Ultraviolet (UV) / heat dual-curing polysiloxane and preparation method thereof

Abstract

The invention discloses UV (ultraviolet) / thermal dual-curing polysiloxane and a preparation method thereof, the structural general formula of the polysiloxane is # imgabs0 #, R1 is # imgabs1 #, R2 is one of methyl or phenyl; r3 is phenyl; the value of a ranges from 150 to 2000, and the preferable value ranges from 200 to 1500; the value of b / a is 0.1%-2%, preferably, the value of b / a is 1.1%-1.5%; c is zero or c / a is 1%-20%, and d / (a + b + c) is 5%-20%. The polysiloxane containing an ultraviolet light curing group, a silicon vinyl group and a silicon hydrogen group at the same time is prepared, light curing reaction and hydrosilylation curing reaction can be carried out, the defect that the curing degree of a UV / moisture dual-curing system in a large-area shadow area is not uniform is overcome, the raw materials of the preparation method are low in cost and easy to obtain, and the preparation method is suitable for industrial production. The method is simple in production process, easy to operate, mild in reaction condition, free of special requirements on equipment and easy to realize industrialization.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic silicon materials, and in particular, relates to a UV / heat dual-curable polysiloxane and a preparation method thereof. Background Art

[0002] In the field of silicone materials, silicone polymers composed of Si-O main chains with functional groups generally have excellent properties such as low surface tension, high and low temperature resistance, stable chemical properties and biocompatibility. Generally, Si-O bonds give polymers excellent thermal and chemical stability, while substituents give silicone polymers greater potential. Due to these excellent properties, silicone polymers have been widely used in products such as adhesives, coatings, films, additive manufacturing and flexible electronics.

[0003] Light curing (mainly UV curing) is regarded as a green and environmentally friendly technology because of its unique characteristics such as high efficiency, low energy consumption, solvent-free formula and mild reaction conditions. Introducing photosensitive groups on the side chains of silicone polymers can achieve rapid curing under ultraviolet light, which can greatly improve its curing efficiency. However, the UV curing system relies on UV irradiation and cannot guarantee the degree of curing in the shadow area, which may cause corrosion, aging or bonding peeling of the unbonded parts. Therefore, using a separate light curing system may affect the quality of the product.

[0004] In order to overcome this shortcoming, the dual-cure system has been widely adopted, which can ensure sufficient curing in the shadow area, thereby broadening the application field and product types of silicone materials. The resins or polymers prepared in the invention patents with publication numbers CN111234234A, CN109929079A, CN103980496A and CN102408569A can all adopt the UV / moisture dual-cure method, which solves the problem that the shadow area cannot be UV-cured. However, the moisture curing method requires the participation of moisture. If the enclosed shadow area is large, the resin or polymer on the outside will fully contact the moisture and the curing reaction will occur relatively quickly. The generated cured layer will block the penetration of external moisture, resulting in incomplete internal curing or uneven curing degree inside and outside, thereby affecting the overall performance of the product.

[0005] Traditional thermal curing (addition curing system) is not affected by moisture, and has a fast curing rate and high efficiency. UV / heat dual curing can not only reduce the curing temperature and shorten the curing time, but also deepen the degree of curing and improve the performance of the polymer. First, relying on the fast curing characteristics of UV curing technology, the sample can be formed quickly. Then, thermal curing is used to improve the overall performance of the material. This dual curing system can broaden the application field of UV curing system.

[0006] Therefore, how to prepare UV / heat dual-curable organic materials has become a hot topic in current research. Summary of the invention

[0007] In order to solve the above problems, the present invention provides a UV / heat dual-curable polysiloxane and a preparation method thereof. Since the polysiloxane contains UV-curable groups, silylene groups and silyl hydrogen groups at the same time, it can undergo photocuring reaction and silyl hydrogen addition curing reaction.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] A UV / heat dual-curable polysiloxane, the general structural formula is as follows:

[0010]

[0011] Among them, R1 is

[0012] R2 is one of methyl or phenyl;

[0013] R3 is phenyl;

[0014] The value of a is 150-2000, preferably 200-1500;

[0015] The b / a value is 1‰-2%, preferably 1.1‰-1.5%;

[0016] c is zero or c / a is 1%-20%,

[0017] The value of d / (a+b+c) is 5%-20%.

