JPS61195170A - Formation of colored coating film on crosslinked polyethylene - Google Patents

Abstract

PURPOSE:To form colored coating film with firm adherability, by coating on the surface of crosslinked polyethylene a colored coating prepared by incorporat ing a pigment in a blend comprising prepolymer and monomer each having (meth)acryloyl group followed by irradiating a radiation. CONSTITUTION:(A) A prepolymer having (meth)acryloyl group [e.g., epoxy poly(meth)acrylate resin] and (B) a monomer and/or oligomer each having (meth)acryloyl group are blended in a weight ratio (A)/(B) pref. 95/5-5/95. The resulting blend is then incorporated with (C) a pigment (e.g., titanium diox ide) to prepare a colored coating. This coating is then applied on the surface of crosslinked polyethylene followed by irradiation of a radiation (e.g., ultravio let light) at a dose, e.g. 300-1,000mJ/cm<2> thus forming the objective colored coating film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a colored coating film on crosslinked polyethylene, and more particularly to a method for forming a colored coating film with strong adhesion on the surface of crosslinked polyethylene by irradiation with radiation. .

Crosslinked polyethylene is generally obtained by chemically crosslinking polyethylene using an organic peroxide or physically crosslinking it by irradiating it with electron beams, and has excellent electrical, mechanical, and thermal properties. Because of this, it is widely used as an insulating coating material for electric wires, cables, etc.

[Conventional technology]

Conventionally, polyethylene, including cross-linked polyethylene,
So-called polyolefin polymers such as polypropylene are non-polar substances and their surfaces are inert, so it is extremely difficult to form a colored coating film with strong adhesion on such polyolefin polymers. ing.

In particular, cross-linked polyethylene is difficult to dissolve even in ordinary organic solvents, and it does not melt to the thermal decomposition temperature when heated, so it is almost impossible to form a colored coating film with good adhesion on the surface using conventional solvent-based paints. has been done.

Therefore, for example, when manufacturing color identification wires from cross-linked polyethylene insulated wires, a method is adopted in which a coloring pigment is kneaded together with the polyethylene during extrusion coating of the polyethylene before cross-linking, and the entire polyethylene resin is colored and then cross-linked. Colored tape attachment methods have been used in which colored nylon or other tape is attached between the conductor and the cross-linked polyethylene coating, but the former method requires many man-hours to change the color and the process is complicated. For this reason, the latter method requires the work of inserting the tape and requires stock of each color, which is disadvantageous economically and reduces production efficiency. Therefore, as a simpler method than these methods, a surface coloring method in which a solvent-based paint using a vehicle is applied to the surface of cross-linked polyethylene can efficiently produce color identification wires of the required length. This method has been proposed as the most effective method and is being used because it does not require complicated color changing operations during extrusion coating.

In other words, this surface coloring method involves applying a paint in which a resin such as cyclized rubber, polyamide, or vinyl chloride is dissolved in a solvent along with a coloring pigment, and then air-dried or heated above the melting point of the vehicle. This is a method in which the solvent is volatilized and the colored pigment is applied to the surface of crosslinked polyethylene along with the vehicle. However, even with this surface coloring method, the adhesion of the paint to cross-linked polyethylene is poor, and in a friction test using felt with a load of 500 g, the paint film peeled off after about 10 to 10 times of back-and-forth friction, and electric wires, cables, etc. When used in applications that are subject to frequent bending or friction, such as in applications where the paint is frequently subjected to bending or friction, the colored paint is likely to peel off in a relatively short period of time, and the coloring may become unclear.
This method cannot be said to be satisfactory since there are problems such as environmental pollution caused by the volatilization of the solvent in the paint during manufacturing.

Therefore, as a method for coloring polyolefin polymers in place of solvent-based paints, a method using paints in which coloring pigments are blended with radiation-curable resins has recently been proposed.

For example, in Japanese Patent Publication No. 50-7966, an ink made of a polyfunctional monomer having two or more reactive functional groups and a pigment is applied to the surface of a plastic object to be colored, and then exposed to radiation ( A coloring method is disclosed in which the monomer is polymerized by irradiation with electron beam (electron beam) and the monomer is chemically bonded to the plastic.

However, this method has the problem that in the case of polyethylene, it is necessary to add the above-mentioned monomer to at least the surface of the polyethylene before applying the ink, making the pretreatment process complicated. Furthermore, the cost of equipment for radiation irradiation equipment for coating is high, and the radiation irradiation process must be carried out in an oxygen-free atmosphere, for example, an inert gas atmosphere.

