 36wt% hydrochloric acid aqueous solution and 30wt% water glass solution were continuously added at flow rates of 200g / min and 800g / min, respectively, and the SiO2 / HCl ratio was 1.53. The power equipment in reactor A was a centrifugal pump, and the mixing equipment was an SL-type static mixer, with an average residence time of 1min, a pH value of 1, a reflux ratio of 20, an aging time of 8min in reactor B, and a tubular reactor was selected for reactor B. All products in reactor B and propanol, divinyltetramethyldisiloxane, and benzene were continuously added to reactor C at 500g / min, 100g / min, and 500g / min, respectively. The reaction temperature of reactor C was 75°C, and the end-capping reaction time was 165min. The product of reactor C was continuously introduced into reactor D, and reactor D was washed and separated for 60min. The crude product in the oil phase was taken out, and then the solvent was removed by rotary evaporation to obtain MQ resin powder.

[0042] Example 1

[0043] Preparation of pressure sensitive adhesive:

[0044] In a 1L glass reactor, add 100g hydroxyl raw rubber-1, 120g MQ resin, and 200g xylene. After fully dissolving, add 0.5g benzoic acid, then heat to reflux, use a water separator to continuously remove the generated water, continue for 4 hours, then evaporate about 40g of xylene, and cool to room temperature. Test its viscosity: 30200cp, solid content 60.1%.

[0045] Curing of pressure sensitive adhesive:

[0046] Take 10g of the above-mentioned pressure-sensitive adhesive, add 0.05g of crosslinking agent-1 and 0.08g of 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane (bis-2,5), mix well, apply it on a 25μm polyimide film, vulcanize at 80℃ for 2min, and then heat to 180℃ for vulcanization for 10min.

[0047] Example 2

[0048] Preparation of pressure sensitive adhesive:

[0049] Same as Example 1

[0050] Curing of pressure sensitive adhesive:

[0051] Take 10g of the above pressure-sensitive adhesive, add 0.05g of crosslinking aid-2 and 0.08g of 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane (bis-2,5), mix well, apply it on a 25μm polyimide film, vulcanize at 80℃ for 2min, and then heat to 180℃ for vulcanization for 10min.

[0052] Example 3

[0053] Preparation of pressure sensitive adhesive:

[0054] In a 1L glass reactor, add 100g hydroxyl raw rubber-2, 120g MQ resin, and 200g xylene. After fully dissolving, add 0.5g benzoic acid, then heat to reflux, use a water separator to continuously remove the generated water, continue for 4 hours, then evaporate about 40g of xylene, and cool to room temperature. Test its viscosity: 30400cp, solid content 60.2%.

[0055] Curing of pressure sensitive adhesive:

[0056] Take 10g of the above-mentioned pressure-sensitive adhesive, add 0.06g of crosslinking agent-1 and 0.08g of 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane (bis-2,5), mix well, apply it on a 25μm polyimide film, vulcanize at 80℃ for 2min, and then heat to 180℃ for vulcanization for 10min.

[0057] Example 4

[0058] Preparation of pressure sensitive adhesive:

[0059] The same as Example 3, except that 140 g of MQ resin and 150 g of xylene were added.

[0060] Curing of pressure sensitive adhesive:

[0061] Take 10g of the above pressure-sensitive adhesive, add 0.05g of crosslinking aid-1 and 0.08g of benzoyl peroxide (BPO), mix well, apply it on a 25μm polyimide film, vulcanize at 80°C for 2min, and then heat to 180°C for vulcanization for 10min.

[0062] Comparative Example 1

[0063] Preparation of pressure sensitive adhesive:

[0064] In a 1L glass reactor, add 100g hydroxyl raw rubber-2, 120g MQ resin, and 200g xylene. After fully dissolving, add 0.5g benzoic acid, then heat to reflux, use a water separator to continuously remove the generated water, continue for 4 hours, then evaporate about 40g of xylene, and cool to room temperature. Test its viscosity: 30400cp, solid content 60.2%.

[0065] Curing of pressure sensitive adhesive:

[0066] Take 10 g of the pressure-sensitive adhesive, add 0.08 g of benzoyl peroxide (BPO), mix well, apply it on a 25 μm polyimide film, vulcanize at 80° C. for 2 min, and then heat to 180° C. for vulcanization for 10 min.

[0067] Comparative Example 2

[0068] Preparation of pressure sensitive adhesive:

[0069] Same as comparative example 1

[0070] Curing of pressure sensitive adhesive:

[0071] Take 10g of the above pressure-sensitive adhesive, add 0.05g of vinyl silane, add 0.08g of benzoyl peroxide (BPO), mix well, apply it on a 25μm polyimide film, vulcanize at 80°C for 2min, and then heat to 180°C for vulcanization for 10min.

