JP6865792B2 - Photocurable gasket resin composition - Google Patents

Description

The present invention relates to a photocurable gasket resin composition suitable as a resin for a field-formed gasket that is cured by light such as ultraviolet rays.

Electronic devices such as smartphones, tablet PCs, and hard disk drives (hereinafter referred to as HDDs) generally seal the housing members with gaskets or the like in order to protect the parts stored inside from external dust and moisture. There is. Conventionally known O-rings are used as sealing materials, but when the shape changes, new molds are required, making it difficult to respond to diversification, and advanced sealing functions are provided to reduce the size of electronic devices and improve reliability. Increasingly, there is an increasing demand for in-situ formed gaskets in which an uncured liquid material is applied to a portion to be sealed and cured.

In the field-formed gasket, CIPG (Cured In Place Gasket), in which a curable resin is applied to only one of the members to be bonded and cured, and then the other member is bonded, is known. For example, a photocurable type gasket is used. A composition containing bifunctional (meth) acrylic, monofunctional alkyl (meth) acrylate, styrene-isobutylene block copolymer, photopolymerization initiator, and silica powder has been proposed as CIPG (Patent Document 1).

By using such a material, it becomes possible to form a CIPG seal layer having excellent mass productivity and a high degree of freedom in design by curing in a short time after irradiation with light such as ultraviolet rays, and further moisture permeability. Performance aspects such as performance are also improving. However, when bonding precision parts such as the top cover of HDD devices and fuel cells, the sealing characteristics become insufficient due to the hardness of the seal layer and the deformed state at the time of bonding, which causes adverse effects on electronic circuit elements and electronic parts. There was room for improvement in terms of ensuring low moisture permeability and more stable sealing performance.

Japanese Unexamined Patent Publication No. 2008-69302

The present invention provides a photocurable gasket resin composition which has good curability, low moisture permeability of the cured product, is easy to secure stable sealing property, and can be used as a field-formed gasket. It is in.

The invention according to claim 1 comprises an acryloyl-terminated polyisobutylene (A), a monofunctional alkyl (meth) acrylate monomer (B) having an alkyl group of C8-18, a polyethylene powder (C), and a photopolymerization initiator ( Provided is a photocurable gasket resin composition comprising D).

The invention according to claim 2 provides the photocurable gasket resin composition according to claim 1, wherein (C) is 5 to 45% by weight based on the total solid content of the composition.

The invention according to claim 3 further comprises a hydrophobic fumed silica (e1) and / or a compound (e2) derived from castor oil as a thixophilic imparting agent (E). The photocurable gasket resin composition according to any one is provided.

The invention according to claim 4 provides the photocurable gasket resin composition according to any one of claims 1 to 3, further comprising a polyfunctional thiol (F).

The invention according to claim 5 is any one of claims 1 to 4, wherein the (B) contains a linear alkyl (meth) acrylate (b1) and an alicyclic skeleton (meth) acrylate (b2). The above-mentioned photocurable gasket resin composition is provided.

Since the present invention has good curability, the cured product has low moisture permeability, and is a photocurable resin composition capable of ensuring stable sealing properties, it is useful as a resin composition for a field-formed gasket.

Hereinafter, the present invention will be described in detail.

The composition of the present invention comprises acryloyl-terminated polyisobutylene (A), C8-12 monofunctional alkyl (meth) acrylate monomer (B), polyethylene powder (C), and photopolymerization initiator (D). is there. In addition, in this specification, (meth) acrylate includes both acrylate and methacrylate.

The acryloyl-terminated polyisobutylene (A) of the present invention is a base oligomer constituting a gasket resin, and is particularly limited as long as it is a polymer having a polyisobutylene skeleton containing _{− [CH 2} C (CH ₃ ) _{2] − units.} is not it. It is an excellent polymer that has high curability by light irradiation, excellent heat resistance and weather resistance, large tensile fracture strain compared to oligomers with a butadiene skeleton, and has both high gas barrier properties and low water vapor permeability.