[Problem that the invention seeks to solve]

As mentioned above, the present invention was made for the purpose of easily forming a colored coating film with excellent adhesion on the surface of cross-linked polyethylene, for which it has been considered extremely difficult to form a strong colored coating film on the surface. , without the need for complicated processes such as adding functional monomers etc. to the resin in advance.
The present invention provides a method for easily and quickly forming a strong colored coating film with excellent adhesion and abrasion resistance on the surface of crosslinked polyethylene in air and with a small amount of ultraviolet irradiation energy.

[Means for solving problems]

That is, the present invention provides a prepolymer having an acryloyl group and/or a methacryloyl group in the molecule and a monomer having the above group in the molecule and/or
Alternatively, there is a method for forming a colored coating film on crosslinked polyethylene, which consists of applying a colored coating composition containing an oligomer and a pigment, and then irradiating the coating with radiation.

In the present invention, examples of the prepolymer having an acryloyl group and/or methacryloyl group in the molecule include the compounds described below. That is, a terminal isocyanate compound obtained by reacting a diisocyanate compound and a polyol in advance is further added with β-hydroxyalkyl (meth)acrylate [(meth)acrylate is a general term for both acrylate and methacrylate. The same applies to the following descriptions and similar descriptions] in the molecule obtained by reacting
Addition polymerization compound having 1 or more (meth)acryloyl groups, obtained by ring-opening polymerization of dibasic acid anhydride such as phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride and glycidyl (meth)acrylate. A linear polyester compound having a large number of pendant (meth)acryloyl groups, a polyhydric alcohol having at least three esterifiable hydroxyl groups on adjacent carbon atoms,
Polymerizable esters prepared by coesterification of (meth)acrylic acid with dicarboxylic acids selected from the group consisting of dicarboxylic acids and their anhydrides, melamine or benzoguanamine with formaldehyde, methyl alcohol and β-hydroxyalkyl Melamine poly(meth)acrylate resin obtained by reacting (meth)acrylate etc., unsaturated polyester resin obtained by reacting glycidyl ether of polyhydroxy compound with (meth)acrylic acid, bisphenol type epoxy resin, novolac type Examples include epoxy poly(meth)acrylate resins obtained by reacting resins containing two or more epoxy groups in the molecule, such as epoxy resins, with (meth)acrylic acid.

In addition, examples of monomers having an acryloyl group and/or methacryloyl group in the molecule include 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and tetrahydrofurfuryl ( Examples include meth)acrylate, hexyldiglycol (meth)acrylate, (meth)acrylamide, methylol(meth)acrylamide, butoxymethyl(meth)acrylamide, and the like. Furthermore, as oligomers having groups similar to the above monomers in the molecule, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1, 6-hexanethiol di(meth)acrylate, neopentyl glycol di(meth)acrylate, bisoxyethylated bisphenol A diacrylate,
Bisoxypropylenated bisphenol A diacrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate,
Examples include dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate.

Therefore, the blending ratio of the monomer and/or oligomer to the prepolymer is 95:5 to 5:95 parts by weight, preferably 80:20 to 10:90 parts by weight.

If the blending ratio of the monomer and/or oligomer to the prepolymer is outside the above range, it will be difficult to obtain a sufficiently cured coating film.In other words, if the prepolymer exceeds 95 parts by weight, the curability will be good but the adhesion will be poor. If the prepolymer is less than 5 parts by weight, the curing properties in air are poor (,
Curing speed will be extremely slow.

In addition, the main resin having the above composition may contain various thermoplastic resins that are compatible with the monomers and oligomers, such as polyvinyl acetate resin and bovinyl, in order to alleviate the curing distortion of the coating film and improve adhesion. Butyral resin, cellulose resin, vinyl acetate acrylate copolymer resin, xylene resin, saturated polyester resin, etc. can be blended.

Such a resin compounding agent has a content of 0.1 parts by weight per 100 parts by weight of the main resin.
It is desirable to add ~100 parts by weight, preferably 0.5 to 30 parts by weight. If the amount of this compounding agent added is less than 0.1 parts by weight, the effect of alleviating the curing distortion of the coating film will be almost gone; If the amount exceeds 1 part by weight, the curability and solvent resistance of the coating film will be extremely reduced, which is not desirable.