[0018] According to an embodiment of the present invention, a is 200-1500; b / a is 1.1‰-1.5%; c is zero or c / a is 3%-18%; d / (a+b+c) is 6%-18%.

[0019] According to an embodiment of the present invention, a is 450 to 890; b / a is 2.25‰ to 1.46%; c / a is 3.1% to 15%; and d / (a+b+c) is 6.25% to 15%.

[0020] By limiting the value ranges of a, b / a, c / a and d / (a+b+c), the curing efficiency and degree of UV / heat dual curing of polysiloxane can be improved.

[0021] In addition to the above range, the selection of the b value must also match the molar content of the silyl vinyl group used in the polysiloxane. The ratio of the molar content of silyl hydrogen to the molar content of vinyl in the polysiloxane must be greater than or equal to 1.0.

[0022] The present invention also provides a method for preparing the above-mentioned UV / heat dual-curable polysiloxane, comprising the following steps:

[0023] S1, after octamethylcyclotetrasiloxane, tetramethylcyclotetrasiloxane, dialkoxysilane and an acid catalyst are mixed and reacted, an acidic substance and 1,5-divinylhexamethyltrisiloxane are added simultaneously to carry out cationic ring-opening, condensation and end-capping reactions;

[0024] S2, vacuuming to remove the generated by-products and unreacted small molecules;

[0025] S3, adding a weak alkaline substance to terminate the reaction, and obtaining the UV / heat dual-curable polysiloxane through a post-treatment step;

[0026] The general reaction formula of step S1 is as follows:

[0027]

[0028]

[0029] Wherein, R is independently selected from methyl or ethyl, R' is independently selected from methyl or ethyl, and R" is independently selected from ethyl, propyl or butyl;

[0030] R1 is

[0031] R2 is selected from methyl or phenyl, and R3 is phenyl;

[0032] The specific value ranges of a, b, c, and d are as described above and will not be repeated here.

[0033] According to an embodiment of the present invention, the dialkoxysilane must include one or two of 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane and 3-acryloxypropylmethyldimethoxysilane; it may also include one or more of methylphenyldimethoxysilane, methylphenyldiethoxysilane, diphenyldimethoxysilane and diphenyldiethoxysilane.

[0034] According to an embodiment of the present invention, in step S1, the acidic catalyst is one or more of concentrated sulfuric acid and trifluoromethanesulfonic acid.

[0035] For example, the concentration of concentrated sulfuric acid is 18.4 mol / L.

[0036] According to an embodiment of the present invention, when the acidic catalyst is concentrated sulfuric acid, the mass ratio of the total mass of octamethylcyclotetrasiloxane, tetramethylcyclotetrasiloxane and dialkoxysilane to the concentrated sulfuric acid is 20-100:1, preferably 30-80:1.

[0037] The total mass ratio of the raw materials to the mass ratio of the concentrated sulfuric acid is limited within the above range in order to achieve the ring-opening polymerization reaction and equilibrium reaction of the raw materials, which is beneficial to improve the yield of polysiloxane; otherwise, it is easy to cause incomplete reaction of the raw materials or break the silicon-carbon bond to produce gelation.

[0038] According to an embodiment of the present invention, when the acidic catalyst is trifluoromethanesulfonic acid, the mass ratio of the total mass of octamethylcyclotetrasiloxane, tetramethylcyclotetrasiloxane and dialkoxysilane to trifluoromethanesulfonic acid is 160-1000:1, preferably 170-700:1.

[0039] The total mass ratio of the raw materials to the mass ratio of trifluoromethanesulfonic acid is limited within the above range in order to achieve the ring-opening polymerization reaction and equilibrium reaction of the raw materials, which is beneficial to improve the yield of polysiloxane; otherwise, it is easy to cause incomplete reaction of the raw materials or break the silicon-carbon bond to produce gelation.