The viscosity of the E-type viscometer (A) at 23 ° C. is preferably 100 to 10000 Pa · s, more preferably 500 to 5000 Pa · s, and particularly preferably 1000 to 4000 Pa · s. When it is 100 Pa · s or more, a sufficient cohesive force can be secured, and when it is 10,000 Pa · s or less, it becomes easy to adjust the viscosity to be suitable for workability. Commercially available EP400V (trade name: manufactured by Kaneka Corporation, acryloyloxy groups at both ends, viscosity 3500 Pa · s / 23 ° C.) is available.

The blending amount of (A) is preferably 8 to 80% by weight, more preferably 10 to 75% by weight, based on the total solid content, from the viewpoint of the moisture permeability of the cured product and the characteristic balance of the composition. When it is 8% by weight or more, sufficient gas barrier property and low moisture permeability can be ensured, and when it is 80% by weight or less, it becomes easy to adjust the viscosity to be suitable for workability.

The monofunctional alkyl (meth) acrylate monomer (B) used in the present invention is blended to dilute (A) and at the same time improve the photocuring reactivity. In particular, in order to improve the sealing property, it is preferable to contain an alkyl (meth) acrylate (b1) having a chain skeleton of C8 to 18 having a good balance between curability and flexibility, and C8 to 12 is further preferable. preferable. If it is smaller than C8, the flexibility of the cured product may decrease, and if it is larger than C18, the curability tends to decrease, which is unsuitable. The ratio of (B) to the total solid content is preferably 5 to 60% by weight, more preferably 7 to 55% by weight. Sufficient curability can be ensured when the content is 5% by weight or more, and sufficient gas barrier property and low moisture permeability can be ensured when the content is 60% by weight or less.

Examples of (b1) include 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, and tetradecyl (meth). Examples thereof include acrylate and stearyl (meth) acrylate, which can be used alone or in combination of two or more. Among these, n-octyl acrylate having a low Tg and good compatibility with (A) is preferable. The ratio of (b1) to the total amount of (B) is preferably 20 to 80% by weight, more preferably 30 to 60% by weight, and particularly preferably 35 to 50% by weight. Sufficient rigidity can be ensured by setting it to 20% by weight, and sufficient gas barrier property and low moisture permeability can be secured by setting it to 80% by weight or less.

In addition to (b1) above, to increase the elastic modulus of the cured film. It is preferable to contain (meth) acrylate (b2) having a highly rigid alicyclic skeleton. For example, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, dicyclopentanyl (meth) acrylate, isobornyl (meth) acrylate, adamantanyl (meth) acrylate, cyclohexyl (meth) acrylate and the like can be mentioned. It can be used alone or in combination of two or more. Among these, isobornyl acrylate is preferable because it is excellent in breaking strain.

The polyethylene powder (C) used in the present invention is blended for the purpose of suppressing stickiness on the surface of the cured film and reducing the coefficient of dynamic friction. Ultra-high molecular weight polyethylene having a molecular weight of 1 million to 7 million is preferable in terms of excellent wear resistance and self-lubricating property. Further, the average particle size is preferably 10 to 50 μm, more preferably 15 to 40 μm so that the unevenness of the cured surface can be made finer (Coulter counter method). The blending amount of (C) with respect to the total solid content is preferably 5 to 45% by weight, more preferably 7 to 40% by weight, and particularly preferably 10 to 25% by weight. When it is 5% by weight or more, sufficient slipperiness can be ensured, and as a result, the coefficient of dynamic friction can be lowered, and when it is 45% by weight or less, appropriate hardness and strain characteristics can be secured. Examples of commercially available products include Miperon (trade name: ultra-high molecular weight polyethylene manufactured by Mitsui Chemicals, Inc.).

The photopolymerization initiator (D) used in the present invention generates radicals by irradiation with ultraviolet rays, electron beams, etc., and the radicals trigger a polymerization reaction. A general-purpose photopolymerization initiator can be used. By arbitrarily selecting the light absorption wavelength of the polymerization initiator, curability can be imparted over a wide wavelength range from the ultraviolet region to the visible light region. Specifically, 2.2-dimethoxy-1.2-diphenylethane-1-one as a benzyl ketal system, 1-hydroxy-cyclohexyl-phenyl-ketone and 1- [4- (2- (2- (2-)) as an α-hydroxyacetophenone system. Hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane-1-one is a 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1 as an α-aminoacetophenone system. -On includes 2.4.6-trimethylbenzoyl-diphenyl-phosphine oxide and bis (2.4.6-trimethylbenzoyl) -phenylphosphine oxide as acylphosphine oxide systems, alone or in combination of two or more. Can be used in combination.

