JP2020143270A - Silicone rubber-based curable composition and structure comprising the same - Google Patents

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

The present invention relates to a silicone rubber-based curable composition and a structure thereof.

So far, various developments have been made in the durability of silicone rubber. As this kind of technique, for example, the technique described in Patent Document 1 is known. Patent Document 1 states that elongation fatigue resistance can be evaluated based on the number of elongations until it breaks by repeating 100% elongation operations, and that the number of elongations is 2.1 million times for silicone rubber (curing of a curable silicone rubber composition). (Things) are described (Example 1 of Patent Document 1).

Japanese Unexamined Patent Publication No. 2008-222849

However, as a result of examination by the present inventor, it has been found that there is room for improvement in the cured product of the curable silicone rubber composition described in Patent Document 1 in terms of durability against repeated bending deformation.

In the technical field of silicone rubber, studies on the characteristics at the time of elongation are generally performed.
However, the characteristics at the time of repeated bending have not been sufficiently studied.

As a result of the study by the present inventor, it has been found that the bending resistance of the silicone rubber-based curable composition can be evaluated during repeated bending by using the hoax-type bending resistance test. As a result of further examination, in accordance with JIS K 6260, after appropriately setting the test conditions for the hoax-type bending resistance test, the rate of change in the cut length in the test piece with a notch is used as an index to obtain such resistance. It was found that the flexibility can be controlled. Further diligent research based on these findings revealed that the rate of change in the cut length in the test piece when the number of bends was 50,000 was within a predetermined range, thereby forming a silicone rubber-based curable composition in a molded product. , It has been found that the durability against repeated bending deformation is improved, and the present invention has been completed.

According to the present invention
Vinyl group-containing organopolysiloxane (A) and
A silicone rubber-based curable composition containing silica particles (C).
Using a test piece made of a cured product of the silicone rubber-based curable composition, a hoax-type bending resistance test conforming to JIS K 6260 is performed, and the number of bendings is 50,000 times, which is measured based on the following procedure. The rate of change in cut length (L ₅ / L ₀ ) in the test piece is 1.1 or more and 11.5 or less.
A silicone rubber-based curable composition is provided.
(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 a test piece having a predetermined shape in accordance with JIS K 6260.
At the center of the obtained test piece, a notch having a predetermined length penetrating the test piece is made parallel to the width direction. Let L ₀ be the initial cut length.
Subsequently, the test piece with a notch is installed between the gripping tools of the testing machine, a hoax-type bending resistance test is performed based on the following test conditions, and the cutting length in the test piece after a predetermined number of bendings ( mm) is measured.
The cut length shall be the average value when the hoax type bending resistance test is performed three times. Let L _{5 be} the average value of this cut length.
The rate of change in cut length is calculated based on the formula: L ₅ / L ₀ .
(Test conditions)
・ Test standard: JIS K 6260 compliant ・ Testing machine: Demacha bending crack tester ・ Test temperature: 23 ± 2 ℃
・ Maximum distance between grippers: 75 mm
・ Reciprocating distance: 57mm
・ Test speed: 300 ± 10 times / minute ・ Number of tests: n = 3

Further, according to the present invention, there is provided a structure including a cured product of the silicone rubber-based curable composition.

According to the present invention, there is provided a silicone rubber-based curable composition capable of realizing a molded product having excellent durability against repeated bending deformation, and a structure thereof.

It is a schematic diagram which shows an example of the structure of a mold. It is a schematic diagram which shows an example of the structure of the test piece. It is a schematic diagram which shows an example of the structure of the hoax type tester.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all drawings, similar components are designated by the same reference numerals, and description thereof will be omitted as appropriate. Moreover, the figure is a schematic view and does not match the actual dimensional ratio.

The outline of the silicone rubber-based curable composition of the present embodiment will be described.

The silicone rubber-based curable composition of the present embodiment contains a vinyl group-containing organopolysiloxane (A) and silica particles (C), and a test piece composed of a cured product of the silicone rubber-based curable composition. The hoax-type bending resistance test conforming to JIS K 6260 was performed using the test piece, and the rate of change in cut length (L ₅ / L) in the test piece when the number of bendings was 50,000, which was measured based on the following procedure. ₀ ) satisfies 1.1 or more and 11.5 or less.

(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 a grooved test piece having a predetermined shape in accordance with JIS K 6260.
At the center of the groove of the obtained test piece, a notch having a predetermined length (2.03 mm) penetrating the test piece is made parallel to the width direction. Let L ₀ be the initial cut length.
Subsequently, the test piece with a notch is installed between the gripping tools of the testing machine, a hoax-type bending resistance test is performed based on the following test conditions, and the cutting length in the test piece after a predetermined number of bendings ( mm) is measured.
The cut length shall be the average value when the hoax type bending resistance test is performed three times. Let L _{5 be} the average value of this cut length.
The rate of change in cut length is calculated based on the formula: L ₅ / L ₀ .
(Test conditions)
・ Test standard: JIS K 6260 compliant ・ Testing machine: Demacha bending crack tester ・ Test temperature: 23 ± 2 ℃
・ Maximum distance between grippers: 75 mm
・ Reciprocating distance: 57mm
・ Test speed: 300 ± 10 times / minute ・ Number of tests: n = 3

According to the findings of the present inventor, it has been found that the bending resistance of a silicone rubber-based curable composition can be evaluated during repeated bending by using a hoax-type bending resistance test.
However, if an appropriate index is not set, the evaluation takes time and the evaluation may vary. For example, when the number of deformations until fracture is used as an index as in the 100% elongation fatigue life of Patent Document 1, the time until fracture becomes long, and the number of deformations may vary. In addition, when a non-cut product is used as the test piece and the fractured state is used as an index, a considerable number of bends are required until the fractured state is different, and even if there is a difference, the variation in the fractured state becomes large. It turned out that it would end up.

