Organopolysiloxane having alkenyl group at both terminal ends of molecular chain, thermally conductive organopolysiloxane composition containing same, thermally conductive member and heat dissipation structure, and other compositions

Abstract

[Problem] To provide an organopolysiloxane which can suppress the viscosity of a composition, has excellent extrusion processability when applied from a cartridge, and gives a uniform cross-linking reaction product by being optionally cured even when used as a matrix polymer of a thermally conductive organopolysiloxane composition having high thermal conductivity, and is unlikely to decrease in density and can maintain planned heat dissipation properties by suppressing the generation of voids and bubbles even when used at a high temperature for a long time, and to provide a composition containing the organopolysiloxane, particularly a thermally conductive composition or the like. [Solution] An organopolysiloxane which has an alkenyl group at both terminal ends of the molecular chain and for which Mw / Mn is 1.20 or less, a production method therefor which is characterized by the living polymerization method and polymer end-capping, a composition containing the organopolysiloxane, particularly a thermally conductive organopolysiloxane composition, a thermally conductive member composed of the same, and a heat dissipation structure using the same.

Description

Organopolysiloxane having alkenyl groups at both molecular chain terminals, thermally conductive organopolysiloxane composition containing same, thermally conductive member and heat dissipation structure, and other compositions

[0001] The present invention relates to an organopolysiloxane having alkenyl groups at both ends of the molecular chain, which has a sharp molecular weight distribution and a relatively low molecular weight, and therefore, when used as a matrix polymer for a thermally conductive organopolysiloxane, exhibits excellent dischargeability from a cartridge and forms a homogeneous crosslinked structure upon curing. It also relates to a method for producing the organopolysiloxane by a living polymerization method, a thermally conductive organopolysiloxane composition containing the organopolysiloxane, a thermally conductive member comprising the organopolysiloxane, and a heat dissipation structure using the organopolysiloxane. Furthermore, the organopolysiloxane preferably has a reduced content of cyclic siloxanes with similar molecular weights that are difficult to remove by equilibration methods. When used as a raw material for a thermally conductive organopolysiloxane composition, the organopolysiloxane having alkenyl groups at both ends of the molecular chain is resistant to density changes even after prolonged heating, suppresses the generation of voids and bubbles, avoids contact failure, is resistant to mold fouling, and is alkali catalyst-free, resulting in high heat resistance. The present invention also relates to compositions containing the organopolysiloxane having alkenyl groups at both molecular chain terminals, such as sealants, and other uses.

[0002] In recent years, with the increasing density and integration of printed circuit boards and hybrid ICs equipped with electronic components such as transistors, ICs, and memory elements, and the increasing capacity of secondary batteries (cell type), thermally conductive silicone compositions comprising organopolysiloxanes and thermally conductive fillers such as aluminum oxide powder and zinc oxide powder have been widely used to efficiently dissipate heat generated by electronic components, batteries, and other electronic and electrical devices. In particular, thermally conductive silicone compositions filled with large amounts of thermally conductive filler have been proposed to accommodate high heat dissipation rates. Thermally conductive silicone compositions have excellent heat resistance, and even when blended with high concentrations and high volume percentages of thermally conductive filler, the cured product is rubbery, so they have a certain degree of flexibility and stress relaxation properties, and are expected to maintain compliance and adhesion to the heat source in heat dissipation structures, thereby maintaining heat dissipation performance. On the other hand, in recent years, there has been a trend toward higher blending amounts of thermally conductive filler, but generally, the rubber properties derived from polymeric silicone cured products tend to be impaired when a large amount of thermally conductive filler is blended in. If the thermally conductive filler content is too high, the resulting cured product will be too hard, causing gaps to form between the product and the heat dissipation target, impairing conformability and stress relaxation properties, and in fact, in some cases making it impossible to achieve sufficient heat dissipation. In other words, in curable thermally conductive silicone compositions, controlling the hardness of the thermoelectrically conductive cured product is an extremely important issue in terms of achieving heat dissipation.

[0003] In addition, when the thermally conductive filler is highly loaded, the fluidity of the composition itself tends to be impaired, and when attempting to load a cartridge or dispenser, etc., for the purpose of small-volume or pinpoint application, a sufficient extrusion rate cannot be ensured, making loading particularly difficult for small-volume packaging, and workability and application properties after loading can decrease, resulting in reduced work efficiency. In addition, the thermally conductive filler cannot be uniformly dispersed in the silicone composition, which can adversely affect the expected thermal conductivity, curability, workability during commercial production, and the like. For this reason, highly thermally conductive silicone compositions containing a high amount of thermally conductive filler, particularly those having a thermal conductivity of 9.0 W / mK or more, have left room for improvement in terms of their performance and workability for industrial widespread use.

[0004] Meanwhile, a living polymerization method using hexaorganocyclotrisiloxane (D3) as a raw material and a lithium salt, sodium salt, or the like as a catalyst is known as a means of obtaining curable organopolysiloxanes, and curable compositions (including those that cure to a gel) containing such methods are also known (see Patent Documents 1 to 5). However, these documents do not disclose any organopolysiloxanes that have alkenyl groups at both ends of the molecular chain and have a relatively small molecular weight, thereby imparting fluidity and uniform crosslinking reactivity, or their remarkable usefulness as matrix polymers for thermally conductive compositions. In particular, they do not describe or suggest anything about the effect of cyclic siloxanes, which can cause the generation of voids and bubbles when compared to the equilibrium method.

[0005] JP 2019-163413 (Special Registration 6907978) JP 01-272633 JP 02-092933 JP 61-275329 JP 01-098631

[0006] Meanwhile, the present inventors have discovered a new problem with highly thermally conductive organopolysiloxane compositions containing a large amount of thermally conductive filler and optionally exhibiting curing reactivity. Highly thermally conductive compositions use curing-reactive organopolysiloxanes as matrix polymers to support the thermally conductive filler. However, when attempting to use low-viscosity organopolysiloxanes to ensure the fluidity of the composition itself, the ease of filling cartridges and dispensers, and the ease of extrusion during application, these low-degree-of-polymerization organopolysiloxanes are primarily obtained by equilibrium polymerization, and therefore have broad molecular weight distributions and lack uniform molecular lengths, making it difficult to form uniform crosslinked products, resulting in insufficient thermal conductivity and rubber physical properties. This has resulted in performance issues with thermally conductive components using these matrix polymers.

[0007] In addition, low-polymerization organopolysiloxanes obtained by equilibrium polymerization methods produce volatile cyclic siloxanes as by-products during their production, which can cause contact problems in electronic components when used in electronic materials. Even if low-polymerization silicones (e.g., tri- to nona-mers) are removed in advance by stripping or other methods, the inherent alkaline catalysts in equilibrium polymerization methods can cause volatile cyclic siloxanes to be by-produced over time, which can cause contact problems and mold contamination. Furthermore, low-polymerization organopolysiloxanes obtained by equilibrium polymerization methods inevitably tend to overlap in molecular weight range with cyclic siloxanes of 20-mer or less (specifically, decamers to 20-mers), making it difficult to adequately remove cyclic siloxanes with similar molecular weights. For this reason, regardless of whether or not a curing reaction occurs, when an existing organopolysiloxane with a low degree of polymerization is used as the matrix polymer of a high thermal conductivity organopolysiloxane composition, these cyclic siloxanes will volatilize over time from the resulting thermal conductive member after prolonged use (aging) at high temperatures, resulting in the generation of voids and bubbles, which can cause a decrease in density and lead to deterioration in the performance and durability of the thermal conductive member, and as a result, the originally intended heat dissipation characteristics may not be fully realized.

[0008] The present invention has been made to solve the above-mentioned problems, and its object is to provide an organopolysiloxane having alkenyl groups at both ends of the molecular chain, which can suppress the viscosity of the final composition even when used as a matrix polymer for a thermally conductive organopolysiloxane composition that contains a thermally conductive filler at a very high volume percentage and has high thermal conductivity, and which has excellent fillability into cartridges and extrusion workability during application, which can be optionally cured to give a uniform crosslinked reaction product, which is unlikely to cause a decrease in density even when used at high temperatures for long periods of time, which can suppress the generation of voids and bubbles and maintain the expected heat dissipation properties, which avoids contact failure, is resistant to mold contamination, and is alkali catalyst-free and therefore highly heat-resistant; a thermally conductive organopolysiloxane composition containing the organopolysiloxane; a thermally conductive member made of the same; and a heat dissipation structure using the same.

[0009] As a result of extensive investigation, the present inventors have discovered that the above-mentioned problems can be solved by an organopolysiloxane having alkenyl groups at both molecular chain terminals and having a ratio of weight-average molecular weight to number-average molecular weight (Mw / Mn) of 1.20 or less. This organopolysiloxane preferably has a number-average molecular weight of 10,000 or less and a content of cyclic dimethylsiloxanes having a monomer unit of 20 or less less than 0.1% by mass. Furthermore, this organopolysiloxane can be obtained by a production method comprising: step (I) of living polymerization of D3 as a raw material in the presence of a lithium-based catalyst; and step (II) of terminal-capping the polymer obtained in step (I) with 1,3-dialkenyl-1,1,3,3-tetraorganodisilazane.

[0010] Similarly, the above-mentioned problems are solved by a thermally conductive organopolysiloxane composition containing 100 parts by mass of an organopolysiloxane having the above-mentioned sharp molecular weight distribution, and preferably having a relatively low molecular weight and a reduced content of cyclic siloxanes, and a thermally conductive filler in an amount ranging from 60 to 90% by volume, based on the total solid content of the composition; a thermally conductive member comprising the same; and a heat dissipation structure using the same.

