JP3226337B2 - Similar coating method with double cured composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION This invention relates generally to dual cure compositions and the use of those compositions, and more particularly to dual cure analogous coatings.
"Similar coating" means a coating that is applied to conform to the surface to be coated, particularly the surface of the electrical circuit board. "Dual cure" means that cure occurs by two mechanisms.

[0002]

BACKGROUND OF THE INVENTION The application of dual-cure compositions includes their use as conformal coatings, potting compounds, adhesives, etc., with dual-cure conformal coatings being particularly useful, especially in the area of electronics. It is well known that, for example, coating printed circuit boards and electronic components with a protective film can avoid or minimize electrical performance degradation due to contamination. U. S. See US Patent No. 4,424,252. However, it is also known that it is difficult to completely cure the coating by typical methods such as UV curing, due to the shape of the surface on the circuit board. Usually these shapes, such as embedded parts,
Casts a shadow on the film during V exposure and prevents the hardening of the protective film.

[0003] Generally, the most damaging and usually most contaminating appears to be moisture or moisture. Excessive moisture or moisture greatly reduces insulation resistance between conductors, promotes high voltage breakdown and dendrite growth, and corrodes conductors. Other contaminants that damage printed circuit boards include a variety of chemicals, such as residues from manufacturing, such as fluxes, organic solvents, release agents, metal particles and marking inks, and carelessly when handled by humans. Includes adhering contaminants, such as body oils, fingerprints, cosmetics and food stains. Ambient operating conditions also contribute to various contaminants such as salt spray, dust, oil, fuel, acids, corrosive vapors and mold. In all but the relatively severe cases, the destructive effects of these contaminants can be effectively eliminated by applying a good conformal coating.

[0004] In addition to protecting against contamination, similar coatings can provide some protection against mechanical shock, vibration and tampering.

Various similar coatings are known, each having its advantages and disadvantages.

[0006] Two-component dual cure systems, such as two-component polyurethane systems, shorten the cure time. Nativi et al. S. See US Patent No. 4,424,252. Especially Nati
The '252 patent to vi et al. discloses a two-component system involving the reaction of a urethane acrylate with an aliphatic or aromatic polyisocyanate adduct. The coating is then cured within two hours to one day by several mechanisms, one of which involves the reaction of free isocyanate on a polyisocyanate adduct with atmospheric moisture. The cure mechanism also involves the reaction of isocyanate groups with hydroxyl groups on urethane acrylate. But as a result of the latter reaction, this system
As with other two-component systems, the pot life is short, so the user must perform the mixing step immediately before use. For example, U. S. See patent 5,013,631.

One-component systems do not contain isocyanate-reactive functional groups in the system, thereby avoiding the pot-life problem that occurs with two-component systems. Nativ
U of i. S. See patent 4,415,604. For example, N
The ativi '604 patent discloses a one-component system that includes an isocyanate-capped polyether diol and triol, an acrylate diluent, and a photoinitiator. However, since the isocyanate-capped diols and triols are based on hydrophilic polyethers, the resulting coatings have some loss of hydrolytic stability and resistance to moisture. Therefore, the film is not effective in a relatively high humidity environment.

[0008] Other types of one-component analogous coatings involve a cure mechanism other than the isocyanate reaction. For example, U.S. Pat. S. Patents 4,451,523 disclose urethane- (meth) acrylates, allyl-group-containing (meth) acrylate monomers, non-allyl (meth) acrylate diluents,
A one-component composition comprising a photoinitiator and a metal dryer is disclosed. Crosslinking of the allylic compound in the presence of a metal dryer provides a second cure mechanism in addition to the UV cure of the (meth) acrylate. However, this system provides metal ionic species, which degrade the electrical properties of the coating. This type causes degradation of electrical components by promoting electrical pathways between closely packed components.