Among these, it is preferable to contain an α-hydroxyacetophenone system that does not easily yellow, and examples of commercially available products include Omnirad 127, 184, and 2959 (trade name: manufactured by IGM Resins). The composition of (B) with respect to 100 parts by weight of the radically polymerizable content is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 8 parts by weight.

In the present invention, it is preferable to further add the tixogenic agent (E). In order to form a seal layer on a member, it is necessary to apply a liquid resin to a height useful as a seal material and maintain its shape until it is further cured. It can be easily realized by doing. For example, an inorganic type such as silica or calcium carbonate, an amide type, an organic type thixophilic imparting agent represented by castor oil type, and the like can be mentioned, and they can be used alone or in combination of two or more kinds. When the ticko value (TI value) is 2.0 or more, it becomes easy to secure the thickness of the seal layer.

Among the above-mentioned inorganic thixophilic imparting agents, hydrophobic fumed silica (e1) surface-treated so as to have good compatibility with (A) and (B) is preferable. The average primary particle size of (e1) is preferably 1 to 80 nm, more preferably 5 to 50 nm, and particularly preferably 10 to 30 nm. When blending (e1), the blending amount with respect to the total solid content is preferably 1 to 10% by weight, more preferably 2 to 8% by weight, and by setting this range, it is possible to impart thixophilicity. Examples of commercially available products include VP-NKC130 (trade name: manufactured by Nippon Aerosil Co., Ltd., primary average particle size 16 nm, n-hexadecane surface treatment).

Further, among the organic thixophilic imparting agents, the castor oil type (e2) having good compatibility with (A) and (B) is preferable, and when used in combination with the above (e1), the effect is higher. Chixo property can be realized. When (e2) is blended alone, the blending amount with respect to the total solid content is preferably 0.3 to 8% by weight, more preferably 0.5 to 5% by weight, and by setting this range, further better thixophilicity can be obtained. Can be secured. When used in combination with (e1), the total of (e1) and (e2) with respect to the total solid content is preferably 10% by weight or less. Examples of the commercially available product (e2) include Rheocin (trade name: manufactured by BYK).

In the present invention, it is preferable to further add a polyfunctional thiol (F). By blending (F), an enthiol reaction capable of suppressing curing inhibition by oxygen becomes possible, photocurability can be improved, and the elongation rate of the cured film can be improved. For example, 1,4 bis (3-mercaptobutyryloxy) butane and tetraethylene glycol bis (3-mercaptopropionate) are bifunctional, and 1,3,5 tris (3-mercaptobutyryloxyethyl) is trifunctional. )-1,3,5-Triazine-2,4,6-trione, trimethylpropanthris (3-mercaptouropionate), pentaerythritol tetrakis (3-mercaptobutyrate), pentaerythritol tetrakis (3-mercaptobutylate) in tetrafunctionality 3-Mercaptopropionate) and the like, and can be used alone or in combination of two or more. Among these, secondary polyfunctional thiols having a good balance between reactivity and storage stability are preferable.

When the above (F) is blended, the blending with respect to 100 parts by weight of the radically polymerizable content is preferably 0.03 to 1 part by weight, and more preferably 0.05 to 0.5 parts by weight. It is possible to improve the reaction and secure a sufficient elongation rate of the cured film. Commercially available products include Karenz MT BD1 (trade name: Showa Denko, 1,4 bis (3-mercaptobutylyloxy) butane).

In the present invention, it is preferable to further add an antioxidant. Antioxidants are compounds that efficiently trap radicals and can improve storage stability. Examples thereof include antioxidants such as 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 include a hindered phenol type or a hindered amine type. When the antioxidant is blended, the blending amount with respect to the total solid content is preferably 0.5 to 5% by weight, preferably 1 to 4% by weight. By setting it within this range, the storage stability can be further improved. Examples of commercially available products include Irganox 1010 (trade name: manufactured by BASF Japan, hindered phenol type) and Tinuvin249 (trade name: manufactured by BASF Japan, hindered amine type).