[0040] According to an embodiment of the present invention, the temperature for reacting octamethylcyclotetrasiloxane, tetramethylcyclotetrasiloxane, dialkoxysilane and the acid catalyst is 30-80° C., preferably 40-70° C.; and the reaction time is 2-8 hours, preferably 3-7 hours.

[0041] According to an embodiment of the present invention, the acidic substance is selected from one or more of acetic acid, propionic acid and butyric acid.

[0042] According to an embodiment of the present invention, the molar ratio of the amount of the acidic substance added to the total amount of alkoxy groups in the dialkoxysilane is 0.5-1.1:1, preferably 0.7-1:1.

[0043] The present invention limits the molar ratio of the acidic substance to the total amount of alkoxy groups in the dialkoxysilane, and its purpose is to completely react and eliminate the alkoxy groups in the dialkoxysilane.

[0044] According to an embodiment of the present invention, the temperature of the condensation and end-capping reaction is 50-90° C., preferably 60-80° C.; the reaction time is 2-6 hours, preferably 3-5 hours.

[0045] According to an embodiment of the present invention, the vacuuming temperature is 50-90°C, preferably 60-80°C; the vacuuming time is 1-6 hours, preferably 2-5 hours; the vacuum degree of the vacuuming is 100-600Pa, preferably 120-500Pa.

[0046] According to an embodiment of the present invention, the weak alkaline substance is one of sodium bicarbonate, sodium carbonate, ammonium bicarbonate and calcium carbonate.

[0047] According to an embodiment of the present invention, the molar ratio of the weakly alkaline substance to the acidic catalyst is 0.5-2.1:1, preferably 0.55-2.05:1.

[0048] According to an embodiment of the present invention, the time for terminating the reaction is 1-4 hours, preferably 2-3 hours.

[0049] According to an embodiment of the present invention, the temperature for terminating the reaction is 30-60°C, preferably 35-50°C.

[0050] According to an embodiment of the present invention, the post-treatment step is to remove solid impurities by means of adsorption filtration, thereby obtaining the UV / heat dual-cured polysiloxane.

[0051] According to an embodiment of the present invention, the adsorbent used in the adsorption filtration is diatomaceous earth, and the amount of the diatomaceous earth used is 0.5%-3%, preferably 0.8%-2.5% of the theoretical mass of the UV / heat dual-curable polysiloxane.

[0052] Beneficial effects of the present invention:

[0053] 1) The present invention has designed and prepared polysiloxane containing UV-curable groups, silylene groups and silyl hydrogen groups at the same time, which can be used for UV / heat dual curing, and can undergo both photocuring reaction and silyl hydrogen addition curing reaction, thus overcoming the disadvantage of UV / moisture dual curing system that the degree of curing is uneven in large shadow areas. The polysiloxane designed by this method also has broad application prospects in the additive manufacturing of liquid silicone rubber.

[0054] 2) The preparation method of the present invention not only has cheap and readily available raw materials, but also has a simple production process and is easy to operate. At the same time, the reaction conditions are mild and there is no special requirement for equipment, so it is easy to realize industrialization. DETAILED DESCRIPTION

[0055] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0056] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available.

[0057] Example 1

[0058] In a 100L mechanical reactor, 50kg of octamethylcyclotetrasiloxane, 580g of tetramethylcyclotetrasiloxane, 9.54kg of 3-methacryloxypropylmethyldimethoxysilane and 106g of trifluoromethanesulfonic acid were added in sequence, and after stirring evenly, the temperature of the reactor was raised to 45°C and the reaction was carried out for 6 hours.

[0059] Afterwards, 3.95 kg of acetic acid and 836 g of 1,5-divinylhexamethyltrisiloxane were added, and the molar ratio of the amount of the acidic substance added to the total amount of alkoxy groups in the dialkoxysilane was 0.76.

