Silicone rubber-based curable composition and structure comprising the same

Abstract

To provide a silicone rubber-based curable composition capable of giving a molded body excellent in durability against repeated flexural deformation.SOLUTION: The silicon rubber-based curable composition of the present invention comprises a vinyl group-containing organopolysiloxane (A) and silica particles (C). When a test piece made of a cured product of the silicon rubber-based curable composition is subjected to a De Mattia flexural test in accordance with JIS K 6260, a change rate of a notch length in the test piece, measured based on a predetermined procedure, is 1.1 or more and 11.5 or less at 50000 times of flexing.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a silicone rubber-based curable composition and a structure thereof. [Background technology]

[0002] Various developments have been made so far in the area of ​​durability of silicone rubber. One known example of this type of technology is described in Patent Document 1. Patent Document 1 describes that resistance to elongation fatigue can be evaluated based on the number of times that a 100% elongation operation is repeatedly performed before the material breaks, and describes a silicone rubber (cured product of a curable silicone rubber composition) that has been elongated 2.1 million times (Example 1 of Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-222849 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, as a result of investigations conducted by the present inventors, it was found that there is room for improvement in terms of durability against repeated bending deformation in the cured product of the curable silicone rubber composition described in Patent Document 1 above. [Means for solving the problem]

[0005] In the technical field of silicone rubber, the properties under elongation are commonly studied. However, the characteristics during repeated bending have not been sufficiently examined.

[0006] The present inventors have studied and found that the bending resistance of a molded body of a silicone rubber-based hardening composition when repeatedly bent can be evaluated by using the De Mattia bending resistance test. As a result of further studies, it has been found that the bending resistance can be controlled by appropriately setting the test conditions of the De Mattia bending resistance test in accordance with JIS K 6260 and using the rate of change in the length of the incision in a test piece with an incision as an index. Based on this knowledge, further intensive research has been conducted and it has been found that the durability of a molded body of a silicone rubber-based hardening composition against repeated bending deformation can be improved by setting the rate of change in the length of the incision in the test piece when it is bent 50,000 times within a predetermined range, thereby completing the present invention.

[0007] According to the present invention, A vinyl group-containing organopolysiloxane (A), A silicone rubber-based curable composition comprising: A test piece made of a cured product of the silicone rubber-based curable composition is subjected to a De Mattia bending test in accordance with JIS K 6260, and the rate of change in incision length (L5 / L0) of the test piece after 50,000 bending cycles, as measured according to the following procedure, is 1.1 or more and 11.5 or less. A silicone rubber-based curable composition is provided. (procedure) The silicone rubber-based hardening composition is pressed at 170° C. and 10 MPa for 15 minutes, and then heated at 200° C. for 4 hours to prepare a test piece of a predetermined shape in accordance with JIS K 6260. At the center of the obtained test piece, a cut of a predetermined length is made parallel to the width direction through the test piece. The initial cut length is designated as L0. Next, the test piece with the notch is placed between the grips of a testing machine, and a De Mattia type bending resistance test is performed based on the test conditions described below, and the length of the notch (mm) in the test piece after a specified number of bending cycles is measured. The cut length is the average value obtained by performing the De Mattia bending test three times. This average cut length is designated as L5. The cut length change rate is calculated based on the formula: L5 / L0. (Test conditions) Test standard: JIS K 6260 compliant Testing machine: Dematcha flex crack testing machine Test temperature: 23±2℃ Maximum distance between grips: 75mm ·Reciprocating distance: 57mm Test speed: 300±10 times / min Number of tests: n=3

[0008] The present invention also provides a structure comprising a cured product of the silicone rubber-based curable composition. Effect of the Invention

[0009] According to the present invention, there are provided a silicone rubber-based hardening composition capable of realizing a molded article having excellent durability against repeated bending deformation, and a structure thereof. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic diagram showing an example of a configuration of a mold. [Diagram 2] FIG. 2 is a schematic diagram showing an example of a configuration of a test piece. [Diagram 3] FIG. 1 is a schematic diagram showing an example of the configuration of a DeMatia type testing machine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In all drawings, the same components are given the same reference numerals and the description will be omitted as appropriate. In addition, the drawings are schematic diagrams and do not correspond to the actual dimensional ratio.

[0012] The silicone rubber-based hardenable composition of this embodiment will be outlined below.

[0013] The silicone rubber-based hardening composition of the present embodiment contains a vinyl group-containing organopolysiloxane (A) and silica particles (C). A test piece made of a hardened product of the silicone rubber-based hardening composition is used to carry out a De Mattia bending test in accordance with JIS K 6260. The rate of change in incision length (L5 / L0) of the test piece after 50,000 bending cycles, as measured according to the following procedure, satisfies a range of 1.1 to 11.5.

[0014] (procedure) The silicone rubber-based hardening composition is pressed at 170° C. and 10 MPa for 15 minutes, and then heated at 200° C. for 4 hours to prepare a grooved test piece of a predetermined shape in accordance with JIS K 6260. At the center of the groove of the obtained test piece, a cut of a predetermined length (2.03 mm) is made parallel to the width direction so as to penetrate the test piece. The initial cut length is designated as L0. Next, the test piece with the notch is placed between the grips of a testing machine, and a De Mattia type bending resistance test is performed based on the test conditions described below, and the length of the notch (mm) in the test piece after a specified number of bending cycles is measured. The cut length is the average value obtained by performing the De Mattia bending test three times. This average cut length is designated as L5. The cut length change rate is calculated based on the formula: L5 / L0. (Test conditions) Test standard: JIS K 6260 compliant Testing machine: Dematcha flex crack testing machine Test temperature: 23±2℃ Maximum distance between grips: 75mm ·Reciprocating distance: 57mm Test speed: 300±10 times / min Number of tests: n=3

[0015] According to the findings of the present inventors, it has been found that the flex resistance of an article molded from a silicone rubber-based hardening composition during repeated flexing can be evaluated by using the De Mattia flex resistance test. However, unless an appropriate index is set, the evaluation takes a long time and there is a risk of variation in the evaluation. For example, when the number of deformations until breakage is used as an index, as in the 100% elongation fatigue life in Patent Document 1, the time until breakage becomes long and the number of deformations may vary. In addition, when a non-notched product is used as a test piece and the breakage state is used as an index, it was found that a considerable number of bending times is required until a difference in the breakage state appears, and even if a difference appears, the variation in the breakage state becomes large.

[0016] As a result of further investigation, it was found that by appropriately setting the test conditions for the De Mattia type bending resistance test in accordance with JIS K 6260 and using the rate of change in the length of the notched test piece as a guideline, it is possible to relatively quickly and stably evaluate the bending resistance of a molded body of a silicone rubber-based curable composition when repeatedly bent, and to control such bending resistance.

[0017] Further intensive research based on this knowledge led to the discovery that by using the rate of change in the cut length in the test piece after 50,000 flexing cycles as an index, it is possible to stably evaluate the bending resistance during repeated bending, and further that by setting this index within the above-mentioned specified range, it is possible to improve the durability of an article molded from the silicone rubber-based curable composition against repeated bending deformation.

[0018] Although the detailed mechanism is unclear, it is believed that by using the above-mentioned cut change rate as an indicator and appropriately adjusting the inter-crosslink distance and crosslink density, it is possible to achieve a well-balanced improvement in the properties of low hardness, high tear strength, and high breaking elongation, thereby obtaining a silicone rubber structure that reduces the load when bending.

[0019] In the above De Mattia type bending resistance test, L0 is the initial cut length before the De Mattia type bending resistance test, and L1, L3, and L5 are the average cut lengths when the number of bending cycles is 10,000, 30,000, and 50,000, respectively, after the De Mattia type bending resistance test. In this case, the upper limit of the incision length change rate (L5 / L0) in the test piece when the number of bending times is 50,000 is 11.5 or less, preferably 10.7 or less, more preferably 8.0 or less, and even more preferably 6.0 or less. This makes it possible to realize a molded body that is excellent in durability against repeated bending deformation and has mechanical strength as a member. The lower limit of the incision length change rate (L5 / L0) may be 1.0 or more, and may be 1.1 or more.

