JPS6048532B2 - Polyurethane resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resin for sealing electronic parts, and in particular to a polyurethane resin composition that has excellent electrical insulation, moisture resistance, and adhesive properties, and can be cured at room temperature without metal corrosion. It is.

Traditionally, electronic components have been coated with thermoplastic resin or coated with thermoplastic resin to protect them from humidity and dust-containing environments, vibrations, and various shocks, and to fully demonstrate the functions of electronic components and prevent malfunctions and deterioration. It is coated with a thermosetting epoxy resin or silicone resin by casting, potting, or other methods.

However, in recent electronic components, the development and introduction of ultra-miniaturization technology for parts has progressed, and the packaging density has been increasing dramatically. There is a tendency for line widths to become smaller and smaller.

Further, the conductor may be formed by vapor deposition, and a slight tension or friction may easily cause a disconnection or peeling accident. Furthermore, if the sealing resin that comes into direct contact with the conductor contains an ino-conductive substance or has poor moisture resistance, electrolytic corrosion of the conductor will occur, resulting in a disconnection accident in a relatively short period of time. Disconnection of conductors caused by mechanical shock or electrolytic corrosion has become a major problem, affecting the lifespan and reliability of electronic components.
Furthermore, if the adhesiveness or moisture permeability of the sealing resin is poor, the mounted electronic components may absorb moisture, causing changes in characteristics and causing accidents such as electronic circuit malfunctions or failures, which is also a major problem. There is.

Therefore, sealing resins used in electronic components undergo various evaluation tests, such as adhesion, moisture permeability, electrical corrosion and corrosion resistance, thermal contraction and expansion resistance, vibration, mechanical and thermal shock resistance, and even low humidity. It is necessary to pass tests such as hardenability.

However, the reality is that the above-mentioned sealing resins have both advantages and disadvantages, and cannot be said to be a material with sufficient performance.

In the case of thermoplastic resins, they lack chemical resistance, moisture resistance, heat resistance, etc., so if they are exposed to high temperature and humidity or to an atmosphere containing dust, etc., they will decompose or melt and lose their effectiveness in protecting electronic components. . In addition, in the case of epoxy resins and silicone resins, which are thermosetting resins, wire breakage may occur due to large internal stress and thermal contraction during curing, and the presence of aliphatic amines used as curing agents or in the epoxy resin. It has drawbacks such as electrolytic corrosion caused by chlorine ions contained as impurities. In the case of silicone resin,
One of its inherent properties is that it has very high moisture permeability, which must be avoided when applied to electronic components that exhibit particular changes in humidity. Furthermore, the adhesion to metals, plastics, etc. is low, and the material cost is also a major drawback that cannot be ignored. The present invention has been made in view of the actual situation of resins for encapsulating electronic components. 50 parts by weight of castor oil and 100 parts by weight of an ester compound reacted with 2 to 2.5 moles of dihydric alcohol.
The main ingredient is a mixed polyol containing ~250 parts by weight,
．． By using an isocyanate compound having two or more isocyanate groups in one molecule as a curing agent, it has excellent moisture resistance, electrical insulation, electrolytic corrosion resistance, adhesion, low-temperature curability, curing shrinkage, and economical efficiency. The present invention provides a polyurethane resin composition for encapsulating electronic components.

The gist of the present invention is to obtain a polyurethane resin composition that is highly elastic and can significantly improve electrical insulation and moisture-heat deterioration properties, which are disadvantages of polyurethane resins, and which does not impair strength, which is an advantage of polyurethane resins. We have conducted various studies on polyols that can achieve the objects of the present invention.

As a result, an electrically nonpolar, hydrophobic, and liquid polyol was obtained by mixing the above-mentioned ester compound consisting of a dibasic acid and a dihydric alcohol with castor oil within a specific range. By performing a curing reaction with the polyol and the above-mentioned isocyanate compound, a resin for encapsulating electronic components that has excellent mechanical and electrical properties and also has excellent water resistance, moisture permeability, adhesiveness, and electrical corrosion resistance is produced. It was obtained. As a method for maintaining the mechanical strength mentioned above, the mixing ratio of the ester compound and castor oil is the most important point. That is, it has become clear that, at a specific mixing ratio, the crystallinity of the ester compound and the number of functional groups (trifunctional) of castor oil give effective results on the mechanical properties of the cured product. The dibasic acid used in the present invention is a linear HOOC-(CH2
)n-COOH HOOC-CH-(CH2)n-℃00H or a branched 1 can be used for R, (wherein n represents an integer of 5 to 20, R represents a lower alkyl group such as a methyl group or an ethyl group) Indicates the group.

