JPS6121118A - Photosetting resin composition - Google Patents

Abstract

PURPOSE:To provide the titled composition having low glass transition temperature and elastic modulus, and excellent thermal aging resistance and hot-water aging resistance, and suitable as the primary coating material for an optical fiber core, by compounding a specific urethane acrylate and a specific monofunctional acrylate at a specific ratio. CONSTITUTION:The objective composition can be produced by compounding (A) 20-80wt% urethane acrylate having (meth)acryloyl groups at both terminals and prepared by (1) reacting a diisocyanate to both terminals of a polycaprolactone and/or a copolymer of polytetramethylene glycol and a polycaprolactone having hydroxyl groups at both terminals and having a molecular weight of >=850, and (2) reacting the reaction product with a compound having (meth)acryloyl group and hydroxyl group (e.g. 2-hydroxyethyl acrylate) and (B) 80-20wt% monofunctional acrylate of formula I (R is 6-8C alkyl; R1 is H or CH3) or a monofunctional acrylate of formula II (R2 is alkyl, phenyl, alicyclic group or heterocyclic group; R3 is H or CH3; n is 1-14) (e.g. butoxyethyl acrylate).

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a photocurable resin composition suitable as a primary coating material for optical fibers.

[Prior art]

Optical fiber consists of a core and a cladding made of glass or plastic with different refractive indexes (core and sheath), and a protective layer is provided on the outer circumferential surface of this core.
Because it has the property of transmitting light from one end to the other without scattering,
Communication technology using this is being put into practical use.

Conventionally, the protective layer of an optical fiber consists of a primary coating material layer (soft layer) that comes in contact with the outer peripheral surface of the core body and directly protects the core body, and a secondary coating material layer (hard layer) that is the outer layer of the primary coating material layer (soft layer). . Various synthetic resins are usually used for these layers.

By the way, as for the primary coating material constituting the primary coating material layer, (1) since this layer is a buffer layer of the core, it is necessary to have flexibility at room temperature, and for this reason, it is necessary to have flexibility at room temperature. It is preferable that the point (Tg) is as low as possible below room temperature, and (2) since this layer is a buffer layer of the core, it needs to have a low elastic modulus, and the tensile elastic modulus is 1.0 kg/
c+II or less, preferably 0.5 kg/cut or less, (3) Since optical fibers are used on the seabed or in the soil for a long period of time, the retention rate of initial physical properties (tensile strength, elongation at break, etc.) is not high. (4) Since optical fibers are bent during use, they must follow the bending, so they have good heat aging resistance and water (moist heat) aging resistance. is 10
% or more, preferably 20% or more.

However, the materials currently used as primary coating materials lack these physical properties, and furthermore, they have a slow curing speed when applied to the optical fiber core to form the primary coating material layer. There are problems such as poor mass production.

[Purpose of the invention]

The present invention has a low glass transition point (Tg), a low elastic modulus,
The object of the present invention is to provide a photocurable resin composition that has excellent heat aging resistance, hot water aging resistance, etc. and is suitable as a primary coating material for an optical fiber core.

[Structure of the invention]

For this reason, the present invention provides polytetramethylene glycol and polycaprolactone having a molecular weight of 8 hydroxyl groups at both ends.
50 or more copolymer and/or polycaprolactone having a molecular weight of 850 or more having hydroxyl groups at both ends, reacting diisocyanate at both ends, and then reacting a compound having an acryloyl group or methacryloyl group with a hydroxyl group. Urethane acrylate having acryloyl or methacryloyl groups at both ends 20-80ffi amount%
and 80 to 20% by weight of a monofunctional acrylate represented by the following formula fl) or (2).

OR.

(R: alkyl group (C, Fl, 3-CI8'!?),
Ri: H, CFIs) (n: l~14, R,:
H+ CHs, Rt' alkyl group, phenyl group, alicyclic group, heterocyclic group, Rs: H, CI, ) Hereinafter, the structure of the present invention will be explained in detail.

ta+ Urethane acrylate having acryloyl or methacryloyl groups at both ends.

This urethane acrylate is a copolymer of polytetramethylene glycol (hereinafter abbreviated as PTMG) and polycaprolactone (hereinafter abbreviated as PCL) having a molecular weight of 850 or more and/or having a hydroxyl group at both ends. It is obtained by reacting a diisocyanate at both ends of PCL having a molecular weight of 850 or more, and then reacting a compound having an acryloyl group or a methacryloyl group with a hydroxyl group. This reaction may be carried out by a conventional method.