[0020] As a result of the DeMatcia bending resistance test using the silicone rubber-based hardening composition, the upper limit of L1 / L0 is, for example, 10.0 or less, preferably 8.0 or less, more preferably 6.0 or less, and even more preferably 4.0 or less. This makes it possible to realize a molded product with excellent durability against repeated bending deformation. In addition, since the properties can be evaluated by a simpler evaluation method, the productivity of the silicone rubber-based hardening composition can be improved. The lower limit of L1 / L0 may be 1.0 or more.

[0021] Furthermore, when the initial cut length L0 is 2.03 mm, the cut length L5 in the test piece after 50,000 flexing cycles may be, for example, 2.2 mm to 22.5 mm, preferably 2.3 mm to 18.0 mm, and more preferably 2.5 mm to 15.0 mm. In this specification, the symbol "to" indicates that the upper and lower limits are included, unless otherwise specified.

[0022] In the silicone rubber-based curable composition, the content of the silica particles (C) may be, for example, 10 parts by weight or more and 60 parts by weight or less, based on 100 parts by weight of the total vinyl group-containing organopolysiloxane (A). The upper limit of the content of the silica particles (C) is preferably 50 parts by weight or less, more preferably 35 parts by weight or less, and even more preferably 30 parts by weight or less. In this way, by making the silica content relatively low, durability against repeated bending deformation can be improved. By making the content of the silica particles (C) 35 parts by weight or less, repeated bending durability can be stably improved.

[0023] In this embodiment, for example, by appropriately selecting the type and amount of each component contained in the silicone rubber-based hardening composition, the method for preparing the silicone rubber-based hardening composition, the method for producing the silicone rubber, etc., it is possible to control the above-mentioned incision length change rate, incision length, and the below-described breaking elongation, tensile strength, tear strength, and hardness. Among these, for example, the use of a vinyl group-containing linear organopolysiloxane (A1-1) having relatively small and few vinyl groups and having vinyl groups only at the terminals as the vinyl group-containing organopolysiloxane (A) to control the crosslink density and crosslink structure of the resin; the timing of addition of the vinyl group-containing organopolysiloxane (A) and its ratio, the blending ratio of the silica particles (C), the specific surface area of ​​the silica particles (C), surface modification of the silica particles (C) with the silane coupling agent (D), addition of water, or the like to more reliably proceed with the reaction between the silane coupling agent (D) and the silica particles (C) can be mentioned as elements for setting the above-mentioned incision length change rate, incision length, and the below-mentioned breaking elongation, tensile strength, tear strength, and hardness in the desired numerical range.

[0024] Next, the characteristics of the silicone rubber-based hardenable composition of this embodiment will be described.

[0025] (Tear strength measurement conditions) A crescent-shaped test piece is prepared using the cured product of the silicone rubber-based curable composition, and the tear strength of the resulting crescent-shaped test piece is measured at 25° C. in accordance with JIS K6252 (2001).

[0026] The lower limit of the tear strength of the cured product of the silicone rubber-based curable composition is, for example, 25 N / mm or more, preferably 28 N / mm or more, more preferably 30 N / mm or more, even more preferably 33 N / mm or more, and even more preferably 35 N / mm or more. This can improve the durability of the silicone rubber during repeated use. In addition, the scratch resistance and mechanical strength of the silicone rubber can be improved. On the other hand, the upper limit of the tear strength is not particularly limited, but may be, for example, 70 N / mm or less, or 60 N / mm or less. This can balance the various properties of the silicone rubber.

[0027] (Measurement conditions for breaking elongation) A dumbbell-shaped No. 3 test piece is prepared using the cured product of the silicone rubber-based curable composition, and the breaking elongation of the resulting dumbbell-shaped No. 3 test piece is measured at 25° C. in accordance with JIS K6251 (2004).

[0028] The lower limit of the breaking elongation of the cured product of the silicone rubber-based curable composition is, for example, 500% or more, preferably 600% or more, and more preferably 700% or more. This can improve the high elasticity and durability of the silicone rubber. On the other hand, the upper limit of the breaking elongation is not particularly limited, but may be, for example, 2000% or less, 1800% or less, or 1500% or less. This can balance the various properties of the silicone rubber.

[0029] (Durometer hardness A measurement conditions) A sheet-like test piece is prepared using the cured product of the silicone rubber-based curable composition, and the durometer hardness A of the obtained sheet-like test piece is measured at 25° C. in accordance with JIS K6253 (1997).

[0030] The upper limit of the durometer hardness A of the cured product of the silicone rubber-based curable composition is not particularly limited, but may be, for example, 70 or less, preferably 55 or less, and more preferably 50 or less. This allows the silicone rubber to have a balanced cured physical property. From the viewpoint of ease of deformation, the upper limit of the durometer hardness A may be 40 or less, 35 or less, or 30 or less. This allows the silicone rubber to have improved ease of deformation, such as bending and stretching. On the other hand, the lower limit of the durometer hardness A is not particularly limited, but may be, for example, not less than 10, preferably not less than 20, and more preferably not less than 25. This can increase the mechanical strength of the silicone rubber.

[0031] (Tensile strength measurement conditions) A dumbbell-shaped No. 3 test piece is prepared using the cured product of the silicone rubber-based curable composition, and the tensile strength of the resulting dumbbell-shaped No. 3 test piece is measured at 25° C. in accordance with JIS K6251 (2004).

[0032] The lower limit of the tensile strength of the cured product of the silicone rubber-based curable composition is, for example, 5.0 MPa or more, preferably 10.0 MPa or more, and more preferably 12.0 MPa or more. This can improve the mechanical strength of the silicone rubber. In addition, a structure having excellent durability and capable of withstanding repeated deformation can be realized. On the other hand, the upper limit of the tensile strength is not particularly limited, but may be, for example, 25 MPa or less, or 20 MPa or less. This can balance the various properties of the silicone rubber.

[0033] The cured product (silicone rubber) of the silicone rubber-based curable composition of the present embodiment is processed and molded into various forms depending on the application. The molded product may be molded into various shapes such as a sheet, a cylinder, or a bag.

[0034] The silicone rubber-based hardening composition has excellent durability against repeated bending and modification, and can be suitably used to form a molded body for a flexible member. The flexible member refers to a member that is repeatedly subjected to stress in a bending direction under a usage environment. The flexible member may be used under a usage environment in which it is subjected to stress in a stretching direction.

[0035] An example of the flexible member is a wearable device, and the silicone rubber-based curable composition can be suitably used to form a molded article for the wearable device.

[0036] The wearable devices are wearable devices that can be attached to the body or clothing, and examples thereof include medical sensors that detect biological phenomena such as heart rate, electrocardiogram, blood pressure, and body temperature, healthcare devices, bendable displays, stretchable LED arrays, stretchable solar cells, stretchable antennas, stretchable batteries, actuators, wearable computers, etc. The molded articles can be used as members for constituting electrodes, wiring, substrates, stretchable and bendable movable members, exterior members, etc. used in these devices.

[0037] A structure comprising a cured product (molded article) of the silicone rubber-based curable composition can be used for various applications.

[0038] Structures comprising the cured product (silicone rubber) of the silicone rubber-based curable composition of this embodiment can be used, for example, for medical applications such as medical instruments and equipment; for automobiles; for robot applications such as industrial robots; for electronic devices; for production equipment and daily life applications such as vibration-proofing materials, seismic isolation materials, and food hoses; and for roller components.

[0039] The silicone rubber of this embodiment can be used for medical instruments and devices, and can be used to form part of, for example, medical tube materials, sealing materials, packing materials, connector materials, keypad materials, drive mechanisms, sensors, etc. For example, by applying the resin movable member of this embodiment to a medical tube, the medical tube has excellent kink resistance, scratch resistance, insertability, transparency, and also excellent restorability. Examples of medical tubes include medical catheters, manipulators, and leads.

[0040] The silicone rubber of the present embodiment can be used in applications such as industrial robots and the like, for example, to form part of drive mechanisms such as joints; wiring mechanisms such as wiring cables and connectors; operating mechanisms such as manipulators; and the like.