[0060] The temperature was raised to 60°C, and the reaction was continued with stirring for 3 hours. The temperature was then raised to 70°C, the vacuum degree was controlled at 400Pa, and the reaction was carried out for 4 hours. The temperature was then lowered to 35°C to remove the generated by-products and unreacted small molecules. 61g of sodium bicarbonate was added, and the reaction was continued with stirring for 2 hours. Then, 610g of diatomaceous earth was added and stirred evenly, and then filtered. After adsorption filtration, a colorless and transparent UV / heat dual-curable polysiloxane was obtained. The product viscosity was 1800mPa·s, which was called polysiloxane A.

[0061] The structural formula of polysiloxane A is as follows:

[0062] Among them, R1 is

[0063] a is 205, b is 3; b / a is 1.46%, c is zero, d is 13, and d / (a+b+c) is 6.25%.

[0064] The ratio of the molar content of silicon hydrogen to the molar content of vinyl in the polysiloxane is 1.5, which is greater than 1.0.

[0065] Example 2

[0066] In a 100L mechanical reactor, 50kg of octamethylcyclotetrasiloxane, 210g of tetramethylcyclotetrasiloxane, 4.96kg of diphenyldimethoxysilane, 14.6kg of 3-methacryloxypropylmethyldiethoxysilane and 147g of trifluoromethanesulfonic acid were added in sequence and stirred evenly. The temperature of the reactor was raised to 55°C and the reaction was carried out for 5 hours.

[0067] Then, 7.34 kg of acetic acid and 352 g of 1,5-divinylhexamethyltrisiloxane were added, and the molar ratio of the amount of the acidic substance added to the total amount of alkoxy groups in the dialkoxysilane was 0.8.

[0068] The temperature was raised to 65°C, and the reaction was continued with stirring for 4 hours. The temperature was then raised to 75°C, and the vacuum degree was controlled at 200 Pa. After evacuation for 3 hours, the temperature was lowered to 35°C, 62.4 g of sodium carbonate was added, and stirring was continued for 3 hours. Then, 1 kg of diatomaceous earth was added and stirred evenly, and filter press was performed. After adsorption filtration, a colorless and transparent UV / heat dual-cured polysiloxane was obtained. The product viscosity was 8500 mPa·s, which was called polysiloxane B.

[0069] The structural formula of polysiloxane B is as follows:

[0070] Among them, R1 is

[0071] R2 and R3 are both phenyl groups;

[0072] a is 450, b is 6, b / a is 1.33%, c is 14, c / a is 3.1%, d is 37, d / (a+b+c) is 7.87%.

[0073] The ratio of the molar content of silicon hydrogen to the molar content of vinyl in the polysiloxane is 3, which is greater than 1.0.

[0074] Example 3

[0075] In a 200L mechanical reactor, 50kg of octamethylcyclotetrasiloxane, 105g of tetramethylcyclotetrasiloxane, 12.3kg of methylphenyldimethoxysilane, 16.3kg of 3-acryloxypropylmethyldimethoxysilane and 720ml of concentrated sulfuric acid were added in sequence. After stirring evenly, the temperature of the reactor was raised to 60°C and the reaction was carried out for 6 hours.

[0076] Afterwards, 21.4 kg of butyric acid and 176 g of 1,5-divinylhexamethyltrisiloxane were added, and the molar ratio of the amount of the acidic substance added to the total amount of alkoxy groups in the dialkoxysilane was 0.85.

[0077] The temperature was raised to 70°C, and the reaction was continued with stirring for 4 hours. The temperature was then raised to 70°C, and the vacuum degree was controlled at 150 Pa. After evacuation for 4 hours, the temperature was lowered to 40°C, 2.13 kg of ammonium bicarbonate was added, and stirring was continued for 3 hours. After that, 1.1 kg of diatomaceous earth was added and stirred evenly, and then filter press was performed. After adsorption filtration, a colorless and transparent UV / heat dual-cured polysiloxane was obtained. The product viscosity was 1.2×10 4 mPa·s, called polysiloxane C.

