JPS6121120A - 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, etc. and suitable as the primary coating material for an optical fiber core, by compounding a specific urethane acrylate and a 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 with a polybutadiene having hydroxyl groups at both terminals and having a molecular weight of 850-10,000, 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 or II (R is 6-18C alkyl; R1 and R3 are H or CH3; R2 is alkyl, phenyl, etc.; n is 1-14) (e.g. 2-ethylhexyl 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 loose IH layer of the core, it needs to have a low elastic modulus, with a tensile modulus of 1.0k.
g/cJ or less, preferably 0.5kg/c+J
(3) Since optical fibers are used on the seabed or in the soil for long periods of time, they must have a high retention rate of their initial physical properties (tensile strength, elongation at break, etc.), so they must have good heat aging resistance and resistance. It has good aging resistance in hot water (humid heat), and (4) since optical fibers are often bent during use,
Since it has to follow that bending, the elongation at break is 1
It must have physical properties such as 0% 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 has a molecular weight of 85 and has hydroxyl groups at both ends.
Urethane acrylate having an acryloyl group or a methacryloyl group at both ends obtained by reacting a diisocyanate with a polybutadiene of 0 to 1,000 and then reacting a compound having an acryloyl group or a methacryloyl group and a hydroxyl group. 80% by weight and the following formula (1
) or monofunctional acrylate 80-2 represented by (2)
The gist of the present invention is a photocurable resin composition characterized in that it contains 0% by weight.

(Margin below this page) (R: Furkyl group (C, II, ic,, H,, l, R
,: )l, C1)3)(n:1-14,R,:
HI CI+3, R2F alkyl group, phenyl group, alicyclic group, heterocyclic group, R3': H, C1 (3) The structure of the present invention will be explained in detail below.

(a) Urethane acrylate having an acryloyl group or a methacryloyl group at both ends.

This urethane acrylate is obtained by reacting polybutadiene having a molecular weight of 850 to io, ooo and having hydroxyl groups at both ends with a diisocyanate, 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.

As polybutadiene, one having the highest possible molecular weight is preferable in order to obtain a low elastic modulus.

Therefore, the molecular weight is 850 or more, preferably 10
00 or more. The upper limit of the molecular weight is 10.000 or less, considering the viscosity and curing speed of the resin composition obtained.
Preferably it is 5000 or less.

The diisocyanate can be any commercially available diisocyanate.
For example, tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hydrogenated MD
r, isophorone diisocyanate (IPDI), and the like.

Examples of compounds having an acryloyl group or a methacryloyl group and a hydroxyl group include 2-hydroxyethyl acrylate (2,-1)E^), 2-hydroxyethyl mechacrylate, 2-hydroxypropyl acrylate, and 2-hydroxypropyl mechacrylate. Examples include, but are not limited to, acrylates such as acrylates and methacrylates. Note that from the viewpoint of improving the curing speed of the resulting resin composition, it is preferable to use acrylate rather than methacrylate.

fb) Monofunctional acrylate.

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

In the formula il+, it is not preferable that the number of carbon atoms in R becomes small because the volatility becomes high and the glass transition point of the resulting resin composition after curing becomes high. Therefore, in the present invention, the carbon number of R is 06 to C+i. Note that this R is an alkyl group containing a branched structure.

As the monofunctional acrylate corresponding to the above formula flll,
For example, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, indecyl acrylate,
indecyl methacrylate, lauryl acrylate,
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 It is a monoacrylate into which polyethylene 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.

(01) The photocurable resin composition of the present invention is composed of 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 it is preferable because a tank will remain on the surface. That's because there isn't. In addition, if the urethane acrylate is more than 80% by weight and the monofunctional acrylate is less than 20% by weight, the viscosity of the resulting resin composition will be very high, causing problems in workability, and furthermore, the final hardening This is because the elastic modulus of the material increases, which is undesirable.

The photocurable resin composition of the present invention may contain other additives, such as photosensitizers, curing accelerators, internal molding agents, adhesion promoters, transparent fillers, anti-sagging agents, dispersants, and polymerization inhibitors. Agents and the like can be added as appropriate. - [Effects of the Invention] As explained above, 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, and therefore has the following effects. be able to.

(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: It has hydroxyl groups at both ends, and has a fine structure of 60% trans-1,4 structure, 20% cis-1,4 structure, and 20% vinyl-1,2 structure. A diisocyanate was reacted on both ends of a certain polybutadiene at 80° C. for 4 hours (dibutyltin dilaurate was used as a catalyst). Next, 80% of 2-hydroxyethyl acrylate (2-HEA) was added to both ends in the same manner.
The reaction was carried out at ℃ for 6 hours to obtain the desired urethane acrylate.

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

These compositions were treated with an ultraviolet lamp (80W/cmIK
It was cured by irradiating ultraviolet rays of 15 J/c+J with a W multimetal lamp) to obtain a sheet having a thickness of 1III1).

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 speed of 10 mm/min.

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 I are expressed as retention rates in comparison with the physical properties before heat and hot water aging (Examples 1 to 5).

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

(3) For comparison, a photocurable resin composition was obtained using urethane acrylate in an amount outside the range of the present invention (90% by weight) and treated in the same manner as above. The test was conducted in the same manner as (Comparative Example 1).

(Space below this page) (Note) Urethane acrylate: 8 Polybutadiene with hydroxyl groups at both ends (molecular weight 28
00) was reacted with MDI at both ends, and then 2-HEA
A reaction.

B Polybutadiene with hydroxyl groups at both ends (molecular weight 14
00) is reacted with hydrogenated-old, and then 2-H[
! A reaction with A.

Monofunctional acrylate: C in the above formula +1), R=C, 2+12. , l? ,
= H's.

D In the above formula (2), n=4, R, -1s R.

-phenyl group, those where R3=H.

Sensitizer: ■-Hydroxycyclohexylbenzophenone.

As is clear from Table 1 above, Examples 1 to 5 using polybutadiene-based urethane acrylate also had an elastic modulus of 1.
0 kg/- or less, and the primary coating material of the optical fiber (
However, if 90% by weight of polybutadiene-based urethane acrylate is used, the elastic modulus becomes high, which is not preferable (Comparative Example 1).

Regarding the molecular weight of polybutadiene having hydroxyl groups at both ends, a lower elastic modulus can be obtained with a molecular weight of 2,800 than 1,400, but even in the case of 1,400, if a large amount of monofunctional acrylate is used, the elastic modulus will decrease to a certain extent ( Example 1). However, if the amount of monofunctional acrylate exceeds 80% by weight, the surface of the resulting cured product becomes sticky, which is not preferable.

Agent: Patent Attorney Nobuo Kogawa - Kenteru Noguchi Kazuhiko Saishita

Claims (1)

[Scope of Claims] Polybutadiene having a molecular weight of 850 to 10,000 and having hydroxyl groups at both ends is reacted with a diisocyanate, and then a compound having an acryloyl group or a methacryloyl group and a hydroxyl group is reacted at both ends. A photocurable resin composition comprising 20 to 80% by weight of a urethane acrylate having an acryloyl group or a methacryloyl group and 80 to 20% by weight of a monofunctional acrylate represented by the following formula (1) or (2). thing. ▲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)