[0041] As an example of applications for electronic devices, the silicone rubber of the present embodiment can form part of elastic wiring or wiring boards used in wearable devices that can be worn on the human body, etc.; cables such as optical fibers, flat cables, wiring structures, and cable guides; sensors such as touch panels, force sensors, MEMS, and seat sensors; and the like.

[0042] In addition, the silicone rubber of this embodiment can be used to form part of everyday items that have flexibility, extensibility, or foldability, such as packaging materials such as gas barrier films; cooking utensils; hoses; fixing belts; switches; sheet materials; and packing materials.

[0043] Each component of the silicone rubber-based hardenable composition of this embodiment will be described in detail.

[0044] <<Vinyl-containing organopolysiloxane (A)>> The silicone rubber-based hardening composition of the present embodiment contains a vinyl group-containing organopolysiloxane (A). The vinyl group-containing organopolysiloxane (A) is a polymer that is the main component of the silicone rubber-based hardening composition.

[0045] The vinyl group-containing organopolysiloxane (A) can contain a vinyl group-containing linear organopolysiloxane (A1) having a linear structure.

[0046] The vinyl group-containing linear organopolysiloxane (A1) has a linear structure and contains vinyl groups, and these vinyl groups become crosslinking points during curing.

[0047] The vinyl group content of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but for example, it is preferable that the vinyl group content is 15 mol% or less, and more preferably 0.01 to 12 mol%, and that the vinyl group content is two or more in the molecule. This optimizes the amount of vinyl groups in the vinyl group-containing linear organopolysiloxane (A1), and ensures the formation of a network with each component described below.

[0048] In this specification, the vinyl group content refers to the mol % of vinyl group-containing siloxane units when all units constituting the vinyl group-containing linear organopolysiloxane (A1) are taken as 100 mol %, where it is considered that there is one vinyl group per vinyl group-containing siloxane unit.

[0049] The degree of polymerization of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but is, for example, preferably within the range of about 1000 to 10000, and more preferably about 2000 to 5000. The degree of polymerization can be determined, for example, as the polystyrene-equivalent number average degree of polymerization (or number average molecular weight) measured by GPC (gel permeation chromatography) using chloroform as a developing solvent.

[0050] The weight average molecular weight Mw of the vinyl group-containing linear organopolysiloxane (A1) is, for example, 5.0×10 4 ~1.0×10 6 Less than or equal to 1.0×10 5 ~9.0×10 5 , more preferably 3.0×10 5 ~8.0×10 5 It is also possible to use the following.

[0051] The vinyl group-containing linear organopolysiloxane (A1) may have a ratio Mw (weight average molecular weight) / Mn (number average molecular weight) of, for example, 1.5 or more and 4.0 or less, preferably 1.8 or more and 3.5 or less, and more preferably 2.0 or more and 2.8 or less. Note that Mw / Mn is the dispersity indicating the width of the molecular weight distribution.

[0052] There are no particular limitations on the specific gravity of the vinyl group-containing linear organopolysiloxane (A1), but it is preferable that it be in the range of about 0.9 to 1.1.

[0053] By using a vinyl group-containing linear organopolysiloxane (A1) having a degree of polymerization and specific gravity within the above ranges, it is possible to improve the heat resistance, flame retardancy, chemical stability, etc. of the resulting silicone rubber.

[0054] As the vinyl group-containing linear organopolysiloxane (A1), those having a structure represented by the following formula (1) are particularly preferred.

[0055] [ka]

[0056] In formula (1), R 1 is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, or a hydrocarbon group consisting of a combination thereof, each having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, and a propyl group, with a methyl group being preferred. Examples of the alkenyl group having 1 to 10 carbon atoms include a vinyl group, an allyl group, and a butenyl group, with a vinyl group being preferred. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

[0057] In formula (1), R 2is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, or a hydrocarbon group consisting of a combination thereof, each having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferable. Examples of the alkenyl group having 1 to 10 carbon atoms include a vinyl group, an allyl group, and a butenyl group. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

[0058] In formula (1), R 3 is a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, an aryl group, or a hydrocarbon group consisting of a combination thereof. Examples of the alkyl group having 1 to 8 carbon atoms include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferable. Examples of the aryl group having 1 to 8 carbon atoms include a phenyl group.

[0059] In addition, R in formula (1) 1 and R 2 Examples of the substituent of R include a methyl group and a vinyl group. 3 Examples of the substituent include a methyl group.

[0060] In addition, in formula (1), multiple R 1 are independent of each other and may be different or the same. 2 , and R 3 The same applies to R in formula (1). 1 and R 2 At least one of these is an alkenyl group.

[0061] Furthermore, m and n are the numbers of repeating units constituting the vinyl group-containing linear organopolysiloxane (A1) represented by formula (1), where m is an integer of 0 to 2000 and n is an integer of 1000 to 10000. m is preferably 0 to 1000 and n is preferably 2000 to 5000.

[0062] A specific example of the structure of the vinyl group-containing linear organopolysiloxane (A1) represented by formula (1) is that represented by the following formula (1-1).

[0063] [ka]

[0064] In formula (1-1), R 1 and R 2 are each independently a methyl group or a vinyl group, and at least one of them is a vinyl group. In the present specification, in the structure represented by formula (1-1), R 1 (A1-1) is a linear organopolysiloxane having a vinyl group (A1) in which only the terminal is a vinyl group, and (A1-2) is a linear organopolysiloxane having a structure represented by the formula (1-1) and R 1 (Terminal) and R 2 The vinyl group-containing linear organopolysiloxane (A1) in which (in the chain) is a vinyl group is represented as (A1-2).

[0065] The vinyl group-containing linear organopolysiloxane (A1) preferably has two or more vinyl groups in the molecule and has a vinyl group content of 15 mol% or less. By using a vinyl group-containing linear organopolysiloxane (A1) having a general vinyl group content as raw rubber, which is the raw material of silicone rubber, it is possible to more effectively form a crosslink density distribution in the crosslinked network of the silicone rubber. As a result, it is possible to more effectively increase the tear strength of the silicone rubber.

[0066] The vinyl group-containing linear organopolysiloxane (A1) preferably contains a first vinyl group-containing linear organopolysiloxane (A1-1) having two or more vinyl groups in the molecule and having a vinyl group content of 0.1 mol % or less. As the vinyl group-containing linear organopolysiloxane (A1), a first vinyl group-containing linear organopolysiloxane (A1-1) having two or more vinyl groups in the molecule and having a vinyl group content of 0.1 mol % or less may be used alone, or two or more kinds including a second vinyl group-containing linear organopolysiloxane (A1-2) having a vinyl group content of more than 0.1 to 15 mol % may be used in combination.

[0067] <<Organohydrogenpolysiloxane (B)>> The silicone rubber-based hardenable composition of this embodiment may contain an organohydrogenpolysiloxane (B). The organohydrogenpolysiloxane (B) is classified into a linear organohydrogenpolysiloxane (B1) having a linear structure and a branched organohydrogenpolysiloxane (B2) having a branched structure, and may contain either one or both of these.

[0068] The linear organohydrogenpolysiloxane (B1) has a linear structure and a structure in which hydrogen is directly bonded to Si (≡Si-H), and is a polymer that undergoes a hydrosilylation reaction with the vinyl groups of the vinyl group-containing organopolysiloxane (A) and with vinyl groups of components blended into the silicone rubber-based curable composition, thereby crosslinking these components.

[0069] The molecular weight of the linear organohydrogenpolysiloxane (B1) is not particularly limited, but for example, the weight average molecular weight is preferably 20,000 or less, and more preferably 1,000 or more and 10,000 or less.

[0070] The weight average molecular weight of the linear organohydrogenpolysiloxane (B1) can be measured, for example, by polystyrene conversion in gel permeation chromatography (GPC) using chloroform as a developing solvent.

[0071] Furthermore, it is usually preferred that the linear organohydrogenpolysiloxane (B1) does not have a vinyl group, which can reliably prevent the crosslinking reaction from proceeding within the molecule of the linear organohydrogenpolysiloxane (B1).