[0009] The use of dual cured coatings in areas other than electronics is also well known. For example, radiation dual-curable coatings have been used in the automotive industry. Noumen et al. S. See US Patent No. 4,173,682. Especially Noom
disclose a two-component automotive coating system comprising (i) an isocyanate group-containing adduct formed from (meth) acrylic hydroxyester and polyisocyanate, and (ii) a multifunctional hydroxy compound. However, not only do these two-component systems have the disadvantages described above in terms of the electrical coating, but also the ambient curing time is clearly longer, for example several days, compared to the curing time of the other two-component systems. Noome
Some of the isocyanates disclosed by N et al., such as the adduct of hexamethylene diisocyanate and water, contain a biuret linkage. Compounds containing such a bond are:
It is not always thermal stable or "weatherproof". "Weather resistance" means stability under ambient humidity, temperature fluctuations and sunlight.

[0010] Bolgiano, U.S.A. S. Patent 4,13
No. 8,299 discloses a one-component, dual-cure composition suitable for glossy abrasion resistant floor coatings. Especially Borgian
o discloses a one-component composition consisting essentially of an isocyanate (NCO) terminated prepolymer (made from aliphatic isocyanate and polyester diol and triol), and an acrylate diluent free of reactive hydroxyl groups. . The NCO-terminated prepolymer is further reacted with enough hydroxy acrylate to cap 5-15% of the available NCO groups. The composition cures firstly by crosslinking of the ethylenically unsaturated groups of the acrylate and secondly by chain extension and crosslinking of the free NCO groups and water. However, like the composition disclosed in the Nativi '604 patent, the composition of Bolgisno contains a hydrophilic moiety, ie, a polyester linkage. Therefore, the hydrolytic stability of the composition in a humid environment is not effective.

As will be apparent from the discussion above and in the art, any dual-cure analogous coatings have applicability (eg, processing speed, pot life and cure conditions) and physical properties (eg, thermal stability, weatherability and water resistance). (Decomposition stability) is not completely satisfactory. Thus, the purpose of the application and the environment associated with the application will typically dictate the composition of a particular coating.

[0012]

SUMMARY OF THE INVENTION It is a particular object of the present invention to prepare dual cured analogous coating compositions having applicability and physical properties most suitable for use in electronics. However, the dual cure compositions disclosed herein can also be used for other specialized applications such as dual cure potting and adhesive compositions.

It is also an object of the present invention to provide a coating composition having a relatively long pot life and excellent heat stability, weather resistance and hydrolysis stability. These and other objects that will become apparent from the detailed description below are set forth in (a) (i)
An isocyanate adduct having a free isocyanate group and (ii) a free photopolymerizable ethylenically unsaturated group,
The product is a polyisocyanate and a hydroxyalkyl (meth
(T) obtained by the addition reaction of acrylate
Thus, the ethylenically unsaturated groups are free isocyanates on the adduct.
Combination of anate groups and free photopolymerizable ethylenically unsaturated groups
A one-component, dual-cure composition comprising 10-70% of the count ; (b) a (meth) acrylate diluent; and (c) optionally a photoinitiator . Can be achieved by

In order to obtain a composition having higher heat stability,
One-component dual-cure compositions containing aliphatic isocyanate trimers with isocyanurate rings can be used.

The compositions of the present invention can be used not only on coatings on electronic products, but also on other products. In particular, the composition described above is applied on a product and subsequently exposed to radiation to provide a primary cure. Secondary curing is obtained by the reaction of free isocyanate groups of the composition with water.

[0016]

DETAILED DESCRIPTION As described above, the composition of the present invention is a one-component composition. The term refers to providing the user with the composition as a single preparation that is suitable for direct use and is relatively stable on storage, such as at room temperature for at least 30 days. Eventually, the one-component composition basically comprises (a)-
(C) and should be substantially free of free isocyanate-reactive functional groups such as hydroxyl groups. As previously discussed, the two-component system is provided to the user as two preparations that require weighing and mixing steps prior to use. Such compositions generally have poor storage stability after mixing.

The isocyanate adduct shown as (a) above is a reaction product of polyisocyanate and hydroxyalkyl (meth) acrylate. The result (a) of this reaction contains not only free isocyanate groups but also free ethylenically unsaturated groups.