The above copolymer of PTMG and PCL is, for example, PTM
This is a PCL/PTMG/PCL type block copolymer having hydroxyl groups at both ends obtained by polymerizing PCL at both ends of G.

The molecular weight is preferably as high as possible in order to obtain a low elastic modulus. For this reason, those having a molecular weight of 850 or more, preferably in the range of 1,000 to 10,000, are used.

The diisocyanate can be any commercially available diisocyanate.
For example, tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), water F
ftMDI, isophorone diisocyanate (IPDI
) etc.

Examples of compounds having an acryloyl group or a methacryloyl group and a hydroxyl group include 2-hydroxyethyl acrylate (2-11E8), 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, etc. acrylates and methacrylates, but are not limited to these. Note that from the viewpoint of improving the curing speed of the resulting resin composition, it is preferable to use acrylate rather than methacrylate.

(b) Monofunctional acrylate.

This monofunctional acrylate is represented by the above formula (1) or (2).

In the above formula (11), it is not preferable that the number of carbon atoms in R decreases because the volatility increases and the glass transition point of the resulting resin composition after curing increases. Therefore, in the present invention, the number of carbon atoms in R is , 06 to CI8. Note that this R is an alkyl group containing a branched structure.

Monofunctional acrylates corresponding to the formula (1)7) include, for example, 2-ethylhexyl acrylate, 2-
Mention may be made of ethylhexyl methacrylate, indecyl acrylate, indecyl methacrylate-1 to lauryl acrylate-1, lauryl methacrylate, stearyl acrylate, and stearyl methacrylate.

Monofunctional acrylates corresponding to the formula (2) include, for example, butoxyethyl acrylate, butoxyethyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, phenoxyprobyl acrylate, phenoxypropyl methacrylate, butoxydiethylene glycol monoacrylate, and polyethylene It is a monoacrylate into which glycol has been introduced (n=4.9.14 in the above formula (2), etc.).

Since the urethane acrylate is a relatively high viscosity liquid or waxy solid, these monofunctional acrylates are used to form the resin composition in order to improve the workability of coating the resulting resin composition onto the optical fiber core. In addition to serving as a diluent to keep the viscosity within a preferred range, it also plays a role in controlling the elastic modulus of the resulting cured product. That is, if urethane acrylate is used alone, there is a problem in workability, and since urethane acrylate is bifunctional, the modulus of elasticity after curing becomes high and exceeds the upper limit of the preferred modulus of elasticity.

fcl The photocurable resin composition of the present invention comprises 20 to 80% by weight of the urethane acrylate and 80 to 20% by weight of the monofunctional acrylate.

That is, if the urethane acrylate is less than 20% by weight and the monofunctional acrylate is more than 80% by weight, the final cured product will have a low modulus of elasticity and will be very flexible, but tack will remain on the surface, which is undesirable. That's because there isn't. Furthermore, if the urethane acrylate content is more than 80% by weight and the monofunctional acrylate content is less than 20% by weight, the viscosity of the resulting resin composition will become extremely high, causing problems in workability, and furthermore, the resulting cured product will become a problem. This is because the modulus of elasticity increases, which is undesirable.

The photocurable resin composition of the present invention may contain other additives, such as photosensitizers, curing accelerators, internal mold release agents, adhesion promoters, transparent fillers, anti-sagging agents, dispersants, and polymerization inhibitors. Agents and the like can be added as appropriate.

〔Effect of the invention〕

As explained above, since the photocurable resin composition of the present invention is composed of 20 to 80% by weight of urethane acrylate and 80 to 20% by weight of monofunctional acrylate, it can exhibit the following effects.

(2) It has a low glass transition point (Tg), low elastic modulus, and excellent heat aging resistance and hot water aging resistance. Therefore, it is suitable as a primary coating material for an optical fiber core.

(2) Since it is a resin that is cured by light, when used as a primary coating material for an optical fiber core, the curing speed is fast, so it is possible to improve the mass production of optical fibers.

Examples are shown below.

Example (1) Synthesis of urethane acrylate: copolymer of PTMG and PCL or PC having hydroxyl groups at both ends
Diisocyanate was reacted with both ends of L at 80° C. for 4 hours (dibutyltin dilaurate was used as a catalyst). Next, 2-hydroxyethyl acrylate (2-H
EA) was similarly reacted at both ends at 80° C. for 6 hours to obtain the desired urethane acrylate.

(2) After mixing a sensitizer with a monofunctional acrylate in the formulation shown in Table 1 below, predetermined urethane acrylates were respectively added and mixed with sufficient stirring to obtain an ultraviolet curable resin composition.

