Photocurable gasket resin composition

Abstract

To provide a photocurable gasket resin composition that exhibits superior workability without containing a silica component, features superior curability and low moisture permeability, and can be used as a CIPG (Cured In Place Gasket) that easily ensures stable sealability.SOLUTION: A photocurable gasket resin composition comprises acryloyl-terminated polyisobutylene, a C8-18 monofunctional alkyl (meth)acrylate monomer, polyethylene powder, calcium carbonate, polyfunctional thiol, and a photopolymerization initiator, while being free of silica components.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a photocurable gasket resin composition that is cured by light such as ultraviolet light and is suitable as a resin for a formed-in-place gasket. [Background technology]

[0002] Sealing agents (gaskets) are used for various purposes in electronic devices such as liquid crystal devices, battery units such as solar cells and fuel cells, and optical communication units such as optical fibers. For example, in precision electronic devices, they are used to protect the components housed inside the device from external dust and moisture, and in battery units, they act as a gas barrier to prevent the leakage of fuel gas and oxygen gas, and to prevent the intrusion of external moisture.

[0003] Recently, there has been a demand for advanced sealing functions to improve reliability, and cured-in-place gaskets (CIPGs), in which an uncured liquid is applied to the area to be sealed and then cured, are becoming more common. CIPGs are viscous fluids before curing, so various inorganic fillers are often blended into the composition to improve their flow properties. In particular, fumed silica, which improves thixotropy and prevents sagging after application, is used in many compositions (see, for example, Patent Document 1).

[0004] Currently, there are few issues with the availability of fumed silica in the domestic market, but most of its suppliers are overseas manufacturers, with the top three overseas manufacturers reportedly holding approximately 80% of the market. In recent years, sudden production stoppages and logistics delays due to infectious disease outbreaks such as COVID-19, energy issues stemming from overseas conflicts, and trade restrictions due to intensifying conflicts between countries have led to sudden supply chain disruptions that would have been unthinkable just a few years ago. From a business continuity perspective, the consideration of alternative materials has become an important issue, particularly for raw materials primarily produced overseas. Regarding CIPG, there are now cases where a composition with the same level of physical properties without containing fumed silica is required, leaving room for improvement. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6865792 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention provides a photocurable gasket resin composition that has good workability even without containing a silica component, has good curability, and can be used as a CIPG that has low moisture permeability and can easily ensure stable sealing properties after curing. [Means for solving the problem]

[0007] In order to solve the above problem, the invention of claim 1 comprises an acryloyl-terminated polyisobutylene (A), Selected from the group consisting of C8-18 monofunctional alicyclic skeleton (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, and stearyl (meth)acrylate. a C8-18 monofunctional (meth)acrylate monomer (B), a polyethylene powder (C), calcium carbonate (D), a multifunctional thiol (E), and a photopolymerization initiator (F), wherein (B) contains an alicyclic skeleton (meth)acrylate (b1); The amount of (D) blended is 15 to 40% by weight based on the total solid content of the composition, The present invention provides a photocurable gasket resin composition that is free of silica components.

[0008] A second aspect of the present invention provides the photocurable gasket resin composition according to the first aspect, wherein (D) is surface-treated precipitated calcium carbonate and has an average particle size of 10 to 500 nm.

[0009] The invention of claim 3 is (b1) contains dicyclopentenyl (meth)acrylate and / or dicyclopentenyloxyethyl (meth)acrylate The photocurable gasket resin composition according to claim 1 or 2 is provided.

[0010] The invention of claim 4 is (E) The amount of 0.5 to 5% by weight of the total solid content of the composition The photocurable gasket resin composition according to claim 1 or 2 is provided, wherein: [Effects of the Invention]

[0012] The present invention has good workability and curability even without containing a silica component, and the cured product has low moisture permeability and stable sealing properties can be easily ensured, making it useful as a photocurable resin composition for CIPG. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below.

[0014] The composition of the present invention comprises an acryloyl-terminated polyisobutylene (A), Selected from the group consisting of C8-18 monofunctional alicyclic skeleton (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, and stearyl (meth)acrylate. The composition comprises a C8-18 monofunctional (meth)acrylate monomer (B), polyethylene powder (C), calcium carbonate (D), a multifunctional thiol (E), and a photopolymerization initiator (F). In this specification, (meth)acrylate encompasses both acrylate and methacrylate. Silica-free does not include silica intentionally blended to achieve a specific purpose, but does not include trace amounts of silica in each blended component. The silica content is 5% by weight or less, typically 1% by weight or less.