[0011] The use of an organopolysiloxane having alkenyl groups at both molecular chain terminals according to the present invention as a matrix polymer makes it possible to reduce the viscosity of a highly thermally conductive composition, even one containing a high content of thermally conductive filler, and to provide excellent fillability into cartridges and extrusion workability during application. The composition can be optionally cured to give a uniform crosslinked reaction product, and is resistant to density loss even under high temperature and long-term use. The composition is also resistant to voids and bubbles, maintaining the intended heat dissipation performance. It also avoids contact failure and mold contamination, and is alkali catalyst-free, making it highly heat-resistant. It is also possible to provide a thermally conductive organopolysiloxane composition, a thermally conductive member comprising the same, and a heat dissipation structure using the same. The present invention also makes it possible to provide a composition suitable for one or more applications selected from a sealant composition, an electrically conductive composition, and a heat insulating composition, which contains the organopolysiloxane having alkenyl groups at both molecular chain terminals.

[0012] [(A) Organopolysiloxane Having Alkenyl Groups at Both Molecular Chain Terminals] Component (A) is an organopolysiloxane that has alkenyl groups at both molecular chain terminals and a sharp molecular weight distribution, with a ratio of weight-average molecular weight to number-average molecular weight (Mw / Mn) of 1.20 or less, preferably in the range of 1.05 to 1.18, and more preferably in the range of 1.07 to 1.17. This organopolysiloxane is a characteristic component of the present invention. Because the bonding positions and molecular lengths of the alkenyl groups, which are reactive functional groups, are uniform, when used as a matrix polymer for a thermally conductive composition, it has the advantage of being resistant to density loss and the resulting deterioration in heat dissipation properties and physical strength, even when used at high temperatures for long periods of time.

[0013] From the perspective of a matrix polymer for a thermally conductive composition having a high content of thermally conductive filler, it is desirable that component (A) not have a high degree of polymerization or high viscosity, in order to suppress the overall viscosity of the composition and improve its fillability into cartridges and extrusion workability during application, and specifically, its number average molecular weight is 10,000 or less, preferably 500 to 10,000, more preferably 1,000 to 7,500, and particularly preferably 2,000 to 5,000. If the number average molecular weight of component (A) is below the lower limit, the mechanical strength of the organopolysiloxane cured product tends to decrease, while if it exceeds the upper limit, the viscosity of the composition tends to increase, particularly when the content of the resulting thermally conductive filler is high, which may prevent the desired technical effect as a low-viscosity matrix polymer from being fully achieved and may decrease handling workability and coatability to fine areas.

[0014] Furthermore, from the viewpoint of preventing contact failure and mold contamination with electronic components, and of preventing density loss when a thermally conductive composition made from component (A) and a thermally conductive member made therefrom are used at high temperatures for long periods of time, suppressing the generation of voids and bubbles and maintaining the intended heat dissipation performance, it is preferable that component (A) contain less than 0.1 mass% of cyclic dimethylsiloxanes having a dimer or less, and particularly preferably less than 0.05 mass% of cyclic dimethylsiloxanes having a dimer to pentamer. As described below, these cyclic siloxanes are easily produced as by-products in equilibrium polymerization methods, and didecameric to didecameric cyclic dimethylsiloxanes, particularly didecameric to pentamer cyclic dimethylsiloxanes, having molecular weights close to that of component (A), are difficult to remove from component (A) afterward by stripping or other methods aimed at removing volatile components. Therefore, component (A) is preferably obtained by a living polymerization method using D3 as the starting material. Furthermore, component (A) preferably contains less than 0.1% by mass (i.e., less than 1,000 ppm) of each cyclic dimethylsiloxane having a degree of polymerization of 20 or less, and particularly preferably contains less than 0.01% by mass (i.e., less than 100 ppm) of each cyclic dimethylsiloxane having a degree of polymerization of 10 to 15, and most preferably contains less than 0.1% by mass (i.e., less than 1,000 ppm) of all cyclic dimethylsiloxanes having a degree of polymerization of 20 or less. Organopolysiloxanes having such a sharp molecular weight distribution and a reduced content of cyclic dimethylsiloxanes having a degree of polymerization of 20 or less can be obtained by the living polymerization method described below.

[0015] Component (A) may be composed of one or more organopolysiloxanes having alkenyl groups at both molecular chain terminals, so long as they satisfy the above-mentioned requirements regarding molecular weight distribution, etc. The molecular structure of such alkenyl-containing organopolysiloxanes is preferably linear, and from the standpoints of molecular length and uniformity of the curing (crosslinking) reaction, linear organopolysiloxanes having alkenyl groups only at both molecular chain terminals are preferred.

[0016] Examples of alkenyl groups in the molecule of component (A) include vinyl, allyl, butenyl, and hexenyl groups. Examples of organic groups other than alkenyl groups in component (A) include monovalent hydrocarbon groups other than alkenyl groups, such as alkyl groups such as methyl, aryl groups such as phenyl, and halogenated alkyl groups such as 3,3,3-trifluoropropyl, with methyl and phenyl being industrially preferred.

[0017] Particularly preferred is a linear alkenyl-containing organopolysiloxane for component (A), such as a dimethylpolysiloxane endblocked at both molecular chain terminals with dimethylvinylsiloxy groups, or a dimethylsiloxane-methylphenylsiloxane copolymer endblocked at both molecular chain terminals with dimethylvinylsiloxy groups. Particularly preferred is a linear dimethylpolysiloxane having alkenyl groups having 2 to 8 carbon atoms only at both molecular chain terminals, which satisfies the requirements for molecular weight distribution, cyclic siloxane content, and molecular weight range described above, and industrially preferred is a dimethylpolysiloxane endblocked at both molecular chain terminals with dimethylvinylsiloxy groups.

[0018] [Applicability: Including one or more applications selected from thermally conductive compositions, sealant compositions, electrically conductive compositions, and heat insulating compositions] As described above, component (A) is suitable as a matrix polymer for thermally conductive compositions, but it can also be used as a raw material for other curable or non-curable compositions. For example, curable or non-curable compositions containing component (A) are included within the scope of the present invention. In particular, compositions applicable to one or more applications selected from thermally conductive compositions, sealant compositions, electrically conductive compositions, and heat insulating compositions are included within the scope of the present invention. Furthermore, the application range of the composition is not limited to electronic materials, electronic components, etc., and it can be used for any application.

[0019] [Production Method Using Living Polymerization] The organopolysiloxane (A) having alkenyl groups at both molecular chain terminals according to the present invention is preferably synthesized by living polymerization rather than equilibrium polymerization in order to satisfy the requirements regarding its molecular weight distribution, cyclic siloxane content, and molecular weight range. When component (A) is synthesized using equilibrium polymerization, the molecular weight distribution becomes broad, preventing uniform crosslinking reactivity. Thermally conductive compositions and thermally conductive members using such organopolysiloxanes as matrix polymers are prone to a decrease in density when used for long periods at high temperatures (120°C or 150°C), and may deteriorate due to the suppression of void and bubble generation, resulting in the inability to maintain the intended heat dissipation performance. Furthermore, using equilibrium polymerization makes it difficult to achieve an alkali catalyst-free composition, and it may be particularly difficult to achieve high purity, with a content of cyclic dimethylsiloxanes of 20 or less units being less than 0.1% by mass. This is because low-polymerized cyclic dimethylsiloxanes similar to component (A) (e.g., decamers to 20-mers) may not be sufficiently removed by ordinary stripping / vacuum distillation methods aimed at volatile content reduction (CV). As a result, the cyclic dimethylsiloxane content may not be sufficiently reduced, and a sharp molecular weight distribution with an Mw / Mn ratio of 1.2 or less may not be achieved.

[0020] The living polymerization method of the present invention preferably comprises step (I) of livingly polymerizing hexaorganocyclotrisiloxane (D3) in the presence of a lithium catalyst using a starting material having at least one type selected from protons (H) and Li at both ends, and step (II) of capping the molecular chain ends of the resulting polymer with an organosilicon compound capable of introducing alkenyl groups, i.e., one or more types selected from known capping agents such as 1,3-dialkenyl-1,1,3,3-tetraorganodisilazane and alkenyl-group-containing organochlorosilane. The reaction is preferably carried out in one or more polar solvents, and the use of a mixed solvent containing a polar solvent for the purpose of accelerating the reaction is particularly preferred.

[0021] Specifically, the component (A) in the present invention is prepared by using a starting material having at least one selected from protons (H) and Li at both ends, and Ａ ２ SiO) ３ (In the above formula, R Ａ each independently represents an alkyl group, an aryl group, or a group in which some of the carbon-bonded hydrogen atoms of these groups have been substituted with halogen atoms), in the presence of a lithium catalyst; and Ｂ R Ａ ２ SiNSiR Ａ ２ R Ｂ (In the above formula, R Ａ is the same group as above, and R Ｂ alkenyl group); and R Ｂ R Ａ ２ SiCl (in the above formula, R Ａ , R Ｂ and (wherein are the same groups as defined above), and (II) blocking with at least one 1,3-dialkenyl-1,1,3,3-tetraorganodisilazane represented by the formula:

[0022] The starting material for this reaction is a material that serves as the initiation point for living polymerization, and specifically, a starting material having at least one type selected from protons (H) and Li at its molecular end. Here, the protons (H) may be H derived from water or OH terminals, and Li may be in the form of a metal salt. Specific examples of such starting materials include water, a siloxane oligomer having hydroxyl groups (=silanol groups) at both molecular chain ends, and LiOH. When synthesizing a polymer having terminal alkenyl groups with high purity, it is preferable to use the above-mentioned R as part of the starting material. Ｂ R Ａ ２A siloxane oligomer or vinyldimethylsilanol having an Si terminal (e.g., a vinyldimethylsilyl group) and an OH terminal may be used in combination. In addition, the amount of starting materials such as water may be appropriately adjusted to improve the polymerization accuracy.

[0023] (R Ａ ２ SiO) ３ Hexaorganocyclotrisiloxane (D3) represented by the formula: Ａ are each independently an alkyl group, an aryl group, or a group in which some of the carbon-bonded hydrogen atoms of these groups have been substituted with halogen atoms, and examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, and a phenyl group. Ａ is a methyl group or a phenyl group. When subjecting the above hexaorganocyclotrisiloxane to living polymerization, it is preferable to carry out a dehydration treatment using an azeotropic dehydration method using an organic solvent such as toluene, or a dehydration treatment using a zeolite-based desiccant such as a molecular sieve or a solid desiccant such as calcium hydride.

