JP5243174B2 - Photo-curable prepreg sheet - Google Patents

Description

  The present invention relates to a photocurable prepreg sheet and an improvement thereof. In the present invention, a photocurable prepreg sheet is a B-stage formed by impregnating a photocurable resin composition into a reinforcing material such as a fiber material or a mesh material and increasing the viscosity, and is cured and adhered by light irradiation. Say what you can.

  A prepreg sheet is used as a molding material for printed wiring boards, aircrafts, automobiles, sports equipment, etc., or as a structural reinforcing material for civil engineering buildings. In particular, a photocurable prepreg sheet that is cured with a light source such as ultraviolet light, visible light, or near infrared light is widely used because of its high workability. For the purpose of improving the strength, a prepreg sheet in which a plurality of reinforcing materials are stacked and a prepreg sheet using a reinforcing material such as carbon fiber or metal have been proposed.

In the case of a prepreg sheet in which a plurality of reinforcing materials are stacked, there is a problem in that the irradiation light hardly reaches the deep part of the sheet by stacking the reinforcing materials, and the curability of the pasting surface is deteriorated. Similarly, in the case of a prepreg sheet using carbon fiber or metal as a reinforcing material, there is a problem in that irradiation light is blocked by the reinforcing material and curing of the pasting surface side is significantly slowed down.
In order to solve this problem, the following Patent Document 1 and Patent Document 2 disclose a prepreg sheet that reflects light and allows the back surface to be cured by using a mesh-like reinforcing material having metallic luster. However, in practice, a sufficient amount of light cannot be obtained only by reflection of the reinforcing material, and there remains a problem that the curing time of the sheet becomes long. Patent Documents 3 and 4 below describe resin compositions in which a thermosetting reaction proceeds in a chain by reaction heat of a photocuring reaction using a light / heat binary catalyst. However, with this technology, uniform application is difficult when used in an environment with large temperature changes such as outdoors.
Japanese Patent No. 3955907 Japanese Patent No. 3979912 Patent No. 3944217 Japanese Patent No. 3950241

  The problem to be solved by the present invention is a photocurable prepreg sheet that shortens the time until the strength is developed and at the same time secures workability even when a reinforcing material is used for the purpose of improving the strength, that is, the sticking surface. It is providing the photocurable prepreg sheet which can be hardened | cured to the side reliably.

  In order to solve the above-mentioned problems, the present inventor has repeatedly conducted experiments and repeated intensive studies, and as a result, the prepreg sheet is designed so that the layer on the attachment surface side is cured with a smaller integrated light amount than the layer on the light irradiation surface side. The present inventors have unexpectedly discovered that it is possible to provide a photocurable prepreg sheet that shortens the time until the strength is developed and at the same time secures workability, and has completed the present invention.

That is, the present invention is the following [1] to [8] :
[1] photocurable main resin, and a layer of the photocurable resin composition containing a photopolymerization initiator, a prepreg sheet having each of the attaching surface side and light-irradiation side, the light irradiation surface Reinforcing material is included in either one or both of the photocurable resin composition layer on the side and the photocurable resin composition layer on the application surface side, and the average molar extinction coefficient ε of the photopolymerization initiator is Formula:
ε = (c ₁ ε ₁ +... + c _n ε _n ) / (c ₁ +... + c _n ) [L / (mol · cm)]
_{Wherein, c n [mol / L] is the molar concentration of the photopolymerization initiator of the photocurable resin composition, and _{ε n [L / (mol ·} cm)] , the photocurable resin composition It is the molar extinction coefficient with respect to the irradiation light of the photopolymerization initiator in the product. }, The average molar extinction coefficient ε of the photopolymerization initiator contained in the photocurable resin composition layer on the light irradiation surface side is contained in the photocurable resin composition layer on the application surface side. The photocuring resin composition layer on the light-irradiation surface side is smaller than the average molar extinction coefficient ε of the photopolymerization initiator and the amount of accumulated light required for curing the photocurable resin composition layer on the application surface side The said prepreg sheet | seat characterized by being smaller than the integrated light quantity required for hardening of this.

[2] A photopolymerization initiator contained in the photocurable resin composition layer on the light irradiation surface side of the photocurable resin composition layer on the application surface side, and an average molar extinction coefficient of the photopolymerization initiator containing a different photoinitiator and the average molar extinction coefficient one lifting the epsilon said photopolymerization initiator is larger than epsilon, prepreg sheet according to [1].

