JP2009013237A - Exoergic polyurethane resin composition and exoergic polyurethane sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyurethane resin composition capable of maintaining a high volume intrinsic resistance value and an excellent flexibility for a long period of time, and an exoergic polyurethane sheet by using the same. <P>SOLUTION: Provided is a polyurethane resin composition containing an inorganic filler and a modified castor oil plasticizer in a polyurethane resin prepared by the reaction of a polyisocyanate and a polybutadiene polyol, wherein, as the polybutadiene polyol, use is made of a polyol having a ratio of (the cis-1,4 structure)/(the trans-1,4 structure)/(the 1,2-vinyl structure) of (5-20)/(10-30)/(50-85). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heat-dissipating polyurethane resin composition and a heat-dissipating polyurethane sheet, and more specifically, a polyurethane resin composition capable of maintaining a high volume resistivity and excellent flexibility over a long period of time, and the same. The present invention relates to a heat dissipating polyurethane sheet.

  Conventionally, in an electronic circuit substrate used for electrical appliances, etc., the substrate is made of a sealing material made of a flame-retardant heat-radiating polyurethane resin composition having a high volume resistance value in order to protect electronic components from moisture or the like. The whole is sealed (Patent Document 1). However, many electronic components that generate heat during operation are attached to the electronic circuit board. In recent years, electronic circuits have been integrated and highly functionalized as seen in LSIs, etc. At the same time, the heat generation is becoming local. Thus, in order to efficiently remove the heat generated from the electronic component, the sealing material needs to be in close contact with the circuit board or the electronic component for a long period of time, so that flexibility can be maintained for a long period of time. It is necessary. In addition, since the heat-dissipating polyurethane resin used as the sealant is used in close contact with the electronic component, it is also necessary to maintain a high volume resistivity value over a long period of time.

In view of such a point, various heat-radiating polyurethane resin compositions have been developed in order to solve the conventional problems (Patent Documents 2 to 7). However, a heat-dissipating polyurethane resin composition that can satisfy all of the performance has not been obtained, and in particular, a polyurethane resin composition that can maintain a high volume resistivity and excellent flexibility over a long period of time has not been obtained. The fact is that there is no.
JP 2000-226426 A JP 2002-121529 A JP 2002-134666 A JP 2003-133493 A JP 2003-138130 A JP 2004-300300 A JP 2007-131830 A

  The present invention has been made in view of the above prior art, and an object of the present invention is to use a polyurethane resin composition capable of maintaining a high volume resistivity and excellent flexibility over a long period of time, and using the same. It is to provide a heat dissipating polyurethane sheet.

  The heat dissipating polyurethane resin composition of the present invention is a heat dissipating polyurethane resin composition containing an inorganic filler and a modified castor oil plasticizer in a polyurethane resin obtained by the reaction of polyisocyanate and polybutadiene polyol. The ratio of (cis-1,4 structure / trans-1,4 structure / 1,2-vinyl structure) in the polybutadiene polyol is 5 to 20/10 to 30/50 to 85. And

  Since the heat-radiating polyurethane resin composition of the present invention uses a polyfunctional polyisocyanate, the resulting polyurethane polymer is formed in a network. On the other hand, since the polybutadiene polyol having a high ratio of 1,2-vinyl structure is used as the polyol, the flexibility of the generated polyurethane resin is increased. As a result, even when an inorganic filler is blended, the flexibility of the obtained heat dissipating polyurethane resin composition is increased.

  The heat dissipating polyurethane sheet of the present invention can be obtained by molding the heat dissipating polyurethane resin composition.

  Since the heat-dissipating polyurethane resin composition and heat-dissipating polyurethane sheet of the present invention can maintain a high volume resistivity over a long period of time, they affect the functions of electronic components constituting the circuit even when used for a long period of time. There is nothing. In addition, since excellent flexibility can be maintained over a long period of time, a large amount of heat generated by being in close contact with the electronic component can be released to the outside.