Suitable polyisocyanates are well known in the art. Preferably, the polyisocyanate contains 2-3 free isocyanate groups. For applications where the appearance of the coating is not important, suitable aromatic polyisocyanates include toluene diisocyanate, diphenylmethane-4,
4'-diisocyanate, naphthalene diisocyanate, 3,3'-bistriene diisocyanate and 5,
Includes, but is not limited to, 5'-dimethyldiphenylmethane-4,4'-diisocyanate.
Also suitable are the isocyanate adducts described above.

For applications where the appearance of the coating is important, aliphatic polyisocyanates are suitable. Suitable aliphatic isocyanates include tetramethylene-1,4-diisocyanate, hexamethylene-1,6-diisocyanate, ω,
ω-dipropyl ether diisocyanate, thiodipropyl diisocyanate, 1,2,4-trimethylhexane-1,6-diisocyanate, 4,4-trimethylhexane-1,6-diisocyanate, cyclohexyl -1,4-diisocyanate, isophorone diisocyanate, adduct of one molecule of 1,4-butanediol and two molecules of isophorone diisocyanate, one molecule of 1,4-butanediol and two molecules of hexamethylene Adduct of diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexyldimethylmethane-4,
4'-diisocyanate, xylene diisocyanate,
1,5-dimethyl (2,4-ω-diisocyanatomethyl) benzene, 1,5-dimethyl (2,4-107-diisocyanatoethyl) benzene, 1,3,5-trimethyl (2,4- ω-diisocyanatomethyl) benzene and 1,3,5-triethyl (2,4-ω-diisocyanatomethyl) benzene.

The preferred aliphatic polyisocyanate is an aliphatic isocyanate trimer having an isocyanurate ring. The trimer is preferably a trimerization product of hexamethylene diisocyanate having the following structure:

[0021]

Embedded image

The above polyisocyanate is obtained from Mobay
Commercially available as DESMODUR ^R N-3300 polyisocyanate from.

Other suitable aliphatic isocyanate trimers include those made from isophorone diisocyanate and dicyclohexylmethane diisocyanate.

Aliphatic isocyanate trimers are more heat and weather resistant than similar polyisocyanates containing biuret bonds, such as those prepared from hexamethylene diisocyanate and water, in which the similar coatings produced therefrom. It is preferable because it is excellent. See the Nomen et al. '682 patent. In fact, such trimers are useful not only for similar coatings containing essentially (a)-(c), but also for other similar coatings.

Hydroxyalkyl (meth) acrylates suitable for reacting with the polyisocyanate include hydroxyethyl (meth) acrylate, 2-hydroxymethyl (meth) acrylate, hydroxybutyl (meth) acrylate
Acrylate (and its isomers), and 2-hydroxypropyl (meth) acrylate (and its isomers)
, But is not necessarily limited to these.

Polyisocyanate and hydroxy (meth)
The preparation of adducts from acrylates can generally be carried out in any chosen manner, optionally at elevated temperatures, by adding the reactants together. The reaction is carried out at a temperature of 5 to 100 ° C,
More preferably, it is carried out under anhydrous conditions at a temperature in the range of 50 ° C to 90 ° C. In general, the reactants can be added together by any of the methods. However, hydroxyalkyl (meth) acrylate is added to the polyisocyanate in several steps if necessary. Usually, the reaction is carried out in the presence of an inert solvent such as methyl isobutyl ketone, toluene, xylene or butyl acetate or an ester such as ethyl glycol acetate, but it is not necessary to use a solvent. The reaction between the isocyanate group and the hydroxy group can be carried out optionally in the presence of a catalyst. Suitable examples of catalysts include tertiary amines and organotin or zinc salts such as dibutyltin dilaurate, tin octoate and zinc octoate. Mixtures of catalysts can also be used.

As mentioned above, at least 10% and not more than 70%, preferably 20-40%, of the free functional groups on (a)
The amount of hydroxyalkyl methacrylate in which the range of the above becomes an ethylenically unsaturated group is added, and the reaction is carried out for a time sufficient for ensuring the above. In other words, the amount of hydroxyalkyl (meth) acrylate and the reaction time are at least 10% on the polyisocyanate and no more than 70%,
Preferably it should be sufficient to terminate 20-40% of the isocyanate groups.

