JP2006022303A - Optical cation crosslinking pattern polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer which can be three-dimensionally cured by crosslinking by means of irradiation of ultra-violet light or the like, and a resin composition comprising the same, wherein distortions and cracks caused by shrinkage etc. at the time of reaction molding and curing failure on the uppermost surface can be prevented. <P>SOLUTION: A plastic, thermoplastic or liquefied polymer is obtained by polymerization of a radically reactive group, wherein the polymerization is done on an epoxy group-containing monomer containing one to three epoxy groups and one radically reactive group in a molecule, as shown in the figure, by itself or in a combination with a non-epoxy group-containing monomer containing one radically reactive group in a molecule. The polymer has epoxy equivalents of 200-2,000 (g/eq) and weight average molecular weights of 2,000-200,000. The curing is performed by three-dimensional crosslinking by an optical cationic polymerization mechanism by means of irradiation with ultraviolet rays or the like. Rate of volumetric shrinkage at the time of this curing can be <2%. And a cured product usable as various optical materials can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polymer that can be three-dimensionally cured by crosslinking by irradiation with ultraviolet rays or other active energy rays (light rays and radiation capable of generating active species), and a resin composition containing the same. In particular, the present invention relates to one that is three-dimensionalized by a cationic polymerization reaction between epoxy groups. It should be noted that terms such as photocationic crosslinking and photocurability are used including the case where a crosslinking reaction is induced by active energy rays other than light.

In recent years, information communication technology has been rapidly developed, and examination of optical materials such as optical fiber for optical communication technology has become active. Among these, resins that can be cured by light irradiation have been studied as polymer-based optical materials. For example, a resin curable by photo radical polymerization such as a copolymer resin of urethane acrylate or epoxy acrylate and a (meth) acrylate monomer has been studied (Japanese Patent Laid-Open No. 2000-81520, Japanese Patent Laid-Open No. 7-233227). The “(meth) acrylic acid ester” refers to an acrylic acid ester, a methacrylic acid ester, or a combination thereof.
JP 2000-81520 A JP-A-7-233227

  However, in the photo radical polymerization type, there is a problem that the shrinkage at the time of curing is large and the cured product is distorted and distorted. Distortion and cracking after molding due to shrinkage during curing is particularly a problem in molded articles such as optical fibers. In addition, since radical polymerization is inhibited by oxygen, there is a drawback that the curability of the outermost surface tends to be deteriorated.

  The inventors of the present invention have paid attention to the fact that the cure shrinkage of the alicyclic epoxy compound is generally smaller than the cure shrinkage of the (meth) acrylic acid ester in the intensive study in view of the above problems. Small cure shrinkage is advantageous in reducing distortion and cracking as much as possible. Further, the present inventors have come to focus on a cationic polymerization type curing reaction (Japanese Patent Application Laid-Open No. 2003-149476, Japanese Patent Application Laid-Open No. 2003-212961) that is not affected by oxygen inhibition. If it is not affected by oxygen inhibition, the curable property on the outermost surface is poor and physical properties are not lost.

  As described above, the present invention is a photocurable resin used for the production of polymer-based optical materials and the like, which can prevent distortion and cracking after curing molding, and the outermost surface is sufficiently cured. The purpose is to provide.

  The photocurable polymer of the present invention contains an epoxy group-containing monomer containing 1 to 3 epoxy groups and one radical reactive group in the molecule alone or one radical reactive group in the molecule. A plastic, thermoplastic or liquid polymer polymerized by reaction of a radical reactive group in combination with a non-epoxy group-containing monomer, having an epoxy equivalent of 200 to 2000 (g / eq), and a weight average molecular weight Is 2000 to 200,000.

  According to the photocationically crosslinked resin composition of the present invention, since the curing shrinkage is small, the problem of distortion and cracking of the cured product is almost eliminated. Since the cured product has good transparency, it can be applied to optical fields such as optical waveguides.

  Moreover, the refractive index and glass transition point of a resin composition can be adjusted with the combination and composition ratio of a structural monomer. Since the glass transition point before curing can be increased, tack-free can be achieved before curing. Therefore, there is an advantage that a dry film can be formed so as not to be dusty even in a state before curing.

  The polymer can be synthesized by a known method. For example, while a predetermined amount of monomers and a solvent are charged all at once and nitrogen is introduced, the polymer is heated to 70 to 80 ° C. in the presence of a radical polymerization initiator. It is obtained by stirring.