  The polyurethane resin component of the present invention is obtained by reacting a polyisocyanate with a polybutadiene polyol having a specific structure. Examples of polyisocyanates that can be used here include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and araliphatic polyisocyanates.

  Aliphatic polyisocyanates include tetramethylene diisocyanate, dodecamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1 , 5-diisocyanate, 3-methylpentane-1,5-diisocyanate and the like.

  Examples of the alicyclic polyisocyanate include isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, and the like. Can be mentioned.

  Aromatic polyisocyanates include tolylene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate (MDI), 4,4′-dibenzyl diisocyanate, 1,5 -A naphthylene diisocyanate, a xylylene diisocyanate, a 1, 3- phenylene diisocyanate, a 1, 4- phenylene diisocyanate etc. can be mentioned.

  Examples of the araliphatic polyisocyanate include dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, α, α, α, α-tetramethylxylylene diisocyanate, and the like.

  Moreover, modified bodies, such as a dimer and a trimer of these organic polyisocyanates, an isocyanurate body, a burette body, and an adduct body, can be mentioned. In addition, these can also be used individually or in combination of 2 or more types.

  Of these, hexamethylene diisocyanate-modified isocyanurate, hexamethylene diisocyanate-modified burette, and hexamethylene diisocyanate-modified adduct are more preferable from the viewpoint that discoloration hardly occurs.

  In the present invention, a urethane prepolymer obtained by reacting the polyisocyanate with a polybutadiene polyol having a specific structure under an excess of isocyanate groups may be used as the polyisocyanate.

  The polyol used in the heat-radiating polyurethane resin composition of the present invention is a polybutadiene polyol, and the ratio of (cis-1,4 structure / trans-1,4 structure / 1,2-vinyl structure) in the polybutadiene skeleton portion. Is a polybutadiene polyol in the range of 5-20 / 10-30 / 50-85. Moreover, as a polyol, you may use what is obtained by making the above-mentioned polyisocyanate and the polybutadiene polyol which has the said specific structure react on hydroxyl-excess conditions. Thus, by making many 1, 2- vinyl structures exist, the polyurethane molecule obtained expresses the property like a synthetic rubber, and the flexibility of a polyurethane resin component will be improved.

  Moreover, it is preferable that the average functional group number of the hydroxyl group of polybutadiene polyol is in the range of 1.5 to 2.1. This is because if the average number of functional groups of the hydroxyl group is smaller than this range, the resulting resin has low heat resistance, and if it is larger than this range, the resin becomes hard and the flexibility may be poor.

  Further, the polybutadiene polyol used in the composition of the present invention preferably has a bromine number of 0.1 to 200 g / 100 g. If the bromine number is smaller than the above range, the resulting resin has low heat resistance, and if it is larger than this range, the hardness may increase excessively over time at high temperatures.

  In the heat-radiating polyurethane resin composition of the present invention, the ratio of polyisocyanate to polybutadiene polyol is such that the molar ratio (NCO / OH) between the isocyanate group of polyisocyanate and the hydroxyl group of polybutadiene polyol is 0.3 to 1. It is preferable to be within the range of 1. This is because if the molar ratio of the isocyanate group to the hydroxyl group is smaller than this range, the resulting resin has low heat resistance, and if it is larger than this range, the resin becomes hard and the flexibility may be poor.

  As the inorganic filler used in the heat-radiating polyurethane resin composition of the present invention, it is preferable to use a material having a low electrical conductivity. Specifically, after the inorganic filler and water are mixed at a weight ratio of 8/80 (inorganic filler / water), the electrical conductivity of the supernatant after leaving at 80 ° C. for 13 hours is 40 μS / cm or less. It will be. Examples of such inorganic fillers include alumina, aluminum hydroxide, aluminum nitride, boron nitride, magnesium hydroxide and the like.