These compositions were exposed to ultraviolet lamp (BOW/cmIK)
It was cured by irradiating with 15 J/- ultraviolet rays using a W multimetal lamp) to obtain a sheet with a thickness of 1+no+.

From this sheet, a strip-shaped test piece of I x 7 cm and a JIS No. 1 dumbbell-shaped test piece were prepared.

The glass transition point (Tg) was determined using a strip-shaped test piece.
It was measured from the peak of tan δ when the torsional elastic modulus was measured by varying the temperature using the A (torsional plaid analysis) method.

The tensile modulus, tensile strength, and elongation at break were measured using a JIS No. 1 dumbbell-shaped test piece at a tensile rate of 11 nm per minute.

Heat aging resistance: 80℃ oven, moist heat aging resistance: 80℃
The tensile properties were measured after 1 month of immersion in warm water at ℃.

The values in Table 1 are expressed as retention rates compared with the physical properties before heat resistance and hot water aging (Examples 1 to 8).

In addition, the numerical values in Table 1 represent parts by weight unless otherwise specified.

(3) For comparison, urethane acrylate was synthesized in the same manner as above using PTMG (molecular weight 2000),
A photocurable resin composition was obtained by mixing in the same manner using a predetermined monofunctional acrylate and sensitizer. This resin composition was tested in the same manner as above (Comparative Example 1).

(Note) Urethane acrylate: A PCL with hydroxyl groups at both ends (molecular weight 550
) /PTMG (molecular weight 850) /PCL
(molecular weight: 550), reacted with MDI at both ends, and then reacted with 2-HE^.

B PCL having hydroxyl groups at both ends (molecular weight 350
) /PTMG (molecular weight 1300) /PCL
(Molecular 1350) was reacted with hydrogenated MDI at both ends, and then reacted with 2-HEA.

PCL with hydroxyl groups at both C-termini (molecular weight 2000
) was reacted with MDI at both ends, and then reacted with 2-HEA.

D PTMG with hydroxyl groups at both ends (molecular weight 200
0) was reacted with MDI at both ends, and then reacted with 2-HEA.

Monofunctional acrylate: E In the above formula (1), R=CH2CFI (Ct
H5) -c4o, , R1''' of CH3.

F In the above formula (1), n=C, □H25, RI”H
Of things.

G In the above formula (2), n=1, R1=Hs R2
-phenyl group, Rs=H.

H In the above formula (2), n = 4, R, = lI,
R2=phenyl group, R3=H.

Sensitizer: 1-Hydroxycyclohexylbenzophenone.

As is clear from Table 1 above, in comparison with Comparative Example 1 using urethane acrylate using PTMG, Example 1 using urethane acrylate using the copolymer of PTMG and PCL or PCL according to the present invention -8, a product having an even lower glass transition point (Tg) is obtained.

Furthermore, when comparing the monofunctional acrylate with a constant monofunctional acrylate and the urethane acrylate molecular weight of approximately 2000, PCL
The higher the molecular weight, the lower the glass transition point (Tg). Therefore, it can be used as a primary coating material for optical fibers in low-temperature regions.

PT? The molecular weight of IG/PCL or PCL is preferably 850 or more, more preferably 1000 or more in terms of low elastic modulus. When PCL having a molecular weight of 550 is used, the elastic modulus exceeds 1.0 kg/aa, which is not preferable.

The monofunctional acrylate has a limit of 80% by weight (Example 1), and if it is less than that, the resulting cured product becomes too soft and has surface tackiness, which is not preferable. The limit is 80% by weight of urethane acrylate (Example 8),
If it is more than that, the elastic modulus becomes high, which is not preferable.

Agent: Patent Attorney Nobuo Kogawa - Kenteru Noguchi Kazuhiko Saishita

Claims (1)

[Scope of Claims] A copolymer of polytetramethylene glycol and polycaprolactone with a molecular weight of 850 or more having hydroxyl groups at both ends, and/or a polycaprolactone having a molecular weight of 850 or more having hydroxyl groups at both ends, reacting with diisocyanate at both ends. , then 20 to 80% by weight of a urethane acrylate having an acryloyl group or a methacryloyl group at both ends obtained by reacting a compound having an acryloyl group or a methacryloyl group and a hydroxyl group, and the following formula (1) or (2).
) A photocurable resin composition comprising 80 to 20% by weight of a monofunctional acrylate represented by: ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(1) (R: Alkyl group (C_6H_1_3 to C_1_8H_
3_7), R_1:H, CH_3) ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(2) (n: 1 to 14, R_1: H, CH_3, R_2: alkyl group, phenyl group, alicyclic group, Heterocyclic group, R_3:H, CH_3)