Therefore, as a result of further examination, in accordance with JIS K 6260, after appropriately setting the test conditions for the hoax-type bending resistance test, the rate of change in the notch length in the test piece with a notch was used as a guideline. It has been found that the bending resistance of the molded product of the silicone rubber-based curable composition at the time of repeated bending can be evaluated relatively quickly and stably, and the bending resistance can be controlled.

As a result of further diligent research based on these findings, the bending resistance during repeated bending is stably evaluated by using the rate of change in the incision length in the test piece when the number of bendings is 50,000 as an index. Furthermore, it has been found that by setting this index within the above-mentioned predetermined range, the durability of the silicone rubber-based curable composition in the molded product against repeated bending deformation can be improved.

Although the detailed mechanism is not clear, the characteristics of low hardness, high tear strength, and high fracture elongation can be improved in a well-balanced manner by appropriately adjusting the distance between crosslinks and the crosslink density using the above rate of change in incision as an index. It is considered that a silicone rubber structure having a small load at the time of bending can be obtained.

In the hoax-type bending resistance test, L ₀ is the initial cut length before the hoax-type bending resistance test, and L ₁ , L ₃ , and L ₅ are each bent 10,000 times after the hoax-type bending resistance test. The average value of the cut lengths when 30,000 times and 50,000 times are used.
At this time, the upper limit of the incision length change rate (L ₅ / L ₀ ) in the test piece when the number of times of bending is 50,000 is 11.5 or less, preferably 10.7 or less, more preferably 8.0. Hereinafter, it is more preferably 6.0 or less. As a result, it is possible to realize a molded body having excellent durability against repeated bending deformation and having mechanical strength as a member. The lower limit of the cut length change rate (L ₅ / L ₀ ) may be 1.0 or more, and may be 1.1 or more.

As a result of a hoax-type bending resistance test using the above silicone rubber-based curable composition, the upper limit of L ₁ / L ₀ is, for example, 10.0 or less, preferably 8.0 or less, more preferably 6.0 or less. More preferably, it is 4.0 or less. As a result, it is possible to realize a molded product having excellent durability against repeated bending deformation. Further, since the characteristics can be evaluated by a simpler evaluation method, the productivity of the silicone rubber-based curable composition can be improved. The lower limit of L ₁ / L ₀ may be 1.0 or more.

Further, when the initial cut length L ₀ is 2.03 mm, the cut length L ₅ in the test piece when the number of times of bending is 50,000 is, for example, 2.2 mm to 22.5 mm, preferably 2. It may be 3 mm to 18.0 mm, more preferably 2.5 mm to 15.0 mm.
In the present specification, "~" means that an upper limit value and a lower limit value are included unless otherwise specified.

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 with respect to 100 parts by weight of the vinyl group-containing organopolysiloxane (A). Good. 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 further preferably 30 parts by weight or less. As described above, by making the silica content relatively low, the durability against repeated bending deformation can be improved. By setting the content of the silica particles (C) to 35 parts by weight or less, the repeated bending durability can be stably increased.

In the present embodiment, for example, by appropriately selecting the type and blending amount of each component contained in the silicone rubber-based curable composition, the method for preparing the silicone rubber-based curable composition, the method for producing silicone rubber, and the like. It is possible to control the above-mentioned rate of change in cut length, the above-mentioned cut length, the following breaking elongation, tensile strength, tear strength, and hardness. Among these, for example, as the vinyl group-containing organopolysiloxane (A), a vinyl group-containing linear organopolysiloxane (A1-1) having a relatively small and small vinyl group and having a vinyl group only at the terminal is used. By controlling the crosslink density and crosslink structure of the resin, the timing and ratio of addition of the vinyl group-containing organopolysiloxane (A), the blending ratio of the silica particles (C), the specific surface area of the silica particles (C), and silica. Surface modification of the particles (C) with the silane coupling agent (D), addition of water, etc., for more reliable progress of the reaction between the silane coupling agent (D) and the silica particles (C), etc. However, the above-mentioned rate of change in cut length, cut length, the following breaking elongation, tensile strength, tear strength, and hardness can be mentioned as factors for setting a desired numerical range.

Next, the characteristics of the silicone rubber-based curable composition of the present embodiment will be described.

(Measurement conditions for tear strength)
A crescent-shaped test piece is prepared using the cured product of the above-mentioned silicone rubber-based curable composition, and the tear strength of the obtained crescent-shaped test piece is measured at 25 ° C. in accordance with JIS K6252 (2001).

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, still more preferably 33 N / mm or more. More preferably, it is 35 N / mm or more. As a result, the durability of the silicone rubber during repeated use can be improved. 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. Thereby, various characteristics of the silicone rubber can be balanced.

(Measurement conditions for elongation at break)
A dumbbell-shaped No. 3 test piece was prepared using the cured product of the above silicone rubber-based curable composition, and the obtained dumbbell-shaped No. 3 test piece was prepared at 25 ° C. in accordance with JIS K6251 (2004). Measure the elongation at break.

The lower limit of the elongation at break 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. Thereby, the high elasticity and durability of the silicone rubber can be improved. On the other hand, the upper limit of the elongation at break is not particularly limited, but may be, for example, 2000% or less, 1800% or less, or 1500% or less. Thereby, various characteristics of the silicone rubber can be balanced.

(Measurement conditions for durometer hardness A)
A sheet-shaped test piece was prepared using the cured product of the above silicone rubber-based curable composition, and the durometer hardness A of the obtained sheet-shaped test piece was measured at 25 ° C. in accordance with JIS K6253 (1997). To do.

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 makes it possible to balance the cured physical properties of the silicone rubber. Further, from the viewpoint of deformability, the upper limit of the durometer hardness A may be 40 or less, 35 or less, or 30 or less. As a result, it is possible to enhance the deformability of the silicone rubber, which facilitates 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, 10 or more, preferably 20 or more, and more preferably 25 or more. As a result, the mechanical strength of the silicone rubber can be increased.

