JPH06128477A - Polyurethane curable composition - Google Patents

Abstract

PURPOSE:To provide a composition containing a specific flame-resistant plasticizer, giving a cured product specified in hardness and excellent in flame retardancy, moisture resistance, electric characteristics, etc., and thereby useful for forming protecting coating films on printed circuit boards. CONSTITUTION:The composition is characterized by giving a cured product having a hardness of <=90 measured with an A type hardness tester regulated by JIS-K-6301 at -90 deg.C and by compounding a flame-resistant plasticizer selected from di(2,6-xylenyl)monocresylphosphate of formula I and a tri-2,6- xylenylphosphate of formula II so as to contain the flameresistant plasticizer in the cured product in an amount of 1-40wt.%. The composition satisfying the above-mentioned conditions may be prepared by combining a polyol component, an isocyanate component, etc. The polyol component is preferably castor oil, polybutadiene polyol, etc., and the polyol and the isocyanate component are usually used in an NCO/OH ratio of 0.7-1.2.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyurethane-based curable composition and a printed wiring board having a cured product of the polyurethane-based curable composition as a protective coating.

[0002]

2. Description of the Related Art Printed wiring boards used for automobile parts, home electric appliances, etc., especially those that are easily affected by moisture, humidity, etc., have a polyurethane resin, silicone resin, A protective coating such as a solvent-type acrylic resin or a solvent-type urethane resin is often provided.

Of these, the protective coating with a polyurethane resin is advantageous in that it can cover the wiring board thickly, so that the entire wiring board can be protected and that the moisture permeability is low. Regarding protective coating with a polyurethane resin, JP-A-62-100513 and JP-A-61-15753.
No. 17, etc., and the urethane resins described therein are blended with a phosphate ester flame retardant plasticizer or the like for the purpose of improving workability, lowering hardness, imparting flame retardancy and the like. ing. However, conventionally used phosphoric acid ester flame-retardant plasticizers are easily hydrolyzed to generate phosphoric acid, and in a resin composition containing such a phosphoric acid ester flame retardant plasticizer, There are problems such as corrosion of the substrate caused by phosphoric acid and deterioration of electrical characteristics.
Moisture resistance is insufficient. Further, the substrate provided with such a moisture-proof coating is usually fixed to a top mark made of styrene resin or the like, but when the urethane resin moisture-proof coating is in direct contact with the styrene resin top mark boss portion, , The plasticizer in the urethane resin migrates to the boss,
There is a problem that cracks occur in the boss portion.

[0004]

The inventor of the present invention has conducted extensive studies to solve the above-mentioned problems of the prior art.
As a result, the phosphoric acid ester-based compound having a specific structure that has never been used as a plasticizer is difficult to undergo hydrolysis and has almost no transferability to styrene parts. The urethane-based curable composition that is blended has good workability, and it is found that the formed cured product has excellent flame retardancy, moisture resistance, electrical characteristics, styrene resistance, and the like. The present invention has been completed.

That is, according to the present invention, the hardness of the cured product measured at -20 ° C. using an A-type hardness tester specified in JIS K 6301 is 90 or less,

[0006]

[Chemical 3]

Di (2,6-xylenyl) monocresyl phosphate represented by the formula:

[0008]

[Chemical 4]

A polyurethane system characterized in that the cured product contains 1 to 40% by weight of a flame-retardant plasticizer comprising at least one compound selected from tri-2,6-xylenyl phosphate represented by It relates to a curable composition.

The polyurethane-based curable composition of the present invention is
After curing the curable composition, JIS K 6301
It is compounded so that the hardness measured at −20 ° C. by using an A-type hardness tester specified in 1) is 90 or less. When the hardness of the urethane resin cured product exceeds this,
When used as a protective coating for a printed wiring board, the protective coating becomes too hard, and the hardness is remarkably increased particularly at low temperatures, which is unfavorable because it may cause solder cracking.

The polyurethane-based curable composition satisfying the above conditions can be easily obtained by appropriately adjusting the combination of the polyol component, the isocyanate component and the like to be used.