[0078] The structural formula of polysiloxane C is as follows:

[0079] Among them, R1 is

[0080] R2 is methyl, and R3 is phenyl;

[0081] a is 890, b is 2, b / a is 2.25‰, c is 89, c / a is 10%; d is 99, d / (a+b+c) is 10.1%.

[0082] The ratio of the molar content of silicon hydrogen to the molar content of vinyl in the polysiloxane is 1.0.

[0083] Example 4

[0084] In a 200L mechanical reactor, 50kg of octamethylcyclotetrasiloxane, 93g of tetramethylcyclotetrasiloxane, 27.56kg of diphenyldiethoxysilane, 25.5kg of 3-acryloxypropylmethyldimethoxysilane and 176g of trifluoromethanesulfonic acid were added in sequence, and after stirring evenly, the temperature of the reactor was raised to 65°C and reacted for 5 hours.

[0085] After that, 29.1 kg of propionic acid and 126 g of 1,5-divinylhexamethyltrisiloxane were added, and the molar ratio of the amount of the acidic substance added to the total amount of alkoxy groups in the dialkoxysilane was 0.9. The temperature was raised to 75°C, and the reaction was continued with stirring for 5 hours. The temperature was raised to 80°C, and the vacuum degree was controlled at 300 Pa. After evacuation for 5 hours, the temperature was lowered to 45°C, 66 g of calcium carbonate was added, and the stirring was continued for 3 hours. After that, 2.0 kg of diatomaceous earth was added and stirred evenly, and then filter press was performed. After adsorption filtration, a colorless and transparent UV / heat dual-cured polysiloxane was obtained, and the product viscosity was 8.0×10 4 mPa·s, called polysiloxane D.

[0086] The specific structural formula of polysiloxane D is as follows:

[0087] Among them, R1 is

[0088] R2 and R3 are both phenyl groups;

[0089] a is 1254, b is 3, b / a is 2.39‰, c is 188, c / a is 15%, d is 215, d / (a+b+c) is 14.88%.

[0090] The ratio of the molar content of silicon hydrogen to the molar content of vinyl in the polysiloxane is 1.5.

[0091] The polysiloxane prepared in Examples 1-4 was mixed with a photoinitiator, a Custer catalyst and an inhibitor in the following proportions, and its performance was tested. The specific data are shown in Table 1.

[0092] Table 1

[0093]

[0094] From the test data in Table 1, it can be seen that when heat-curing alone, its hardness is low. When UV / heat dual-curing is adopted, its hardness under the same conditions is increased by at least one time, indicating that the preparation method of the present invention can simultaneously introduce UV light-curable and heat-curable reactive functional groups into the polymer molecular chain, and the obtained polysiloxane can achieve the effect of UV / heat dual-curing.

[0095] The above is only a preferred application implementation 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 UV / heat dual-curable polysiloxane, characterized in that: The general structure is as follows: Among them, R1 is R2 is independently selected from methyl or phenyl, and R3 is phenyl; a is 150 to 2000, preferably 200 to 1500; The b / a value is 1‰ to 2%, preferably 1.1‰ to 1.5%; c is zero or c / a is 1% to 20%, and d / (a+b+c) is 5% to 20%.

2. The polysiloxane according to claim 1, characterized in that The value of a is 200-1500; the value of b / a is 1.1‰-1.5%; c is zero or the value of c / a is 3%-18%; the value of d / (a+b+c) is 6%-18%. Preferably, a is 450 to 890; b / a is 2.25‰ to 1.46%; c / a is 3.1% to 15%; and d / (a+b+c) is 6.25% to 15%.

3. The polysiloxane according to claim 1, wherein the ratio of the molar content of silicon hydrogen to the molar content of vinyl in the polysiloxane is greater than or equal to 1.

0.