(Measurement conditions for tensile strength)
A dumbbell-shaped No. 3 test piece was prepared using the cured product of the above silicone rubber-based curable composition, and the obtained dumbbell-shaped No. 3 test piece was prepared at 25 ° C. in accordance with JIS K6251 (2004). Measure the tensile strength.

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. Thereby, the mechanical strength of the silicone rubber can be improved. In addition, it is possible to realize a structure having excellent durability that can withstand repeated deformation. 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. Thereby, various characteristics of the silicone rubber can be balanced.

The cured product (silicone rubber) of the silicone rubber-based curable composition of the present embodiment is a molded product that has been processed and molded into various forms depending on the application. The molded body may be molded into various shapes such as a sheet shape, a tubular shape, and a bag shape.

Since the silicone rubber-based curable composition is excellent in durability against repeated bending modification, it can be suitably used for forming a molded product for a flexible member. The flexible member refers to a member that is repeatedly stressed in the bending direction under a usage environment, for example. This flexible member may be used in a usage environment where stress is applied in the expansion / contraction direction.

An example of the flexible member is a wearable device. That is, the silicone rubber-based curable composition can be suitably used for forming a molded product for a wearable device.

The wearable device is a wearable device that can be worn on the body or clothes, and includes, for example, a medical sensor that detects phenomena from a living body such as heart rate, electrocardiogram, blood pressure, and body temperature, a healthcare device, and a foldable display. Examples include stretchable LED arrays, stretchable solar cells, stretchable antennas, stretchable batteries, actuators, wearable computers and the like. The molded body can be used as a member for forming electrodes, wiring, a substrate, a movable member that can be expanded / contracted / bent, an exterior member, and the like used for these.

The structure including the cured product (molded product) of the silicone rubber-based curable composition can be used for various purposes.

Examples of the structure provided with the cured product (silicone rubber) of the silicone rubber-based curable composition of the present embodiment include medical applications such as medical instruments and equipment applications; automobile applications; robot applications such as industrial robots; electronic devices. Applications: Production equipment and daily applications such as anti-vibration materials, seismic isolation materials, food hoses; roller members; etc.

The silicone rubber of the present embodiment constitutes a part of, for example, a medical tube material; a sealing material; a packing material; a connector material; a keypad material; a drive mechanism; a sensor; etc., as an example of medical instruments / equipment applications. be able to. For example, by applying the resin movable member of the present embodiment to a medical tube, the medical tube is excellent in kink resistance, scratch resistance, insertability and transparency, and further excellent in resilience. Become. In addition, examples of the medical tube include a medical catheter, a manipulator, a lead, and the like.

The silicone rubber of the present embodiment constitutes a part of, for example, a drive mechanism such as a joint; a wiring mechanism such as a wiring cable and a connector; an operation mechanism such as a manipulator; as an example of robot use such as an industrial robot. Can be done.

The silicone rubber of the present embodiment is an example of an electronic device application, for example, a stretchable wiring or wiring substrate used for a wearable device that can be worn on the human body or the like; an optical fiber, a flat cable, a wiring structure, a cable. A part of a cable such as a guide; a sensor such as a touch panel, a force sensor, a MEMS, a seat sensor; and the like can be configured.

In addition, the silicone rubber of the present embodiment is one of living products having flexibility, extensibility or foldability such as packaging material such as gas barrier film; cooking utensil; hose; fixing belt; switch; sheet material; packing material; The part can be composed.

Each component of the silicone rubber-based curable composition of the present embodiment will be described in detail.

<< Vinyl group-containing organopolysiloxane (A) >>
The silicone rubber-based curable 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 curable composition.

The vinyl group-containing organopolysiloxane (A) can include a vinyl group-containing linear organopolysiloxane (A1) having a linear structure.

The vinyl group-containing linear organopolysiloxane (A1) has a linear structure and contains a vinyl group, and the vinyl group serves as a cross-linking point at the time of curing.

The content of the vinyl group of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but is preferably, for example, having two or more vinyl groups in the molecule and 15 mol% or less. , 0.01-12 mol%, more preferably. As a result, the amount of vinyl groups in the vinyl group-containing linear organopolysiloxane (A1) is optimized, and a network with each component described later can be reliably formed.

In the present specification, the vinyl group content is the mol% of the vinyl group-containing siloxane unit when all the units constituting the vinyl group-containing linear organopolysiloxane (A1) are 100 mol%. However, it is considered that there is one vinyl group for each vinyl group-containing siloxane unit.

The degree of polymerization of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but is preferably in the range of, for example, 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) in GPC (gel permeation chromatography) using chloroform as a developing solvent.

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 or less, preferably 1.0 × ¹⁰ 5 to 9.0 × 10 ^5, more preferably it is ^{3.0 × 10 5 ~8.0 × 10 5} .

The Mw (weight average molecular weight) / Mn (number average molecular weight) of the vinyl group-containing linear organopolysiloxane (A1) is, for example, 1.5 or more and 4.0 or less, preferably 1.8 or more and 3.5 or less. It may be preferably 2.0 or more and 2.8 or less. Mw / Mn is a degree of dispersion indicating the width of the molecular weight distribution.

The specific gravity of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but is preferably in the range of about 0.9 to 1.1.

By using a vinyl group-containing linear organopolysiloxane (A1) having a degree of polymerization and specific gravity within the above range, the obtained silicone rubber has heat resistance, flame retardancy, chemical stability, etc. Can be improved.

The vinyl group-containing linear organopolysiloxane (A1) preferably has a structure represented by the following formula (1).

In formula (1), R ¹ is a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, an alkenyl group, an aryl group, or a hydrocarbon group in which these are combined. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group and the like, and among them, 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 and the like, and among them, a vinyl group is preferable. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group and the like.

In formula (1), R ² is a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, an alkenyl group, an aryl group, or a hydrocarbon group in which these are combined. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group and the like, and among them, 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.

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 in which these are combined. Examples of the alkyl group having 1 to 8 carbon atoms include a methyl group, an ethyl group, a propyl group and the like, and among them, a methyl group is preferable. Examples of the aryl group having 1 to 8 carbon atoms include a phenyl group.