[0015] The acryloyl-terminated polyisobutylene (A) of the present invention is a base oligomer constituting a gasket resin, and is not particularly limited as long as it is a polymer having a polyisobutylene skeleton containing -[CHC(CH)]- units. It is an excellent polymer that has high photocurability, excellent heat resistance and weather resistance, a larger tensile break strain than oligomers with a butadiene skeleton, and combines high gas barrier properties with low water vapor permeability.

[0016] The viscosity of (A) at 23°C as measured by an E-type viscometer is preferably 100 to 10,000 Pa·s, more preferably 500 to 5,000 Pa·s, and particularly preferably 1,000 to 4,000 Pa·s. A viscosity of 100 Pa·s or higher ensures sufficient cohesive strength, while a viscosity of 10,000 Pa·s or lower facilitates adjustment to a viscosity suitable for workability. A commercially available product is EP400V (trade name: manufactured by Kaneka Corporation, both terminal acryloyloxy groups, viscosity 3,500 Pa·s / 23°C).

[0017] The blending amount of (A) is preferably 10 to 55 wt %, more preferably 15 to 50 wt %, and particularly preferably 20 to 48 wt %, based on the total solid content, in terms of the balance between the moisture permeability of the cured product and the properties of the composition. By making it 10 wt % or more, sufficient gas barrier properties and low moisture permeability can be ensured, and by making it 55 wt % or less, it is easy to adjust the viscosity to suit workability.

[0018] Used in the present invention Selected from the group consisting of C8-18 monofunctional alicyclic skeleton (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, and stearyl (meth)acrylate. The C8-18 monofunctional (meth)acrylate monomer (B) is blended to dilute (A) and simultaneously improve photocuring reactivity. The number of carbon atoms is C8-18, preferably C8-C16, and more preferably C8-C14. If the number of carbon atoms is less than C8, the flexibility of the cured product may decrease, while if the number of carbon atoms is more than C18, the curability tends to decrease. In particular, to improve sealing properties, it is preferable to include a C8-18 (meth)acrylate (b1) with a highly rigid alicyclic skeleton and / or a linear alkyl (meth)acrylate (b2) with a good balance between curability and flexibility.

[0019] The ratio of (B) to the total solid content is preferably 5 to 50% by weight, more preferably 10 to 45% by weight, and particularly preferably 15 to 42% by weight. By making it 5% by weight or more, sufficient curability can be ensured, and by making it 50% by weight or less, sufficient gas barrier properties and low moisture permeability can be ensured.

[0020] Examples of (b1) include dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, isobornyl (meth)acrylate, and adamantanyl (meth)acrylate. Tona These can be used alone or in combination of two or more. Among these, dicyclopentenyl (meth)acrylates are preferred as they can increase the elastic modulus of the cured film.

[0021] Examples of (b2) include 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, and stearyl (meth)acrylate, which can be used alone or in combination of two or more. Among these, n-octyl acrylate is preferred because it has a low Tg and good compatibility with (A).

[0022] When (b1) and (b2) are used in combination, the ratio of (b1) to the total amount of (B) is preferably 30 to 95% by weight, more preferably 40 to 80% by weight, and particularly preferably 50 to 70% by weight. A ratio of 30% by weight ensures sufficient rigidity, while a ratio of 95% by weight or less ensures sufficient gas barrier properties and low moisture permeability.

[0023] The polyethylene powder (C) used in the present invention is blended to reduce stickiness of the cured coating surface and the coefficient of dynamic friction. Ultra-high molecular weight polyethylene with a molecular weight of 1,000,000 to 7,000,000 is preferred for its excellent wear resistance and self-lubrication properties. Furthermore, the average particle size is preferably 10 to 50 μm, more preferably 15 to 40 μm, so that the cured surface can have fine irregularities (Coulter Counter method).

[0024] The blending amount of (C) is preferably 5 to 35% by weight, more preferably 8 to 30% by weight, and particularly preferably 10 to 25% by weight, based on the total solid content. A blending amount of 5% by weight or more ensures sufficient slipperiness, resulting in a low coefficient of dynamic friction, while a blending amount of 35% by weight or less ensures appropriate hardness and distortion characteristics. An example of a commercially available product is Mipelon (trade name: ultra-high molecular weight polyethylene, manufactured by Mitsui Chemicals, Inc.).