[0024] The lithium-based catalyst is a catalyst for promoting living polymerization in the production method of the present invention, and metallic lithium, lithium hydride, buterurinium, lithium hydroxide, or a mixture of two or more of these can be used, with lithium hydroxide being preferred. Note that the use of catalysts other than these lithium-based catalysts, such as other alkali metal compounds, can result in a reduced yield of the desired general formula organopolysiloxane. The lithium-based catalyst may be introduced into the system in the form of an aqueous solution, for example, a 0.5 to 5% by weight aqueous solution, in a range of 0.005 to 0.050% by weight based on the raw material D3.

[0025] The reaction solvent (common to steps (I) and (II)) used in carrying out the living polymerization reaction of the present invention is not particularly limited. However, from the viewpoint of smooth progress of the living polymerization reaction, a mixed solvent containing (S1) one or more polar solvents selected from acetonitrile, methyl ethyl ketone, and methyl isobutyl ketone, and (S2) one or more polar solvents selected from dimethyl sulfoxide and dimethylformamide is preferred. Here, the polar solvent (S2) is a polar solvent used for the purpose of promoting the reaction, and the mass ratio of (S1):(S2) may be appropriately selected from the range of 9:1 to 3:1 depending on the reaction conditions and the scale of the reaction. However, this does not preclude the use of other reaction solvents known in living polymerization, such as tetrahydrofuran.

[0026] The living polymerization reaction in step (I) is a ring-opening polymerization reaction of D3, and can be carried out by stirring the raw material D3 together with a lithium-based catalyst under heating conditions of 10 to 40°C, preferably room temperature to 35°C, depending on the scale of the reaction. The reaction time is not particularly limited, but is generally carried out within a range of 30 minutes to 10 hours, preferably 2 to 8 hours, while monitoring the conversion rate of D3 by GLC (gas chromatography) or the like.

[0027] Step (II) is a step of capping the molecular chain terminals of the organopolysiloxane polymer obtained in step (I) with 1,3-dialkenyl-1,1,3,3-tetraorganodisilazane, and alkenyl groups derived from the disilazane are introduced into the molecular chain terminals of the organopolysiloxane. From the standpoint of achieving a purity and a molecular weight distribution of the final product that approaches a single peak, it is preferable to distill off the low-boiling point components under reduced pressure after step (I) and prior to carrying out step (II), and a filtration operation may also be carried out optionally.

[0028] In step (II), the molecular chain terminal of the organopolysiloxane polymer obtained in step (I) is substituted with R Ｂ R Ａ ２ SiNSiR Ａ ２ R Ｂ (In the above formula, R Ａ is the same group as above, and RＢ is an alkenyl group); and R Ｂ R Ａ ２ SiCl (in the above formula, R Ａ , R Ｂ and R are the same groups as defined above. Ａ is the same group as above, and a methyl group is preferable. Ｂ is an alkenyl group, and from the viewpoint of the alkenyl group in the final component (A), it is preferably an alkenyl group having 2 to 8 carbon atoms, particularly a vinyl group or a hexenyl group. Specific examples of capping agents include tetramethyldivinyldisilazane and vinyldimethylchlorosilane, and are preferred.

[0029] The reaction conditions for blocking are preferably as follows: an acidic catalyst such as trifluoroacetic acid (including neutralized salts) is added to the organopolysiloxane polymer obtained in step (I) or a reaction solution containing it, and the molecular chain end-blocking reaction is carried out while stirring the reaction solution at 40 to 140°C. The reaction time is generally 1 to 8 hours. This reaction may be carried out without a solvent. If the reaction temperature is too low, molecular end-blocking may not occur sufficiently; if the reaction temperature is too high, the capping agent used for end-blocking, such as a silazanes, may volatilize, and molecular end-blocking may not proceed sufficiently. Furthermore, if the reaction time is too short, molecular end-blocking may not proceed sufficiently, and the desired organopolysiloxane having alkenyl groups at both molecular chain terminals may not be obtained with high purity.

[0030] After completion of the reaction in step (II), unreacted components, solid components, reaction residues, and the like that were not involved in the polymerization reaction among the original raw material components can be removed by known methods such as filtration and / or vacuum distillation. Specifically, vacuum distillation is carried out under conditions such as a reduced pressure of 1,000 Pa or less, preferably 500 Pa or less, and more preferably 300 Pa or less, and at a temperature of preferably about 100 to 180°C, and more preferably about 120 to 150°C. Furthermore, from the viewpoint of ensuring the quality of component (A), the filtration step is preferably a sterilizing filtration step.

[0031] [Thermal Conductive Organopolysiloxane Composition] The thermally conductive organopolysiloxane composition of the present invention comprises a matrix polymer, (A) the organopolysiloxane having alkenyl groups at both molecular chain terminals, and (B) a thermally conductive filler. Preferably, the amount of component (B) is in the range of 60 to 90 volume % based on the total solids content of the composition per 100 parts by mass of component (A). Such a thermally conductive organopolysiloxane composition or its curing reaction product preferably has a thermal conductivity of 9.0 W / mK or higher. It may be optionally curable and may form a thickener, gel, or cured product, or may be a non-curable composition such as a grease. When the composition is curable, since the curable reactive group of component (A) is an alkenyl group, it is preferable that the composition exhibits one or more curing reactivities selected from hydrosilylation and radical polymerization.

[0032] Furthermore, the thermally conductive organopolysiloxane composition of the present invention may contain (C) an organohydrogenpolysiloxane, (D) a catalytic amount of a hydrosilylation reaction catalyst, (E) an organosilicon compound that functions as a specific surface treatment agent, (F) at least one selected from fatty acids, fatty acid esters, and fatty acid metal salts, (G) a heat resistance imparting agent, and (H) a component selected from a hydrosilylation reaction inhibitor, an adhesion promoter, an organic solvent, and other additives. Furthermore, the composition of the present invention may be in the form of a one-component composition or a multi-component composition such as a two-component composition. Each component and its addition amount will be described below.

[0033] Component (A) is the matrix polymer of the thermally conductive organopolysiloxane composition of the present invention, and has a sharp molecular weight distribution with uniform bonding positions and molecular lengths of the alkenyl groups, which are reactive functional groups, and is also highly pure. Therefore, when used as the matrix polymer of a thermally conductive composition, it has the advantage of being less likely to experience a decrease in density and the resulting deterioration in heat dissipation properties and physical strength, even when used at high temperatures for long periods of time.

[0034] The present composition can be designed as a curable or non-curable composition. Here, the curing reactive group is a functional group that can cure the entire composition (including gelation, the same applies hereinafter) through a crosslinking reaction, and in component (A), is an alkenyl group that has hydrosilylation reactivity and radical polymerization reactivity.

[0035] Because component (A) has alkenyl groups at both molecular chain terminals, it is suitable as a base component for curable thermally conductive organopolysiloxane compositions, such as curable thermally conductive elastomers, thermally conductive gels, curable thermally conductive gap filler materials, etc. When designing a curable composition, it is possible and preferred to include (C) an organohydrogenpolysiloxane and (D) a catalytic amount of a hydrosilylation reaction catalyst as curing agents for the composition, as described below.

[0036] [(B) Thermally Conductive Filler] Component (B) is a thermally conductive filler that imparts thermal conductivity to the present composition and the thermally conductive member obtained by curing the present composition. Component (B) is preferably at least one powder and / or fiber selected from the group consisting of pure metals, alloys, metal oxides, metal hydroxides, metal nitrides, metal carbides, metal silicides, carbon, soft magnetic alloys, and ferrites, and is preferably a metal-based powder, a metal oxide-based powder, a metal nitride-based powder, or a carbon powder. The shape of component (B) is not particularly limited, but examples include spherical, acicular, discoid, rod, and irregular shapes. Preferably, it is spherical or irregular. The average particle size of component (B) is also not particularly limited, but is preferably in the range of 0.01 to 500 μm, more preferably 0.01 to 300 μm.

[0037] Suitable examples of component (B) include silver powder, aluminum powder, aluminum oxide powder, zinc oxide powder, magnesium oxide powder, aluminum nitride powder, boron nitride powder, and graphite. When electrical insulation is required for the composition, metal oxide powders or metal nitride powders are preferred, and aluminum oxide powder, zinc oxide powder, magnesium oxide powder, and aluminum nitride powder are particularly preferred.

[0038] The thermally conductive filler may be, and preferably is, surface-treated in whole or in part with an organosilicon compound, component (E), described below. Furthermore, in addition to these components, the powder and / or fiber may be treated with various surface treatment agents known as coupling agents. Examples of surface treatment agents for treating the powder and / or fiber of component (B) include, in addition to component (E), surfactants, other silane coupling agents, aluminum-based coupling agents, and silicone-based surface treatment agents.

[0039] In order to improve the packing efficiency of component (B), for example, by combining powders with large particle sizes and powders with small particle sizes in a ratio that follows the theoretical closest packing distribution curve, the packing efficiency is improved, thereby enabling lower viscosity and higher thermal conductivity. In the present invention, a mixture of two or more powders with different particle sizes or shapes may be used, selected from (B1) spherical and crushed aluminum oxide powders having an average particle size of 0.01 to 100 μm, (B2) spherical and crushed magnesium oxide powders having an average particle size of 0.01 to 100 μm, and (B3) amorphous aluminum nitride powders having an average particle size of 0.01 to 50 μm, in order to improve the packing efficiency, and this is also preferable.