[0028] When the polyisocyanate adducts are produced, at least one thereof, preferably two or greater
It is blended with the above (meth) acrylate diluent. Suitable diluents include diluents well known in the art, including, but not necessarily, isobornyl acrylate, isodecyl acrylate, phenoxyethyl acrylate, dicyclopentenyl ethoxy methacrylate, and dicyclopentenyl ethoxy acrylate. It is not limited. Others include trimethylolpropane ethoxylate triacrylate, dicyclopentadiene methacrylate and lauryl methacrylate.

[0029] The formulation may contain additives known in the art. For example, a photoinitiator or a blend of two or more photoinitiators can be added. Suitable photoinitiators include, but are not necessarily limited to, ultraviolet (hereinafter "UV") activated free radical generators,
It can be used in an amount from about 1% to about 10% by weight of the coating composition. For example, a UV activated initiator is represented by the formula M _x (C
O) can be selected from the metal carbonyls of _y , where M
Is a metal atom, x is 1 or 2, y is an integer determined by the total valency of the metal atom, and generally 4-1
0. Preferred UV activated initiators are
(A) a C _1-16 straight or branched alkyl dione; and (b) a carbonyl compound of the general formula R ⁵ (CO) R ⁶ , wherein R ⁵ is C _1-10 alkyl, aryl, aralkyl. Or an alkaryl group, and R ⁶ is R ⁵ or hydrogen. Further, R ⁵ or R ⁶ can include substituents that do not adversely affect the function of the compound. For example, R ⁵
Or, R ⁶ can be alpha-substituted by an alkyl, aryl, alkaryl, alkoxy or aryloxy group having up to 6 carbon atoms, or an amino or mono- or dialkylamino derivative thereof. Further, R ⁵ and R ⁶ have a maximum of 16 carbon atoms together with a carbonyl group.
To form an aromatic or heterocyclic ketone.

When the composition is used as a film or adhesive, it is useful, but not necessary, to insert a fixative therein. Suitable fixing agents include those known in the art. Suitable fixatives include mono- and dicarboxylic acids that can be copolymerized with acrylate or methacrylate reactive diluents, well-known silane fixatives, organotitanates and organozirconates. Suitable amounts are in the range of 0.01-20% of the composition.

[0031] One or more chelating agents, crosslinking agents and / or polymerization inhibitors may optionally be included. Chelating agents and inhibitors are effective in amounts of about 0.1 to about 1% by weight of the total composition. Generally ethylenediaminetetraacetic acid and its sodium salt (Na ₄ 1,1-ethylene-bis - nitrile main dust Denji pyridine) and beta-diketones are the most effective, preferred. The crosslinker comprises about 0-
It can be present in an amount of about 10% by weight and includes compounds such as copolymerizable di (meth) acrylate.

The concentration of inhibitor left in the monomer from the manufacturing process is often sufficient for good stability. However, to ensure the highest pot life, the above proportions (about 0.1 to about 1% by weight of the composition) are recommended. Suitable inhibitors include the group consisting of hydroquinone, benzoquinone, naphthoquinone, phenanthraquinone, anthraquinone and substituted compounds of any of the foregoing. A variety of phenols can be used as inhibitors, the preferred being p-methoxyphenol. Further, alkyl or aryl phosphites can be used, and preferred are triphenyl phosphite and triisodecyl phosphite.

[0033] The viscosity or thixotropy of the composition can be varied according to the particular application required. Thickeners, plasticizers, diluents and various other reagents commonly used in the art can be used in a rational manner to achieve the desired properties.

[0034] For optimal performance, a surfactant may optionally also be present in the coating system. Suitable surfactants are well known in the art and are surfactants that are soluble in the film and are non-reactive with the isocyanate-cap composition.
Suitable surfactants include siloxanes and fluorocarbons. Other suitable surfactants include anionic materials such as petroleum sulfonates, sodium alkyl or alkylaryl sulfonates and sulfonated ethoxylated versions.