[3] Both the photocurable resin composition layer on the light irradiation surface side and the photocurable resin composition layer on the application surface side contain one or more photopolymerization initiators having photobleaching properties. The prepreg sheet according to [1] or [2] .

[4] The prepreg sheet according to any one of [1] to [3] , including an acylphosphine oxide compound as the photopolymerization initiator.

[5] The prepreg sheet according to any one of [1] to [4] , which contains a bisacylphosphine oxide compound as the photopolymerization initiator.

[6] The prepreg sheet according to [5] , wherein the photopolymerization initiator includes a bisacylphosphine oxide-based compound only in the photocurable resin composition layer on the sticking surface side.

[7] The prepreg sheet according to any one of [1] to [6] , wherein the light transmittance of irradiation light used for curing is 1 to 20% in the entire prepreg sheet.

[8] The prepreg sheet according to any one of [1] to [7] , wherein the reinforcing material contained in the prepreg sheet has a light transmittance of 5 to 50% of irradiation light used for curing.

Hereinafter, the present invention will be described in more detail.
The photo-curable prepreg sheet of the present invention is impregnated with a photo-curable resin composition containing a photo-curable main resin and a photo-polymerization initiator in a reinforcing material such as a fiber material or a mesh material, and is made into a B-stage by thickening. Since the integrated light amount required for curing the layer on the application surface side is less than the integrated light amount required for curing the layer on the light irradiation surface side, the time required for curing the entire sheet when cured and bonded by light irradiation This prepreg sheet is shortened and has improved workability.

  In this invention, a light irradiation surface refers to the surface where the light source used for hardening is arrange | positioned, and a sticking surface refers to the surface of the direction affixed on an adhesion body. The impregnation means that the photocurable resin composition covers at least one surface of the reinforcing material and a part thereof is held in the gap of the reinforcing material. Further, the entire reinforcing material may be wetted with the resin.

  The amount of light required for curing is determined by measuring the time required for curing when the photocurable resin composition constituting each layer is formed into a plate with a certain thickness and irradiated with the same light source at the same illuminance. It is defined as the product of illuminance and time. The determination of curing can be performed by a spectroscopic method such as infrared spectroscopic measurement or dynamic viscoelasticity measurement, but it can also be more simply performed by hardness measurement such as indentation hardness and scratch hardness. The hardness can take any numerical value depending on the measurement method and the main resin constituting the prepreg sheet. For example, when a mixture of epoxy acrylate and styrene is used as the main resin, it is defined in JIS-K-5600-5-4. In the measurement of the scratch hardness (pencil method), it can be determined that the hardness is H or higher.

  The photocurable main resin is a monomer or oligomer having at least one of radical active functional group, cationic active functional group or anionic active functional group. For example, acrylate compounds such as epoxy acrylate and urethane acrylate, polyene It can be selected from thiol compounds, unsaturated polyester resins, epoxy compounds, oxetane compounds, vinyl ether compounds and the like. A mixture of these compounds and polymerizable monomers such as acrylic acid ester, methacrylic acid ester and aromatic vinyl compound can also be used. The photopolymerization initiator is, for example, a benzyl ketal type initiator such as 2,2-dimethoxy-1,2-diphenylethane-1-one, 2-hydroxy-2-methyl-1-phenylpropane as a radical initiator. Α-hydroxyacetophenone type initiators such as -1-one, aminoacetophenone type initiators, acylphosphines such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide and bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide From an oxide type initiator, an O-acyloxime type initiator, a titanocene type initiator, etc., as a cationic initiator, for example, from an onium salt, an aryldiazonium salt, an iron-arene complex, etc., as an anionic initiator, for example, Can be selected from alkyl lithium compounds and the likeBoth the main resin and the photopolymerization initiator are not limited to the above examples, and even one kind of compound can be used as a mixture containing a plurality of compounds as components. When used outdoors, it is preferable to select a radical curing system that is not easily affected by temperature and humidity. In this case, an epoxy acrylate having excellent weather resistance is preferably used as the main resin.

  By making the concentration of the photopolymerization initiator in the layer on the application surface side higher than the concentration of the photopolymerization initiator in the layer on the light irradiation surface side, the layer on the application surface side with less integrated light quantity than the layer on the light irradiation surface side. Can be cured.