There are no particular restrictions on the coloring pigments added to the main ingredient of the present invention, but typical examples include titanium oxide, lead white, tin oxide, carbon black, zinc white, lead zinc oxide, red iron oxide,
Examples include red lead, chrome vermilion, cobalt red, yellow lead, yellow iron oxide, zinc yellow, titanium yellow, ultramarine blue, chrome green, Hansa yellow, permanent yellow, permanent orange, permanent red, phthalocyanine blue, and phthalocyanine green.

In addition to the photopolymerization initiator, aggravating agent, filler, etc. that are generally added to photocurable coating compositions, the base composition may further contain a leveling agent, an antifoaming agent, a surfactant, and the like, if necessary. Polymerization inhibitors, diluting solvents, etc. can be appropriately blended.

Among the above, photopolymerization initiators include benzophenone,
Benzyl, benzyl methyl ketal, 4,4'-bisdiethylaminobenzophenone, 2,2-jethoxyacetophenone, thioxanthone, alkylanthraquinone, 2,2-dimethoxy-2-phenylacetophenone,
α-Azyloxime ester, l-phenyl-1,2-propanedione-2-(0-ethoxycarbonyl)oxime, 1-phenyl-1,2-propanedione-2-(0
-benzoyl)oxime, chlorinated acetophenone derivative, 2-hydroxy-2-methylpropiophenone, 4'
Examples include -isopropyl-2-hydroxy-2-methylpropiophenone and the like alone or in a mixture of two or more.

In addition, sensitizers include aliphatic amines, amines containing aromatic groups, sulfur compounds such as sodium diethyldithiophosphate, NN-disubstituted-P-aminobenzonitrile compounds, and phosphorus compounds such as tri-n-butylphosphine. compounds, nitrogen compounds such as N-nitrone hydroxylamine derivatives, and the like.

The amount of these photopolymerization initiators and sensitizers is usually 0.05 to 10.0 parts by weight, preferably 0.05 to 10.0 parts by weight, and preferably 0.
．． It is added in an amount of 1 to 5 parts by weight.

Further, as the filler, fillers commonly used in paints can be used, such as extender pigments such as talc, mica, and calcium carbonate, and thixotropic agents (thixotropy imparting agents) such as silica, aluminum hydroxide, and bentonite.

Next, the radiation-curable resin coating of the present invention (hereinafter simply referred to as UV coating) prepared by blending each of the above components is uniformly applied to the surface of the crosslinked polyethylene to a thickness of about 10 μm or less, preferably about 5 μm.

If the coating thickness is about 10 μm or more or if the coating thickness is non-uniform, this is not preferable because it will hinder the rapid formation of a cured coating film with a small amount of irradiation energy. In addition, general methods such as spray coating, electrostatic coating, flow coating, roller coating, and dipping coating may be used as the coating method, but As a method for forming a thin and uniformly thick coating film, it is recommended to use the following means.

That is, an elastic and wear-resistant fiber tow such as an ultra-fine stainless steel wire with an outer diameter of several tens of microns or less, preferably about 20 microns or less is cut into appropriate lengths, and the fiber tow is opened using a fiber opening machine or the like. Then, as shown in Fig. 1(a), the elastic fiber web l formed into a mat shape is wound around a long object 2 to be coated as shown in Fig. 1(a). It is installed in a coating device A as shown in the side-line sectional view in the figure, and coating is performed. That is, the applicator A includes a hollow part 4 through which the elongated object 2 passes in the direction of the central axis of the cylindrical housing 3, and a hollow part whose outlet side of the elongated object 2 passing through the hollow part 4 is constricted into a funnel shape. 4a
At the same time, a threaded portion 5 is provided in the entrance-side hollow portion 4b of the elongated object 2, and a perforated bolt 6 having a through hole 7 of the elongated object 2 in the central axis direction is screwed into this threaded portion 5. It consists of
After loading the elastic fiber web 1 wound around a long object 2 into the hollow part 4 of the coating device A, the elastic fiber web 1 can be compressed to an appropriate pressure by a perforated bolt 6. .

Therefore, while the UV paint applied in advance to the surface of the long object 2 by a dipping method or the like passes through the coating device A, the excess amount is absorbed and removed by the elastic fiber web 1, and the UV paint is coated in a uniform desired thickness. be adjusted. This adjustment is carried out smoothly by adjusting the tightness of the bolt 6 to adjust the amount of paint held in the gap of the elastic fiber web f. In addition, since the elastic fiber web l has appropriate elasticity and abrasion resistance, it is possible to form a uniform film thickness by following irregularities on the coating surface of a long object and variations in the outer diameter. Moreover, a uniform coating film can be continuously formed for a long period of time without forming coating unevenness, streaks, etc. over the entire surface length of a long object.