) Furthermore, unsaturated dihydrochloric acid containing some double bonds in the linear chain of methylene groups can also be used.

A specific example of a dibasic acid is SL, which is a saturated linear dibasic acid.
-12, SL-16, SL-20 (Product name: 0SK-D
A) Okamura Oil (+wa), SB- with saturated branched dibasic acid
12 (Product name: 0SK-DA) Okamura Oil Co., Ltd.) Unsaturated linear dibasic UL-16, UL-20 (Product name: 0
SK-DA) Okamura Oil Co., Ltd. (Sikki) etc. are commercially available and can be easily obtained. In the present invention, the dibasic acids can be used alone or in combination of two or more types. Next, as the dihydric alcohol to be reacted with the dibasic acid,
Ethylene glycol, diethylene glycol, neopentyl glycol, 1,3-propanediol, 1,3-
Butanediol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, etc. can be used.

The ester compound obtained from the above dibasic acid and dihydric alcohol has a ratio of 2 to 2 to 1 mole of dihydric alcohol to 1 mole of dibasic acid.
It is obtained by reacting in a range of 2.5 moles.
If a ester compound reacted below the above-mentioned range is used in the present invention, the cured product will foam, which is not preferable. Furthermore, if an ester compound having a content exceeding the above range is used, the cured product will have extremely low elasticity, which is not preferable. Ester value reaction between dibasic acid and dihydric alcohol 1 can be easily obtained by a normal esterification reaction, but the ester compound used in the present invention is an ester compound whose acid value has decreased to 1 or less. Therefore, it is preferable to continue the reaction at a high temperature of 200°C or higher for 3 hours or more.

When the acid value is 1 or more, the free carboxylic acid and the isocyanate group of the curing agent cause a decarbonation reaction to generate an amide bond, and the cured product foams. Therefore, when synthesizing ester compounds, controlling the acid value is most important. A mixed polyol, which is the main component of the present invention, is obtained by mixing 50 to 2 parts by weight of castor oil with 100 parts by weight of the ester compound.

The castor oil used in the present invention can be commercially available industrial castor oil, refined castor oil, or hydrogenated castor oil. Castor oil is preferred. If the blending ratio of castor oil is below the above range, the resulting cured product will have poor water resistance, while mixing above the above range will reduce the strength and extensibility of the cured product, so it is best to mix within the above range. Effective.

Furthermore, examples of the curing agent used in the present invention, that is, an isocyanate compound having two or more isocyanate groups in one molecule, include ethylene diisocyanate, propylene diisocyanate, tetramethylene diisocyanate,
Pentamethylene diisocyanate, octamethylene diisocyanate, undecamethylene diisocyanate, dodecamethylene isocyanate, 3-3'-diisocyanate: topropyl ether, 3-isocyanate methyl-3-5-5-trimethylcyclohexyl isocyanate, cyclohexylene 1,4- Diisocyanate, 2.4-Toluylene diisocyanate, 2.6-
Toluylene diisocyanate, xyfurylene 1,4-diisocyanate, xylylene-1,3-diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenylpropane diisocyanate,
m-phenylene diisocyanate, naphthylene-1,4
-diisocyanate, P-phenylene diisocyanate, P.P'.P''-triphenylmethane triisocyanate, diphenyl-4.6.4'-triisocyanate, etc. The isocyanate compound may be used alone or in combination of two or more. It can also be used as a mixture.The mixing ratio of the mixed polyol and the isocyanate compound is preferably within the range of 0.8 to 1.2 isocyanate groups to the hydroxyl groups of the mixed polyol.

If it is outside this range, only a sticky cured product or a cured product lacking in comb elasticity can be obtained, which is not preferable. The polyurethane resin composition of the present invention composed of the above-mentioned composition has an extremely low viscosity, and its cured product has excellent mechanical and electrical properties, and is also a rubber with excellent water resistance, adhesiveness, and moisture permeability. It is a shaped elastic body.