  The radically polymerizable monomer containing an epoxy group, which is an essential component as a polymerization component of the polymer, has 1 to 3 epoxy groups and one radical reactive group. The epoxy group may be either an alicyclic epoxy group or a glycidyl group, but an alicyclic epoxy group is generally preferred from the reactivity of photocationic polymerization. As the epoxy group-containing monomer, a radical reactive monomer having an alicyclic epoxy group is preferably used alone or in combination with a radical reactive monomer having a glycidyl epoxy group. The number of epoxy groups per molecule is preferably 1 to 2. Usually, only a monomer having 1 epoxy group is used, or a monomer having 1 to 3 epoxy groups is used in combination, and the average number of epoxy groups is 1 to 1.5 on the whole. It is preferable to be within the range. The part other than the epoxy group of the epoxy group-containing monomer is a low molecular unit composed of an unsaturated double bond that is easy to control and control radical polymerization.

Examples of such epoxy group-containing monomers include (meth) acrylic acid esters containing epoxy groups, styrene derivatives containing epoxy groups, fumaric acid esters containing epoxy groups, and vinyl compounds containing epoxy groups. It is done. Specifically, epoxy cyclohexyl methyl acrylate (I), epoxy cyclohexyl methyl methacrylate (II), glycidyl acrylate (III), glycidyl methacrylate (IV), [(4-ethenylphenyl) methyl] oxirane (V), 4- (Glycidyloxy) styrene (VI), 4-vinyl epoxycyclohexane (VII), diglycidyl fumarate (VIII), and diepoxycyclohexyl methyl fumarate (IX). The structural formulas of these compounds are shown below.

  As a monomer that does not contain an epoxy group and is used as a polymerization component for other polymers, known monomers can be used. For example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, benzyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxy Butyl (meth) acrylate, phenoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) acryloylmorpholine, (meth) acrylamide, dicyclohexyl fumarate, dibenzyl Examples include fumarate, dibutyl fumarate, and styrene.

  When such a non-epoxy group-containing monomer is used, the mole fraction of the epoxy group-containing monomer, that is, the mole number of the epoxy group-containing monomer / the total mole number of the radical polymerizable monomer is, for example, 0.2 to 0.75. is there. By such copolymerization, the physical properties of the cured product can be easily adjusted to a preferable one.

  The polymer of the present invention has an epoxy equivalent of 200 to 2000 (g / eq). When the epoxy equivalent exceeds 2000, the density of the photocation crosslinking becomes insufficient, and when the epoxy equivalent is less than 200, the density of the photocation crosslinking becomes excessive, which leads to a decrease in toughness. In addition, the measurement of an epoxy equivalent can be performed by the method of JISK7236-1986.

  The polymer of the present invention has a weight average molecular weight (GPC by THF solvent, in terms of polystyrene) of 2000 to 200,000, preferably 3000 to 50,000. When the weight average molecular weight of the polymer is less than 2,000, the concentration of radical reactive end groups becomes excessive. In addition, tackiness remains and handling properties are poor. On the other hand, when the weight average molecular weight of the polymer exceeds 200,000, the viscosity becomes excessive and handling becomes difficult, and in particular, it becomes difficult to prevent mixing of bubbles and the like.

  The polymer of the present invention has a volume shrinkage at the time of three-dimensional curing by photocation crosslinking, preferably less than 3%, more preferably less than 2%, and can sufficiently reduce strain and residual stress caused by reaction curing. . Moreover, since a highly transparent cured product can be easily obtained, it can be used for production of a polymer-based optical material.

  When the resin composition of the present invention is made into a paint, it can be diluted with an organic solvent and monomers such as ethyl acetate and toluene, and when diluted with a monomer, the polymer in the sum of the polymer and the monomer can be diluted. The content is desirably 30% by weight or more.

  As the monomers used for the dilution, known and commonly used monomers such as vinyl ether compounds, propenyl ether compounds, styrene derivatives, epoxy compounds, lactone compounds, oxetane compounds can be used. These may be used independently and may use multiple types together.

  If necessary, a photocationic polymerization initiator (a reaction initiator that generates active species by irradiation with active energy rays) is added to the photocationically crosslinked resin composition of the present invention.

  The kind of the cationic photopolymerization initiator is not particularly limited, and known ones can be used, but typical examples include diphenyliodonium salt, triphenylsulfonium salt, alkyliodonium salt, alkylsulfonium salt, diaryliodonium salt. And diarylsulfonium salts. These may be used alone or in combination.

  Moreover, the addition amount in the case of using a photocationic polymerization initiator is about 0.1 to 10 weight% with respect to the sum total of a polymer and the monomer used as needed, and about 1 to 3 weight%. preferable.