Next, the UV paint applied to the surface of the crosslinked polyethylene as described above is irradiated with radiation and cured. In this case, electron beams and ultraviolet rays are used as the radiation to be irradiated, but since the UV paint according to the present invention can be rapidly cured even with a small amount of irradiation energy, a carbon arc lamp that generates ultraviolet rays with a wavelength of about 200 to 500 nm is used. Sufficient curing can be achieved by short-time irradiation using a mercury vapor lamp, an ultraviolet fluorescent lamp, a tungsten lamp, a xenon lamp, an argon glow lamp, a metal halide lamp, or the like.

Although the amount of ultraviolet irradiation varies depending on the coating thickness, composition, etc., a satisfactory coating film can be formed with an irradiation energy of about 300 to 10,100 O/cd.

〔Example〕

Examples of the present invention will be described below with reference to a case where a colored coating film is formed on the surface of a crosslinked polyethylene-coated insulated wire.

Table 1 shows the composition of the UV paint used in each example and the paint used in the comparative example.

Note: xl is a prepolymer with two acryloyl groups in one molecule obtained by adding acrylic acid to a bisphenol-type epoxy resin.

*2 is a prepolymer with two acryloyl groups in one molecule obtained by adding 2-hydroxyethyl acrylate to isophorone diisocyanate.

*3 uses U, C, C, product name Vinyrite VAOH.

Example 1 A UV paint having the composition and blending ratio shown in Table 1 was applied by dipping to a cross-linked polyethylene (gel fraction approximately 80%) insulated wire with an outer diameter of 3.4 m that runs continuously at a speed of 100 m/min. After adhering, the wires were passed through the coating device shown in Fig. 2 filled with an elastic web made of stainless steel fibers with an outer diameter of 4μ, and coated to a coating thickness of 5μ. Ultraviolet rays were irradiated using two metal halide lamps (manufactured by Eye Graphics, input 8, effective lamp length 50 cm) equipped with reflectors to form a colored cured coating.

24,000 m of surface-colored cross-linked polyethylene insulated wire was obtained after 4 hours of continuous operation, but the coating was uneven over the entire length.
A uniform coating film with no streaks or scratches was formed.

Regarding this coating film, an abrasion tester (Toyo Seiki Seisakusho model, P,
V, F type E1 electric Wire Abratia
As a result of performing a felt friction test under a load of 500 g using a 500 g load, there was no peeling of the coating film even after too many reciprocating frictions, indicating strong adhesion and excellent abrasion resistance.

Example 2 A UV paint having the composition and blending ratio shown in Table 1 was applied by dipping to a cross-linked polyethylene (gel fraction approximately 73%) insulated wire with an outer diameter of 10.21 mm that runs continuously at a speed of 40 m/min. After adhesion, it was passed through a coating device similar to that of Example 1 filled with an elastic web made of stainless steel fibers having an outer diameter of 8 μm, and coated to a coating Mw of 8 μm. Next, using one metal halide lamp used in Example 1, ultraviolet rays were irradiated to form a colored cured coating film.

After 4 hours of continuous operation, a 9,600 m surface-colored cross-linked polyethylene insulated wire was obtained, and a uniform coating film was formed over the entire length without any unevenness or scratches, and there were no irregularities on the surface of the insulator due to the twisting of the conductor. A uniform coating thickness was also formed. This coating film was subjected to the same friction test as in Example 1. As a result, there was no peeling of the coating film even after 1000 reciprocating frictions, and it showed strong adhesion and excellent abrasion resistance.

Example 3 A UV paint having the composition and blending ratio shown in Table 1 was applied by dipping to a cross-linked polyethylene (gel fraction approximately 75%) insulated wire with an outer diameter of 17.0 mm that was continuously running at a speed of 15 m/min. After that, the coating was applied in the same manner as in Example 1 filled with an elastic web made of stainless steel fibers having an outer diameter of 8 μm, and then passed through a coating device and coated to a coating thickness of 5 μm. A colored cured coating film was formed by irradiating ultraviolet rays.