The polyol component is not particularly limited and various ones conventionally used as the polyol component can be used, but castor oil, castor oil transesterification product, polybutadiene polyol and the like are particularly suitable. is there. Further, the hydroxyl value of the polyol component cannot be unconditionally specified by the structure of the polyol component, the type of the isocyanate component used, etc., but in general,
If the hydroxyl value is too large, it is difficult to obtain a cured product having low hardness, which is not preferable. Usually, a castor oil, a castor oil transesterification product and the like have a hydroxyl value of about 130 to 170, and a polybutadiene polyol having a hydroxyl value of about 40 to 50 is suitable. Specific examples of these polyol components include Yulic H-30 and Yulic H-35 (both manufactured by Ito Oil Co., Ltd., castor oil,
Hydroxyl value 160), Yulic Y-403, Yulic Y-
202, Yulic Y-406, Yulic Y-808 (all manufactured by Ito Oil Co., Ltd., castor oil transesterification product, hydroxyl value 160), R = 45HT, R = 15HT (manufactured by Idemitsu Petrochemical Co., Ltd., polybutadiene polyol) The hydroxyl value is 46.5) and the like.

The isocyanate component is also not particularly limited and may be appropriately selected and used from the commonly used isocyanate compounds in relation to the polyol compound to be used. Specific examples of the isocyanate component include tolylene diisocyanate, diphenylmethane diisocyanate, carbodiimide modified products of diphenylmethane diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, diphenyl sulfone diisocyanate, triphenylmethane diisocyanate, hexamethylene diisocyanate, 3-isocyanate methyl-
3,5,5-Trimethylcyclohexyl isocyanate, 3-isocyanate ethyl-3,5,5-triethylcyclohexyl isocyanate, diphenylpropane diisocyanate, phenylene diisocyanate, cyclohexylylene diisocyanate, 3,3'-diisocyanate dipropyl ether, triphenylmethane tri Isocyanates, polyisocyanates such as diphenyl ether-4,4'-diisocyanate, or the isocyanates thereof are phenols, oximes, imides,
Mercaptans, alcohols, ε-caprolactam,
Ethyleneimine, α-pyrrolidone, diethyl malonate,
Examples thereof include those blocked with sodium hydrogen sulfite, boric acid and the like.

In the composition of the present invention, the compounding ratio of the polyol compound and the isocyanate compound is usually NCO /
OH may be about 0.7 to 1.2.

In the curable composition of the present invention, the above formula (I) is used.
Di (2,6-xylenyl) monocresyl phosphate represented by and tri-2,6-represented by the above formula (II).
At least one of xylenyl phosphate is blended as a flame retardant plasticizer. These flame-retardant plasticizers are plasticizers having excellent flame-retardant properties, are hardly susceptible to hydrolysis, and have almost no transferability to styrene resins. Therefore, a urethane resin cured product containing this compound has appropriate flexibility and flame retardancy, and also has good moisture resistance, and when used as a protective coating for moisture-proof insulation of a wiring board, it does not dissolve the plasticizer. It does not cause deterioration of electrical properties or corrosion of the substrate due to decomposition. Further, even when the plasticizer comes into contact with the styrene component, the plasticizer does not migrate to the styrene component and cause cracking.

In the curable composition of the present invention, the flame retardant plasticizer may be added to the cured product in an amount of about 1 to 40% by weight.

If necessary, talc, clay, calcium carbonate, baryta powder, silica powder, alumina, carbon black, titanium oxide, iron oxide and the like can be added to the composition of the present invention as a filler. .

In the present invention, various additives such as a pigment, a phosphorus compound, a halogen compound, a flame retardant such as antimony oxide, an antioxidant, an antiaging agent, an ultraviolet absorber and the like may be blended, if necessary. it can.

The composition of the present invention is useful, for example, for forming a protective coating on a printed wiring board.

The method for forming a cured product using the composition of the present invention is not particularly limited and may be a conventional method. The curing condition is from room temperature to 100 ° C. for about 30 minutes to 3 days. It can be left alone.

[0021]

EFFECTS OF THE INVENTION The curable composition of the present invention has good workability because it contains an appropriate amount of a plasticizer, and the cured product has appropriate hardness and flexibility, flame retardancy, It has excellent water resistance, moisture resistance, etc., and has almost no migration of plasticizer to styrene, and can be effectively used especially for forming a protective coating on a printed wiring board.