4. The method for preparing the UV / heat dual-curable polysiloxane according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, after octamethylcyclotetrasiloxane, tetramethylcyclotetrasiloxane, dialkoxysilane and an acid catalyst are mixed and reacted, an acidic substance and 1,5-divinylhexamethyltrisiloxane are added simultaneously to carry out cationic ring-opening, condensation and end-capping reactions; S2, vacuuming and cooling to remove the generated by-products and unreacted small molecules; S3, adding a weak alkaline substance to terminate the reaction, and obtaining the UV / heat dual-curable polysiloxane through a post-treatment step; The reaction formula of step S1 is as follows: Wherein, R is independently selected from methyl or ethyl, R' is independently selected from methyl or ethyl, and R" is independently selected from ethyl, propyl or butyl; R1 is R2 is selected from methyl or phenyl, and R3 is phenyl; a is 150 to 2000, preferably 200 to 1500; The b / a value is 1‰ to 2%, preferably 1.1‰ to 1.5%; c is zero or c / a is 1% to 20%, The value of d / (a+b+c) is 5% to 20%.

5. The preparation method according to claim 4, characterized in that: The dialkoxysilane includes one or two of 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane and 3-acryloxypropylmethyldimethoxysilane; and includes or does not include one or more of methylphenyldimethoxysilane, methylphenyldiethoxysilane, diphenyldimethoxysilane and diphenyldiethoxysilane.

6. The preparation method according to claim 4, characterized in that: In step S1, the acidic catalyst is one or more of concentrated sulfuric acid and trifluoromethanesulfonic acid; Preferably, when the acidic catalyst is concentrated sulfuric acid, the mass ratio of the total mass of octamethylcyclotetrasiloxane, tetramethylcyclotetrasiloxane and dialkoxysilane to the concentrated sulfuric acid is 20-100:1, preferably 30-80:1; Preferably, when the acidic catalyst is trifluoromethanesulfonic acid, the mass ratio of the total mass of octamethylcyclotetrasiloxane, tetramethylcyclotetrasiloxane and dialkoxysilane to trifluoromethanesulfonic acid is 160 to 1000:1, preferably 170 to 700:

1.

7. The preparation method according to claim 6, characterized in that: The temperature for reacting the octamethylcyclotetrasiloxane, tetramethylcyclotetrasiloxane, dialkoxysilane and the acid catalyst is 30-80° C., preferably 40-70° C.; the reaction time is 2-8 hours, preferably 3-7 hours. Preferably, the acidic substance is selected from one or more of acetic acid, propionic acid and butyric acid. Preferably, the molar ratio of the amount of the acidic substance added to the total amount of alkoxy groups in the dialkoxysilane is 0.5 to 1.1:1, preferably 0.7 to 1:

1.

8. The preparation method according to claim 4, characterized in that: The temperature of the condensation and end-capping reaction is 50-90°C, preferably 60-80°C; the reaction time is 2-6 hours, preferably 3-5 hours; Preferably, the vacuuming temperature is 50-90°C, preferably 60-80°C; the vacuuming time is 1-6 hours, preferably 2-5 hours; the vacuum degree is 100-600Pa, preferably 120-500Pa.

9. The preparation method according to claim 7, characterized in that: The weakly alkaline substance is selected from one of sodium bicarbonate, sodium carbonate, ammonium bicarbonate and calcium carbonate. Preferably, the molar ratio of the weakly alkaline substance to the acidic catalyst is 0.5-2.1:1, preferably 0.55-2.05:

1. Preferably, the temperature for terminating the reaction is 30-60°C, preferably 35-50°C; the time for terminating the reaction is 1-4 hours, preferably 2-3 hours.

10. The preparation method according to claim 4, characterized in that: The post-treatment step is to remove solid impurities by means of adsorption filtration, thereby obtaining the UV / heat dual-cured polysiloxane; The adsorbent used in the adsorption filtration is diatomaceous earth, and the amount of the diatomaceous earth used is 0.5%-3% of the theoretical mass of the UV / heat dual-curable polysiloxane, preferably 0.8%-2.5%.

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