  Examples of the modified castor oil plasticizer used in the heat-radiating polyurethane resin composition of the present invention include methyl acetyl ricinoleate, butyl acetyl ricinolate, acetylated ricinoleic acid triglyceride, acetylated polyricinoleic acid triglyceride and the like. . If the modified castor oil is blended as a plasticizer, the viscosity when blended with polyisocyanate, polybutadiene polyol, and inorganic filler can be reduced, and the production of the heat-dissipating polyurethane resin composition of the present invention is facilitated. .

  In the heat-dissipating polyurethane resin composition of the present invention, the blending ratio of the polyurethane resin obtained by the reaction of the polyisocyanate and the polybutadiene polyol, the inorganic filler, and the modified castor oil plasticizer is 1 to 69% by weight. It is preferably in the range of / 30 to 95% by weight / 1 to 30% by weight. If the blending ratio is out of the above range, the flexibility of the heat-dissipating polyurethane resin composition may decrease, the thermal conductivity may decrease, or the viscosity at the time of manufacture may increase, which may cause undesirable situations. is there.

  Various additives such as an antioxidant and a dispersant can be added to the heat-radiating polyurethane resin composition of the present invention as required. For example, as an antioxidant, phenol-containing antioxidants such as dibutylhydroxytoluene (BHT), tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4-hydroxyphenyl) propionate] methane, Phosphorus-containing antioxidants such as phenyl diisodecyl phosphite, sulfur-containing antioxidants such as dilauryl-3,3′-thiodipropionic acid ester, 2,4-bis (n-octylthio) -6- (4-hydroxy- An antioxidant containing phenol and sulfur in one molecule such as 3 ′, 5′-di-t-butylanilino) -1,3,5-triazine can be mentioned. When using an antioxidant, when the heat-dissipating polyurethane resin composition is 100% by weight, it is preferably added in the range of 0.01 to 5% by weight. Moreover, as a dispersing agent, the phosphoric ester type thing shown to following Chemical formula 1 can be used. When using a phosphoric ester-based dispersant, it is preferable to add in a range of 0.01 to 2% by weight when the heat-dissipating polyurethane resin composition is 100% by weight.

  In preparing the heat-dissipating polyurethane resin composition of the present invention, a catalyst may be added to accelerate the curing of the polyurethane resin. As the catalyst, a metal catalyst or an amine-based catalyst usually used for producing a polyurethane resin can be used. Metal catalysts include tin catalysts such as dibutyltin dilaurate, dioctyltin dilaurate and dibutyltin dioctate, lead catalysts such as lead octylate, lead octenoate and lead naphthenate, bismuth catalysts such as bismuth octylate and bismuth neodecanoate, etc. Can be mentioned. Examples of the amine catalyst include diethylenetriamine.

The heat-radiating polyurethane resin composition of the present invention preferably has a hardness of 80 or less according to type A after curing. Further, it is preferable that the volume resistivity value immediately after being left for 100 hours at 121 ° C. under a relative humidity of 100% is 10 ⁹ Ω · cm or more. Furthermore, the thermal conductivity after curing is preferably in the range of 1 to 2.5 W / m · K.

  The heat dissipating polyurethane sheet of the present invention is obtained by molding using a heat dissipating polyurethane resin composition. It is preferable that this sheet does not break even if it is bent 180 °. Moreover, it is preferable that the hardness by Type A after leaving at 150 degreeC for 60 hours is 90 or less.

  Hereinafter, based on an Example and a comparative example, the heat dissipation polyurethane resin composition and heat dissipation polyurethane sheet of this invention are demonstrated in detail. In the present specification, “parts” and “%” represent “parts by weight” and “% by weight”, respectively, unless otherwise specified.

  Table 1 shows the ratio of (cis-1,4 structure / trans-1,4 structure / 1,2-vinyl structure) and bromine number (g / 100 g) for the polyols used in the examples and comparative examples of the present invention. ), Hydroxyl value (OHV), and average number of functional groups of the hydroxyl group.