[0025] The calcium carbonate (D) used in the present invention is blended in for the purpose of imparting thixotropy to the composition. In CIPG, which forms a sealing layer on a component, it is necessary to apply a liquid resin to a height useful as a sealing material and maintain that shape until it hardens, and this can be achieved by blending (D) into the liquid composition to impart thixotropy. Calcium carbonate includes chemically produced light calcium carbonate and physically crushed and crushed heavy calcium carbonate, but light calcium carbonate is preferred because of its uniform particle size and shape and low impurity content.

[0026] The (D) is preferably surface-treated in order to improve compatibility with the (A) to (C) components and to obtain excellent thixotropy even at low viscosity. For example, surface treatment with a fatty acid can be used. The BET specific surface area is preferably 5 to 50 m. 2 / g, and 10 to 40m 2 / g, and more preferably 15 to 35m 2 / g is particularly preferred. 2 / g or more, it is possible to give sufficient thixotropy, and 2 / g or less, it is possible to sufficiently suppress the increase in viscosity. The BET specific surface area is measured in accordance with the JPCS test method established by the Japan Light Calcium Carbonate Industry Association.

[0027] The average primary particle diameter of (D) is preferably 10 to 500 nm, more preferably 20 to 300 nm, and particularly preferably 20 to 150 nm. By adjusting the average primary particle diameter within this range, sufficient thixotropy can be imparted even with a small amount added. The average particle diameter was measured by observation with a scanning electron microscope. A commercially available product is Hakuenka CC (trade name: manufactured by Shiraishi Kogyo Co., Ltd., fatty acid surface-treated light calcium carbonate, average primary particle diameter 50 nm, BET specific surface area 26 m 2 / g) etc.

[0028] The blending amount of (D) is preferably 3 to 40% by weight, more preferably 5 to 35% by weight, and particularly preferably 15 to 30% by weight, based on the total solid content. By making it 3% by weight or more, it is possible to impart sufficient thixotropy, and by making it 40% by weight or less, it is possible to easily control the viscosity to be suitable for workability.

[0029] The multifunctional thiol (E) used in the present invention is incorporated to improve the photocurability of the composition. This enables an enethiol reaction that suppresses curing inhibition by oxygen, thereby improving reactivity and the elongation of the cured film. Examples of suitable thiols include bifunctional thiols such as 1,4-bis(3-mercaptobutyryloxy)butane and tetraethylene glycol bis(3-mercaptopropionate), trifunctional thiols such as 1,3,5-tris(3-mercaptobutyryloxyethyl)-1,3,5-triazine-2,4,6-trione and trimethylolpropane tris(3-mercaptopropionate), and tetrafunctional thiols such as pentaerythritol tetrakis(3-mercaptobutyrate) and pentaerythritol tetrakis(3-mercaptopropionate). These thiols can be used alone or in combination. Among these, secondary multifunctional thiols are preferred, as they offer a good balance between reactivity and storage stability.

[0030] The amount of (E) added is preferably 0.5 to 5 wt. % of the total solid content, more preferably 0.8 to 3 wt. %, and particularly preferably 1.0 to 2.0 wt. Furthermore, the amount added per 100 wt. parts of the radically polymerizable component is preferably 1 to 8 wt. % and more preferably 2 to 5 wt. By keeping the amount within this range, photoreactivity can be improved and sufficient elongation of the cured film can be ensured. A commercially available product is Karenz MT-BD1 (trade name: 1,4-bis(3-mercaptobutyryloxy)butane, manufactured by Showa Denko KK).

[0031] The photopolymerization initiator (F) used in the present invention generates radicals upon irradiation with ultraviolet light or an electron beam, and these radicals trigger the polymerization reaction, and general-purpose photopolymerization initiators such as benzyl ketals, acetophenones, and phosphine oxides can be used. By arbitrarily selecting the light absorption wavelength of the polymerization initiator, it is possible to impart curability over a wide wavelength range from the ultraviolet region to the visible light region. Specifically, benzyl ketals include 2,2-dimethoxy-1,2-diphenylethan-1-one, α-hydroxyacetophenones include 1-hydroxy-cyclohexyl-phenyl-ketone and 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, α-aminoacetophenones include 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, and acylphosphine oxides include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and these can be used alone or in combination of two or more.