  Furthermore, the photocation cross-linking resin composition of the present invention includes a light stabilizer, an ultraviolet absorber, a catalyst, a leveling agent, an antifoaming agent, a polymerization accelerator, an antioxidant, a flame retardant, and an infrared absorption as necessary. An agent, etc. can be added.

  The active energy rays for curing the photocationically crosslinked resin composition of the present invention are ultraviolet rays, visible rays, electron rays, γ rays, etc., and the light source is not particularly limited, but examples include high pressure mercury lamps, carbon arcs. Lamp, xenon lamp, metal halide lamp and the like.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. In the following, the blending ratio and “%” are all based on weight unless otherwise specified.

[Synthesis Example 1]
A flask was charged with 52 g (0.5 mol) of styrene, 98 g (0.5 mol) of epoxycyclohexylmethyl methacrylate, 300 g of chlorobenzene, 7.5 g of α-methylstyrene dimer, and 1.5 g of lauroyl peroxide, and nitrogen was introduced. The reaction was allowed to proceed for 8 hours at 70 ± 2 ° C. Then, it refine | purified with methanol and the polymer A was obtained.

[Synthesis Example 2]
A flask is charged with 203.2 g of chlorobenzene and heated while introducing nitrogen to a reflux temperature. In this solution, 78 g (0.75 mol) of styrene, 49 g (0.25 mol) of epoxycyclohexylmethyl methacrylate, 50.8 g of chlorobenzene, 25.4 g of α-methylstyrene dimer, and 12.7 g of lauroyl peroxide were dissolved. The reaction was carried out at 120 to 130 ° C. while dropping. Then, it refine | purified with methanol and the polymer B was obtained.

[Synthesis Example 3]
A flask is charged with 262 g of chlorobenzene and heated while introducing nitrogen to a reflux temperature. There, 52 g (0.5 mol) of styrene, 52 g (0.25 mol) of isobornyl acrylate, 45.5 g (0.25 mol) of epoxycyclohexylmethyl acrylate, 38 g of chlorobenzene, 7.5 g of α-methylstyrene dimer, And it was made to react at 120-130 degreeC, dripping what melt | dissolved 7.5 g of lauroyl peroxide. Then, it refine | purified with methanol and the polymer C was obtained.

[Synthesis Example 4]
A flask is charged with 280 g of chlorobenzene and heated while introducing nitrogen to a reflux temperature. There, 123.2 g (0.8 mol) of cyclohexyl acrylate, 36.4 g (0.2 mol) of epoxycyclohexylmethyl acrylate, 40 g of chlorobenzene, 1.2 g of α-methylstyrene dimer, and 8.0 g of lauroyl peroxide are dissolved. It was made to react at 120-130 degreeC, dripping what was made to drop. Then, it refine | purified with methanol and the polymer D was obtained.

[Synthesis Example 5]
A flask is charged with 295 g of chlorobenzene and heated while introducing nitrogen to a reflux temperature. While the solution in which 123.2 g (0.8 mol) of cyclohexyl acrylate, 36.4 g (0.2 mol) of epoxy cyclohexyl methyl acrylate, 24 g of chlorobenzene, and 4.8 g of lauroyl peroxide were dropped, 120 to 120- The reaction was performed at 130 ° C. Then, it refine | purified with methanol and the polymer E was obtained.

Table 1 shows the reaction molar ratio and the molecular weight of the obtained polymer in the above synthesis examples. The molecular weight of the polymer was measured by a GPC apparatus using tetrahydrofuran (THF) as a solvent, and the weight average molecular weight as a polystyrene conversion value was obtained. Specific measurement conditions are as follows.
Column: Tosoh Co., Ltd. polystyrene gel column (TSK gel G4000H _XL + TSK gel G3000H _XL + TSK gel G2000H _XL + TSK gel G1000H _XL x 2)
Column temperature: 40 ° C
Detector: Differential refractive index detector (Shimadzu RID-6A)
Flow rate: 1 ml / min.

[Comparative Synthesis Example 1]
504 g (1 mol) of isocyanurate type trimer of hexamethylene diisocyanate, 0.47 g of hydroquinone monomethyl ether, 429 g (3.3 mol) of 2-hydroxypropyl acrylate, and the residual isocyanate concentration is 70 to 80 ° C. It was made to react until it became 0.1%, and urethane acrylate was obtained.

[Comparative Synthesis Example 2]
380 g (1 mol) of bisphenol A diglycidyl ether (standard type), 144 g (2 mol) of acrylic acid, 0.26 g of hydroquinone monomethyl ether and 2.62 g of tetrabutylammonium bromide are charged, and the acid value is 90 to 100 ° C. Was reacted until 5 mgKOH / g or less was obtained, to obtain an epoxy acrylate.