Further, by using a photopolymerization initiator contained in the layer on the light irradiation surface side having an average molar extinction coefficient ε relatively smaller than the photopolymerization initiator contained in the layer on the attachment surface side, Absorption can be suppressed, and the curability of the layer on the sticking surface side can be improved.
Here, the average molar extinction coefficient ε for the light source used for curing the photopolymerization initiator is defined by the following formula:
ε = (c ₁ ε ₁ +... + c _n ε _n ) / (c ₁ +... + c _n ) [L / (mol · cm)]
_{Wherein, c n [mol / L] is the molar concentration of the photopolymerization initiator of the photocurable resin composition, and _{ε n [L / (mol ·} cm)] , the photocurable resin composition This is the molar extinction coefficient of the photopolymerization initiator with respect to the irradiation light in the product. }.

When the photopolymerization initiator is composed of a single photopolymerization initiator component, the average molar extinction coefficient ε is equal to the molar extinction coefficient of the photopolymerization initiator component. The molar extinction coefficient ε _n of the photopolymerization initiator component can be measured with a spectrophotometer, but when the light source used for curing the sheet has a wide wavelength distribution, the illuminance I ₀ and The illuminance I of the transmitted light can also be measured and calculated from the following formula:
ε _n = (1 / c _n L) · log (I ₀ / I) [L / (mol · cm)]
{Wherein, c n _[mol / L] is the molar concentration of the photopolymerization initiator of the photocurable resin composition, L [cm] the thickness of the transmission optical path length (the photocurable resin composition layer I ₀ [W / cm ² ] is the illuminance of the irradiated light, and I [W / cm ² ] is the illuminance of the transmitted light. }.

  A photopolymerization initiator having the same composition as the photopolymerization initiator contained in the layer on the light irradiation surface side is blended with the photocurable resin composition on the layer on the application surface side, and the average molar extinction coefficient ε is By further adding a photopolymerization initiator component larger than the polymerization initiator, the average molar extinction coefficient ε of the photopolymerization initiator contained in the layer on the light irradiation surface side can be relatively reduced. By using the same photopolymerization initiator for the layer on the light irradiation surface side and the layer on the application surface side, both layers can be efficiently cured simultaneously with the same light source, that is, light in the same wavelength region.

  Inclusion of one or more photopolymerization initiator components with photobleaching properties in both the light-irradiation side layer and the sticking side layer will allow more light to reach the deeper part as it hardens. The curability of the layer on the side of the sticking surface can be improved. Here, the photobleaching property means that as radicals are generated by light irradiation, the absorption of irradiated light is reduced and the light transmittance is improved.

  When an acylphosphine oxide compound such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide is used as the photopolymerization initiator component having photobleaching properties, the curability of the layer on the side of the sticking surface can be improved.

  In particular, by using a bisacylphosphine oxide compound such as bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide as a photopolymerization initiator component, the curability of the layer on the sticking surface side can be greatly improved. .

  Since the bisacylphosphine oxide-based compound has a large molar extinction coefficient, it is preferable that it be blended only in the layer on the sticking surface side to suppress the absorption of irradiation light.

The blending amount of the photopolymerization initiator is about 0.05 to 3 parts by weight with respect to 100 parts by weight of the main resin, so that the deep curability can be improved while maintaining the light transmittance of the entire sheet.
The above technique is particularly effective for a prepreg sheet having a low light transmittance of irradiation light used for curing. Here, the light transmittance is the ratio of the illuminance of the transmitted light to the illuminance of the irradiated light when the sample is irradiated with a parallel light beam vertically. The low light transmittance specifically indicates that the light transmittance is about 1 to 20%, particularly about 1 to 10%.

  Further, the above technique is particularly effective for a prepreg sheet containing a reinforcing material having a light transmittance of irradiation light used for curing of about 5 to 50%, particularly about 10 to 40%. The light transmittance of the reinforcing material is measured in a state in which the reinforcing material is impregnated with the photocurable resin composition, and the light transmittance of the reinforcing material alone is obtained by setting the light transmittance of only the photocurable resin composition as a blank. Ask. At that time, light that leaks from the gap between the reinforcing materials and reaches the back surface and light that reaches the back surface due to reflection or diffraction are also included in the transmitted light.

  As a reinforcing material constituting the prepreg sheet, for example, woven fabric, nonwoven fabric, mesh, knit, mat, or a combination thereof made of materials such as glass, vinylon, phenol resin, aramid fiber, carbon fiber, boron fiber, ceramic, metal, etc. Although it can be used, it is not limited to these examples. These reinforcing materials are not only reinforcing materials having no directionality, such as nonwoven fabrics and mats, but also, for example, giving directionality to strength such as woven fabrics in which the orientation of fibers is changed vertically and horizontally. Reinforcing materials can also be used. Furthermore, a plurality of reinforcing materials can be stacked or several types of reinforcing materials can be stacked. You may arrange | position only to one layer of the light irradiation surface side or the sticking surface side, and you may use a different reinforcing material in each layer.