Further, examples of the substituent of R ¹ and R ^{2 in} the formula (1) include a methyl group, a vinyl group and the like, and examples of the substituent of R ³ include a methyl group and the like.

In the formula (1), a plurality of R ¹ is independent from each other, may be different from each other, it may be the same. The same applies to R ² and R ³ . Further, in the formula (1), at least one of a plurality of R ¹ and R ² is an alkenyl group.

Further, m and n are the number of repeating units constituting the vinyl group-containing linear organopolysiloxane (A1) represented by the formula (1), m is an integer of 0 to 2000, and n is 1000 to 10000. Is an integer of. m is preferably 0 to 1000, and n is preferably 2000 to 5000.

Further, as a specific structure of the vinyl group-containing linear organopolysiloxane (A1) represented by the formula (1), for example, the one represented by the following formula (1-1) can be mentioned.

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, a vinyl group-containing linear organopolysiloxane (A1) having a structure represented by the formula (1-1) and having only R ¹ (terminal) as a vinyl group is designated as (A1-1) and formula (1-). A vinyl group-containing linear organopolysiloxane (A1) having a structure represented by 1) in which R ¹ (terminal) and R ² (inside the chain) are vinyl groups is referred to as (A1-2).

The vinyl group-containing linear organopolysiloxane (A1) preferably has a vinyl group content of 2 or more vinyl groups in the molecule and is 15 mol% or less. By using a vinyl group-containing linear organopolysiloxane (A1) having a general vinyl group content as the raw rubber which is a raw material of the silicone rubber, the crosslink density of the silicone rubber can be more effectively determined in the crosslink network of the silicone rubber. Denseness can be formed. As a result, the tear strength of the silicone rubber can be increased more effectively.

The vinyl group-containing linear organopolysiloxane (A1) is a first vinyl group-containing straight chain having a vinyl group content of 2 or more in the molecule and 0.1 mol% or less. It preferably contains a state organopolysiloxane (A1-1).
The vinyl group-containing linear organopolysiloxane (A1) contains a first vinyl group having a vinyl group content of 2 or more in the molecule and 0.1 mol% or less. The linear organopolysiloxane (A1-1) may be used alone, but a second vinyl group-containing linear organopolysiloxane (A1-) having a vinyl group content of more than 0.1 to 15 mol%. 2) or more may be used in combination of two or more.

<< Organohydrogen Polysiloxane (B) >>
The silicone rubber-based curable composition of the present embodiment may contain organohydrogenpolysiloxane (B).
Organohydrogenpolysiloxane (B) is classified into linear organohydrogenpolysiloxane (B1) having a linear structure and branched organohydrogenpolysiloxane (B2) having a branched structure. Either one or both can be included.

The linear organohydrogenpolysiloxane (B1) has a linear structure and a structure in which hydrogen is directly bonded to Si (≡Si—H), and is a vinyl group-containing organopolysiloxane (A). In addition to the vinyl group, it is a polymer that hydrosilylates with the vinyl group of the component blended in the silicone rubber-based curable composition and crosslinks these components.

The molecular weight of the linear organohydrogenpolysiloxane (B1) is not particularly limited, but for example, the weight average molecular weight is preferably 20000 or less, and more preferably 1000 or more and 10000 or less.

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

Further, the linear organohydrogenpolysiloxane (B1) is usually preferably one having no vinyl group. As a result, it is possible to accurately prevent the cross-linking reaction from proceeding in the molecule of the linear organohydrogenpolysiloxane (B1).

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

In the formula (2), R ⁴ is a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, an alkenyl group, an aryl group, a hydrocarbon group combining these, or a hydride group. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group and the like, and among them, 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 and the like. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

Also, R ⁵ is a hydrocarbon group or a hydride group, in combination a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, an alkenyl group, an aryl group, these. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group and a propyl group, and among them, 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 and the like. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

In the formula (2), a plurality of R ⁴ are independent from each other, may be different from each other, it may be the same. The same is true for R ^5. However, of the plurality of R ⁴ and R ⁵ , at least two or more are hydride groups.

Further, R ⁶ is a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, an aryl group, or a hydrocarbon group in which these are combined. Examples of the alkyl group having 1 to 8 carbon atoms include a methyl group, an ethyl group, a propyl group and the like, and among them, a methyl group is preferable. Examples of the aryl group having 1 to 8 carbon atoms include a phenyl group. A plurality of R ⁶ are independent from each other, may be different from each other, it may be the same.

Examples of the substituent of R ⁴ , R ⁵ , and R ^{6 in} the formula (2) include a methyl group and a vinyl group, and a methyl group is preferable from the viewpoint of preventing an intramolecular cross-linking reaction.

Further, m and n are the number of repeating units constituting the linear organohydrogenpolysiloxane (B1) represented by the formula (2), m is an integer of 2 to 150, and n is 2 to 150. It is an integer. Preferably, m is an integer of 2 to 100 and n is an integer of 2 to 100.

As the linear organohydrogenpolysiloxane (B1), only one type may be used alone, or two or more types may be used in combination.

Since the branched organohydrogenpolysiloxane (B2) has a branched structure, it forms a region having a high crosslink density and is a component that greatly contributes to the formation of a sparsely packed structure with a crosslink density in the silicone rubber system. Further, like the linear organohydrogenpolysiloxane (B1), it has a structure (≡Si—H) in which hydrogen is directly bonded to Si, and in addition to the vinyl group of the vinyl group-containing organopolysiloxane (A), silicone. It is a polymer that hydrosilylates with the vinyl group of the component contained in the rubber-based curable composition and crosslinks these components.

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

Further, the branched organohydrogenpolysiloxane (B2) is usually preferably one having no vinyl group. As a result, it is possible to accurately prevent the cross-linking reaction from proceeding in the molecule of the branched organohydrogenpolysiloxane (B2).