In addition, the polyurethane resin composition of the present invention may be
When the current flowing through the resin layer between the patterned electrodes was coated on 97 comb-shaped electrodes and 45 volts were applied under the conditions of 60°C and 96% RH, a current of about 10-”° to 10-°A only flowed. There was also very little change over time.
On the other hand, when the current was measured under the same conditions using a comb-shaped electrode coated with an epoxy resin using an aliphatic polyamine as a curing agent, a current of 10-° to 10-° flowed, and the current value increased as time elapsed, and the current value increased for several hours. Electrolytic corrosion occurs on the anode side, which can be observed with the naked eye.

The polyurethane resin composition obtained according to the present invention shows extremely excellent properties in the above-mentioned electrolytic corrosion test, so it is clear that it is an extremely effective composition for casting, dipping, coating, etc. of electronic and electrical parts. It became.

The polyurethane resin composition of the present invention will be described in detail below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 A 500m1 four-tube flask was equipped with a nitrogen gas introduction tube, a thermometer, a stirring rod, and a water distillation tube, and a saturated linear dibasic acid (
Product name: 0SK-DASL-16, manufactured by Okamura Oil Co., Ltd.) 286
Weigh y into a flask and add 100% while flowing nitrogen gas.
The temperature was raised to °C.

After raising the temperature, add 130.3y of ethylene glycol and
The temperature was raised to 0°C, and the reaction continued for about 1 hr. The reaction temperature was further increased to 200°C and the reaction was continued for about 2 hours. During this time, 7711 of water was distilled out from the reaction system. The reaction temperature was further increased to 230° C., and the reaction was continued for approximately one hour, and the acid value was measured. Since the acid value had dropped to 0.7, the reaction was immediately cooled to terminate the reaction. Ester compound 392y having a melting point of 43° C. and an OH value of 184 was obtained by the method described above. 100y of the ester compound and 50g of purified castor oil (manufactured by Nicca Oil) were placed in a 300wt1 beaker and heated at 80°C.
The mixture was heated and mixed in an oil bath to obtain a mixed polyol, which is the main ingredient of the present invention.

Liquid diphenylmethane diisocyanate (manufactured by Kasei Upjiyon Co., Ltd.) 10 was added to the mixed polyol as a curing agent.
2y was added, thoroughly mixed, and the viscosity was measured.

The viscosity was approximately 510 Cp (25°C), and the mixture had excellent fluidity**. After measuring the viscosity, place the beaker in a desiccator and perform vacuum degassing treatment, then inject into a mold with a thickness of 2TWL and harden at 100°C for 1 hour to form a 20cm x 20cm size.
A cured sheet of ×0.2C7Tt was obtained. In order to investigate the properties of the cured sheet, JISK72Ol and JISK69 were used.
Mechanical and electrical properties were measured under normal conditions and after moist heat aging according to the following. The measurement results are shown in Table 2. Examples 2 to 9 An ester compound was synthesized in the same manner as in Example 1, a mixed polyol was prepared from the ester compound and castor oil, an isocyanate compound as a curing agent was blended with the mixed polyol, and the mixture was synthesized in the same manner as in Example 1. 2Tn1f1 by the method of
A cured sheet was obtained.

Tables 1 and 2 show the composition and properties of the cured sheet of each example. As mentioned above, the polyurethane resin composition obtained by the present invention has excellent mechanical and electrical properties as shown in Table 2, and also has excellent water resistance and stability against electrolytic corrosion. It is clear that this material is particularly effective as a sealing resin for electronic components.

Claims (1)

[Claims] 1 1 mol of dibasic acid shown by the following structural formula and 2 HOOC-(CH_2)_n-COOH in 1 molecule or ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, n is 5 5 to 20, and R represents a lower alkyl group such as a methyl group or an ethyl group.) 5 parts by weight of castor oil per 100 parts by weight of an ester compound prepared by reacting 2 to 2.5 moles of a dihydric alcohol having a hydroxyl group.
A polyurethane resin composition characterized by using a mixed polyol containing 0 to 250 parts by weight and an isocyanate compound having two or more isocyanate groups in one molecule as a curing agent for the polyol.