  Table 2 shows the results of examining the electrical conductivities of various aluminas and aluminum hydroxides having various average particle diameters used as inorganic fillers in the examples and comparative examples of the present invention. The electrical conductivity was examined by measuring the electrical conductivity of the supernatant after mixing at a weight ratio of inorganic filler / water = 8/80 and leaving it at 80 ° C. for 13 hours.

(Examples 1-7)
The heat dissipation polyurethane resin composition of Examples 1-7 was prepared by the formulation shown in Table 3. During the preparation, components excluding the polyisocyanate component among the components shown in Table 3 were mixed, and the isocyanate component was added to this mixture to obtain a heat-dissipating polyurethane resin composition of each example.

  As a method for preparing the heat-dissipating polyurethane resin composition, a polyurethane prepolymer-containing material is prepared in advance by mixing the total amount of polyisocyanate, a part of the polybutadiene polyol, and a part of the modified castor oil plasticizer. A mixture of the remaining amount of polybutadiene polyol, the remaining amount of modified castor oil plasticizer, and the remaining other components is prepared in advance, and the polyurethane prepolymer-containing material and the mixture are mixed together. Also good. Thus, according to the method of preparing the polyurethane prepolymer-containing material in advance, there is an advantage that the curing rate is increased and the production efficiency is improved as compared with the method of adding the polyisocyanate component later.

Next, a test piece of a heat-dissipating polyurethane sheet was prepared using the heat-dissipating polyurethane resin composition. First, 278 g of the heat-dissipating polyurethane resin composition was filled in a 110 × 110 × 10 mm (121 cm ³ ) mold. Next, the mold was covered, pressed at a pressure of 10 kgf / cm ² , cured at 23 ° C. for 48 hours, and then removed from the mold to obtain a heat-dissipating polyurethane test piece.

(Comparative Examples 1-7)
By the formulation shown in Table 4, polyurethane resin compositions of Comparative Examples 1-7 were obtained in the same manner as in Examples 1-7. Moreover, the test piece of heat-radiating polyurethane was produced like these Examples 1-7 using these polyurethane resin compositions.

<Performance test>
For the test pieces of Examples 1 to 7 and Comparative Examples 1 to 7 obtained above, the viscosity at the initial stage of mixing at the time of preparing the composition, the hardness of the test piece after standing at 150 ° C. for 60 hours (type A) Evaluation of the volume resistivity, thermal conductivity, and flame retardancy at the initial stage and after standing for 100 hours under a relative humidity of 100% at 121 ° C. was performed. In addition to the above, a 3 mm thick sheet was prepared in the same manner as described above, and a bending fracture test was performed on the 3 mm thick sheet. Each test result was combined with Table 3 and Table 4, and was shown. Each test method is as follows.

(Mixed viscosity)
The viscosity at the time of preparation of the heat dissipating polyurethane resin composition was measured at 25 ° C. using a BH viscometer.

(Hardness (Type A))
Hardness (type A) was measured according to JIS K6253.

(Thermal conductivity)
The thermal conductivity was measured according to JIS R2618 using a thermal conductivity meter (manufactured by Kyoto Electronics Industry Co., Ltd., QTM-D3).

(Volume resistivity)
For the volume resistivity, TR8601 manufactured by ADVANTEST was used, and the value after 5 minutes from the start of measurement was taken as the volume resistivity.

(Flame retardance)
The flame retardancy was measured according to UL standard UL94 (flame retardance of plastic materials).

(3mm thick sheet bending fracture test)
Whether a sheet having a width of 25 mm, a length of 100 mm, and a thickness of 3 mm is produced, bent 180 ° at 23 ° C. at the center in the length direction (50 mm length), and whether or not a crack occurs after 5 seconds. I investigated. The case where no crack occurred was represented as “◯”, and the case where crack occurred was represented as “x”.