The composition may contain reactive diluents, silane coupling agents, colorants, thermal polymerization initiators, defoamers, flame retardants, leveling agents, dispersants, polymerization inhibitors, phosphate esters, organic fine particles, etc., as required. Additives can also be used in combination.

As a method of using the photocurable gasket resin composition of the present invention, a seal layer is formed by applying it on a member and then curing it by irradiation with light such as ultraviolet rays. As a light source, a known light source such as a high-pressure mercury lamp, a medium-pressure mercury lamp, a low-pressure mercury lamp, a metal halide lamp, a xenon lamp, an LED lamp, or an electrodeless ultraviolet lamp can be applied, and the ultraviolet irradiation condition is 50 mW / cm ^2. in the irradiation intensity of ~3,000mW / cm ^2, as the accumulated amount of light may be exemplified ^{500mJ / cm 2 ~10,000mJ / cm 2} .

Preferably less 40g ^/ m 2 · 24h as moisture permeability at 60 ° C. 90% RH in conformity with JIS Z0208 photocurable gasket resin composition sealing layer obtained by curing the present invention, 30g ^/ m 2 · 24h is More preferred. If the cured product is within these ranges, the permeation of moisture and foreign matter from the seal layer can be suppressed, and the cured product can be sufficiently used as CIPG.

The hardness of the seal layer obtained by curing the photocurable gasket resin composition of the present invention is preferably a type A hardness of 6 to 50, more preferably 10 to 35. The elastic modulus is preferably 0.5 to 10 MPa. If the cured product is within these ranges, the followability to the bonded surface becomes good, the seal reliability is high, and the cured product can be sufficiently used as CIPG.

Hereinafter, the present invention will be described in detail based on Examples and Comparative Examples, but specific examples are shown and the present invention is not particularly limited thereto. Unless otherwise specified, the measurement was performed under the conditions of room temperature of 25 ° C. and relative humidity of 65%.

Examples 1 to 13
EPION EP400V (trade name: Kaneka Co., Ltd., acryloyl-terminated polyisobutylene) is used as (A), and NOAA (trade name: Osaka Organic Chemical Industry Co., Ltd., n-octyl acrylate) and IB-XA (trade name) are used as (B). : Osaka Organic Chemical Industry Co., Ltd., Isobornyl Acrylate) and FA-511AS (Product Name: Hitachi Kasei Co., Ltd., Dicyclopentenyl Acrylate) as (C), Miperon XM-200 (Product Name: Mitsui Chemical Co., Ltd., NKC130 (trade name: Nippon Aerozil, primary) with (D) Omnirad 184 (trade name: IGM, α-hydroxyacetophenone) as (e1), with an average molecular weight of 2 million and an average particle size of 30 μm by the Coulter counter method. Average particle size 16 nm, n-hexadecane surface treatment), Rheocin (trade name: BKY) as (e2), and Karenz MT-BD1 (trade name: Showa Denko, 1,4-bis) as (F). (3-Mercaptobutyryloxy) butane) and Irganox1010 (trade name: manufactured by BASF Japan) as an antioxidant are stirred until uniformly dissolved in the formulation shown in Table 1, and the photocurable type of Examples 1 to 13 is used. The gasket resin composition was adjusted.

Comparative Examples 1-5
In addition to the materials used in the examples, UC-203 (trade name: manufactured by Kuraray Co., Ltd., methacrylic-modified polyisoprene, Mn35000) and TE-2000 (trade name: manufactured by Nippon Soda Co., Ltd., terminal acrylic group polybutadiene, Mn2500) as acrylic oligomers. ) As monofunctional monomers, 4HBA (trade name: manufactured by Osaka Organic Chemical Industry Co., Ltd., 4-hydroxybutyl acrylate) and HOP (N) (trade name: manufactured by Kyoeisha Chemical Co., Ltd., 2-hydroxypropyl methacrylate) and ACMO (trade name). : Acryloylmorpholine manufactured by KJ Chemicals Co., Ltd.) was used to prepare the photocurable gasket resin compositions of Comparative Examples 1 to 5 by stirring until they were uniformly dissolved with the formulations shown in Table 1.