[0040] [Content of Component (B)] In the present invention, to achieve high thermal conductivity, the content of component (B) is preferably in the range of 60 to 90 vol%, 65 to 90 vol%, 70 to 90 vol%, or 70 to 85 vol% of the total solids content (components that form a cured product upon curing reaction) in the composition. If the content of component (B) is below the lower limit, the high thermal conductivity targeted in the present invention, particularly a high thermal conductivity of 9.0 W / mK or more, may not be achieved. On the other hand, if the content exceeds the upper limit of the above range, even when component (A) is used or component (E) is blended or used for surface treatment of component (B), the viscosity of the resulting composition may be significantly increased, or the initial cured product may become significantly hard, resulting in reduced handling, stress relaxation properties, and adhesion to substrates.

[0041] The amount of component (B) used is more preferably in the range of 600 to 4,500 parts by mass, and particularly preferably in the range of 800 to 4,000 parts by mass, per 100 parts by mass of component (A). When the amount of component (B) used is in the above-mentioned volume percent range and the amount relative to component (A) satisfies the above-mentioned range, the problem of the present invention can be particularly suitably solved.

[0042] [Other Inorganic Fillers] The composition of the present invention may optionally contain inorganic fillers (also referred to as "inorganic fillers") such as fumed silica, wet silica, crushed quartz, titanium oxide, magnesium carbonate, zinc oxide, iron oxide, diatomaceous earth, and carbon black, as well as inorganic fillers obtained by hydrophobizing the surface of such inorganic fillers with component (E) described below and / or other organosilicon compounds (silazanes, etc.). From the standpoint of achieving the technical effects of the present invention, particularly high thermal conductivity, flexibility and stress relaxation properties of the cured product, and adhesion to the substrate, the composition may be substantially free of fillers other than component (B). On the other hand, for the purpose of achieving other functions such as improving mechanical strength (reinforcement) and adjusting viscosity, the above fillers may be used in combination within a range that does not impair the technical effects of the present invention, and this is included in one of the preferred embodiments of the present invention.

[0043] [Surface Treatment of Component (B)] Component (B) according to the present invention is preferably surface-treated with component (E), which will be described later. The surface treatment method using these components is not particularly limited, but examples include direct treatment of the thermally conductive inorganic filler (component (B)), integral blending, and dry concentrate. From the standpoint of improving the overall filling property of the composition and the adhesive strength of the cured product, the most suitable example of a thermal surface treatment method according to the present invention is a premixing of all or part of component (A) with component (E), followed by sequential mixing of component (B) into the mixture, homogenization, and subsequent heating (base heat). In this surface treatment method, the mixture can be heated and stirred at 100 to 200°C under reduced pressure. The temperature conditions and stirring time can be tailored to the sample amount, but are preferably in the range of 120 to 180°C and 0.25 to 10 hours. The surface treatment step of component (B) is optional, but from the viewpoint of improving the fluidity, gap-filling property, and thixotropy of the present composition, it may be a stepwise treatment step including a step in which at least a part of component (B) is surface-treated with component (E1) or (E2), and then component (B) is surface-treated with component (E3).

[0044] The apparatus used for the above mixing is not particularly limited, and examples thereof include a single-screw or twin-screw continuous mixer, a two-roll mill, a Ross mixer, a Hobart mixer, a dental mixer, a planetary mixer, a kneader mixer, and a Henschel mixer.

[0045] [(C) Organohydrogenpolysiloxane] Component (C) is the primary crosslinking agent of the composition of the present invention, and any organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms in the molecule can be used without particular limitation, but from the standpoint of flexibility of the resulting cured product and adhesion retention to substrates, it is preferable that the number (average) of silicon-bonded hydrogen atoms in the organohydrogenpolysiloxane molecule does not exceed 8. In particular, it is preferable to include at least (C1) a linear organohydrogenpolysiloxane having a viscosity at 25°C of 1 to 1,000 mPa s and containing an average of 2 to 4 silicon-bonded hydrogen atoms in the molecule, with at least one of these, on average, located in a side chain on the molecular chain.

[0046] Examples of such component (C1) include a methylhydrogensiloxane-dimethylsiloxane copolymer terminated at both molecular chain terminals with trimethylsiloxy groups, and a methylhydrogensiloxane-dimethylsiloxane copolymer terminated at both molecular chain terminals with dimethylhydrogensiloxy groups. Note that these examples are not limiting, and some of the methyl groups may be substituted with phenyl groups, hydroxyl groups, alkoxy groups, etc.

[0047] The viscosity of component (C1) at 25°C is not particularly limited, but is preferably in the range of 1 to 500 mPa s, and particularly preferably in the range of 1 to 100 mPa s. Furthermore, from the standpoint of preventing contact failure, it is preferable that the content of low-molecular-weight siloxane oligomers (octamethyltetrasiloxane (D4), decamethylpentasiloxane (D5)) be reduced or eliminated.

[0048] [Amount of Organohydrogenpolysiloxane (Crosslinking Agent) in Composition] From the viewpoint of the rubber properties, mechanical strength, and adhesive properties of the resulting organopolysiloxane cured product, the composition of the present invention contains component (C) in an amount such that the number of silicon-bonded hydrogen atoms in component (C) is 0.2 to 5.0 moles, particularly preferably 0.3 to 3.0 moles, or 0.4 to 2.0 moles per mole of alkenyl groups in component (A).

[0049] [(D) Hydrosilylation Catalyst] The hydrosilylation catalyst is a component used to cure the composition. Examples include platinum-based catalysts, rhodium-based catalysts, and palladium-based catalysts. Platinum-based catalysts are preferred because they significantly accelerate the curing of the composition. Examples of platinum-based catalysts include platinum fine powder, chloroplatinic acid, alcohol solutions of chloroplatinic acid, platinum-alkenylsiloxane complexes, platinum-olefin complexes, platinum-carbonyl complexes, and catalysts in which these platinum-based catalysts are dispersed or encapsulated in thermoplastic resins such as silicone resins, polycarbonate resins, and acrylic resins. Platinum-alkenylsiloxane complexes are particularly preferred. Platinum 1,3-divinyl-1,1,3,3-tetramethyldisiloxane complexes are particularly preferred, and the complex is preferably added in the form of an alkenylsiloxane solution. In addition, from the viewpoint of improving handling and workability and the pot life of the composition, a platinum-containing hydrosilylation catalyst in the form of fine particles dispersed or encapsulated in a thermoplastic resin may be used. Note that non-platinum metal catalysts such as iron, ruthenium, and iron / cobalt may also be used as catalysts for promoting the hydrosilylation reaction.

[0050] On the other hand, the hydrosilylation reaction catalyst may be a so-called high-energy ray-activated catalyst or photoactivated catalyst, such as a (methylcyclopentadienyl)trimethylplatinum(IV) complex or a bis(2,4-pentanedionato)platinum(II) complex. By using such a hydrosilylation reaction catalyst, the composition as a whole can be cured even at low temperatures using high-energy ray irradiation as a trigger, and the composition may have excellent storage stability and easy reaction control, resulting in excellent handling and workability. In this case, ultraviolet light is preferred as the high-energy ray from the viewpoint of catalyst activation efficiency, and ultraviolet light with a wavelength in the range of 280 to 380 nm is preferred from the viewpoint of industrial use. The irradiation dose varies depending on the type of high-energy ray-activated catalyst, but in the case of ultraviolet light, the cumulative irradiation dose at a wavelength of 365 nm is 100 mJ / cm. ２ ~100 J / cm ２ It is preferable that the range is within the range of

[0051] The amount of the hydrosilylation catalyst added may be any catalytic amount, and more specifically, an amount that provides a metal atom concentration, by mass, of the entire composition in the range of 0.01 to 500 ppm, 0.01 to 100 ppm, or 0.01 to 50 ppm.

[0052] [Component (E)] Component (E) functions as a surface treatment agent for component (B) and other inorganic fillers and may coexist with these components in the composition. It is particularly preferred that component (A) be surface-treated with at least a portion of component (E), from the viewpoints of uniform dispersion of these components and ease of handling and workability of the resulting composition. Component (E) is one or more components selected from siloxane compounds having an alkoxy group at one end (components (E1) and (E2)) and / or alkoxysilanes having a long-chain alkyl group (component (E3)), and more specifically, is one or more components selected from the following components (E1) to (E3):

[0053] (E1) General formula (1): (In the formula, R 1 are independently unsubstituted or substituted monovalent hydrocarbon groups having no carbon-carbon double bonds, and R ２ are independently a hydrogen atom, an alkyl group, an alkoxyalkyl group, or an acyl group, a is an integer of 5 to 250, and b is an integer of 1 to 3, and has a viscosity at 25°C of 10 to less than 10,000 mPa·s.

[0054] In general formula (1), R 1 are independently unsubstituted or substituted monovalent hydrocarbon groups having no carbon-carbon double bond, examples of which include linear alkyl groups, branched alkyl groups, cyclic alkyl groups, aryl groups, aralkyl groups, and halogenated alkyl groups. 1 is preferably a methyl group or a phenyl group, and from the viewpoint of heat resistance, a methyl group is preferred.

[0055] R ２ are independently a hydrogen atom, an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group.２ is preferably an alkyl group, and particularly preferably a methyl group or an ethyl group.

[0056] In general formula (1), a is an integer ranging from 5 to 250, preferably from 10 to 200. Furthermore, b is an integer ranging from 1 to 3, preferably 2 or 3. Component (E1) according to the present invention is preferably a copolymer in which b is 3, one molecular chain terminal has a trialkoxysiloxy group, and R 1 A suitable example is polydimethylsiloxane in which is a methyl group.

[0057] (E2) General formula (2): R alk R ３ ２ SiO(R ３ ２ SiO) ｃ R ３ ２ Si-R ４ -SiR ３ (3-ｄ) (OR ５ ) ｄ (In the formula, R alk is an alkenyl group, and R ３ are independently unsubstituted or substituted monovalent hydrocarbon groups having no carbon-carbon double bonds, and R ４ is an oxygen atom or a divalent hydrocarbon group, and R ５ are independently a hydrogen atom, an alkyl group, an alkoxyalkyl group, or an acyl group, c is an integer of 1 to 250, and d is an integer of 1 to 3. A siloxane compound having an alkenyl group and a hydrolyzable silyl group at the molecular chain terminal, and having a viscosity at 25°C in the range of 10 to 10,000 mPa·s.

