JPS6121181B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to materials for coating optical glass fibers for light transmission. Optical glass fibers used for light transmission are brittle, easily damaged, and have poor flexibility, and are easily destroyed by even the slightest external force due to such scratches. Therefore, conventionally, optical glass fibers have been coated with a resin on their surfaces immediately after being manufactured from glass rods. Conventionally, epoxy resins, urethane resins, etc. have been used as such resin coating materials, but they require a long time to cure, resulting in poor productivity, and due to insufficient curing, they do not have sufficient adhesion to glass fibers. However, long-term reliability should not be satisfied. Furthermore, such fiber coatings have the disadvantage that their transmission properties are impaired by lateral pressure, since they lack flexibility. This invention was made to solve the above problems, and in particular, it has a low viscosity, excellent adhesion to optical glass fibers, a high curing speed, and a flexible resin coating. The purpose of the present invention is to provide a coating material for optical glass fibers. That is, the present invention relates to a thermosetting coating material for optical glass fibers, which is mainly composed of diacrylate or dimethacrylate of polyether polyol having an average molecular weight of 200 or more, and which is blended with a thermal polymerization initiator. Acrylate or dimethacrylate can be adjusted to a suitable viscosity for coating optical glass fibers, and can be applied to optical glass fibers and quickly cured, while the cured coating has excellent flexibility and Gives very good results to the transmission properties of glass fiber. Typical diacrylates or dimethacrylates of the present invention are polyethylene glycol di(meth)acrylate and polypropylene glycol di(meth)acrylate with an average molecular weight of 200 or more, but other polyethers such as polyethylene-propylene glycol Diacrylate or dimethacrylate of polyol can be used. The reason why the average molecular weight of these diacrylates or dimethacrylates is set to 200 or more is because if it is lower than this, the flexibility after curing becomes poor and it becomes unsuitable as a coating material for optical glass fibers. Note that if the average molecular weight becomes too high, it will be disadvantageous in terms of viscosity characteristics, so it is better to set a suitable range depending on the type of polyether polyol. The coating material of the present invention is mainly composed of diacrylate or dimethacrylate as described above, but if necessary, a compound having at least one addition-polymerizable double bond can be blended as a crosslinking agent. Typical examples of these compounds are acrylic esters, methacrylic esters and allyl esters, among which polyvalent allyl esters are particularly preferred. Specific examples of acrylic esters or methacrylic esters include monofunctional ones such as 2-ethylhexyl (meth)acrylate, ethyldiethylene glycol (meth)acrylate, butyltriethylene glycol (meth)acrylate, and 1,6-hexanediol. Di(meth)acrylate, trimethylolpropane tri(meth)acrylate, neopentyl glycol di(meth)
Examples include polyfunctional ones such as acrylate, pentaerythritol tetra(meth)acrylate, and diethylene glycol di(meth)acrylate. Examples of polyvalent allyl esters include diallyl adipate, diallyl sebacate, diallyl phthalate, diallyl isophthalate, diallyl terephthalate, diethylene glycol bis(allyl carbonate), diallyl itaconate, triallyl cyanurate, triallyl isocyanurate, etc. . These crosslinking agents may be used alone or in combination of two or more. The usage ratio is 100% of the polyether polyol type diacrylate or dimethacrylate.
The amount is desirably 50 parts by weight or less, and if too much is used, the properties of the polyether polyol type diacrylate or dimethacrylate, particularly flexibility, may be impaired. The coating material of the present invention is of a thermosetting type, and a conventionally known thermal polymerization initiator is used as an essential component. Specific examples of this initiator include benzoyl peroxide and t-butyl peroxybenzoate. These initiators are usually used in an amount of 0.1 to 10% by weight of the total coating material. The optical glass fiber coating material of the present invention may further contain a modifying resin and various additives as necessary, and may be diluted with a solvent for use if desired. The modifying resin is used in an amount equal to or less than the amount of the diacrylate or dimethacrylate of the polyether polyol type used, preferably in an amount not more than 1/4 of the amount. Examples of the modifying resin include epoxy resin, polyamide, polyurethane, polyether, polyamideimide, silicone resin, and phenol resin. It is also possible to use a polyester having an acrylic or methacrylic group at least at both ends of the molecule and having an average molecular weight of 300 or more, and this polyester provides better flexibility after curing. Further, examples of the additives include curing accelerators such as cobalt naphthenate, zinc naphthenate, and dimethylaniline, organosilicon compounds, and surfactants. As detailed above, the coating material of the present invention is
A liquid composition consisting mainly of diacrylate or dimethacrylate of a specific polyether polyol type, blended with a thermal polymerization initiator, and optionally blended with a compound having at least one addition-polymerizable double bond. As shown in the examples below, this coating material has a significantly lower viscosity than conventional coating materials, such as epoxy resin materials, and has a high curing speed and excellent productivity for optical glass fibers. First, it forms a flexible coating that increases the strength and reliability of optical glass fibers. This invention will be explained below with reference to Examples.
This invention is not limited in any way by these Examples. In addition, parts indicate parts by weight. Example 1 1 part of benzoyl peroxide was dissolved in 100 parts of polyethylene glycol diacrylate (viscosity 60 centipoise/25°C) having an average molecular weight of 600.
A coating material for optical glass fiber of this invention was prepared. Example 2 Polypropylene glycol dimethacrylate with an average molecular weight of 400 (viscosity 70 centipoise/25°C)
A coating material for optical glass fiber of the present invention was prepared by dissolving 1 part of benzoyl peroxide in 100 parts. Example 3 A coating material for optical glass fibers of the present invention was prepared by dissolving 10 parts of diallyl adipate and 1 part of benzoyl peroxide in 90 parts of polyethylene glycol diacrylate having an average molecular weight of 600. Comparative example Epoxy resin Epon-828 (manufactured by Shell Oil Co., Ltd.)
5 parts of 2-ethyl-4-methylimidazole was dissolved in 100 parts to obtain a coating material for optical glass fibers different from that of the present invention. When the characteristics of each material of Examples 1 to 3 and Comparative Example were investigated, they were as shown in Table 1 below.