[0072] As the linear organohydrogenpolysiloxane (B1) as described above, for example, one having a structure represented by the following formula (2) is preferably used.

[0073] [ka]

[0074] In formula (2), R 4 is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, a hydrocarbon group combining these groups, or a hydride group having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, etc., and among these, a methyl group is preferable. Examples of the alkenyl group having 1 to 10 carbon atoms include a vinyl group, an allyl group, a butenyl group, etc. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

[0075] Also, R 5 is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, a hydrocarbon group combining these groups, or a hydride group having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferable. Examples of the alkenyl group having 1 to 10 carbon atoms include a vinyl group, an allyl group, and a butenyl group. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

[0076] In addition, in formula (2), multiple R 4 are independent of each other and may be different or the same. 5 The same applies to R. 4 and R5 At least two of these are hydride groups.

[0077] Also, R 6 is a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, an aryl group, or a hydrocarbon group combining these. Examples of the alkyl group having 1 to 8 carbon atoms include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferable. Examples of the aryl group having 1 to 8 carbon atoms include a phenyl group. 6 are independent of each other and may be different from each other or may be the same.

[0078] In addition, R in formula (2) 4 ,R 5 ,R 6 Examples of the substituent include a methyl group and a vinyl group, and from the viewpoint of preventing an intramolecular crosslinking reaction, a methyl group is preferred.

[0079] Furthermore, m and n are the numbers of repeating units constituting the linear organohydrogenpolysiloxane (B1) represented by formula (2), where m is an integer of 2 to 150 and n is an integer of 2 to 150. Preferably, m is an integer of 2 to 100 and n is an integer of 2 to 100.

[0080] The linear organohydrogenpolysiloxane (B1) may be used alone or in combination of two or more kinds.

[0081] Since the branched organohydrogenpolysiloxane (B2) has a branched structure, it forms regions with high crosslink density, and is a component that greatly contributes to the formation of a sparsely-dense structure of crosslink density in the silicone rubber system. Also, like the linear organohydrogenpolysiloxane (B1), it has a structure in which hydrogen is directly bonded to Si (≡Si-H), and undergoes a hydrosilylation reaction with the vinyl groups of the vinyl group-containing organopolysiloxane (A) and with the vinyl groups of the components blended in the silicone rubber-based hardening composition, forming a polymer that crosslinks these components.

[0082] The specific gravity of the branched organohydrogenpolysiloxane (B2) is in the range of 0.9 to 0.95.

[0083] Furthermore, it is usually preferred that the branched organohydrogenpolysiloxane (B2) does not have a vinyl group, which can reliably prevent the crosslinking reaction from proceeding within the molecule of the branched organohydrogenpolysiloxane (B2).

[0084] As the branched organohydrogenpolysiloxane (B2), one represented by the following average composition formula (c) is preferred.

[0085] Average composition formula (c) (H a (R 7 ) 3-a SiO 1 / 2 ) m (SiO 4 / 2 ) n (In formula (c), R 7 is a monovalent organic group, a is an integer ranging from 1 to 3, and m is H a (R 7 ) 3-a SiO 1 / 2 The number of units, n, is SiO 4 / 2 (the number of units)

[0086] In formula (c), R 7 is a monovalent organic group, preferably a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, an aryl group, or a hydrocarbon group consisting of a combination thereof. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferred. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

[0087] In formula (c), a is the number of hydride groups (hydrogen atoms directly bonded to Si) and is an integer ranging from 1 to 3, and preferably 1.

[0088] In addition, in formula (c), m is H a(R 7 ) 3-a SiO 1 / 2 The number of units, n, is SiO 4 / 2 It is the number of units.

[0089] The branched organohydrogenpolysiloxane (B2) has a branched structure. The linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) differ in that their structures are linear or branched, and the number of alkyl groups R bonded to Si (R / Si) when the number of Si is 1 is in the range of 1.8 to 2.1 for the linear organohydrogenpolysiloxane (B1) and 0.8 to 1.7 for the branched organohydrogenpolysiloxane (B2).

[0090] Since the branched organohydrogenpolysiloxane (B2) has a branched structure, for example, when heated in a nitrogen atmosphere to 1000° C. at a heating rate of 10° C. / min, the amount of residue is 5% or more. In contrast, since the linear organohydrogenpolysiloxane (B1) is linear, the amount of residue after heating under the above conditions is almost zero.

[0091] Specific examples of the branched organohydrogenpolysiloxane (B2) include those having a structure represented by the following formula (3).

[0092] [ka]

[0093] In formula (3), R 7 R is a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, an aryl group, or a hydrocarbon group combining these, or a hydrogen atom. Examples of the alkyl group having 1 to 8 carbon atoms include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferable. Examples of the aryl group having 1 to 8 carbon atoms include a phenyl group. 7 Examples of the substituent include a methyl group.

[0094] In addition, in formula (3), multiple R 7 are independent of each other and may be different from each other or may be the same.

[0095] In addition, in formula (3), "-O-Si≡" indicates that Si has a branched structure extending three-dimensionally.

[0096] The branched organohydrogenpolysiloxane (B2) may be used alone or in combination of two or more kinds.

[0097] In addition, the amount of hydrogen atoms (hydride groups) directly bonded to Si in the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) is not particularly limited. However, in the silicone rubber-based curable composition, the total amount of hydride groups in the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) is preferably 0.5 to 5 moles, more preferably 1 to 3.5 moles, per mole of vinyl group in the vinyl group-containing linear organopolysiloxane (A1). This ensures that a crosslinked network is formed between the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) and the vinyl group-containing linear organopolysiloxane (A1).

[0098] <<Silica particles (C)>> The silicone rubber-based hardenable composition of this embodiment contains silica particles (C).

[0099] The silica particles (C) are not particularly limited, but for example, fumed silica, calcined silica, precipitated silica, etc. may be used. These may be used alone or in combination of two or more. The silica particles (C) may contain one or more types of silica particles surface-treated with a silane coupling agent (D).

[0100] The silica particles (C) have a specific surface area of, for example, 200 m2 as measured by the BET method. 2 / g~500m 2 / g, 220m 2 / g~400m 2 / g, and 250m 2 / g~400m 2 It is more preferable that the weight ratio is 1 / g. The average primary particle size of the silica particles (C) is, for example, preferably from 1 to 100 nm, and more preferably from about 5 to 20 nm.

[0101] By using silica particles (C) having a specific surface area and average particle size within this range, it is possible to improve the hardness and mechanical strength, particularly the tensile strength, of the silicone rubber that is formed.

[0102] <<Silane coupling agent (D)>> The silicone rubber-based hardenable composition of this embodiment may contain a silane coupling agent (D). The silane coupling agent (D) may have a hydrolyzable group. The hydrolyzable group is hydrolyzed by water to become a hydroxyl group, and the hydroxyl group undergoes a dehydration condensation reaction with the hydroxyl group on the surface of the silica particles (C), thereby modifying the surface of the silica particles (C).

[0103] The silane coupling agent (D) may include a silane coupling agent having a hydrophobic group. As the silane coupling agent having a hydrophobic group, a silane coupling agent having a trimethylsilyl group may be used. This provides the surface of the silica particles (C) with this hydrophobic group, so that the cohesive force of the silica particles (C) in the silicone rubber-based hardening composition and thus in the silicone rubber is reduced (there is less cohesion due to hydrogen bonds caused by silanol groups), and as a result, it is presumed that the dispersibility of the silica particles in the silicone rubber-based hardening composition is improved. This increases the interface between the silica particles and the rubber matrix, and the reinforcing effect of the silica particles is enhanced. Furthermore, it is presumed that the slipperiness of the silica particles in the matrix is ​​improved during deformation of the rubber matrix. And, due to the improvement in the dispersibility and slipperiness of the silica particles (C), the mechanical strength (for example, tensile strength, tear strength, etc.) of the silicone rubber due to the silica particles (C) is improved.