After 6 hours of continuous operation, 5,400 m of surface-colored crosslinked polyethylene insulated wire was obtained, and a uniform coating film was formed over the entire length without coating unevenness, streaks, etc. This coating film was subjected to the same friction test as in Example 1, and as a result, there was no #JIl of the coating film even after 1000 reciprocating frictions, indicating strong adhesion and excellent abrasion resistance.

Example 4 A cross-linked polyethylene insulated wire similar to that in Example 2 was coated with a UV paint having the composition and blending ratio shown in Table 1 using the same coating equipment and metal halide lamp as in Example 2 to a coating thickness of 8 μm. A colored cured coating film was formed.

After continuous operation for 4 hours, a surface-colored crosslinked polyethylene insulated wire of 9600 nm was obtained, and a uniform coating film was formed over the entire length without coating unevenness, streaks, etc. This coating film was subjected to the same friction test as in Example 1. As a result, there was no peeling of the coating film even after 1000 reciprocating frictions, and it showed strong adhesion and excellent abrasion resistance.

Comparative Example 1 A cross-linked polyethylene insulated wire similar to that used in Example 2 was coated with a UV paint having the composition and blending ratio shown in Table 1 to a film thickness of 5 μm using the same coating equipment and metal halide lamp as used in Example 2. A colored cured coating film was formed.

After continuous operation for 4 hours, a surface-colored crosslinked polyethylene insulated wire of 9600 nm was obtained, and a uniform coating film was formed over the entire length without coating unevenness, streaks, etc. A friction test similar to that in Example 1 was performed on this coating film, and as a result, the coating peeled off after about 500 reciprocating frictions.

Comparative Example 2 A cross-linked polyethylene insulated wire similar to that in Example 3 was coated with a UV paint having the composition and blending ratio shown in Table 1 using the same applicator and metal halide lamp as in Example 2 to a coating thickness of 8 μm. A colored cured coating film was formed.

After 3 hours of continuous operation, 2,700 m of surface-colored crosslinked polyethylene insulated wire was obtained, but the surface remained slightly sticky. A friction test similar to that in Example 1 was conducted on this coating, and the results showed that the coating did not peel off after several times of back-and-forth friction.
There was some color transfer to the felt.

Comparative Example 3 A solvent-based paint consisting of 40% polyamide resin, 10% colored pigment, and 50% solvent was applied to the same cross-linked polyethylene insulated wire as in Example 1 using the dipping method, and then allowed to dry and solidify to determine the coating thickness. A colored coating film with a thickness of about 10 μm was formed.

A friction test similar to that in Example 1 was performed on this coating film, and as a result, the coating peeled off after about 20 reciprocating frictions.

・[Effect of the invention] As is clear from the above examples and comparative examples, the formation of a satisfactory colored coating film on the surface of crosslinked polyethylene is
This can be done only when using the UV paint of the present invention, which is a prepolymer having an acryloyl group and/or methacryloyl group in the molecule, and a suitable range of hepatomers and/or oligomers having similar organic groups. It will be done. Moreover, this colored coating can be formed quickly in the air with a small amount of ultraviolet irradiation, so there is no need for large equipment or an inert atmosphere as with conventional electron beam irradiation, and the equipment cost required for radiation irradiation is reduced. can be significantly reduced.

In addition, when the object to be coated is a long object, by applying the UV paint to a uniform coating thickness of about 10 μm or less using the above-mentioned coating device separately devised by the present inventors, A strong colored coating film can be effectively formed.

Therefore, the present invention makes it possible to form a strong surface colored coating film on crosslinked polyethylene, which was conventionally considered difficult to form, thereby producing a color-discriminating capeple made from crosslinked polyethylene. This will greatly contribute to the improvement of surface coloring technology for other molded products.

[Brief explanation of the drawing]