[Table] In Table 1 above, shore hardness A is for each material.
Heat cured at 150℃ for 15 minutes to a thickness of 2.
A plate-shaped body of mm was prepared and used for measurements. Next, using the coating materials of Example 1 and Comparative Example, optical glass fibers were actually coated and their performance was tested as shown in Test Examples 1 and 2 below. Test Example 1 After applying the coating material shown in Example 1 to the surface of an optical glass fiber with a diameter of 125 μm spun at a speed of 20 m/min in a step subsequent to the spinning step,
It was cured using an electric furnace (length 1 m) at 450°C. The outer diameter of the optical glass fiber after coating is approximately 230μm
The surface was uniform. In addition, the breaking strength of the obtained optical glass fiber (sample length 10 m, number of samples 20
The average value of the book) was 5.3Kg, and no increase in transmission loss was observed up to -40℃. Test Example 2 In Test Example 1, the coating material shown in Comparative Example was used instead of the coating material of Example 1, and was cured in an electric furnace heated to 650° C. to obtain an optical glass fiber. The outer diameter of the fibers varied in the range of 150 to 310 μm. Furthermore, a rapid increase in transmission loss was observed in the obtained optical glass fiber at temperatures below -20°C. As mentioned above, the coating material for optical glass fibers of the present invention has a fast curing speed, so it can be coated quickly and with good adhesion in the yarn protection process of optical glass fibers, and it is highly flexible after curing.
There is an advantage that an optical glass fiber coating with excellent transmission characteristics can be obtained.

Claims (1)

[Scope of Claims] 1. A thermosetting coating material for optical glass fibers, which is mainly composed of diacrylate or dimethacrylate of polyether polyol having an average molecular weight of 200 or more, and contains a thermal polymerization initiator. 2 Diacrylate or dimethacrylate of polyether polyol with an average molecular weight of 200 or more,
The coating material for optical glass fibers according to claim 1, which contains a compound having at least one addition-polymerizable double bond. 3. The coating material for optical glass fibers according to claim 2, wherein the compound having at least one addition-polymerizable double bond is selected from acrylic esters, methacrylic esters, and allyl esters.