[0058] In general formula (2), R alk is an alkenyl group, and examples thereof include alkenyl groups having 2 to 10 carbon atoms, such as vinyl, allyl, and hexenyl. Because component (E2) has an alkenyl group at one end of the molecular chain, it may be possible to improve the curability and adhesive properties when used in combination with other crosslinking agents, etc.

[0059] In the formula, R ３R are independently unsubstituted or substituted monovalent hydrocarbon groups having no carbon-carbon double bond, and examples thereof include linear alkyl groups, branched alkyl groups, cyclic alkyl groups, alkenyl groups, aryl groups, aralkyl groups, and halogenated alkyl groups. From an industrial viewpoint, R is preferably a methyl group or a phenyl group, and from the viewpoint of heat resistance, R is preferably a methyl group. ４ is an oxygen atom or a divalent hydrocarbon group. ４ Examples of the divalent hydrocarbon group include alkylene groups such as a methylene group; and alkyleneoxyalkylene groups such as an ethyleneoxyethylene group and an ethyleneoxypropylene group. ４ may be, and preferably is, an oxygen atom.

[0060] In the formula, R ５ are independently a hydrogen atom, an alkyl group, an alkoxyalkyl group, or an acyl group, and are preferably alkyl groups. From the viewpoint of surface treatment, methyl groups and ethyl groups are particularly preferred. Component (G2) is Si(OR ５ ) has a hydrolyzable silyl group in the molecule, and therefore has an excellent surface treatment effect when used in combination with component (C).

[0061] In the formula, c is the degree of polymerization of the diorganosiloxane units of component (E2) (excluding the terminals) and is an integer of 1 to 250, preferably an integer of 1 to 100, and particularly preferably an integer of 1 to 50. In the formula, d is an integer of 1 to 3, preferably 3. When d is 3, one terminal of component (E2) is particularly preferably a trimethoxysilyl group (-Si(OMe) ３ )

[0062] The blending amounts of component (E1) and component (E2) (the total amount when both are used in combination) are not particularly limited as long as they are sufficient for surface treatment of the filler, but as an example, they are in the range of 0.005 to 100 parts by mass, preferably 0.05 to 100 parts by mass, and more preferably 0.5 to 50 parts by mass, per 100 parts by mass of component (F) in the entire composition.

[0063] (E3) An alkoxysilane having an alkyl group having 6 or more carbon atoms in the molecule, or a hydrolysis condensate thereof.

[0064] Like component (E1) or (E2), component (E3) functions as a surface treatment agent for the thermally conductive filler containing components (A) to (D) in the composition, improving the blending amount, improving the viscosity and flowability of the entire composition, and improving the adhesive properties. Such alkoxysilanes must have an alkyl group of 6 or more carbon atoms. When alkylalkoxysilanes containing only alkyl groups of less than 6 carbon atoms, such as methyl groups, or their hydrolysis condensates are used, sufficient adhesive properties may not be achieved, even when an adhesion promoter, as described below, is used in combination.

[0065] Specific examples of alkyl groups having 6 or more carbon atoms include alkyl groups such as hexyl, octyl, dodecyl, tetradecyl, hexadecyl, and octadecyl groups, and aralkyl groups such as benzyl and phenylethyl groups, with alkyl groups having 6 to 20 carbon atoms being particularly preferred.

[0066] Preferably, component (E3) has the following structural formula: ｎ Si(OR) ４－ｎ (wherein Y is an alkyl group having 6 to 18 carbon atoms, R is an alkyl group having 1 to 5 carbon atoms, and n is a number from 1 to 3), and examples of the OR group include methoxy, ethoxy, propoxy, and butoxy groups, with methoxy and ethoxy groups being particularly preferred. Note that n is 1, 2, or 3, with 1 being particularly preferred.

[0067] Specifically, such component (E3) is CH 13 Si(OCH3)3, C8H 17 Si(OC2H5)3,C 10 H 21 Si(OCH3)3, C 11 H 23 Si(OCH3)3, C 12 H 25 Si(OCH3)3, C 14 H 29 Examples include Si(OC2H5)3, and the most preferred is decyltrimethoxysilane.

[0068] The amount of component (E3) to be blended is not particularly limited as long as it is an amount sufficient for surface treatment of the filler. As an example, it is in the range of 0.005 to 20 parts by mass, preferably 0.05 to 10 parts by mass, and more preferably 0.5 to 7.5 parts by mass, per 100 parts by mass of component (B) in the entire composition.

[0069] [(F) Fatty Acid Compound] When the composition of the present invention is curable, in addition to the above-mentioned components, it may optionally contain at least one fatty acid compound selected from fatty acid esters and fatty acid metal salts. This component suppresses changes in hardness during heat aging of the composition and the cured product obtained by curing the composition, which is a silicone-based thermally conductive member. In particular, when the amount of the thermally conductive filler is within the above range, if component (F) is not used, the cured product may rapidly harden during heat aging, resulting in a loss of its stress relaxation properties, flexibility, and substrate adhesion. However, by using component (F) in combination with, preferably, a heat resistance imparting agent (component (G) described below) in the hydrosilylation curing reactive composition, the resulting cured product has high thermal conductivity, maintains its initial hardness and rubber physical properties, and achieves good stress relaxation properties, flexibility, and substrate adhesion.

[0070] Specifically, component (F) is at least one selected from fatty acids, fatty acid esters, and fatty acid metal salts, and examples thereof include fatty acids such as caproic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, and oleic acid; fatty acid esters that are alkyl esters thereof; alkali metal salts of fatty acids such as sodium, lithium, and potassium; and alkaline earth metal salts of fatty acids such as calcium. Preferably, component (F) is at least one selected from (F1) saturated fatty acids and saturated fatty acid metal salts, and particularly preferably one or more selected from (F1-1) stearic acid, alkali metal salts of stearic acid, and alkaline earth metal salts of stearic acid.

[0071] Although the mechanism by which component (F) inhibits changes in hardness of the cured product, particularly when used in combination with component (G), has not been clearly identified, it is speculated that the presence of limited amounts of fatty acid-based compounds such as fatty acids, fatty acid salts (soaps), and fatty acid esters in the silicone cured product matrix, whose heat resistance has been improved in the presence of component (G), causes the formation of a water-resistant and lubricating thin film or local structure composed of these fatty acid-based compounds on or near the particle surfaces of the thermally conductive filler, chemically reducing or inactivating the particle surfaces at high temperatures and effectively preventing aggregation of the surfaces of the thermally conductive filler and the formation of coarse particles. However, since component (F) exerts its technical effect simply by being uniformly mixed with other components without being used as a surface treatment agent for the thermally conductive filler, the timing of adding component (F) to the composition in the present invention is not limited.

[0072] The amount of component (F) is preferably in the range of 0.05 to 2.0 parts by mass per 100 parts by mass of the thermally conductive filler (total amount if multiple components are present). In particular, the amount of component (F) must be within this range to achieve the technical effects described above, and this range is critical. That is, if the amount of component (F) is below the lower limit, even when used in combination with component (G), it may not be possible to suppress changes in hardness of the cured product. On the other hand, if the amount of component (F) exceeds the upper limit, it may not be possible to suppress changes in hardness of the cured product.

[0073] [(G) Heat Resistance Imparting Agent] In addition to the above-mentioned components, the composition of the present invention may optionally contain a heat resistance imparting agent. While the heat resistance imparting agent may be blended alone, the composition of the present invention and its cured product can more effectively achieve its technical effects by containing a certain amount of the above-mentioned (F) fatty acid compound and using the (G) heat resistance imparting agent in combination. The blending amount of the heat resistance imparting agent may be in the range of 0.01 to 5.0 mass %, 0.05 to 2.0 mass %, or 0.07 to 0.5 mass % of the total composition (solid content).

[0074] Examples of heat resistance-imparting agents include metal oxides such as iron oxide, titanium oxide, cerium oxide, magnesium oxide, and zinc oxide; metal hydroxides such as cerium hydroxide; phthalocyanine compounds; cerium silanolates; cerium fatty acid salts; and reaction products of organopolysiloxanes and cerium carboxylates. Particularly preferred are (G1) phthalocyanine compounds, such as additives selected from the group consisting of metal-free phthalocyanine compounds and metal-containing phthalocyanine compounds disclosed in JP-A-2014-503680. Of the metal-containing phthalocyanine compounds, copper phthalocyanine compounds are particularly preferred. One particularly preferred, non-limiting example of a heat resistance-imparting agent is 29H,31H-phthalocyaninato(2-)-N29,N30,N31,N32 copper. Such phthalocyanine compounds are commercially available, for example Stan-tone™ 40SP03 from PolyOne Corporation (Avon Lake, Ohio, USA).

[0075] [(H) Hydrosilylation Reaction Inhibitor, Adhesion Promoter, Organic Solvent, and Other Additives] When the composition of the present invention is curable, it preferably further contains component (H), and more preferably contains one or more selected from component (F) and component (G), and it is particularly preferred to use components (F) and (G) in combination. However, the composition may further contain the following other components. In particular, when the composition is curable, it is particularly preferred to use a hydrosilylation reaction inhibitor.

[0076] [Hydrosilylation Reaction Inhibitor] When the composition of the present invention is curable, it is preferable from the viewpoint of handling and workability that it further contain a hydrosilylation reaction inhibitor. The hydrosilylation reaction inhibitor is a component for inhibiting the hydrosilylation reaction of the thermally conductive organopolysiloxane composition of the present invention, and specific examples include acetylene-based inhibitors such as ethynylcyclohexanol, amine-based inhibitors, carboxylic acid ester-based inhibitors, and phosphite-based inhibitors. The amount of reaction inhibitor added is usually 0.001 to 5 mass% of the total thermally conductive organopolysiloxane composition. In particular, for the purpose of improving the handling properties of the present composition, acetylene compounds such as 3-methyl-1-butyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol, and 3-phenyl-1-butyn-3-ol (=phenylbutynol); enyne compounds such as 3-methyl-3-penten-1-yne and 3,5-dimethyl-3-hexen-1-yne; cycloalkenylsiloxanes such as 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane and 1,3,5,7-tetramethyl-1,3,5,7-tetrahexenylcyclotetrasiloxane; and triazole compounds such as benzotriazole can be used without particular limitation.