[Examples 1 to 5, Comparative Examples 1 and 2]
The physical properties of the polymer obtained in the above synthesis example and the urethane acrylate and epoxy acrylate obtained in the comparative synthesis example were measured as follows. The results are shown in Table 2.

・ Tackiness: After volatilizing the solvent, touch the surface with your finger to see if there is tack.
○: No stickiness ×: Stickiness / curing property: The cured film is immersed in methylene chloride for 18 hours to extract an uncured portion and dried at 105 ° C. for 3 hours. From the weight before methylene chloride immersion and the weight after drying, the gelation rate was calculated by the following formula
Gelation rate (%) = weight after drying ÷ weight before immersion × 100
Refractive index * Polymer before curing: obtained polymer / toluene = 75/25, 50/50, 25/75, 0/100 (weight ratio) are blended and uniformly dissolved, and each obtained The resin composition was measured with an Abbe refractometer at a measurement temperature of 25 ° C. The refractive index of polymer / toluene = 100/0 was obtained by extrapolation from a graph in which the horizontal axis represents the blending ratio and the vertical axis represents the measured value of each ratio.
* Urethane acrylate / epoxy acrylate before curing: measured with an Abbe refractometer at a measurement temperature of 25 ° C.

Curing shrinkage: Specific gravity at 20 ° C. before and after curing of a resin cured under the following conditions was measured with a pycnometer, and volume shrinkage (%) = [(specific gravity after curing− Specific gravity before curing) / specific gravity after curing] × 100
・ Glass transition point (before curing): Determined from DSC inflection point ・ Glass transition point (after curing): Determined from rheographic tan δ maximum ・ Transparency: Visual determination of transparency of cured product did
○: Transparent. X: There is turbidity.

Curing conditions: A resin composition blended and uniformly dissolved at the ratio shown in Table 2 was applied onto a glass plate with a 200 μm applicator bar, dried at 70 ° C. for 1 hour in a vacuum dryer, and then a high pressure of 80 W / cm. Ultraviolet rays with an integrated illuminance of 200 mJ / cm ² were irradiated using a mercury lamp. In the table below, Rhodosyl photoinitiator (trademark of Rhodia) PI-2074 is a photocationic polymerization initiator, and Irgacure (trademark of Geigy) 184 is an initiator of photoradical polymerization.

  As is known from the results in Table 2, in Examples 1 to 5, the volume shrinkage during curing could be less than 2%. In particular, in Examples 2 to 5, it could be 0.2% or less. As shown in Table 1, the epoxy equivalent of the polymer (A) of Example 1 is 320 g / eq, whereas the polymers (B to E) of Examples 2 to 5 have an epoxy equivalent of 500 g / eq or more. is there. That is, in Examples 2 to 5, the volume shrinkage rate could be particularly reduced by setting the epoxy equivalent to 500 g / eq or more.

  Moreover, in any Example, compared with general urethane acrylate (Comparative Example 1) and epoxy acrylate (Comparative Example 2), the curability represented by the gelation rate and the transparency of the cured product are completely different. There was no dark blue. Furthermore, there was no tackiness and good handleability, and there was almost no trouble due to dust adhesion.

Claims (5)

  An epoxy group-containing monomer containing 1 to 3 epoxy groups and one radical reactive group in the molecule, alone or in combination with a non-epoxy group-containing monomer containing one radical reactive group in the molecule; A photo-cationic cross-linked polymer, which is a polymer polymerized by a reaction of a radical reactive group, having an epoxy equivalent of 200 to 2000 (g / eq) and a weight average molecular weight of 2000 to 200,000 .   The epoxy group-containing monomer is any one of (meth) acrylic acid ester containing an epoxy group, a styrene derivative containing an epoxy group, and a fumaric acid ester containing an epoxy group, or any combination thereof. The photocationically crosslinked polymer according to claim 1.   A copolymer with a non-epoxy group-containing monomer, the non-epoxy group-containing monomer comprising styrene, a styrene derivative, (meth) acrylic acid ester, fumarate ester, (meth) acryloylmorpholine, and (meth) acrylamide. The photocation cross-linked polymer according to claim 1 or 2, which is any one or any combination thereof.   A photocurable resin composition comprising the photocationically crosslinked polymer according to any one of claims 1 to 3 and having a volume shrinkage ratio of less than 3% during three-dimensional crosslinking. An optical material obtained by curing the photocurable resin composition according to claim 4.