Further, as the branched organohydrogenpolysiloxane (B2), those represented by the following average composition formula (c) are preferable.

Average composition formula (c)
^{_{(H a (R 7) 3}} -a SiO 1/2) m (SiO 4/2) n
(In the formula (c), ^{R 7} is a monovalent organic group, a is 1 to 3 in the range of integers, m is ^{_{H a (R 7) 3-}} a number of _{SiO 1/2} units, n represents SiO _{4 /} It is a number of ₂ units)

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 in combination thereof. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group and the like, and among them, a methyl group is preferable. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

In the formula (c), a is the number of hydride groups (hydrogen atoms directly bonded to Si), and is an integer in the range of 1 to 3, preferably 1.

Further, in the equation (c), m is ^{_{H a (R 7) 3-}} a number of _{SiO 1/2} units, n is the number of _{SiO 4/2} units.

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 are different from Si when the number of Si is 1. The number of alkyl groups R to be bonded (R / Si) is 1.8 to 2.1 for the linear organohydrogenpolysiloxane (B1) and 0.8 to 1 for the branched organohydrogenpolysiloxane (B2). It is in the range of 0.7.

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

Further, specific examples of the branched organohydrogenpolysiloxane (B2) include those having a structure represented by the following formula (3).

In formula (3), R ⁷ 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, a propyl group and the like, and among them, a methyl group is preferable. Examples of the aryl group having 1 to 8 carbon atoms include a phenyl group. Examples of the substituent of R ⁷ include a methyl group and the like.

In the equation (3), the plurality of R ^7s are independent of each other and may be different from each other or may be the same.

Further, in the equation (3), "-O-Si≡" indicates that Si has a branched structure that spreads three-dimensionally.

As the branched organohydrogenpolysiloxane (B2), only one type may be used alone, or two or more types may be used in combination.

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 linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpoly are added to 1 mol of the vinyl group in the vinyl group-containing linear organopolysiloxane (A1). The total amount of hydride groups of siloxane (B2) is preferably 0.5 to 5 mol, more preferably 1 to 3.5 mol. 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). Can be made to.

<< Silica particles (C) >>
The silicone rubber-based curable composition of the present embodiment contains silica particles (C).

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

Silica particles (C) are, for example, the specific surface area by the BET method for ^example, a 200m ² / g~500m 2 / ^g, is preferably from ^{220m 2 / g~400m 2 / g,} 250m 2 / g~400m More preferably, it is ² / g.
The average primary particle size of the silica particles (C) is preferably, for example, 1 to 100 nm, and more preferably about 5 to 20 nm.

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

<< Silane Coupling Agent (D) >>
The silicone rubber-based curable composition of the present embodiment may contain a silane coupling agent (D).
The silane coupling agent (D) can have a hydrolyzable group. The hydrolyzing group is hydrolyzed by water to become a hydroxyl group, and this hydroxyl group undergoes a dehydration condensation reaction with the hydroxyl group on the surface of the silica particles (C), whereby the surface of the silica particles (C) can be modified.

The silane coupling agent (D) can 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 can be used. As a result, this hydrophobic group is imparted to the surface of the silica particles (C), so that the cohesive force of the silica particles (C) is reduced in the silicone rubber-based curable composition and thus in the silicone rubber (hydrogen due to silanol groups). Aggregation due to bonding is reduced), and as a result, it is presumed that the dispersibility of silica particles in the silicone rubber-based curable composition is improved. As a result, the interface between the silica particles and the rubber matrix is increased, and the reinforcing effect of the silica particles is increased. Further, it is presumed that the slipperiness of the silica particles in the matrix is improved when the rubber matrix is deformed. Then, by improving 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.

Further, the silane coupling agent (D) can include a silane coupling agent having a vinyl group. As a result, a vinyl group is introduced on the surface of the silica particles (C). Therefore, when the silicone rubber-based curable composition is cured and a network (crosslinked structure) is formed, the vinyl group of the silica particles (C) also participates in the crosslinking reaction, so that the silica particles (crosslinked structure) are contained in the network. C) will also be incorporated. As a result, it is possible to reduce the hardness and increase the modulus of the formed silicone rubber.

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. Thereby, the dispersibility of silica in the rubber and the crosslinkability of the rubber can be balanced. The silane coupling agent (D) may be used alone or in combination of two or more.

Examples of the silane coupling agent (D) include those represented by the following formula (4).

Y _n- Si- (X) _4-n ... (4)
In the above equation (4), n represents an integer of 1 to 3. Y represents a functional group of any of 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. It is a hydrophobic group. X represents a hydrolyzable group.

The hydrophobic group is an alkyl group having 1 to 6 carbon atoms, an aryl group, or a hydrocarbon group in which these are combined, and examples thereof include a methyl group, an ethyl group, a propyl group, a phenyl group, and the like. Methyl groups are preferred.

Examples of the hydrophilic group include a hydroxyl group, a sulfonic acid group, a carboxyl group and a carbonyl group, and among them, a hydroxyl group is particularly preferable. The hydrophilic group may be contained as a functional group, but it is preferably not contained from the viewpoint of imparting hydrophobicity to the silane coupling agent (D).

Further, examples of the hydrolyzable group include an alkoxy group such as a methoxy group and an ethoxy group, a chloro group or a silazane group, and among them, a silazane group is preferable because it has high reactivity with the silica particles (C). A hydrolyzable group having a silazane group has two structures of (Y _{n −} Si −) in the above formula (4) due to its structural characteristics.

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 methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, and n-propyltrimethoxysilane. alkoxysilanes such as n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, decyltrimethoxysilane; chlorosilanes such as methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane; hexamethyldisilazane. Can be mentioned. Among these, a silane coupling agent having a trimethylsilyl group containing at least one selected from the group consisting of hexamethyldisilazane, trimethylchlorosilane, trimethylmethoxysilane, and trimethylethoxysilane is preferable.