[0104] The silane coupling agent (D) may also contain a silane coupling agent having a vinyl group. This allows the vinyl group to be introduced onto the surface of the silica particles (C). Therefore, when the silicone rubber-based curable composition is cured, the vinyl group of the silica particles (C) also participates in the crosslinking reaction when a network (crosslinked structure) is formed, so that the silica particles (C) are also incorporated into the network. This allows the formed silicone rubber to have a low hardness and a high modulus.

[0105] As the silane coupling agent (D), a silane coupling agent having a hydrophobic group and a silane coupling agent having a vinyl group can be used in combination. This allows the balance between the dispersibility of silica in the rubber and the crosslinking property of the rubber to be achieved. The silane coupling agent (D) may be used alone or in combination of two or more of them.

[0106] An example of the silane coupling agent (D) is one represented by the following formula (4).

[0107] Y n -Si-(X) 4-n (4) In the above formula (4), n represents an integer of 1 to 3. Y represents any functional group having a hydrophobic group, a hydrophilic group, or a vinyl group, and when n is 1, it is a hydrophobic group, and when n is 2 or 3, at least one of them is a hydrophobic group. X represents a hydrolyzable group.

[0108] The hydrophobic group is an alkyl group having 1 to 6 carbon atoms, an aryl group, or a hydrocarbon group formed by combining these groups, and examples thereof include a methyl group, an ethyl group, a propyl group, and a phenyl group, with a methyl group being particularly preferred.

[0109] In addition, the hydrophilic group may be, for example, a hydroxyl group, a sulfonic acid group, a carboxyl group, or a carbonyl group, and among these, a hydroxyl group is particularly preferred. Note that, although a hydrophilic group may be included as a functional group, it is preferable that the hydrophilic group is not included from the viewpoint of imparting hydrophobicity to the silane coupling agent (D).

[0110] Further, examples of the hydrolyzable group include alkoxy groups such as methoxy and ethoxy groups, chloro groups, and silazane groups. Among these, silazane groups are preferred because of their high reactivity with the silica particles (C). In addition, those having a silazane group as a hydrolyzable group can be easily obtained by adding (Y n -Si-) structures.

[0111] Specific examples of the silane coupling agent (D) represented by the above formula (4) are as follows. Examples of the functional group having a hydrophobic group include alkoxysilanes such as methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, and decyltrimethoxysilane; chlorosilanes such as methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, and phenyltrichlorosilane; and hexamethyldisilazane.Among these, the silane coupling agent having a trimethylsilyl group, which includes one or more selected from the group consisting of hexamethyldisilazane, trimethylchlorosilane, trimethylmethoxysilane, and trimethylethoxysilane, is preferred.

[0112] Examples of the functional group having a vinyl group include alkoxysilanes such as methacryloxypropyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, methacryloxypropylmethyldimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, and vinylmethyldimethoxysilane; chlorosilanes such as vinyltrichlorosilane and vinylmethyldichlorosilane; and divinyltetramethyldisilazane.Among these, preferred is a silane coupling agent having a vinyl group-containing organosilyl group, including one or more selected from the group consisting of methacryloxypropyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, methacryloxypropylmethyldimethoxysilane, divinyltetramethyldisilazane, vinyltriethoxysilane, vinyltrimethoxysilane, and vinylmethyldimethoxysilane.

[0113] Furthermore, when the silane coupling agent (D) contains two types of silane coupling agents, a silane coupling agent having a trimethylsilyl group and a silane coupling agent having a vinyl group-containing organosilyl group, it is preferable that the silane coupling agent having the hydrophobic group is hexamethyldisilazane, and the silane coupling agent having the vinyl group is divinyltetramethyldisilazane.

[0114] When the silane coupling agent (D1) having a trimethylsilyl group and the silane coupling agent (D2) having a vinyl-containing organosilyl group are used in combination, the ratio of (D1) to (D2) is not particularly limited, but for example, the weight ratio of (D1):(D2) is 1:0.001 to 1:0.35, preferably 1:0.01 to 1:0.20, more preferably 1:0.03 to 1:0.15. By making it such a numerical range, the desired physical properties of the silicone rubber in the silicone rubber can be obtained. Specifically, the dispersibility of silica in the rubber and the crosslinking property of the rubber can be balanced.

[0115] <<Platinum or platinum compounds (E)>> The silicone rubber-based hardenable composition of this embodiment may contain platinum or a platinum compound (E). Platinum or a platinum compound (E) is a catalytic component that acts as a catalyst during curing. The amount of platinum or a platinum compound (E) added is a catalytic amount.

[0116] As the platinum or platinum compound (E), known substances can be used, such as platinum black, platinum supported on silica or carbon black, chloroplatinic acid or an alcohol solution of chloroplatinic acid, a complex salt of chloroplatinic acid and an olefin, and a complex salt of chloroplatinic acid and a vinylsiloxane.

[0117] The platinum or platinum compound (E) may be used alone or in combination of two or more kinds.

[0118] The silicone rubber-based hardenable composition of this embodiment may also contain an organic peroxide (H). The organic peroxide (H) is a component that acts as a catalyst during curing. The amount of organic peroxide (H) added is a catalytic amount. The organic peroxide (H) can be used in place of the organohydrogenpolysiloxane (B) and platinum or a platinum compound (E), or the organohydrogenpolysiloxane (B) and platinum or a platinum compound (E) can be used in combination with the organic peroxide (H).

[0119] Examples of the organic peroxides (H) include ketone peroxides, diacyl peroxides, hydroperoxides, dialkyl peroxides, peroxyketals, alkyl peresters, peroxyesters, and peroxydicarbonates. Specific examples include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, o-methylbenzoyl peroxide, dicumyl peroxide, 2,5-dimethyl-bis(2,5-t-butylperoxy)hexane, di-t-butyl peroxide, t-butyl perbenzoate, 1,6-hexanediol-bis-t-butylperoxycarbonate, and the like.

[0120] <<Water(F)>> Furthermore, the silicone rubber-based hardening composition of this embodiment may contain water (F) in addition to the above components (A) to (E) and (H).

[0121] Water (F) functions as a dispersion medium for dispersing each component contained in the silicone rubber-based hardening composition, and is also a component that contributes to the reaction between the silica particles (C) and the silane coupling agent (D). Therefore, the silica particles (C) and the silane coupling agent (D) can be more reliably linked to each other in the silicone rubber, and uniform properties can be exhibited overall.

[0122] Furthermore, the silicone rubber-based hardening composition of this embodiment may contain, in addition to the above components (A) to (F), known additive components that are blended into silicone rubber-based hardening compositions. Examples include diatomaceous earth, iron oxide, zinc oxide, titanium oxide, barium oxide, magnesium oxide, cerium oxide, calcium carbonate, magnesium carbonate, zinc carbonate, glass wool, mica, etc. In addition, dispersants, pigments, dyes, antistatic agents, antioxidants, flame retardants, thermal conductivity improvers, etc. may be blended as appropriate.

[0123] In the silicone rubber-based hardening composition, the content ratio of each component is not particularly limited, but is set, for example, as follows.

[0124] In this embodiment, the upper limit of the content of the silica particles (C) may be, for example, 60 parts by weight or less, preferably 50 parts by weight or less, and more preferably 35 parts by weight or less, based on 100 parts by weight of the total amount of the vinyl group-containing organopolysiloxane (A). This allows for a good balance of mechanical strength such as hardness and tensile strength. The lower limit of the content of the silica particles (C) is not particularly limited, but may be, for example, 10 parts by weight or more, based on 100 parts by weight of the total amount of the vinyl group-containing organopolysiloxane (A).

[0125] The silane coupling agent (D) is preferably contained in an amount of 5 parts by weight or more and 100 parts by weight or less, more preferably 5 parts by weight or more and 40 parts by weight or less, per 100 parts by weight of the vinyl group-containing organopolysiloxane (A), which can reliably improve the dispersibility of the silica particles (C) in the silicone rubber-based curable composition.

[0126] The content of the organohydrogenpolysiloxane (B) is preferably, for example, 0.5 parts by weight or more and 20 parts by weight or less, and more preferably 0.8 parts by weight or more and 15 parts by weight or less, based on 100 parts by weight of the total amount of the vinyl group-containing organopolysiloxane (A), the silica particles (C), and the silane coupling agent (D). By keeping the content of (B) within the above range, a more effective curing reaction may be achieved.