  The photocurable resin composition constituting the prepreg sheet is composed of a main resin and a photopolymerization initiator, polynuclear aromatics such as pyrene and perylene, xanthenes, cyanines, merocyanines, thiazines, acridines, anthraquinones , Photosensitizers such as squariums, acridones and coumarins, solvents such as acetone, ethyl acetate and toluene, polymerizable monomers such as acrylic esters, methacrylic esters and aromatic vinyl compounds, diethylene glycol dimethacrylate, Crosslinking agents such as N, N'-methylenebisacrylamide, thickeners such as thermoplastic resin powder and silica powder, fillers such as calcium carbonate, bentonite, mica and aluminum hydroxide, pigments such as titanium dioxide and carbon black, Various additives such as polymerization inhibitors such as hydroquinone and nitrosamine It can be contained. The blending of these additives may be different between the layer on the light irradiation side and the layer on the sticking side. By making the photosensitizer concentration of the layer on the affixing surface side higher than the layer on the light irradiation surface side, the integrated light quantity required for curing of the layer on the affixing surface side can be relatively reduced.

  A protective film can also be laminated on one side or both sides of the photocurable prepreg sheet. In this case, one or both of the protective films can be given release properties by silicon processing or the like. Moreover, in order to improve the preservability of a prepreg sheet, you may give light-shielding property to one or both of a protective film. The prepreg sheet can be cured by irradiating light with the protective film laminated. Although the material of a protective film is not specifically limited, For example, polyolefin resins, such as polyethylene and a polypropylene, polyester resins, such as a polyethylene terephthalate, etc. can be used conveniently.

Hereinafter, the present invention will be described with reference to examples and comparative examples.
Example 1
Preparation of photopolymerization initiator 50% by weight of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 20% by weight of 2,2-dimethoxy-1,2-diphenylethane-1-one, 2-hydroxy-2-methyl-1 -A photopolymerization initiator a was prepared by mixing 30% by weight of phenylpropan-1-one.

Preparation of photocurable resin composition 100 parts by weight of resin composition comprising epoxy acrylate and styrene as main resin, 5 parts by weight of diethylene glycol dimethacrylate as crosslinking agent, 14 parts by weight of methacrylate polymer as thickener, and polymerizable monomer As a diluent of 10.5 parts by weight of diallyl phthalate, 0.25 parts by weight of the photopolymerization initiator a, and styrene 0 as a polymerizable monomer as a diluent for the photopolymerization initiator a. A photocurable resin composition A was prepared by adding .25 parts by weight and mixing uniformly. In the photocurable resin composition A, the molar extinction coefficient of the photopolymerization initiator a for an ultraviolet fluorescent lamp (wavelength: 320 to 400 nm, peak wavelength: 360 nm) is 7.5 × 10 ¹ [L / (mol · cm)]. ]Met.

On the other hand, 100 parts by weight of a resin composition comprising epoxy acrylate and styrene as the main resin, 5 parts by weight of diethylene glycol dimethacrylate as the crosslinking agent, 14 parts by weight of the methacrylate polymer as the thickening agent, and 10.5% by weight of diallyl phthalate as the polymerizable monomer 0.25 parts by weight of the photopolymerization initiator a as a photopolymerization initiator and 0.1 parts by weight of bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide as a photopolymerization initiator, and a polymerizable monomer styrene as the diluent 1.15 weight part was added and the photocurable resin composition B was prepared by mixing uniformly. In photocurable resin composition B, the molar extinction coefficient of bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide with respect to the ultraviolet fluorescent lamp is 6.3 × 10 ² [L / (mol · cm)]. The average molar extinction coefficient ε of all photopolymerization initiator components was 1.9 × 10 ² [L / (mol · cm)].