Examples of those having a vinyl group as the functional group include methaloxypropyltriethoxysilane, methaloxypropyltrimethoxysilane, methaloxypropylmethyldiethoxysilane, methaloxypropylmethyldimethoxysilane, vinyltriethoxysilane, and vinyltrimethoxy. Alkoxysilanes such as silanes and vinylmethyldimethoxysilanes; chlorosilanes such as vinyltrichlorosilanes and vinylmethyldichlorosilanes; and divinyltetramethyldisilazane. Among these, methacryloxypropyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, methacryloxypropylmethyldimethoxysilane, divinyltetramethyldisilazane, vinyltriethoxysilane, vinyltrimethoxysilane, and vinyl. A silane coupling agent having a vinyl group-containing organosilyl group containing at least one selected from the group consisting of methyldimethoxysilane is preferable.

When the silane coupling agent (D) contains two types of a silane coupling agent having a trimethylsilyl group and a silane coupling agent having a vinyl group-containing organosilyl group, hexamethyldisilazane as having a hydrophobic group is used. Those having a vinyl group preferably contain divinyltetramethyldisilazane.

When a silane coupling agent having a trimethylsilyl group (D1) and a silane coupling agent having a vinyl group-containing organosilyl group (D2) are used in combination, the ratio of (D1) to (D2) is not particularly limited, but for example, By weight ratio (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. It is .15. With such a numerical range, the desired physical properties of the silicone rubber in the silicone rubber can be obtained. Specifically, it is possible to balance the dispersibility of silica in the rubber and the crosslinkability of the rubber.

<< Platinum or platinum compound (E) >>
The silicone rubber-based curable composition of the present embodiment may contain platinum or a platinum compound (E).
Platinum or the platinum compound (E) is a catalytic component that acts as a catalyst during curing. The amount of platinum or platinum compound (E) added is the amount of catalyst.

As the platinum or the platinum compound (E), known ones can be used, for example, platinum black, platinum supported on silica, carbon black or the like, platinum chloride acid or an alcohol solution of platinum chloride acid, chloride. Examples thereof include a complex salt of platinum acid and olefin, and a complex salt of platinum chloride acid and vinyl siloxane.

As the platinum or the platinum compound (E), only one type may be used alone, or two or more types may be used in combination.

Further, the silicone rubber-based curable composition of the present embodiment may contain an organic peroxide (H).
The organic peroxide (H) is a component that acts as a catalyst during curing. The amount of the organic peroxide (H) added is the amount of the catalyst. The organic peroxide (H) is an organic peroxide in place of the organohydrogenpolysiloxane (B) and the platinum or platinum compound (E), or with the organohydrogenpolysiloxane (B) and the platinum or platinum compound (E). The thing (H) can be used together.

Examples of the organic peroxide (H) include ketone peroxides, diacyl peroxides, hydroperoxides, dialkyl peroxides, peroxyketals, alkyl peroxides, peroxyesters and peroxydi. Examples thereof include carbonates, and specific examples thereof include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, o-methylbenzoyl peroxide, dicumyl peroxide, and 2,5-dimethyl-. Examples thereof include bis (2,5-t-butylperoxy) hexane, di-t-butyl peroxide, t-butylperbenzoate, and 1,6-hexanediol-bis-t-butylperoxycarbonate.

<< Water (F) >>
Further, the silicone rubber-based curable composition of the present embodiment may contain water (F) in addition to the above components (A) to (E) and (H).

Water (F) functions as a dispersion medium for dispersing each component contained in the silicone rubber-based curable composition, and is a component that contributes to the reaction between the silica particles (C) and the silane coupling agent (D). .. Therefore, in the silicone rubber, the silica particles (C) and the silane coupling agent (D) can be more reliably connected to each other, and uniform characteristics can be exhibited as a whole.

Further, the silicone rubber-based curable composition of the present embodiment may contain known additive components to be blended in the silicone rubber-based curable composition in addition to the above components (A) to (F). For example, diatomaceous earth, iron oxide, zinc oxide, titanium oxide, barium oxide, magnesium oxide, cerium oxide, calcium carbonate, magnesium carbonate, zinc carbonate, glass wool, mica and the like can be mentioned. In addition, dispersants, pigments, dyes, antistatic agents, antioxidants, flame retardants, thermal conductivity improvers and the like can be appropriately blended.

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

In the present 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, based on 100 parts by weight of the total amount of the vinyl group-containing organopolysiloxane (A). However, it may be more preferably 35 parts by weight or less. As a result, it is possible to balance mechanical strength such as hardness and tensile strength. The lower limit of the content of the silica particles (C) is not particularly limited with respect to 100 parts by weight of the total amount of the vinyl group-containing organopolysiloxane (A), but may be, for example, 10 parts by weight or more.

The silane coupling agent (D) is preferably contained in a proportion of, for example, 5 parts by weight or more and 100 parts by weight or less of the vinyl group-containing organopolysiloxane (A) with respect to 100 parts by weight. It is more preferably contained in a proportion of 5 parts by weight or more and 40 parts by weight or less. Thereby, the dispersibility of the silica particles (C) in the silicone rubber-based curable composition can be surely improved.

The content of the organohydrogenpolysiloxane (B) is specifically, for example, with respect to 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). , 0.5 part by weight or more and 20 parts by weight or less is preferable, and 0.8 parts by weight or more and 15 parts by weight or less is more preferable. When the content of (B) is within the above range, a more effective curing reaction may be possible.

The content of platinum or the platinum compound (E) means the amount of catalyst and can be appropriately set. Specifically, vinyl group-containing organopolysiloxane (A), silica particles (C), and silane coupling agent ( With respect to 100 parts by weight of the total amount of D), the amount of the platinum group metal in this component is 0.01 to 1000 ppm in weight units, preferably 0.1 to 500 ppm. By setting the content of platinum or the platinum compound (E) to the above lower limit or more, the obtained silicone rubber composition can be sufficiently cured. By setting the content of platinum or the platinum compound (E) to the above upper limit or less, the curing rate of the obtained silicone rubber composition can be improved.