[0072] Comparative Example 3

[0073] Preparation of pressure sensitive adhesive:

[0074] Same as comparative example 1

[0075] Curing of pressure sensitive adhesive:

[0076] Take 10g of the above pressure-sensitive adhesive, add 0.05g of vinyl silicone oil, add 0.08g of benzoyl peroxide (BPO), mix well, apply it on a 25μm polyimide film, vulcanize at 80°C for 2min, and then heat to 180°C for vulcanization for 10min.

[0077] Table 1 Silicone rubber mechanical properties test data

[0078]

[0079] The pressure-sensitive adhesive prepared in Example 1 or 2, in addition to having good initial adhesion and steel plate adhesion, can last for 30 minutes at high temperature without debonding at a higher temperature, and has higher heat resistance. Compared with Comparative Example 2, the addition of vinyl silane as a crosslinking aid can improve heat resistance to a certain extent, but its probe initial adhesion and steel plate adhesion will be seriously affected. In Comparative Example 3, the addition of vinyl silicone oil as a crosslinking aid can improve the probe initial adhesion and steel plate adhesion to a certain extent, but it still does not achieve the excellent effect of Example 1 or 2.

Claims

1. A peroxide-cured silicone pressure-sensitive adhesive, characterized in that: The raw material components include the following parts by weight: The hydroxylated rubber is selected from the polymers having the structure shown in formula I: In the formula, R1 is methyl or phenyl; n=7000-12000, m=0-1600, p=0-40; The cross-linking aid is selected from the polymer with the structure shown in Formula II: (Ⅱ) Wherein, x = 10-80; y = 1-10; The MQ resin is methyl MQ resin.

2. The organic silicone pressure-sensitive adhesive according to claim 1, characterized in that: The raw material components include the following parts by weight:

3. The organic silicone pressure-sensitive adhesive according to claim 1, characterized in that: n=8000-10000; m=0-800; p=1-15.

4. The organic silicone pressure-sensitive adhesive according to claim 1, characterized in that: x=10-30, y=2-5.

5. The organic silicone pressure-sensitive adhesive according to claim 1, characterized in that: The hydroxyl content of the MQ resin is 1-5wt%.

6. The organic silicone pressure-sensitive adhesive according to claim 5, characterized in that: The hydroxyl content of the MQ resin is 2.5-3.5wt%.

7. The organic silicone pressure-sensitive adhesive according to claim 1, characterized in that: The initiator is a peroxide compound.

8. The organic silicone pressure-sensitive adhesive according to claim 7, characterized in that: The initiator is benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butyl perbenzoate, di-tert-butyl peroxide, and 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane.

9. The organic silicone pressure-sensitive adhesive according to claim 1, characterized in that: The solvent is a benzene series compound.

10. The organic silicone pressure-sensitive adhesive according to claim 9, characterized in that: The solvent is toluene, xylene, or ethylbenzene.

11. A method for preparing the organosilicon pressure-sensitive adhesive according to any one of claims 1 to 10, wherein the preparation process of the pressure-sensitive adhesive is as follows: hydroxyl raw rubber, MQ resin and solvent are uniformly mixed, then an acidic or alkaline catalyst is added, and reflux reaction is performed for 4-6 hours, during which the generated water is continuously removed from the system through a water separator, and then the temperature is lowered to obtain a solution; The above solution, cross-linking aid and initiator are mixed evenly, applied on the polyimide or polyester film, placed in an oven, vulcanized at 70-80°C for 2-3 minutes, and then heated to 170-180°C for vulcanization for 8-10 minutes.

12. The preparation method according to claim 11, wherein The acidic catalyst is selected from benzoic acid, cation exchange resin, and acidic clay.

13. The preparation method according to claim 12, wherein: The acid catalyst is benzoic acid.

14. The preparation method according to claim 11, wherein: The amount of the acid catalyst added is 0.05-0.2 wt%.

15. The preparation method according to claim 14, wherein: The amount of the acid catalyst added is 0.1-0.15 wt%.

16. The preparation method according to claim 11, wherein The alkaline catalyst is lithium hydroxide, sodium hydroxide, potassium hydroxide or tetramethylammonium hydroxide.

17. The preparation method according to claim 16, wherein: The alkaline catalyst is sodium hydroxide.

18. The preparation method according to claim 11, wherein: The added mass of the alkaline catalyst is 5-100 ppm.

19. The preparation method according to claim 18, wherein: The added mass of the alkaline catalyst is 10-30 ppm.

Images