[0022]

EXAMPLES The present invention will be described in more detail with reference to the following examples.

Example 1 Flame-retardant plasticizers represented by the following formulas (I) and (II) used in the present invention, and conventional flame-retardant plasticizers represented by the following formulas (III) and (IV) The volume specific resistance value, acid value and viscosity were measured. Then, each flame retardant plasticizer 250g
Under saturated vapor pressure of 2 atm, 121 ° C / 100% RH
After performing a pressure cooker test for 96 hours, the acid value was measured and the hydrolysis resistance was evaluated. In addition, as a styrene resistance test, a boss made of styrene with an inner diameter of 3 mm was used.
Apply stress with a strength of kgf · cm by applying screws, wrap it with absorbent cotton and impregnate each flame retardant plasticizer with 2
After standing at 3 ° C. for 240 hours, the presence or absence of cracks in the styrene boss was observed. The above results are shown in Table 1 below.

Flame-retardant plasticizer A-1

[0025]

[Chemical 5]

Flame-retardant plasticizer A-2

[0027]

[Chemical 6]

Flame-retardant plasticizer TCP

[0029]

[Chemical 7]

Flame-retardant plasticizer TXP

[0031]

[Chemical 8]

[0032]

[Table 1]

Further, a urethane resin composition was prepared by using each of the above flame retardant plasticizers in the formulations shown in Tables 2 and 3 below, and cured at 60 ° C. for 16 hours to obtain a cured product. The mixing ratio of the isocyanate compound and the polyol compound is NC
O / OH = 1.0, each component is 100 ℃, 5mmH
What was dehydrated for 1 hour was used. The results of the physical property test of the obtained cured product are also shown in Tables 2 and 3. The test method is as follows.

Initial hardness: cured at 60 ° C. for 16 hours to obtain a cured product, and then at 23 ° C. for 2 hours.
After standing for a time, the hardness was measured at 23 ° C. using an A type hardness tester specified in JIS K 6301.

Styrol resistance The boss made of styrene is fixed with screws at 15 kgf · cm, and a urethane cured product having a thickness of 3 mm is adhered to the boss made of styrene and allowed to stand at 40 ° C. for 240 hours. It was confirmed.

Boiling resistance After the cured product was immersed in boiling water, the hardness of the cured product was measured. The hardness is measured by removing the sample from boiling water and
The sample was left to stand at 3 ° C. for 2 hours, and the test was performed at 23 ° C. by an A type hardness tester specified in JIS K6301. The immersion time and hardness are shown in Tables 2 and 3.

Flame retardance Measured according to the UL-94 combustion test method.

Electrical Properties The volume resistivity (Ω · cm) was measured.

Hardness The hardness was measured at -20 ° C using an A type hardness tester specified in JIS K6301.

[0040]

[Table 2]

[0041]

[Table 3]

(* 1) Castor oil: Trade name Yulic H-3
0, manufactured by Ito Oil Co., Ltd. (* 2) Castor oil transesterification product: Trade name Yuric Y-
808, manufactured by Ito Oil Co., Ltd. (* 3) Modified MDI (carbodiimide modified product of diphenylmethane diisocyanate): Trade name Isonate 14
3L, manufactured by Mitsubishi Kasei Dow As is clear from the above results, the curable composition of the present invention containing the flame retardant plasticizer A-1 or A-2 is flame retardant,
It is excellent in hydrolysis resistance (moisture resistance) and styrene migration resistance.

Claims (2)

[Claims] 1. The hardness of a cured product measured by using an A type hardness tester specified in JIS K 6301 at -20 ° C. is 90 or less, and the formula: And a di (2,6-xylenyl) monocresyl phosphate represented by the formula: A polyurethane-based curable composition containing 1 to 40% by weight of a flame-retardant plasticizer composed of at least one compound selected from tri-2,6-xylenyl phosphate represented by object. 2. A printed wiring board having a cured product of the polyurethane-based curable composition according to claim 1 as a protective coating.