[0127] The content of platinum or platinum compound (E) means the amount of catalyst, and can be appropriately set, but specifically, the amount of platinum group metal in this component is 0.01 to 1000 ppm by weight, preferably 0.1 to 500 ppm, based on 100 parts by weight of the total amount of vinyl group-containing organopolysiloxane (A), silica particles (C), and silane coupling agent (D). By making the content of platinum or platinum compound (E) above the lower limit, the obtained silicone rubber composition can be sufficiently cured. By making the content of platinum or platinum compound (E) below the upper limit, the curing speed of the obtained silicone rubber composition can be improved.

[0128] The content of the organic peroxide (H) means the amount of catalyst, and can be set appropriately, but specifically, for example, 0.001 parts by weight or more, preferably 0.005 parts by weight or more, more preferably 0.01 parts by weight or more, based on 100 parts by weight of the total amount of the vinyl group-containing organopolysiloxane (A), the silica particles (C), and the silane coupling agent (D). This ensures the minimum strength of the cured product. In addition, the upper limit of the content of the organic peroxide (H) is, for example, 10 parts by weight or less, preferably 5 parts by weight or less, more preferably 3 parts by weight or less, based on 100 parts by weight of the total amount of the vinyl group-containing organopolysiloxane (A), the silica particles (C), and the silane coupling agent (D). This can suppress the influence of by-products.

[0129] Furthermore, when water (F) is contained, its content can be appropriately set, but specifically, for example, it is preferably in the range of 10 to 100 parts by weight, more preferably in the range of 30 to 70 parts by weight, relative to 100 parts by weight of the silane coupling agent (D). This makes it possible to more reliably proceed with the reaction between the silane coupling agent (D) and the silica particles (C).

[0130] <Silicone rubber manufacturing method> Next, a method for producing the silicone rubber of this embodiment will be described. In the method for producing the silicone rubber of this embodiment, a silicone rubber-based hardening composition is prepared, and the silicone rubber can be obtained by hardening the silicone rubber-based hardening composition. Details are provided below.

[0131] First, the components of the silicone rubber-based hardening composition are mixed uniformly using any kneading device to prepare the silicone rubber-based hardening composition.

[0132] [1] For example, a predetermined amount of vinyl group-containing organopolysiloxane (A), silica particles (C), and a silane coupling agent (D) are weighed out, and then kneaded using any kneading device to obtain a kneaded product containing these components (A), (C), and (D).

[0133] It is preferable to prepare this mixture by first kneading the vinyl-containing organopolysiloxane (A) with the silane coupling agent (D) and then kneading (mixing) the silica particles (C), which improves the dispersibility of the silica particles (C) in the vinyl-containing organopolysiloxane (A).

[0134] In addition, when obtaining this kneaded product, water (F) may be added to the kneaded product of the components (A), (C), and (D) as necessary, which allows the reaction between the silane coupling agent (D) and the silica particles (C) to proceed more reliably.

[0135] Furthermore, it is preferable that the kneading of each of the components (A), (C), and (D) is carried out through a first step of heating at a first temperature and a second step of heating at a second temperature. This allows the surface of the silica particles (C) to be surface-treated with the coupling agent (D) in the first step, and allows the by-products generated by the reaction between the silica particles (C) and the coupling agent (D) to be reliably removed from the kneaded product in the second step. After that, the component (A) may be added to the obtained kneaded product as necessary, and further kneaded. This allows the compatibility of the components in the kneaded product to be improved.

[0136] The first temperature is preferably, for example, about 40 to 120° C., and more preferably, for example, about 60 to 90° C. The second temperature is preferably, for example, about 130 to 210° C., and more preferably, for example, about 160 to 180° C.

[0137] Moreover, the atmosphere in the first step is preferably an inert atmosphere such as a nitrogen atmosphere, and the atmosphere in the second step is preferably a reduced pressure atmosphere.

[0138] Furthermore, the time for the first step is, for example, preferably about 0.3 to 1.5 hours, and more preferably about 0.5 to 1.2 hours, and the time for the second step is, for example, preferably about 0.7 to 3.0 hours, and more preferably about 1.0 to 2.0 hours.

[0139] By setting the above conditions for the first and second steps, the above effects can be obtained more significantly.

[0140] [2] Next, the organohydrogenpolysiloxane (B) and platinum or a platinum compound (E) are weighed out in predetermined amounts, and then the components (B) and (E) are kneaded into the mixture prepared in the above step [1] using any kneading device to obtain a silicone rubber-based curable composition. The obtained silicone rubber-based curable composition may be a paste containing a solvent.

[0141] In addition, when mixing the components (B) and (E), it is preferable to mix the mixture prepared in the above step [1] with the organohydrogenpolysiloxane (B) and the mixture prepared in the above step [1] with platinum or a platinum compound (E), and then mix the mixtures together. This allows the components (A) to (E) to be reliably dispersed in the silicone rubber-based curable composition without allowing the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B) to proceed.

[0142] The temperature at which the components (B) and (E) are kneaded is, for example, preferably about 10 to 70°C, and more preferably about 25 to 30°C, as the roll setting temperature.

[0143] Furthermore, the kneading time is, for example, preferably about 5 minutes to 1 hour, and more preferably about 10 to 40 minutes.

[0144] In the above steps [1] and [2], by setting the temperature within the above range, the progress of the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B) can be more reliably prevented or inhibited. In addition, in the above steps [1] and [2], by setting the kneading time within the above range, the components (A) to (E) can be more reliably dispersed in the silicone rubber-based curable composition.

[0145] The kneading device used in each of steps [1] and [2] is not particularly limited, but for example, a kneader, a two-roll mill, a Banbury mixer (continuous kneader), a pressure kneader, etc. can be used.

[0146] In addition, a reaction inhibitor such as 1-ethynylcyclohexanol may be added to the kneaded mixture in step [2], which makes it possible to more effectively prevent or inhibit the progress of the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B) even if the temperature of the kneaded mixture is set to a relatively high temperature.

[0147] In step [2], an organic peroxide (H) may be added in place of the organohydrogenpolysiloxane (B) and platinum or a platinum compound (E), or in combination with the organohydrogenpolysiloxane (B) and platinum or a platinum compound (E). The preferred conditions, such as temperature and time, and the apparatus used when kneading the organic peroxide (H) are the same as those used when kneading the organohydrogenpolysiloxane (B) and platinum or a platinum compound (E).

[0148] [3] Next, the silicone rubber-based hardenable composition is hardened to form a silicone rubber.

[0149] In this embodiment, the curing step of the silicone rubber-based curable composition is carried out, for example, by heating at 100 to 250° C. for 1 to 30 minutes (first curing) and then post-baking at 200° C. for 1 to 4 hours (second curing). By going through the steps described above, the silicone rubber of the present embodiment is obtained.

[0150] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various configurations other than those described above can be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of the present invention are included in the present invention. EXAMPLES

[0151] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the descriptions of these examples.