(Test results)
The heat-radiating polyurethane resin compositions of Examples 1 to 7 had lower initial viscosity compared to the compositions of Comparative Examples 1 to 7. This is considered to have a great effect by adding the modified castor oil plasticizer.

  It can be seen that the hardness at the initial stage and after standing at 150 ° C. for 60 hours is lower in Examples 1 to 7 than in Comparative Examples 1 to 7 and rich in flexibility.

  Also about the bending fracture test of a 3 mm-thick sheet, Examples 1-7 are lower than Comparative Examples 1-7, and it turns out that it is rich in a softness | flexibility.

  Regarding the volume specific resistance value, the heat-dissipating polyurethane resin compositions of Examples 1 to 7 were at a practical level both at the initial stage and after being allowed to stand at 121 ° C. and 100% relative humidity for 100 hours. On the other hand, the polyurethane resin compositions of Comparative Examples 1 to 7 all exhibited low volume resistivity values.

  About heat conductivity, any heat dissipation polyurethane resin composition of Examples 1-7 and Comparative Examples 1-7 was high. In particular, the thermal conductivity of Example 7 having a large blending ratio of alumina was high.

  About the flame retardance, any heat-radiating polyurethane resin composition of Examples 1-7 and Comparative Examples 1-7 was favorable.

  Since the heat-dissipating polyurethane resin composition of the present invention is a heat-dissipating polyurethane sheet, it can maintain a high volume resistivity and excellent flexibility over a long period of time, so that it can be used in the fields of electrical products and electronic parts. Is possible.

Claims (10)

A heat-dissipating polyurethane resin composition containing an inorganic filler and a modified castor oil plasticizer in a polyurethane resin obtained by a reaction between polyisocyanate and polybutadiene polyol,
The heat-dissipating polyurethane resin composition in which the ratio of (cis-1,4 structure / trans-1,4 structure / 1,2-vinyl structure) in the polybutadiene polyol is 5 to 20/10 to 30/50 to 85 .   The heat-dissipating polyurethane resin composition according to claim 1, wherein the polyisocyanate is selected from a hexamethylene diisocyanate-modified isocyanurate body, a hexamethylene diisocyanate-modified burette body, and a hexamethylene diisocyanate-modified adduct body.   The heat-dissipating polyurethane resin composition according to claim 1 or 2, wherein the polybutadiene polyol has an average number of functional groups of hydroxyl groups in the range of 1.5 to 2.1.   The heat-dissipating polyurethane resin composition according to any one of claims 1 to 3, wherein the polybutadiene polyol has a bromine value in a range of 0.1 to 200 g / 100 g.   The heat-radiating polyurethane resin composition according to any one of claims 1 to 4, wherein the molar ratio (NCO / OH) of the isocyanate group of the polyisocyanate to the hydroxyl group of the polybutadiene polyol is in the range of 0.3 to 1.1. .   6. The inorganic filler is mixed at a weight ratio of the inorganic filler / water = 8/80 and left to stand at 80 ° C. for 13 hours, and the supernatant has an electrical conductivity of 40 μS / cm or less. The heat-radiating polyurethane resin composition according to any one of the above.   The blending ratio of the polyurethane resin, the inorganic filler, and the modified castor oil plasticizer is in the range of 1 to 69 wt% / 30 to 95 wt% / 1 to 30 wt%. A heat-dissipating polyurethane resin composition according to claim 1.   The heat dissipating polyurethane resin according to any one of claims 1 to 7, further comprising an antioxidant in a range of 0.01 to 5% by weight when the heat dissipating polyurethane resin composition is 100% by weight. Composition.   The heat dissipation according to any one of claims 1 to 8, further comprising a phosphoric ester dispersant in a range of 0.01 to 2% by weight when the heat dissipation polyurethane resin composition is 100% by weight. -Based polyurethane resin composition.   A heat dissipating polyurethane sheet obtained by molding the heat dissipating polyurethane resin composition according to claim 1.