The concentration of the surfactant will depend on the particular surfactant used and the reactive diluent. Usually, however, a minimum concentration of surfactant of about 0.25% by weight of the composition is required, with a concentration of at least about 0.5% being preferred. The highest surfactant concentration is usually about 10%, above which the surfactant may interfere with the properties of the coating and potting system, for example by adversely affecting the cure speed, stability or cured product. Because it starts to do. actually,
An upper concentration limit of about 5% should normally be satisfactory. For most surfactants or combinations of surfactants,
The optimal concentration is probably about 1.0-2.5% by weight of the total composition
Will be within the range.

The components (a)-(c) and the optional additives
It can be compounded at the same time, or the adduct (a) can be compounded with other components using a conventional masterbatch method.

Once the desired components have been prepared, the one-component composition can be applied to the product using conventional dipping, spraying, flow coating, curtain coating and brushing methods.

As with other isocyanate-containing dual cure compositions, the compositions of the present invention cure by two mechanisms. Primary curing is obtained by exposing the coating to radiation, preferably UV, causing crosslinking of the free ethylenically unsaturated groups. Subsequent exposure to moisture, preferably atmospheric moisture, causes crosslinking and chain extension of the free isocyanate groups in the composition. In this manner, the exposed portion of the coating is "touch-to-dry" so that the coated product can be handled directly and retain the shape of the coating that would otherwise sag or creep. The secondary cure substantially completes the cure of the unexposed areas of the coating at ambient temperature and humidity.

When the composition of the present invention is used as a similar coating on an electric circuit board provided with various components, the coated board can be further processed immediately after coating.
"Touch dry" curing is important. Secondary curing is a mechanism that cures portions of the coating that are shaded from radiation by the attached components. Products with surface shapes that cause similar shadow problems would also benefit.

The coatings of the present invention also exhibit very good physical properties such as thermal stability, weather resistance and hydrolytic stability. See Example 6. These features are particularly important in the case of electrical circuit board similar coatings, as previously described, which are constantly exposed to solvents, fluxes and are handled by hand. These features are also suitable for other uses of the present invention, including but not limited to potting compounds and adhesives.

The following examples are provided to further illustrate the practice of the present invention, but are not meant to be limiting.

[0042]

EXAMPLE 1 Synthesis of polyisocyanate adduct

[0043]

TABLE 1 Reactant% by weight grams DESMODUR ^R N-3300 ^a 88.72 625.0 Hydroxyethyl acrylate ^b 10.73 75.6 Triphenyl phosphite 0.50 3.5 p-methoxyphenol 0.05 0. 4 Total 100.00 704.5 Footnotes: ^a- Polyisocyanate from Mobay (CAS2
8182-81-20); based on 5.2 meq isocyanate (NCO) / g by titration (21.8% NC
O).

[0044] ^b - ROCRYL ^R 420 hydroxy-et dust acrylate from Rohm and Haas (HEA) (CAS818-6-1 ). 20% of stoichiometric based on 8.6 meq hydroxy (OH) / g
use. Dry on 4A molecular sieve before use.

[0045] DESMODUR of 625g ^R N-33
00 polyisocyanate was charged to a dry 1 liter polymerization kettle equipped with a glass and Teflon paddle stirrer, a stainless steel clad thermocouple, a vented dropping funnel and a dry air blanket. The polyisocyanate was loaded in such a way as to minimize contact with moisture in the air. The polyisocyanate was heated to 45-50 ° C. (113-122 ^° F.) with stirring at 200 rpm, at which point 3.5 g of triphenyl phosphite and 0.4 g of p-methoxyphenol were added to the kettle. .
The mixture was stirred for 5 minutes, the temperature of the kiln 55 ° C. (131 ^o
F). Speed up the stirrer to 400 rpm, 75.6
g of HEA was added dropwise to the reaction mixture via a dropping funnel over 15 minutes (average addition rate 5 g / min). During the HEA addition, the reaction mixture exothermed, from 55 ° C. (131 ^° F.) to 6 ° C.
The temperature reached 5 ° C (149 ^° F). After the HEA addition, the temperature of the mixture was raised to 85-90 ° C. (1
85-194 ^° F). Thereafter, the isocyanate value measured by a conventional titration method is 3.65 to 3.75.
The mixture is brought to 85-90 ° C (18
The mixture was further stirred at 5-194 ^° F).