The content of the organic peroxide (H) means the amount of the catalyst and can be appropriately set. Specifically, the vinyl group-containing organopolysiloxane (A), the silica particles (C), and the silane coupling agent ( For example, 0.001 parts by weight or more, preferably 0.005 parts by weight or more, and more preferably 0.01 parts by weight or more with respect to 100 parts by weight of the total amount of D). Thereby, the minimum strength as a cured product can be guaranteed. The upper limit of the content of the organic peroxide (H) is, for example, with respect to 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). It is 10 parts by weight or less, preferably 5 parts by weight or less, and more preferably 3 parts by weight or less. As a result, the influence of by-products can be suppressed.

Further, when water (F) is contained, the content thereof can be appropriately set, but specifically, for example, 10 to 100 parts by weight with respect to 100 parts by weight of the silane coupling agent (D). The range is preferably in the range of 30 to 70 parts by weight, and more preferably in the range of 30 to 70 parts by weight. As a result, the reaction between the silane coupling agent (D) and the silica particles (C) can proceed more reliably.

<Manufacturing method of silicone rubber>
Next, the method for producing the silicone rubber of the present embodiment will be described.
As a method for producing a silicone rubber of the present embodiment, a silicone rubber-based curable composition is prepared, and the silicone rubber-based curable composition is cured to obtain a silicone rubber.
The details will be described below.

First, each component of the silicone rubber-based curable composition is uniformly mixed by an arbitrary kneading device to prepare a silicone rubber-based curable composition.

[1] For example, the vinyl group-containing organopolysiloxane (A), the silica particles (C), and the silane coupling agent (D) are weighed in a predetermined amount, and then kneaded by an arbitrary kneading device. A kneaded product containing each of these components (A), (C), and (D) is obtained.

The kneaded product is preferably obtained by kneading the vinyl group-containing organopolysiloxane (A) and the silane coupling agent (D) in advance, and then kneading (mixing) the silica particles (C). As a result, the dispersibility of the silica particles (C) in the vinyl group-containing organopolysiloxane (A) is further improved.

Further, when obtaining this kneaded product, water (F) may be added to the kneaded product of each component (A), (C), and (D), if necessary. As a result, the reaction between the silane coupling agent (D) and the silica particles (C) can proceed more reliably.

Further, it is preferable that the kneading of each component (A), (C), and (D) goes through a first step of heating at the first temperature and a second step of heating at the second temperature. As a result, in the first step, the surface of the silica particles (C) can be surface-treated with the coupling agent (D), and in the second step, the silica particles (C) and the coupling agent (D) are combined. By-products produced by the reaction can be reliably removed from the kneaded product. Then, if necessary, the component (A) may be added to the obtained kneaded product and further kneaded. Thereby, the familiarity of the components of the kneaded product can be improved.

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

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.

Further, the time of the first step is preferably, for example, about 0.3 to 1.5 hours, and more preferably about 0.5 to 1.2 hours. The time of the second step is, for example, preferably about 0.7 to 3.0 hours, and more preferably about 1.0 to 2.0 hours.

By setting the first step and the second step under the above-mentioned conditions, the effect can be obtained more remarkably.

[2] Next, the organohydrogenpolysiloxane (B) and platinum or the platinum compound (E) are weighed in a predetermined amount, and then the kneaded product prepared in the above step [1] using an arbitrary kneading device. , Each component (B) and (E) is kneaded to obtain a silicone rubber-based curable composition. The obtained silicone rubber-based curable composition may be a paste containing a solvent.

When kneading the respective components (B) and (E), the kneaded product previously prepared in the above step [1] and the organohydrogenpolysiloxane (B) were prepared in the above step [1]. It is preferable to knead the kneaded product with platinum or the platinum compound (E), and then knead the respective kneaded products. As a result, each component (A) to (E) is surely contained in the silicone rubber-based curable composition without proceeding the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B). Can be dispersed in.

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

Further, the kneading time is preferably, for example, about 5 minutes to 1 hour, and more preferably about 10 to 40 minutes.

By setting the temperature within the above range in the above steps [1] and [2], the progress of the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B) is more accurate. Can be prevented or suppressed. Further, in the above-mentioned step [1] and the above-mentioned step [2], by setting the kneading time within the above range, each component (A) to (E) is more reliably dispersed in the silicone rubber-based curable composition. Can be done.

The kneading apparatus used in each of the steps [1] and [2] is not particularly limited, and for example, a kneader, two rolls, a Banbury mixer (continuous kneader), a pressurized kneader, or the like can be used.

Further, in this step [2], a reaction inhibitor such as 1-ethynylcyclohexanol may be added to the kneaded product. As a result, even if the temperature of the kneaded product is set to a relatively high temperature, the progress of the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B) is more accurately prevented or suppressed. be able to.

Further, in this step [2], instead of the organohydrogenpolysiloxane (B) and the platinum or platinum compound (E), or in combination with the organohydrogenpolysiloxane (B) and the platinum or platinum compound (E). , Organic peroxide (H) may be added. Preferred conditions such as temperature and time for kneading the organic peroxide (H), and the conditions for kneading the organohydrogenpolysiloxane (B) and platinum or the platinum compound (E) with respect to the apparatus to be used. Is similar to.

[3] Next, a silicone rubber is formed by curing the silicone rubber-based curable composition.

In the present embodiment, the curing step of the silicone rubber-based curable composition is, for example, heating at 100 to 250 ° C. for 1 to 30 minutes (primary curing) and then post-baking (secondary curing) at 200 ° C. for 1 to 4 hours. ) Is done.
By going through the above steps, the silicone rubber of the present embodiment can be obtained.

Although the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than the above can be adopted. Further, the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within the range in which the object of the present invention can be achieved are included in the present invention.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the description of these Examples.