[0152] The raw material components used in the examples and comparative examples shown in Table 1 are shown below. (Vinyl-containing organopolysiloxane (A)) Vinyl-containing linear organopolysiloxane (A1-1a): Vinyl-containing dimethylpolysiloxane (having the structure represented by formula (1-1) and R 1 (Structure in which only the terminal is vinyl group) Vinyl-containing linear organopolysiloxane (A1-1b): Vinyl-containing dimethylpolysiloxane (having the structure represented by formula (1-1) and R 1 (Structure in which only the terminal is vinyl group) Vinyl-containing linear organopolysiloxane (A1-2a): Vinyl-containing dimethylpolysiloxane (having the structure represented by formula (1-1) and R 1 (Terminal) and R 2 (Structure in which the (inner chain) is a vinyl group) Vinyl-containing linear organopolysiloxane (A1-2b): Vinyl-containing dimethylpolysiloxane (having the structure represented by formula (1-1) and R 1 (Terminal) and R 2 (Structure in which the (inner chain) is a vinyl group)

[0153] (Organohydrogenpolysiloxane (B)) Momentive: "TC-25D"

[0154] (Silica particles (C)) Silica particles (C-1): Silica particles (particle size 7 nm, specific surface area 300 m 2 / g), Nippon Aerosil Co., Ltd., "AEROSIL 300" Silica particles (C-2): Silica particles (particle size 16 nm, specific surface area 110 m 2 / g), Nippon Aerosil Co., Ltd., "AEROSIL R972"

[0155] (Silane coupling agent (D)) Silane coupling agent (D-1): Hexamethyldisilazane (HMDZ), manufactured by Gelest, "HEXAMETHYLDISILAZANE (SIH6110.1)" Silane coupling agent (D-2): Divinyltetramethyldisilazane, manufactured by Gelest, "1,3-DIVINYLTETRAMETHYLDISILAZANE (SID4612.0)"

[0156] (Platinum or platinum compounds (E)) Momentive: "TC-25A"

[0157] (Synthesis of vinyl group-containing organopolysiloxane (A))

[0158] [Synthesis Scheme 1: Synthesis of vinyl group-containing linear organopolysiloxane (A1-1a)] A low-vinyl-group-containing linear organopolysiloxane (A1-1a) was synthesized according to the following formula (5). That is, 74.7 g (252 mmol) of octamethylcyclotetrasiloxane and 0.1 g of potassium siliconate were placed in a 300 mL separable flask equipped with a cooling tube and stirring blade and replaced with Ar gas, and the temperature was raised and the mixture was stirred at 120° C. for 30 minutes. At this time, an increase in viscosity was confirmed. The mixture was then heated to 155° C. and stirred for 3 hours, after which 0.1 g (0.6 mmol) of 1,3-divinyltetramethyldisiloxane was added and the mixture was stirred at 155° C. for an additional 4 hours. After four hours, the mixture was diluted with 250 mL of toluene and then washed three times with water. The washed organic layer was washed several times with 1.5 L of methanol for reprecipitation purification, and the oligomer and polymer were separated. The resulting polymer was dried overnight at 60°C under reduced pressure to synthesize a low-vinyl-group-containing linear organopolysiloxane (A1-1a) (Mn = 2.2 × 10 5 , Mw=4.8×10 5 The vinyl group content calculated from H-NMR spectrum measurement was 0.039 mol %.

[0159] [ka]

[0160] [Synthesis Scheme 2: Synthesis of vinyl group-containing linear organopolysiloxane (A1-1b)] A linear organopolysiloxane (A1-1b) having a low vinyl group content (Mn=2.7×10 5 , Mw=5.2×10 5 The vinyl group content calculated from H-NMR spectrum measurement was 0.031 mol %.

[0161] [Synthesis Scheme 3: Synthesis of vinyl group-containing linear organopolysiloxane (A1-2a)] A vinyl group-containing linear organopolysiloxane (A1-2a) was synthesized as shown in the following formula (6) (Mn=2.5×10 5 , Mw=5.0×10 5 The vinyl group content calculated from H-NMR spectrum measurement was 0.130 mol %.

[0162] [ka]

[0163] [Synthesis Scheme 4: Synthesis of vinyl group-containing linear organopolysiloxane (A1-2b)] A vinyl-rich linear organopolysiloxane (A1-2b) was synthesized (Mn=2.5×10 5 , Mw=5.4×10 5 The vinyl group content calculated from H-NMR spectrum measurement was 2.826 mol %.

[0164] <Preparation of Silicone Rubber-Based Curable Composition> (Test Examples 1 to 5) A mixture of vinyl-containing organopolysiloxane (A), silane coupling agent (D) and water (F) was pre-kneaded in the ratios shown in Table 1 below, and then silica particles (C) were added to the mixture and further kneaded to obtain a kneaded product (silicone rubber compound). Here, the kneading after the addition of the silica particles (C) was carried out through a first step of kneading for 1 hour under conditions of 60 to 90°C in a nitrogen atmosphere for the coupling reaction, and a second step of kneading for 2 hours under conditions of 160 to 180°C in a reduced pressure atmosphere for the removal of the by-product (ammonia), followed by cooling and kneading for 20 minutes. Next, organohydrogenpolysiloxane (B) (TC-25D) and platinum or platinum compound (E) (TC-25A) were added to 100 parts by weight of the obtained kneaded product (silicone rubber compound) in the ratios shown in Table 1 below, and the mixture was kneaded with a roll to obtain a silicone rubber-based curable composition.

[0165] [Table 1]

[0166] <Dematcha type bending resistance test> The silicone rubber-based hardening composition thus obtained was subjected to a De Mattia bending test according to the following procedure, and the incision length of the test piece was measured after bending 10,000 times, 30,000 times, and 50,000 times. The evaluation results are shown in Table 2.

[0167] (Creating test pieces) In accordance with JIS K 6260, the obtained silicone rubber-based curable composition was placed in the molding space 30 of the mold 10 shown in Fig. 1, pressed at 170°C and 10 MPa for 15 minutes, and then heated at 200°C for 4 hours to prepare a rectangular test piece 50 (width: 25 mm, length: 150 mm, thickness: 6.3 mm) with a groove 60. In the center of the groove 60 of the obtained test piece 50, a cut 70 with a length of 2.03 mm was made parallel to the width direction using a blade, and a test piece 50 with a cut was obtained (Fig. 2). The cut 70 penetrated the test piece 50 in the thickness direction.

[0168] Fig. 1(a) is a top view of a mold 10, and Fig. 1(b) is a side cross-sectional view taken along line AA of the mold 10. The mold 10 has a curved protrusion 20 on the bottom surface of a molding space 30. FIG. 2(a) is a top view of the test piece 50 having a groove 60 in which a cut 70 is formed, and FIG. 2(b) is a side cross-sectional view of the test piece 50 as viewed from the arrow BB.

[0169] (procedure) As shown in FIG. 3, the test piece 50 obtained above (preparation of test piece) was held between a fixed grip 102 and a movable grip 104 of a testing machine 100 (DeMatia flex crack testing machine). Specifically, the distance between the two grips was maximized, and the test piece 50 was attached to the grips so that the center of the groove 60 of the test piece 50 was located at the center between the grips. At this time, the test piece 50 was held flat so as not to apply any extra strain. Next, the movable grip 104 was reciprocated up and down based on the fixed grip 102 under the following test conditions. The period from when the movable grip 104 approached the fixed grip 102 from the maximum distance to the reciprocating distance (the test piece 50 was bent) until the movable grip 104 then moved away to the maximum distance (the test piece 50 became flat) was defined as one reciprocating motion (one cycle), and the number of times that cycle (times) was defined as the number of bendings. The length (mm) of the notch 70 in the test piece 50 when the number of bending cycles was 10,000, 30,000, and 50,000 was measured using a digital caliper (manufactured by Mitutoyo Corporation). The length of the incision 70 was determined by averaging three measured values ​​obtained by performing the De Mattia bending test three times. The results are shown in Table 2. The rate of change in cut length was calculated based on the formula: L5 / L0. L0 is the initial cut length before the De Mattia type bending resistance test, and L1, L3, and L5 are the average cut lengths at 10,000, 30,000, and 50,000 bending cycles, respectively, after the De Mattia type bending resistance test.

[0170] (Test conditions) Test standard: JIS K 6260 (2017) compliant Testing machine: Demacha bending crack testing machine with low temperature chamber (manufactured by Yasuda Manufacturing Co., Ltd.) Test temperature: 23±2℃ Maximum distance between grippers: 75 mm (D in Fig. 3) max ) Reciprocating motion distance: 57 mm (D in Fig. 3) mv ) Conditioning: Before the first test, the specimen was left to stand at 23°C for 10 minutes. Before the second and third tests, the specimen was left to stand in the same environment for 5 minutes. Test speed: 300±10 times / min Number of tests: n=3

[0171] In the above-mentioned De Mattia bending endurance test, when the test piece broke after bending 10,000 times, 30,000 times, and 50,000 times, the value was 25.0 mm.