FIG. 1(a) is a perspective view of an elastic fiber web, and FIG. 1(a) is a perspective view showing the web wound around a long object.
FIG. 2 shows a side sectional view of the coating device. DESCRIPTION OF SYMBOLS 1... Elastic fiber web, 2... Long object, 3... Housing, 4... Hollow part, 4a... Funnel-shaped hollow part,
6...Perforated bolt, 7...Through hole. Patent applicant: Yazaki Sogyo Co., Ltd.
Yazaki Electric Cable Co., Ltd. Nippon Oil & Fats Co., Ltd. (a) (b) Procedural amendment (spontaneous) February 7, 1986 □ Director Michibu Uga 1, Indication of the case 1985 Special Fraud Application No. 035264
No. 2, Name of the invention Method for forming a colored coating film on cross-linked polyethylene 3, Relationship with the person making the amendment Address: 1-4-28 Mita, Minato-ku, Tokyo Name (689)
) Yasaki Sogyo Co., Ltd. and two others 4. Contents of amendment by agent (Japanese Patent Application No. 60-035264) 1. The scope of claims is amended as follows. (1) On the surface of cross-linked polyethylene, apply a colored paint consisting of a prepolymer having an acryloyl group and/or methacryloyl group in the molecule, a monomer and/or oligomer having the above group in the molecule, and a pigment, respectively. A method for forming a colored coating film on crosslinked polyethylene, the method comprising: (2) The method for forming a colored coating film on crosslinked polyethylene according to claim 1, wherein the blending ratio of the prepolymer to the monomer and/or oligomer is 95:5 to 5:95 parts by weight. (3) The radiation energy of ultraviolet rays is 300 to 1000
The method for forming a colored coating film on crosslinked polyethylene according to claim 1 or 2, wherein m J / ctA. 2. On page 2, line 5 of the specification, "radiation" is corrected to "ultraviolet light." 3. Same, page 6, lines 14-15, "radiation" is corrected to "ultraviolet light." 4. Same, page 7, line 13, "to adjacent carbon atoms" is deleted. 5. Same, page 10, lines 9-10, “Bobi...”
is corrected as "Boribi...". 6, same, page 13, line 5, "radiation" is corrected to "ultraviolet light". 7, same, page 15, line 10, "radiation" is corrected to "ultraviolet light". 8. Same, 15th true, lines 11-12, “In this case...
...is used, but delete it. 9, page 15, line 14, "r500" is corrected to r400J. 10, same, page 15, line 19, "irradiation amount" is corrected to "irradiation energy." 11, same, page 15, line 20, “about 300” is changed to “300
” he corrected. 12, same page, page 16, line 2, insert the following sentence after ``can do''. “If the irradiation energy is less than 300 mJ/-, the UV coating will not be sufficiently cured and the durability of the coating will be poor, and if the irradiation energy exceeds 10,100 O/alI, there will be excess energy, which is disadvantageous in terms of manufacturing costs. Yes, UV
Paint films and cross-linked polyethylene coatings may deteriorate. ” 13, same, page 17, Table 1, compound group column, line 13,
"Carbon black" and "carbon black", same, No. 14
row, "cyanine blue" is corrected as "phthalocyanine blue", respectively. 14, same, page 19, line 3, "ultraviolet rays" is corrected to "ultraviolet rays from a distance of 1Qcs." 15. Ibid., page 19, line 4, ``let'' be corrected to ``let. (irradiation energy: 420 mJ/cj) J. 16. Ibid., page 20, line 3, ``ultraviolet rays'' should be changed to ``let me.'' Correct the UV rays from a distance of 1001. 17. Ibid., page 20, line 4, "Madeta" is corrected to "Irradiation energy: 520 mJ/cd."
and correct it. 19, Ibid., page 21, line 2, "Made." is corrected to "I caused it. (irradiation energy 840 mJ/aj) J. 20, Ibid., page 22, line 5, line 17, rUV paint " is corrected to "paint." 21, same, page 24, line 4, "irradiation amount" is corrected to "irradiation energy." 22, ibid., page 24, line 8, "...can be done."
Insert the following statement after . "Furthermore, since UV paint is a solvent-free paint, it has the advantage of not causing problems of environmental pollution due to solvent volatilization." Patent applicant Yazaki Sogyo Co., Ltd. and two others

Claims (3)

[Claims] (1) On the surface of crosslinked polyethylene, apply a colored paint made by blending a prepolymer having an acryloyl group and/or a methacryloyl group in the molecule, a monomer and/or oligomer having said group in the molecule, and a pigment, respectively. A method for forming a colored coating film on crosslinked polyethylene, the method comprising: followed by irradiation with radiation. (2) The method for forming a colored coating film on crosslinked polyethylene according to claim 1, wherein the blending ratio of the prepolymer to the monomer and/or oligomer is 95:5 to 5:95 parts by weight. (3) The radiation is ultraviolet rays, and the irradiation dose is 300 to 1
000 mJ/cm^2. The method for forming a colored coating film on crosslinked polyethylene according to claim 1 or 2.