Preparation of prepreg sheet One sheet of E glass roving (weight per unit area: 450 g / m ² ) was laminated on polyethylene film D, impregnated with photocurable resin composition B, and heated at 60 ° C. for 30 minutes to form a B stage. Three sheets of E glass roving (weight per unit area: 450 g / m ² ) were stacked on the obtained structure, and impregnated with the photocurable resin composition A. A polyethylene film C was layered on the photocurable resin composition A layer, heated at 60 ° C. for 30 minutes to form a B stage, and a photocurable prepreg sheet having the cross-sectional structure of FIG. 1 was prepared. The total thickness of the sheet was 2.7 mm, and the light transmittance of the ultraviolet fluorescent lamp was 5.2%. Among them, the light transmittance of four E glass rovings was 36%.

Comparative Example 1
A photocurable prepreg sheet was prepared in the same manner as in Example 1 except that the photocurable resin composition A was used instead of the photocurable resin composition B. The light transmittance of the ultraviolet fluorescent lamp was 6.2%.
The photocurable prepreg sheet obtained in Example 1 and Comparative Example 1 was irradiated with 2000 μW / cm ² of light for 15 minutes using the ultraviolet fluorescent lamp from the side where three E glass rovings were arranged as a reinforcing material. After curing for 1 week, the scratch hardness (pencil method) of the light-irradiated surface and the applied surface was measured according to JIS-K-5600-5-4, and the case where hardness equal to or higher than H was determined to be cured. The results are shown in Table 1. In Table 1, when it is determined to be cured, it is indicated by ◯, and when it is determined that it is not cured, it is indicated by ×. In this experimental condition, Example 1 cured to the pasting surface, but in Comparative Example 1, only the light irradiation surface cured and the pasting surface did not cure.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used as a molding material for printed wiring boards, aircrafts, automobiles, sports equipment, etc., or as a structural reinforcing material for civil engineering buildings.

It is sectional drawing of the photocurable prepreg sheet which is one form of this invention.

Explanation of symbols

A Photocurable resin composition (light irradiation surface side)
B Photocurable resin composition (Attached side)
C Polyethylene film (no mold release)
D Polyethylene film (with mold release)
E Glass roving

Claims (8)

Photocurable main resin, and a layer of the photocurable resin composition containing a photopolymerization initiator, a prepreg sheet having each of the attaching surface side and light-irradiation side, of the light irradiation surface side light A reinforcing material is contained in one or both of the curable resin composition layer and the photocurable resin composition layer on the sticking surface side, and the average molar extinction coefficient ε of the photopolymerization initiator is expressed by the following formula:
ε = (c ₁ ε ₁ +... + c _n ε _n ) / (c ₁ +... + c _n ) [L / (mol · cm)]
_{Wherein, c n [mol / L] is the molar concentration of the photopolymerization initiator of the photocurable resin composition, and _{ε n [L / (mol ·} cm)] , the photocurable resin composition It is the molar extinction coefficient with respect to the irradiation light of the photopolymerization initiator in the product. }, The average molar extinction coefficient ε of the photopolymerization initiator contained in the photocurable resin composition layer on the light irradiation surface side is contained in the photocurable resin composition layer on the application surface side. The photocuring resin composition layer on the light-irradiation surface side is smaller than the average molar extinction coefficient ε of the photopolymerization initiator and the amount of accumulated light required for curing the photocurable resin composition layer on the application surface side The said prepreg sheet | seat characterized by being smaller than the integrated light quantity required for hardening of this. The photocurable resin composition layer on the sticking surface side is a photopolymerization initiator contained in the photocurable resin composition layer on the light irradiation surface side, and an average molar extinction coefficient ε of the photopolymerization initiator. containing a different photoinitiator larger average one lifting a molar extinction coefficient ε the photopolymerization initiator, the prepreg sheet according to claim 1. The photocurable resin composition layer on the light irradiation surface side and the photocurable resin composition layer on the application surface side both contain one or more photopolymerization initiators having photobleaching properties. Or the prepreg sheet of 2 . It comprises an acyl phosphine oxide-based compound as the photopolymerization initiator, the prepreg sheet according to any one of claims 1-3. Including bisacylphosphine oxide compound as the photopolymerization initiator, the prepreg sheet according to any one of claims 1-4. The prepreg sheet according to claim 5 , wherein the photopolymerization initiator contains a bisacylphosphine oxide-based compound only in the photocurable resin composition layer on the sticking surface side. The prepreg sheet according to any one of claims 1 to 6 , wherein a light transmittance of irradiation light used for curing in the whole prepreg sheet is 1 to 20%. The prepreg sheet according to any one of claims 1 to 7 , wherein the reinforcing material contained in the prepreg sheet has a light transmittance of 5 to 50% for irradiation light used for curing.

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