[0032] Among the (F), it is preferable to contain an α-hydroxyacetophenone-based compound that is resistant to yellowing, and examples of commercially available products include Omnirad 127, 184, and 2959 (trade names: manufactured by IGM Resins), etc. The amount of (B) added per 100 parts by weight of the radical polymerizable component is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 8 parts by weight.

[0033] In the present invention, it is preferable to further incorporate an antioxidant. Antioxidants are compounds that efficiently trap radicals and can improve shelf life. Examples include hindered phenol-based, hindered amine-based, phosphorus-based, and sulfur-based antioxidants, which can be used alone or in combination of two or more. Among these, it is preferable to incorporate a hindered phenol-based or hindered amine-based antioxidant. When an antioxidant is incorporated, the amount incorporated relative to the total solid content is preferably 0.5 to 5 wt%, and more preferably 1 to 4 wt%. By maintaining the amount within this range, shelf life can be further improved. Commercially available products include Irganox 1010 (trade name: manufactured by BASF Japan, hindered phenol-based) and Tinuvin 249 (trade name: manufactured by BASF Japan, hindered amine-based).

[0034] If necessary, the composition may also contain additives such as silane coupling agents, colorants, thermal polymerization initiators, antifoaming agents, flame retardants, leveling agents, dispersants, polymerization inhibitors, phosphate esters, and organic fine particles.

[0035] The photocurable gasket resin composition of the present invention is used by applying it to a member and then curing it by irradiation with light such as ultraviolet light to form a sealing layer. Known light sources such as high-pressure mercury lamps, medium-pressure mercury lamps, low-pressure mercury lamps, metal halide lamps, xenon lamps, LED lamps, and electrodeless ultraviolet lamps can be used as the light source. The ultraviolet irradiation conditions are 50 mW / cm. 2 ~3,000mW / cm 2 The irradiation intensity is 500mJ / cm 2 ~10,000mJ / cm 2 Examples include:

[0036] The moisture permeability of the sealing layer obtained by curing the photocurable gasket resin composition of the present invention at 60°C and 90% RH according to JIS Z0208 is 40 g / m 2 24 hours or less is preferable, 30 g / m 2If the cured product is within this range, it can be used satisfactorily as a CIPG because it can prevent moisture and foreign matter from permeating through the sealing layer.

[0037] The present invention will be described in detail below based on examples and comparative examples, but these are intended to be specific examples and are not intended to limit the scope of the invention. Unless otherwise specified, measurements were carried out under conditions of a room temperature of 25°C and a relative humidity of 65%.

[0038] Examples 1 to 7 The (A) was EPION EP400V (trade name: acryloyl-terminated polyisobutylene, manufactured by Kaneka Corporation), the (b1) was FA-512AS (trade name: dicyclopentenyloxyethyl acrylate, manufactured by Hitachi Chemical Co., Ltd.), the (b2) was NOAA (trade name: n-octyl acrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd.), the (C) was Mipelon XM-200 (trade name: Mitsui Chemicals, Inc., average molecular weight 2 million, average particle size measured by Coulter counter method 30 μm), and the (D) was Hakuenka CC (trade name: fatty acid surface-treated light calcium carbonate, average primary particle size 4 0 nm), Karenz MT-BD1 (trade name: 1,4-bis(3-mercaptobutyryloxy)butane, manufactured by Showa Denko K.K.) as (E), Omnirad 184 (trade name: α-hydroxyacetophenone, manufactured by IGM) as (F), and Tinuvin 249 (trade name: hindered amine, manufactured by BASF Japan Ltd.) and Irganox 1010 (trade name: hindered phenol, manufactured by BASF Japan Ltd.) as antioxidants were stirred until uniformly dissolved in the formulation shown in Table 1 to prepare the photocurable gasket resin compositions of Examples 1 to 7.

[0039] Comparative Examples 1 to 4 In addition to the materials used in the examples, UV-3700B (product name: urethane acrylate, Mw38000, manufactured by Mitsubishi Chemical Corporation) was used as an acrylic oligomer, and the photocurable gasket resin compositions of Comparative Examples 1 to 4 were prepared by stirring until uniformly dissolved in the formulation shown in Table 2.

[0040] Table 1 JPEG0007784369000001.jpg75135

[0041] Table 2 JPEG0007784369000002.jpg121132

[0042] The evaluation method was as follows.