[0077] [Adhesion Imparting Agent] The composition of the present invention may further contain an adhesion imparting agent for the purpose of improving the adhesive strength of the cured product and the permanent adhesion to substrates. The adhesion imparting agent usable in the present invention may be one or more selected from conventionally known adhesion imparting agents, such as reaction mixtures of amino group-containing organoalkoxysilanes and epoxy group-containing organoalkoxysilanes (including carbasilatrane derivatives and silatrane derivatives having specific structures), organic compounds having two or more alkoxysilyl groups in the molecule, such as disilaalkane compounds (e.g., 1,6-bis(trimethoxysilyl)hexane), and epoxy group-containing silanes or partial hydrolysis condensates thereof. Two or more adhesion imparting agents selected from these may also be used in combination, and this is preferred.

[0078] Preferably, the tackifier is represented by the general formula (L-1): ａ ｎ Si(ORｂ ) ４－ｎ (In the formula, R ａ is a monovalent epoxy group-containing organic group, and R ｂ is an alkyl group having 1 to 6 carbon atoms or a hydrogen atom. n is a number ranging from 1 to 3), and (L-2) an organic compound having at least two alkoxysilyl groups per molecule and containing a bond other than a silicon-oxygen bond between the silyl groups, in a mass ratio of 5:95 to 95:5, preferably 50:50 to 95:5, and more preferably 60:40 to 90:30. While each of these components alone improves the initial adhesion of the organopolysiloxane cured product, using them in combination in the above mass ratio can significantly improve the initial adhesion, adhesion durability, and adhesive strength (permanent adhesion) of the organopolysiloxane cured product.

[0079] Examples of the component (L-1) include 3-glycidoxyprolyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 2-(3,4-epoxycyclohexyl)ethylmethyldimethoxysilane.

[0080] Examples of the component (L-2) include disilaalkanes such as 1,6-bis(trimethoxysilyl)hexane, 1,6-bis(triethoxysilyl)hexane, 1,4-bis(trimethoxysilyl)hexane, 1,5-bis(trimethoxysilyl)hexane, 2,5-bis(trimethoxysilyl)hexane, 1-methyldimethoxysilyl-6-trimethoxysilylhexane, 1-phenyldiethoxysilyl-6-triethoxysilylhexane, and 1,6-bis(methyldimethoxysilyl)hexane.

[0081] As an adhesion promoter other than the above components (L-1) and (L-2), a reaction mixture of an amino group-containing organoalkoxysilane and an epoxy group-containing organoalkoxysilane (including carbasilatrane derivatives and silatrane derivatives having specific structures), as disclosed in JP-B No. 52-8854 and JP-A No. 10-195085, may also be used in combination.

[0082] [Organic Solvents and Other Additives] In addition to the components described above, the thermally conductive composition of the present invention can contain optional components within the scope of the present invention. Examples of optional components include cold resistance imparting agents, flame retardant imparting agents, pigments, dyes, etc. Furthermore, the thermally conductive composition of the present invention can optionally contain one or more antistatic agents such as known surfactants; dielectric fillers; electrically conductive fillers; release components; thixotropic agents; antifungal agents, etc. Furthermore, an organic solvent may be added as desired.

[0083] [Composition Manufacturing Method and Formulation] The thermally conductive composition of the present invention can be prepared by mixing the above-mentioned components. Examples of the mixing device include the same devices as those exemplified in the surface treatment of the filler. As mentioned above, component (F) may be added after the surface treatment / base heat of the filler, or together with the surface treatment agent for the filler. The technical effects of the present invention can be achieved regardless of the timing of addition. More specifically, the composition of the present invention is preferably produced by one of the following manufacturing methods (mixing processes): i) a manufacturing method comprising a step of mixing component (A), filler, and component (E), followed by a step of heat-mixing the mixture, and then optionally mixing component (F) and other components; or ii) a manufacturing method comprising a step of mixing component (A), filler, and optionally component (E), followed by a step of heat-mixing the mixture, followed by mixing other components. The heating conditions are the same as the base heat conditions described above in the surface treatment of the filler, and it is preferable to mix the entire mixture so that it is substantially uniform.

[0084] The thermally conductive composition of the present invention may be a one-component composition, optionally containing the hydrosilylation reaction inhibitor and other components, or a multi-component composition consisting of two or more components stored separately. Multi-component compositions must not contain the above-mentioned components (A), (C), and (D) simultaneously. This is because combining these components (base, crosslinker, and catalyst) simultaneously can cause a spontaneous crosslinking reaction, resulting in a loss of storage stability within a short period of time, potentially preventing the long-term storage stability and ease of handling that are the objectives of multi-component compositions. When used, multi-component compositions are mechanically stirred in a common container using a mixer or other device, or mixed using a dispenser designed for mixing multiple components, and then applied or coated.

[0085] The thermally conductive composition of the present invention has extremely high thermal conductivity, and the cured product thereof exhibits excellent flexibility and stress relaxation properties. It can be easily extruded from a cartridge or dispenser, and has excellent work efficiency, filling properties, and applicability. Therefore, even when the composition is used by filling a small amount, for example, a small-scale syringe of about 10 to 300 ml, it has the advantages of excellent application and extrusion workability to a heat-dissipating portion. Therefore, the composition can be easily filled into a small-scale cartridge or syringe, and has the advantage of being easily applicable to small-scale package production.

[0086] [Use of Non-Cured / Uncured Composition] The thermally conductive composition of the present invention can be applied in an uncured or uncured state to a heat dissipation component or a circuit board on which the heat dissipation component is mounted, to obtain a heat dissipation structure comprising an uncured heat dissipation member (examples of which include thermal dissipation grease and uncured thermally conductive gap filler material).

[0087] [Curability] When a crosslinking agent (component (C)) is used, the thermally conductive organopolysiloxane composition of the present invention cures via a hydrosilylation reaction to form a cured product that exhibits excellent thermal conductivity, suppresses hardness change even after heat aging, and exhibits excellent flexibility and stress relaxation properties. The temperature conditions for curing this hydrosilylation reaction-curable composition are not particularly limited, but are typically within the range of 20°C to 200°C, preferably 20°C to 150°C, and more preferably 20°C to 80°C. If desired, the composition may be cured at a high temperature for a short period of time, or at a low temperature such as room temperature for a long period of time (e.g., several hours to several days), and are not particularly limited. Furthermore, by selecting a high-energy ray-activated catalyst or a photoactivatable catalyst for at least a portion of component (D), curing may be triggered by irradiation with high-energy rays.

[0088] By using the thermally conductive composition of the present invention, the curable thermally conductive composition can be applied to a heat dissipation component or a circuit board on which the heat dissipation component is mounted, and a cured product can be formed at a temperature in the range of 20°C to 150°C, preferably less than 130°C, for example, 20 to 125°C, to obtain a heat dissipation structure provided with a heat dissipation member.

[0089] [Thermal Conductivity] The thermally conductive organopolysiloxane composition of the present invention exhibits excellent dischargeability from cartridges even when stably loaded with a high amount of thermally conductive filler. It forms a homogeneous crosslinked structure upon curing, which reduces density changes even after prolonged heating at high temperatures. It also suppresses the formation of voids and bubbles, avoids contact failure, and is less likely to cause mold contamination. It also features high heat resistance due to its alkali catalyst-free nature. Therefore, the thermal conductivity of the composition is preferably 9.0 W / mK or greater, and particularly preferably 9.1 W / mK or greater. The thermally conductive composition of the present invention can be designed to have a thermal conductivity of 9.0 to 15.0 W / mK, or optionally, a thermal conductivity of 9.1 to 14.0 W / mK. It also offers excellent workability, such as extrudability and dispensability from cartridges. It also exhibits the advantages of maintaining heat dissipation and physical strength due to the lack of density changes even after prolonged heating at high temperatures. Furthermore, the present composition may be non-curable or curable. When the composition is curable, the optional use of component (F) / (G) can suppress changes in hardness even after heat aging, making it possible to realize a thermally conductive cured product that is excellent in flexibility and stress relaxation properties.

[0090] [Uses and Heat Dissipation Structures] The thermally conductive composition of the present invention and its cured product are useful as heat transfer materials (thermally conductive members) to be interposed at the interface between the thermal boundary surface of a heat-generating component and a heat dissipation member such as a heat sink or circuit board for cooling the heat-generating component by heat conduction, and a heat dissipation structure including the composition can be formed. Here, the type, size, and detailed structure of the heat-generating component are not particularly limited. However, the thermally conductive composition of the present invention or a cured product obtained by curing the composition has high thermal conductivity and excellent initial adhesion and adhesive strength to the component. Furthermore, it suppresses hardness change over a long period of time, even after heat aging, and maintains flexibility and stress relaxation properties. Therefore, it is less likely to peel off from the heat-generating component or form voids due to vibration, etc., has high adhesion and conformability, and is highly industrially productive. Therefore, it is suitable for use in heat dissipation structures for automobile parts, electrical and electronic components, and electrical and electronic devices, including cell-type secondary batteries.

[0091] The structure of such a heat dissipation structure is not particularly limited, but an example is a heat dissipation structure in which a heat dissipation member is provided on a heat dissipation component or a circuit board on which the heat dissipation component is mounted, via the thermally conductive composition or a cured product thereof. An example of such a structure is a structure in which an electronic component, which is a heat dissipation component, is mounted on a circuit board, and heat generated from the electronic component is dissipated by the heat dissipation member via a thin film layer of the thermally conductive composition or a cured product thereof. These components exhibit small changes in hardness after heat aging, which is a feature of the present invention, maintain the flexibility and stress relaxation properties of the heat dissipation component, and have excellent adhesion and conformability, so they may be suitably arranged not only on horizontal surfaces but also on inclined or vertical surfaces.