The product obtained was a clear to slightly cloudy, colorless, somewhat viscous liquid at room temperature. 25 ° C
A typical Brookfield RVT viscosity using a 14 spindle and SC4-6R sample chamber at (77 ^° F.) is 1
1,500 centipoise (cps).

Example 2 Similar Coating Compositions Two coating compositions based on the polyisocyanate / HEA adduct prepared in Example 1, A and B, were prepared by combining a (meth) acrylate monomer, a photoinitiator and a stabilizer. It was prepared using a masterbatch. The material and amount of the monomer masterbatch, and the films A and B formed, include:

[0048]

TABLE 2 Monomer masterbatch A B component weight% gram weight% gram SR-506 38.6 320.0-(isobornyl acrylate) ^a SR-395--32.1 257.0 (isodecyl acrylate) ^a SR-339 32.2 266.0 35.6 286.0 (phenoxyethyl acrylate) ^a QM-57 25.9 21.40--(dicyclopentenylethoxy methacrylate) ^b QM-672--28.6 229 2.0 (dicyclopentenylethoxy acrylate) ^b Irgacure 651 ^c 3.2 26.6 3.6 28.6 p-methoxyphenol 0.1 0.6 0.1 0.8 (MEHQ) Total 100.0 827.2 100.0 801.4 Footnotes : ^a- Sartomer Co. ^b -Rohm and Haas ^c -Ciba Geigy

[0049]

TABLE 3 coating A B Component wt% g wt% g ^{Desmodur R N-3300 / HEA 40.0} 250.0 45.0 280.0 Monomer Master Batch A 60.0 375.0 - - Monomer Master Batch B - - 55.0 342.0 total 100.0 625.0 100.0 622.0 monomers and MEHQ were charged into amber glass bottles, ME
Shake together until HQ dissolved. IRGACURE ^R 6
51 Photoinitiator was added and the mixture was shaken for an additional 5 minutes until the stabilizer and photoinitiator dissolved. Then 40g each
The monomer masterbatch was dried by loading the 4A molecular sieve (8-12 mesh) of the above and left in a sealed bottle for about 4-6 hours.

Thereafter, two coatings were prepared in a dry box (relative humidity <15%) to minimize contact with moisture. Contact with air was kept to a minimum. The adduct prepared according to Example 1 was placed in a dry amber glass or plastic bottle, followed by a corrected dry monomer masterbatch. The mixture was shaken at room temperature for 5 minutes to dissolve the oligomer.

Both coatings (A and B) were transparent and essentially colorless liquids. The Brookfield viscosities of A and B were each 115 cps. After storage in a sealed container for 7 weeks, the viscosity is about 125-130 cps,
The composition was shown to be storage stable.

Example 3 One 28.4 g copper and 1.6 mm with "dummy" surface-embedded device (SMD) soldered with a hard coat tin-lead
A printed circuit board (PCB) made from the core wire FR-4 was cleaned by methods commonly used in electronics technology. The PCBs A and B from Example 2 were then dip coated by dipping the PCB into the coating bath at a constant rate of 25.4 cm / min and removing the coated portion at about 10 cm / min.

The coating was cured by exposure to UV radiation, leaving the coating dry to the touch. Exposure method is Col
Each PCB using light curing equipment (2x200 watt / Hg ramp, belt speed 30 ft / min)
Exposure to UV. 3 total on each side (top and bottom)
Passed twice. The film under the SMD remained liquid, but the exposed areas were tack-free. The coated UV-cured parts were then placed in a room with 100% relative humidity for 48 hours.
After a period of time, it was placed in an open room with a relative humidity of 30% for 13 days, at which time the SM for the "A" and "B" coated plates
One of D was removed. In each case, the coating under the SMD part was tack-free.

Example 4 Each coating A from Example 2 in aluminum weighing dish
And B, respectively, at a relative humidity of 50% and 1%
Placed in a room kept at 00%. After 72 hours in a 100% relative humidity chamber, both films were tack free. Samples kept at 50% relative humidity for 144 hours were also tack-free.