[0043] Viscosity and TI value: Measurements were taken using a Toki Sangyo RE-215R cone-plate viscometer with a cone angle of 3° x R7.7 at 25±1°C and rotation speeds of 10 rpm and 1 rpm, and the ratio of these values ​​was taken as the thixotropy value (TI value).If the viscosity was outside the measurement range, the rotation speed was reduced from 10 rpm to 0.1 rpm so that it was within the measurable range, and the ratio of this value to the viscosity value measured at one-tenth the rotation speed was taken as the TI value. The TI value was evaluated as follows: less than 1.5 was marked x, 1.6 to 2.5 was marked ◯, and more than 2.5 was marked ⊚.

[0044] Surface curing: The composition prepared above was filled up to the brim in a dedicated mold (made of PP, 6 mm thick, Φ26 mm), and cured at an irradiation intensity of 300 mW / cm using a UV irradiation device UV LIGHT HAMMER 6D bulb manufactured by FUSIONUV Systems. 2 , cumulative light intensity 6,000mJ / cm 2 The coating was cured under the conditions of (a) and (b), and the tackiness of the surface was evaluated by touching with a finger. When there was no tackiness, it was marked as ◯, and when there was tackiness, it was marked as x.

[0045] Compression set: The composition prepared above was applied to a release PET film to a thickness of 2 mm, and then subjected to irradiation at an irradiation intensity of 300 mW / cm using a UV irradiation device UV LIGHT HAMMER 6D bulb manufactured by FUSIONUV Systems. 2 , cumulative light intensity 6,000mJ / cm 2This was cut into a piece 5 mm wide x 15 mm long, compressed and fixed between SUS plates with a 1 mm spacer, and cured at 80°C for 16 hours. After the specified time, the test piece was removed, and those with large cracks or three or more cracks 1 mm or longer were rated as ×, those with fewer than two cracks less than 1 mm long were rated as ◯, and those with no cracks were rated as ◎.

[0046] Moisture permeability: Measured according to JIS Z0208. UV irradiation conditions were the same as above, with an irradiation intensity of 300 mW / cm. 2 , cumulative light intensity 6,000mJ / cm 2 The measurement conditions were a 60°C / 90% RH environment in which a 1 mm thick sample was left for 24 hours, and the moisture permeability was calculated from the change in weight. 2 Less than 24 hours: 30-40g / m 2 24h: ○, 40g / m 2 -If it exceeds 24 hours, it is marked as ×.

[0047] Example evaluation results Table 3 JPEG0007784369000003.jpg60135

[0048] Comparative Example Evaluation Results Table 4 JPEG0007784369000004.jpg105135

[0049] The examples were satisfactory with no problems in terms of TI value, surface hardening property, compression set and moisture permeability.

[0050] On the other hand, Comparative Example 1, which did not contain (C), had poor surface curability, and Comparative Example 2, which did not contain (D), had a low TI value and also had poor surface curability. Comparative Example 3, which did not contain (E), had poor compression set, and Comparative Example 4, which used a binder other than (A), had high moisture permeability, and none of these were suitable for the present invention.

Claims

1. 1. A photocurable gasket resin composition comprising: acryloyl-terminated polyisobutylene (A); C8-18 monofunctional (meth)acrylate monomer (B) selected from the group consisting of C8-18 monofunctional alicyclic skeleton (meth)acrylates, 2-ethylhexyl (meth)acrylate, n-octyl acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, and stearyl (meth)acrylate; polyethylene powder (C); calcium carbonate (D); a polyfunctional thiol (E); and a photopolymerization initiator (F), wherein (B) contains an alicyclic skeleton (meth)acrylate (b1); the blend amount of (D) is 15 to 40 wt % based on the total solids content of the composition; and the composition is free of silica components.

2. 2. The photocurable gasket resin composition according to claim 1, wherein (D) is surface-treated precipitated calcium carbonate having an average particle size of 10 to 500 nm.

3. 3. The photocurable gasket resin composition according to claim 1, wherein (b1) contains dicyclopentenyl (meth)acrylate and / or dicyclopentenyloxyethyl (meth)acrylate.

4. 3. The photocurable gasket resin composition according to claim 1, wherein the blending amount of (E) is 0.5 to 5% by weight based on the total solid content of the composition.

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