[0092] In such a heat dissipation structure, the thickness of the thermally conductive composition or its cured product is not particularly limited, but may be in the range of 0.1 to 100 mm, and heat generated from an electronic component filled with the composition or its cured product without gaps can be efficiently conducted to the heat dissipation member.

[0093] Electrical and electronic devices equipped with members made from the thermally conductive composition are not particularly limited, and examples thereof include secondary batteries such as cell-type lithium-ion electrode secondary batteries and cell-stack type fuel cells; electronic circuit boards such as printed circuit boards; IC chips packaged with optical semiconductor elements such as diodes (LEDs), organic electroluminescent devices (organic EL), laser diodes, and LED arrays; CPUs used in electronic devices such as personal computers, digital video disks, mobile phones, and smartphones; and LSI chips such as driver ICs and memories. In particular, in high-performance digital switching circuits formed with high integration density, heat removal (heat dissipation) is a key factor in the performance and reliability of integrated circuits. Thermally conductive members made using the thermally conductive organopolysiloxane composition of the present invention have excellent heat dissipation properties and handling properties even when applied to power semiconductor applications such as engine control, powertrain systems, and air conditioning control in transportation vehicles. They maintain strong adhesion to components and achieve excellent heat resistance and thermal conductivity even when incorporated into on-board electronic components such as electronic control units (ECUs) and used in harsh environments.

[0094] The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In the examples and comparative examples shown below, the following compounds or compositions were used as raw materials.

[0095] [Example 1 (Synthesis Example) * Living Polymer] After replacing the atmosphere with nitrogen gas, a 3L flask equipped with a stirrer, thermometer, dropping funnel, and condenser was charged with 1,000 grams (4.50 moles) of hexamethylcyclotrisiloxane (D3) and 830 grams of toluene, mixed, and subjected to azeotropic dehydration for 1 hour, followed by cooling to room temperature. A mixture of 67 grams of dimethylformamide, 333 grams of acetonitrile, and 8.23 ​​grams of a 1.5% by weight aqueous solution of lithium hydroxide was added and stirred at room temperature. The conversion of D3 was monitored by GLC (gas chromatography), and after 3 hours and 30 minutes, when the conversion reached 97%, 5.13 grams of acetic acid was added to terminate the polymerization. Furthermore, low boilers were distilled off under reduced pressure by heating, followed by sterilization filtration. In a separate reaction flask, 891 g of this filtrate, 125 g of tetramethyldivinyldisilazane, and 0.5 g of trifluoroacetic acid were added and stirred at 80°C for 2 hours, and low boiling point substances were distilled off under reduced pressure by heating, followed by sterilization filtration to obtain 1024 g of a colorless, transparent liquid.

[0096] The resulting reaction product had a kinematic viscosity of 27.7 mm ２ / s, and gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) analyses revealed that the polymer was a polydimethylsiloxane containing vinyl groups at both molecular chain terminals, with a number average molecular weight of 3,890 and a dispersity (ratio of weight average molecular weight to number average molecular weight (Mw / Mn)) of 1.15, and a vinyl group content of 2.16% by mass.

[0097] The low molecular weight dimethylsiloxanes in this polydimethylsiloxane were extracted with acetone and quantified by temperature-programmed GLC equipped with an FID detector using n-undecane as the standard substance. The content of cyclic polydimethylsiloxane D13 was found to be 47 ppm, and the content of D14 was found to be 60 ppm.

[0098] Comparative Example 1 (Comparative Synthesis Example) *Equilibrium Polymerization Product A 3 L flask equipped with a stirrer, a thermometer, a small Dean-Stark tube, and a condenser was purged with nitrogen gas, and then 854 g (2.89 mol) of hexamethylcyclotetrasiloxane (D4), 795 g of polydimethylsiloxane containing vinyl groups at both ends and having a vinyl group content of 7.6% by mass, tetramethylammonium hydroxide [(CH ３ ) ４ 0.5 g of a 25% by mass aqueous solution of 2,4-dimethylaminopropyltrimonials such as 2,4-dimethylaminopropyltrimonials (NOH) was added and mixed, and the mixture was stirred at 80°C for 3 hours under a nitrogen gas flow while removing water. After heating to 180°C, the pressure was reduced to 70 hectopascals or less, and low boiling point substances were distilled off under reduced pressure by heating, followed by sterilization filtration to obtain 1,148 g of a colorless, transparent liquid.

[0099] The resulting reaction product had a kinematic viscosity of 28 mm ２ / s, and GPC and NMR analyses revealed that the polymer was a polydimethylsiloxane containing vinyl groups at both ends, with a number average molecular weight of 3,480 and a dispersity (ratio of weight average molecular weight to number average molecular weight (Mw / Mn)) of 1.38, and a vinyl group content of 2.20 mass%.

[0100] The low molecular weight dimethylsiloxanes in this polydimethylsiloxane were extracted with acetone and quantified by temperature-programmed GLC equipped with an FID detector using n-undecane as the standard substance. The content of cyclic polydimethylsiloxane D13 was found to be 325 ppm, and the content of D14 was found to be 254 ppm.

[0101] [Summary] The polydimethylsiloxane containing vinyl groups at both molecular chain terminals obtained by living polymerization according to the present invention (Example 1) had a molecular weight dispersity expressed by Mw / Mn of 1.15, a number-average molecular weight of 3890, and a content of 13,14-mer cyclic siloxanes (D13 and D14) of less than 100 ppm in both cases. In contrast, the polydimethylsiloxane containing vinyl groups at both molecular chain terminals obtained by equilibrium polymerization (Comparative Example 1) had a molecular weight dispersity expressed by Mw / Mn of 1.37, a number-average molecular weight of 3480, and a content of 13,14-mer cyclic siloxanes (D13 and D14) of more than 100 ppm in both cases.

[0102] [Preparation of Composition and Production of Thermally Conductive Organopolysiloxane Cured Product (Evaluation Sample)] The components were mixed as described below to obtain the thermally conductive compositions of Example 2 and Comparative Example 2 (hereinafter sometimes referred to as "thermally conductive organopolysiloxane compositions"). The thermally conductive organopolysiloxane composition was filled into a mold 6 mm high, 50 mm long, and 30 mm wide, and cured at 80°C for 30 minutes. The composition was then removed from the mold to obtain a thermally conductive organopolysiloxane cured product. The hardness of the obtained thermally conductive organopolysiloxane cured product was measured using the following method.

[0103] [Hardness (Type E Hardness)] Two sheets of the thermally conductive organopolysiloxane cured product obtained under the above conditions were stacked on top of each other, and the hardness was measured after 3 seconds using an ASKER TYPE E hardness tester manufactured by ASKER Corporation. [Thermoelectric Conductivity] Thermal conductivity was measured using two sheets of the thermally conductive organopolysiloxane cured product obtained under the above conditions, using a TPS-500 (hot disk method) manufactured by Kyoto Electronics Manufacturing Co., Ltd. [Density / Density Change] Density was measured by measuring the specific gravity in water using an EW-300SG manufactured by Alpha Mirage Co., Ltd., and then converting the density. Density change was calculated from the initial density of the thermally conductive organopolysiloxane cured product obtained under the above conditions and the density of the same cured product aged for 100 hours in an oven at 120°C or 150°C. When voids are formed inside due to aging, the density decreases compared to the initial value, and it can be determined that internal foaming or cracks have occurred. [Extrusion amount] The extrusion amount was measured by filling a 30 cc EFD syringe (manufactured by Nordson Corporation) with the thermally conductive composition and extruding it at an extrusion pressure of 80 psi, and measuring the extrusion weight per minute.

[0104] The composition of the present invention is formed from the following components: Component (A): A-P: Dimethylpolysiloxane end-blocked at both molecular chain ends with dimethylvinylsiloxy groups (molecular weight dispersity 1.15, number average molecular weight 3890, Vi content 2.16% by mass) *Example 1 A-C: Dimethylpolysiloxane end-blocked at both molecular chain ends with dimethylvinylsiloxy groups (molecular weight dispersity 1.37, number average molecular weight 3480, Vi content 2.20% by mass) *Comparative Example 1

[0105] Component (B): B-1: Irregular zinc oxide powder with an average particle size of 0.12 μm B-2: Polyhedral spherical α-type aluminum oxide powder with an average particle size of 2 μm B-3: Irregular aluminum nitride powder with an average particle size of 30 μm B-4: Spherical aluminum nitride powder with an average particle size of 80 μm B-5: Spherical magnesium oxide powder with an average particle size of 120 μm Component (C): C-1: Methylhydrogensiloxane-dimethylsiloxane copolymer capped at both molecular chain ends with trimethylsiloxy groups, with an average of 2 per molecule and an average of 2 per side chain (viscosity 20 mPa s, Si—H content 0.10% by mass) C-2: Methylhydrogensiloxane-dimethylsiloxane copolymer capped at both molecular chain ends with trimethylsiloxy groups, with an average of 5 per molecule and an average of 5 per side chain (viscosity 5 mPa s, Si—H content 0.75% by mass)

[0106] Component (D): D-1: A complex of platinum and 1,3-divinyl-1,1,3,3-tetramethyldisiloxane having a platinum concentration of 0.6% by weight

[0107] Component (E): E-1: Formula: (CH ３ ) ３ SiO[(CH ３ ) ２ SiO ３０ Si(OCH ３ ) ３ Organopolysiloxane E-2: Decyltrimethoxysilane

[0108] Component (F): F-1: Calcium stearate (Fujifilm Wako Pure Chemical Industries, Ltd.) Component (G): G-1: 29H,31H-phthalocyaninato(2-)-N29,N30,N31,N32 copper Component (H): H-1: Phenylbutynol