Example 5 0.15 g of a 1% (by weight) solution of dibutyltin laurate in accelerated moisture-cured isodecyl acrylate was added to 15 g of each of coatings A and B.
, Accelerated moisture curing. The moisture curing of these mixtures was tested in the same manner as in Example 4. Both of these mixtures containing dibutyltin laurate were clear solids after 24 hours at 50% and 100% relative humidity and became tack free within 48-72 hours. Examination of moisture cure at a relative humidity of 30% showed that both of these mixtures became tack-free after 48 hours, but the tin compound-free coating remained liquid. After storage in a sealed plastic bottle for 30 days, the viscosity of the composition went from 125 cps to 140 cps at 25 ° C.

Example 6 Properties of Cured Film Prepared according to Example 2 and prepared for MIL-I-46058-C
The following properties were tested on the cured similar films cured in a manner similar to that described in Example 3 except that the method according to Example 3 was included. In particular, the film test piece (coupon) is 10 cm /
Dip-coat at a dip and take-out speed of
UV cured with multiple passes. After curing, the pieces were placed in a humid chamber (100% relative humidity) for 72 hours. It was then removed and placed in an open room for at least 24 hours before testing. Both A and B passed the test.

(1) Chemical resistance: Measured by rubbing the coated piece back and forth with a cotton swab impregnated with methyl ethyl ketone (one double rub); a similar test was performed using a stick immersed in a mixture of Freon and isopropyl alcohol. Repeated; A
Both B and B withstood 100 double rubs for each solvent.

(2) Thermal shock: US military standard MIL-I-46
058C, measured substantially; both A and B, -5
-55 ° C and 125 including 17 cycles at 5 ° C and 125 ° C and 33 cycles at -65 ° C and 125 ° C
Passed 50 cycles of alternating exposure to ° C.

(3) Moisture proof: US Military Standard MIL-I-46
058C; before, during and after testing, including resistance testing at 25 ° C to 65 ° C under electrical load and high humidity (90-95% relative humidity), both A and B at least 10 Insulation resistance measurements of ¹⁰ ohms or more were shown.

(4) Withstand voltage: US military standard MIL-I-46
Both A and B passed this test with no burst discharge and a leakage current of less than 10 microamps under a test voltage of 1500 volts AC at 60 Hz.

(5) Insulation resistance: US Military Standard MIL-I-4
Measured according to 6058C and used as insulation resistance before the moisture resistance test of (3) above; both A and B passed the insulation resistance of 2.0 × 10 ¹⁴ ohms.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-1-104664 (JP, A) JP-A-59-222480 (JP, A) JP-A-53-8698 (JP, A) JP-A-53-8698 5697 (JP, A) JP-A-63-293155 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 75/00-75/16 C08F 299/06 C09D 175/00- 175/16

Claims (5)

(57) [Claims] 1. A process for applying a similar coating to a product, comprising : [A] (a) (i) a free isocyanate group and (i)
i) Isocyanates having free photopolymerizable ethylenically unsaturated groups
Nate adducts, which are polyisocyanates and hydrides
The addition reaction of roxyalkyl (meth) acrylate
Wherein the ethylenically unsaturated group is
Free isocyanate groups and free photopolymerizable ethyls on materials
A film comprising a composition comprising 10-70% of the total number of leneically unsaturated groups ; (b) a (meth) acrylate diluent; and (c) optionally a photoinitiator. the [C] curing said coating in [B] by atmospheric moisture; applied; [B] the said coating in the [a] exposure to radiation
A method characterized by being completed . 2. The method of claim 1, wherein (a)
Is aliphatic isocyanate and hydroxyalkyl (meth)
Write which is a reaction product of acrylate
Law . 3. The method of claim 2, wherein the aliphatic
Wherein the isocyanate is a trimerization product of hexamethylene diisocyanate. 4. The method according to claim 1, wherein the free ethylenically unsaturated groups comprise 20% of the total number of free isocyanate groups and free photopolymerizable ethylenically unsaturated groups on the adduct. A method characterized by comprising : 5. The method according to claim 1 , wherein the product is a circuit board.