[0172] [Table 2]

[0173] Based on the obtained results of the cut length, Test Examples 1, 2, and 3 were designated as Examples 1, 2, and 3, and Test Examples 4 and 5 were designated as Comparative Examples 1 and 2.

[0174] The obtained silicone rubber-based hardening compositions of each of the Examples and Comparative Examples were evaluated based on the following evaluation items.

[0175] <Preparation of silicone rubber> The obtained silicone rubber-based hardening composition was pressed at 170°C and 10 MPa for 15 minutes to form a sheet having a thickness of 1 mm and was hardened primarily, and then heated at 200°C for 4 hours to be hardened secondary. In this manner, a sheet-shaped silicone rubber (cured product of the silicone rubber-based curable composition) was obtained.

[0176] Hardness was measured using two samples, n=5 for each sample, and the average of 10 measurements was used. Tensile stress and breaking elongation were measured using three samples, and the average of the three measurements was used. Tear strength was measured using five samples, and the average of the five measurements was used. The respective average values ​​are shown in Table 2.

[0177] (hardness) Six of the obtained 1 mm thick sheet-like silicone rubbers were laminated to prepare a 6 mm test piece. The type A durometer hardness of the obtained test piece was measured at 25°C in accordance with JIS K6253 (1997).

[0178] (tear strength) A crescent-shaped test piece was prepared in accordance with JIS K6252 (2001) using the obtained 1 mm-thick sheet-like silicone rubber, and the tear strength of the obtained crescent-shaped test piece was measured at 25° C. The unit is N / mm.

[0179] (Tensile strength) Using the obtained 1 mm thick sheet-like silicone rubber, dumbbell-shaped No. 3 test pieces were prepared in accordance with JIS K6251 (2004), and the tensile strength of the obtained dumbbell-shaped No. 3 test pieces was measured at 25°C. The unit is MPa.

[0180] (Elongation at break) Using the obtained 1 mm thick sheet-like silicone rubber, dumbbell-shaped No. 3 test pieces were prepared in accordance with JIS K6251 (2004), and the breaking elongation of the obtained dumbbell-shaped No. 3 test pieces was measured at 25°C. The breaking elongation was calculated by [chuck movement distance (mm)] ÷ [initial chuck distance (60 mm)] × 100. The unit is %.

[0181] (Durability evaluation) The silicone rubber-based curable compositions obtained in each Example and Comparative Example were cured at 170°C for 5 minutes and 200°C for 4 hours to prepare a cylindrical member (tube) having a thickness of 1 mm and an inner diameter of 2 mm. A durability test sample was prepared by inserting a steel wire (TRUSCO steel wire, small roll type, wire diameter 1.6 mm x 15 m) into the obtained cylindrical member, and a durability test was performed. Specifically, a 90° bending test was performed on the durability test sample 100 times to determine the durability. A cylindrical member that had no abnormal appearance after the test was marked with ○, and a cylindrical member that had cracks or breakage after the test was marked with ×.

[0182] It was found that the silicone rubber-based curable compositions of Examples 1 to 3 had excellent durability against repeated bending deformation when cured, compared with Comparative Examples 1 and 2. Such molded articles of the silicone rubber-based curable compositions of Examples 1 to 3 can be suitably used for flexible members, preferably wearable devices, and more preferably substrates for wearable devices. [Explanation of symbols]

[0183] 10. Mold 20 Convex 30 Molding space 50 test pieces 60 grooves 70 Cut 100 Testing Machine 102 Fixed gripping tool 104 Movable gripper

Claims

1. A silicone rubber-based curable composition used to form a flexible member that constitutes part of a wearable device having wiring or a wiring board, Vinyl group-containing organopolysiloxane (A), Organohydrogenpolysiloxane (B) and Silica particles (C) and A silane coupling agent (D) containing a vinyl group-containing silane coupling agent, Platinum or platinum compound (E), The vinyl group-containing organopolysiloxane (A) is Only use a first vinyl group-containing linear organopolysiloxane (A1-1) having a vinyl group content of 0.1 mol% or less, or The present invention comprises a first vinyl group-containing linear organopolysiloxane (A1-1) having a vinyl group content of 0.1 mol% or less, and a second vinyl group-containing linear organopolysiloxane (A1-2) having a vinyl group content of more than 0.1 to 15 mol%, The specific surface area of ​​the silica particles (C) measured by the BET method is 200 m² / g or more and 500 m² / g or less. The content of the silica particles (C) is 10 parts by weight or more and 60 parts by weight or less, based on 100 parts by weight of the total vinyl group-containing organopolysiloxane (A). A silicone rubber-based curable composition, The cured product of the silicone rubber-based curable composition, measured under the following conditions, has a durometer hardness A of 30 or less, a tear strength of 30 N / mm or more, and a tensile strength of 8.3 MPa or more. Using a test specimen made from the cured product of the silicone rubber-based curable composition, a demacha-type bending resistance test in accordance with JIS K 6260 is performed, and the rate of change in the cut length (L) of the test specimen after 50,000 bending cycles is measured according to the following procedure. ５ / L ０ ) is between 1.1 and 11.5, A silicone rubber-based curable composition. (procedure) The silicone rubber-based curable composition is pressed at 170°C and 10 MPa for 15 minutes, and then heated at 200°C for 4 hours to prepare test specimens of a predetermined shape in accordance with JIS K 6260. In the center of the obtained test specimen, a cut of a predetermined length is made parallel to the width direction and penetrates the test specimen. The initial cut length is L. ０ Let's assume that. Next, the test piece with the notch is placed between the grips of the testing machine, and a demacha-type bending resistance test is performed based on the following test conditions, and the length of the notch (mm) in the test piece after a predetermined number of bending cycles is measured. The cut length shall be the average value obtained from three Demacha bending tests. This average cut length shall be L ５ Let's assume that. The rate of change in the cutting depth is given by the formula: L ５ / L ０ It is calculated based on the following. (Test conditions) • Test standard: Compliant with JIS K 6260 • Testing machine: Demacha flexural crack tester • Test temperature: 23±2℃ Maximum distance between gripping parts: 75 mm ・Reciprocating distance: 57mm • Test speed: 300 ± 10 times / minute • Number of tests: n = 3 (Measurement conditions for durometer hardness A) A sheet-like test specimen is prepared using the cured product of the silicone rubber-based curable composition, and the durometer hardness A of the obtained sheet-like test specimen is measured at 25°C in accordance with JIS K6253 (1997). (Measurement conditions for tear strength) A crescent-shaped test specimen is prepared using the cured product of the silicone rubber-based curable composition, and the tear strength of the obtained crescent-shaped test specimen is measured at 25°C in accordance with JIS K6252 (2001). (Measurement conditions for tensile strength) A dumbbell-shaped test specimen of type 3 was prepared using the cured product of the silicone rubber-based curable composition, and the tensile strength of the obtained dumbbell-shaped test specimen of type 3 was measured at 25°C in accordance with JIS K6251 (2004).

2. A silicone rubber-based curable composition according to Claim 1, A Demacha-type bending resistance test is performed according to the above procedure, and when the number of bending cycles in the test piece is 10,000, the cut length in the test piece is L1, and L1 / L0 satisfies the condition of being 1.0 or more and 10.0 or less. A silicone rubber-based curable composition.

3. A silicone rubber-based curable composition according to claim 1 or 2, A silicone rubber-based curable composition in which the content of the silica particles (C) is 30 parts by weight or less per 100 parts by weight of the total vinyl group-containing organopolysiloxane (A).

4. A silicone rubber-based curable composition according to any one of claims 1 to 3, A silicone rubber-based curable composition in which the elongation at break of the cured product, measured under the following conditions, is 500% or more. (Measurement conditions for elongation at break) A dumbbell-shaped No. 3 test specimen was prepared using the cured product of the silicone rubber-based curable composition in accordance with JIS K6251 (2004), and the elongation at break of the obtained dumbbell-shaped No. 3 test specimen was measured at 25°C. The elongation at break was calculated as [chuck travel distance (mm)] ÷ [initial chuck distance (60 mm)] × 100. The unit is %.

5. A structure comprising a cured product of a silicone rubber-based curable composition according to any one of Claims 1 to 4.

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