[0109] Example 2: Two-part thermally conductive organopolysiloxane composition according to Example 1. 100.0 parts by mass of component (A-P), 58.8 parts by mass of component (E-1), 7.84 parts by mass of component (E-2), and 3.92 parts by mass of component (F-1) were weighed, and over a period of 60 minutes, 647 parts by mass of component (B-1), 1157 parts by mass of component (B-2), 706 parts by mass of component (B-3), 424 parts by mass of component (B-4), and 813 parts by mass of component (B-5) were sequentially mixed. This mixture was then homogenized over a period of 30 minutes. After homogenization, the mixture was heated and mixed at 160°C under reduced pressure for 60 minutes, and then cooled to room temperature to obtain a mixture. 0.89 parts by mass of component (D-1) was homogenized with this mixture to obtain part (I) of the thermally conductive organopolysiloxane composition. Next, 39.2 parts by mass of component (A-P), 51.0 parts by mass of component (C-1), 58.8 parts by mass of component (E-1), 7.84 parts by mass of component (E-2), and 3.92 parts by mass of component (F-1) were weighed out, and over a period of 60 minutes, 647 parts by mass of component (B-1), 1157 parts by mass of component (B-2), 706 parts by mass of component (B-3), 424 parts by mass of component (B-4), and 813 parts by mass of component (B-5) were sequentially mixed. This was then uniformly mixed over a period of 30 minutes. After homogenization, the mixture was heated and mixed at 160°C under reduced pressure for 60 minutes, and then cooled to room temperature to obtain a mixture. 2.0 parts by mass of component (C-2), 3.92 parts by mass of component (G-1), and 0.12 parts by mass of component (H-1) were uniformly mixed with this mixture to obtain liquid (II) of a thermally conductive organopolysiloxane composition. The extrusion amounts of the thermally conductive organopolysiloxane compositions (I) and (II) were measured, and then the two liquids were mixed in equal amounts, after which the hardness, thermal conductivity, density, and density change were measured.

[0110] Comparative Example 2: Two-component thermally conductive organopolysiloxane composition according to Comparative Example 1 A thermally conductive organopolysiloxane composition was obtained in the same manner as in Example 2, except that component (A-P) in Example 2 was replaced with component (A-C).

[0111] Table 1 shows the composition, extrusion amount, thermal conductivity, hardness, density, and density change after heat aging of the thermally conductive organopolysiloxane compositions of Example 2 and Comparative Example 2.

[0112] [Summary] The thermally conductive organopolysiloxane composition of Example 2, which used AP: a dimethylpolysiloxane terminated at both molecular chain ends with dimethylvinylsiloxy groups obtained by Example 1 (living polymerization method), achieved a high thermal conductivity of more than 11 W / m K, and showed a density change of less than 1% after 100 hours at high temperature (120°C or 150°C), suppressed the generation of voids and bubbles, and exhibited good dischargeability from a cartridge (extrusion workability). Therefore, the thermally conductive organopolysiloxane composition of the present example is highly expected to maintain the expected heat dissipation characteristics and mechanical strength, such as rubber physical properties, even when used for long periods of time at high temperatures, in addition to being easy to handle.

[0113] In contrast, the thermally conductive organopolysiloxane composition of Comparative Example 2, which used A-C: dimethylpolysiloxane capped at both molecular chain terminals with dimethylvinylsiloxy groups, obtained by Comparative Example 1 (equilibration polymerization method), showed similar favorable results in terms of thermal conductivity, hardness, and dischargeability from the cartridge (extrusion workability) as in Example 2. However, after 100 hours at high temperature (120°C or 150°C), a large change in density occurred, and the rate of density loss due to the generation of voids and bubbles was significant. Therefore, there is concern that the heat dissipation characteristics and mechanical strength, such as rubber properties, of the thermally conductive organopolysiloxane of Comparative Example 2 may deteriorate when used for long periods of time, particularly at high temperatures.

Claims

1. An organopolysiloxane having alkenyl groups at both ends of the molecular chain, wherein the ratio of the weight average molecular weight to the number average molecular weight (Mw / Mn) is 1.20 or less.

2. The organopolysiloxane according to claim 1, wherein the number average molecular weight is 10,000 or less, and the content of cyclic dimethylsiloxane having 20 or less monomers is less than 0.1% by mass.

3. The organopolysiloxane according to claim 1, which is a linear dimethylpolysiloxane having alkenyl groups with 2 to 8 carbon atoms only at both ends of the molecular chain, and the content of cyclic dimethylsiloxane having 10 to 20 monomers is less than 0.1% by mass.

4. The organopolysiloxane according to claim 1, wherein the ratio of the weight average molecular weight to the number average molecular weight (Mw / Mn) is in the range of 1.05 to 1.18, the number average molecular weight is in the range of 2,000 to 5,000, the content of cyclic dimethylsiloxane having 10 to 15 monomers is less than 0.01% by mass, and it is a linear dimethylpolysiloxane having alkenyl groups with 2 to 8 carbon atoms only at both ends of the molecular chain.

5. (R Ａ ２ SiO) ３ (In the above formula, each R Ａ is independently an alkyl group, an aryl group, or a group in which a part of the hydrogen atoms bonded to the carbon atoms thereof is substituted by a halogen atom), a step (I) of living polymerization of hexaorganocyclotrisiloxane represented by the formula, and the molecular chain end on the polymerization termination side of the polymer obtained in step (I) is represented by R Ｂ R Ａ ２ SiNSiR Ａ ２ R Ｂ (In the above formula, R Ａ is the same group as described above, and R Ｂ is an alkenyl group); and at least one selected from alkenyldiorganochlorosilanes represented by R Ｂ R Ａ ２ SiCl (in the above formula, R Ａ , R Ｂ are the same groups as described above) to block the step (II). The method for producing an organopolysiloxane according to any one of claims 1 to 4, characterized by comprising the above steps.

6. In step (I) and step (II), the reaction solvent is a mixed solvent containing (S1) one or more polar solvents selected from acetonitrile, methyl ethyl ketone, and methyl isobutyl ketone, and (S2) one or more polar solvents selected from dimethyl sulfoxide and dimethylformamide. The method for producing an organopolysiloxane according to claim 5.

7. A thermally conductive organopolysiloxane composition containing (A) 100 parts by mass of the organopolysiloxane according to any one of claims 1 to 4, and (B) a thermally conductive filler in an amount in the range of 60 to 90% by volume based on the total solid content in the composition.

8. The thermally conductive organopolysiloxane composition according to claim 7, which is non-curable.

9. The thermally conductive organopolysiloxane composition according to claim 7, which has one or more curable reactivities selected from hydrosilylation reaction and radical polymerization reaction.

10. Further, (C) an organohydrogenpolysiloxane: an amount such that the silicon atom-bonded hydrogen atoms in component (C) are 0.2 to 5 moles per 1 mole of the curable reactive group having a carbon-carbon double bond contained in component (A), and (D) a catalytic amount of a catalyst for hydrosilylation reaction. The thermally conductive organopolysiloxane composition according to claim 7, which has hydrosilylation reactivity.

11. Further, (E) (E1) General formula (1): (In the formula, R 1 is independently a monovalent hydrocarbon group having no unsubstituted or substituted carbon-carbon double bond, R ２ is independently a hydrogen atom, an alkyl group, an alkoxyalkyl group, or an acyl group, a is an integer of 5 to 250, and b is an integer of 1 to 3.) represented by the formula, and having a viscosity at 25 ° C. of 10 to less than 10,000 mPa·s Organopolysiloxane; (E2) General formula (2): R alk R ３ ２ SiO(R ３ ２ SiO) ｃ R ３ ２ Si-R ４ -SiR ３ (3-ｄ) (OR ５ ) ｄ (In the formula, R alk is an alkenyl group, R ３ is independently a monovalent hydrocarbon group having no unsubstituted or substituted carbon-carbon double bond, R ４ is an oxygen atom or a divalent hydrocarbon group, R ５ is independently a hydrogen atom, an alkyl group, an alkoxyalkyl group, or an acyl group, c is an integer of 1 to 250, and d is an integer of 1 to 3.) represented by the formula, and having a viscosity at 25 ° C. in the range of 10 to 10,000 mPa·s, a siloxane compound having an alkenyl group and a hydrolyzable silyl group at the molecular chain ends; and (E3) an alkoxysilane having an alkyl group having 6 or more carbon atoms in the molecule or a hydrolytic condensate thereof A thermally conductive organopolysiloxane composition according to claim 7, comprising one or more components selected from the group consisting of:

12. Further, at least one selected from (F) fatty acids, fatty acid esters, and fatty acid metal salts; and one or more components selected from (G) heat resistance imparting agents, the thermally conductive organopolysiloxane composition according to claim 7.

13. The thermally conductive organopolysiloxane composition according to any one of claims 7 to 12, characterized in that the thermal conductivity of the composition or its cured reaction product is 9.0 W / mK or more.

14. The thermally conductive organopolysiloxane composition according to any one of claims 7 to 13, wherein the density change of the composition or its cured reaction product is within 1% even after 150 °C for 100 hours.

15. A thermally conductive member comprising the thermally conductive organopolysiloxane composition according to any one of claims 7 to 13 or its cured reaction product.

16. A heat dissipation structure provided with the thermally conductive member according to claim 15.

17. A heat dissipation structure in which a heat dissipation member is provided on a heat dissipation component or a circuit board on which the heat dissipation component is mounted via the thermally conductive organopolysiloxane composition according to any one of claims 7 to 13 or its cured reaction product.

18. The heat dissipation structure according to claim 16 or claim 17, which is an electric / electronic device.

19. The heat dissipation structure according to claim 16 or claim 17, which is an electric / electronic component or a secondary battery.

20. A method for manufacturing a heat dissipation structure, comprising the step of applying the thermally conductive composition according to any one of claims 7 to 12 to a heat dissipation component or a circuit board on which the heat dissipation component is mounted and curing it at a temperature of less than 130 °C.

21. A composition applied to one or more uses selected from a sealant composition, a conductive composition, and a heat insulating composition, the composition containing the organopolysiloxane according to any one of claims 1 to 4.

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