Table 1

The evaluation method was as follows.

Surface curability: The composition prepared above was completely filled in a special mold (PP, 6 mmT, Φ26 mm), and the UV irradiance device UV LIGHT HAMMER 6Dbulb manufactured by FUSION UV System was used to irradiate 300 mw / cm ² , It was cured under the condition of an integrated light intensity of 6,000 mJ / cm ² , and the tack on the surface was evaluated by touch. The case where there was no tack was evaluated as ◯, and the case where the tack remained was evaluated as x.

Type A hardness: Using the test piece prepared above, the measurement was performed using a type A hardness tester manufactured by Teclock Co., Ltd. according to JIS K 6253. The evaluations were 6 to 10 and over 35 to 60 as ◯, over 10 to 35 as ⊚, and others as x.

Viscosity: Using a cone plate type viscometer RC-550 manufactured by Toki Sangyo, measurements were taken at a cone angle of 3 ° x R7.7 at 25 ± 1 ° C. And said. If the viscosity is out of the measurement range, measure by lowering the rotation speed from 1 rpm to 0.1 rpm so that it is within the measurable range from 10 rpm, and compare the ratio with the viscosity value measured at 1/10 of the rotation speed. The TI value was used.

Elastic modulus: Using Minevea technograph TGI-1KgN, JIS K 6251 tension No. 8 dumbbell shape 1 mm thick test piece (UV irradiation conditions are irradiation degree 300 mw / cm ² with the above irradiation device, integrated light intensity 6, It was measured at 000 mJ / cm ² ) under the condition of a cross head speed of 10 mm / min. The evaluation was evaluated as ◯ for 0.5 to 10 MPa, and x for the others.

Strength: The maximum strength at the time of measuring the above elastic modulus was measured.

Breaking strain: The breaking strain at the time of measuring the above elastic modulus was measured. The evaluation was x for less than 50%, ◯ for 50% or more, and ⊚ for 100-500%.

Moisture permeability: Measurement was performed according to JIS Z0208. The UV irradiation conditions were an irradiance degree of 300 mw / cm ² and an integrated light intensity of 6,000 mJ / cm ² with the above irradiation device, and the measurement conditions were a sample having a thickness of 0.5 mm left in a 60 ° C./90% RH environment for 24 hours. The moisture permeability was calculated from the change in weight. In the evaluation, a moisture permeability of 40 or less was evaluated as ◯, 30 or less was evaluated as ⊚, and more than 40 was evaluated as x.

Evaluation result <br /> Table 2

In the examples, there were no problems in all aspects of Type A hardness, surface curability, viscosity, elastic modulus, strength, breaking strain, and moisture permeability test, and they were good.

On the other hand, Comparative Example 1 and Comparative Example 2 having different (A) had a small breaking strain and a high moisture permeability, and in particular, Comparative Example 2 had a high A hardness and a high elastic modulus. Further, Comparative Example 3 not containing (C) has poor surface curability, and Comparative Examples 4 and 5 using a monofunctional acrylate other than (B) have poor compatibility with (A), and neither is suitable for the present invention. It was a thing.

The resin composition of the present invention is useful as a resin composition for a photocurable on-site-formed gasket, which has good curability, low moisture permeability, and is easy to secure stable sealing properties.

Claims (5)

It is characterized by containing acryloyl-terminated polyisobutylene (A), a monofunctional alkyl (meth) acrylate monomer (B) having an alkyl group of C8-18, a polyethylene powder (C), and a photopolymerization initiator (D). Photocurable gasket resin composition. The photocurable gasket resin composition according to claim 1, wherein (C) is 5 to 45% by weight based on the total solid content of the composition. The photocurable gasket according to any one of claims 1 or 2, further comprising a hydrophobic fumed silica (e1) and / or a compound (e2) derived from castor oil as the thixophilicity-imparting agent (E). Resin composition. The photocurable gasket resin composition according to any one of claims 1 to 3, further comprising a polyfunctional thiol (F). The photocurable gasket resin composition according to any one of claims 1 to 4, wherein the (B) contains a linear alkyl (meth) acrylate (b1) and an alicyclic skeleton (meth) acrylate (b2). Stuff.