The raw material components used in the examples and comparative examples shown in Table 1 are shown below.
(Vinyl group-containing organopolysiloxane (A))
-Vinyl group-containing linear organopolysiloxane (A1-1a): A vinyl group-containing dimethylpolysiloxane synthesized by Synthesis Scheme 1 (a structure represented by the formula (1-1), in which only R ¹ (terminal) is a vinyl group. A certain structure)
-Vinyl group-containing linear organopolysiloxane (A1-1b): A vinyl group-containing dimethylpolysiloxane synthesized by Synthesis Scheme 2 (a structure represented by the formula (1-1) in which only R ¹ (terminal) is a vinyl group. A certain structure)
-Vinyl group-containing linear organopolysiloxane (A1-2a): Vinyl group-containing dimethylpolysiloxane (structure represented by the formula (1-1), R ¹ (terminal) and R ² (chain) synthesized by Synthesis Scheme 3). (Inside) is a vinyl group)
-Vinyl group-containing linear organopolysiloxane (A1-2b): Vinyl group-containing dimethylpolysiloxane (structure represented by the formula (1-1), R ¹ (terminal) and R ² (chain) synthesized by Synthesis Scheme 4. (Inside) is a vinyl group)

(Organohydrogenpolysiloxane (B))
Made by Momentive: "TC-25D"

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

(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)"

(Platinum or platinum compound (E))
Made by Momentive: "TC-25A"

(Synthesis of vinyl group-containing organopolysiloxane (A))

[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 silicate were placed in a 300 mL separable flask having a cooling tube and a stirring blade substituted with Ar gas, and the temperature was raised at 120 ° C. for 30 minutes. Stirred. At this time, an increase in viscosity was confirmed.
Then, the temperature was raised to 155 ° C., and stirring was continued for 3 hours. Then, after 3 hours, 0.1 g (0.6 mmol) of 1,3-divinyltetramethyldisiloxane was added, and the mixture was further stirred at 155 ° C. for 4 hours.
After 4 hours, it was diluted with 250 mL of toluene and then washed 3 times with water. The organic layer after washing was washed several times with 1.5 L of methanol to reprecipitate and separate the oligomer and the polymer. The obtained polymer was dried under reduced pressure at 60 ° C. overnight to synthesize a low vinyl group-containing linear organopolysiloxane (A1-1a) (Mn = 2.2 × 10 ⁵ and Mw = 4.8 × 10 ^5). ). The vinyl group content calculated by 1 H-NMR spectrum measurement was 0.039 mol%.

[Synthesis scheme 2: Synthesis of vinyl group-containing linear organopolysiloxane (A1-1b)]
The low vinyl group was obtained in the same manner as in the synthesis step of (A1-1a) except that the reaction time after raising the temperature to 155 ° C. was changed to 3.5 hours in the synthesis step of (A1-1a). containing was synthesized linear organopolysiloxanes (A1-1b) (Mn = 2.7 × 10 5, Mw = 5.2 × 10 5). The vinyl group content calculated by 1 H-NMR spectrum measurement was 0.031 mol%.

[Synthesis scheme 3: Synthesis of vinyl group-containing linear organopolysiloxane (A1-2a)]
In the synthesis step of (A1-1a) above, in addition to 75.3 g (254 mmol) of octamethylcyclotetrasiloxane, 2,4,6,8-tetramethyl 2,4,6,8-tetravinylcyclotetrasiloxane 0. By repeating the same procedure as the synthesis step of (A1-1a) except that 12 g (0.35 mmol) was used, a vinyl group-containing linear organopolysiloxane (A1-2a) was used as shown in the following formula (6). ) was synthesized ^{(Mn = 2.5 × 10 5,} Mw = 5.0 × 10 5). The vinyl group content calculated by 1 H-NMR spectrum measurement was 0.130 mol%.

[Synthesis Scheme 4: Synthesis of Vinyl Group-Containing Linear Organopolysiloxane (A1-2b)]
In the above synthesis step (A1-2a), the amount of octamethylcyclotetrasiloxane added was 73.2 g (247 mmol), 2,4,6,8-tetramethyl 2,4,6,8-tetravinylcyclotetrasiloxane. A high vinyl group-containing linear organopolysiloxane (A1-2b) was obtained in the same manner as in the synthesis step of (A1-2a) except that the amount of the above was changed to 2.61 g (7.6 mmol). synthesized ^{(Mn = 2.5 × 10 5,} Mw = 5.4 × 10 5). The vinyl group content calculated by 1 H-NMR spectrum measurement was 2.826 mol%.

<Preparation of silicone rubber-based curable composition>
(Test Examples 1 to 5)
A mixture of vinyl group-containing organopolysiloxane (A), silane coupling agent (D) and water (F) is kneaded in advance at the ratio shown in Table 1 below, and then silica particles (C) are added to the mixture. Further kneading was performed to obtain a kneaded product (silicone rubber compound).
Here, the kneading after the addition of the silica particles (C) is carried out in the first step of kneading for 1 hour under the condition of 60 to 90 ° C. under a nitrogen atmosphere for the coupling reaction, and the removal of the by-product (ammonia). Therefore, the mixture was kneaded under a reduced pressure atmosphere at 160 to 180 ° C. for 2 hours through the second step, then cooled and kneaded for 20 minutes.
Subsequently, 100 parts by weight of the obtained kneaded product (silicone rubber compound) was added with organohydrogenpolysiloxane (B) (TC-25D) and platinum or platinum compound (E) (TC) in the proportions shown in Table 1 below. -25A) was added and kneaded with a roll to obtain a silicone rubber-based curable composition.

<Hoax type bending resistance test>
The obtained silicone rubber-based curable composition was subjected to a hoax-type bending resistance test measured by the following procedure, and the cut length in the test piece when the number of bendings was 10,000, 30,000, and 50,000. Was measured. The evaluation results are shown in Table 2.

(Creation of test piece)
According to 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 subsequently at 200 ° C. By heating for 4 hours, a strip-shaped test piece 50 (width: 25 mm, length: 150 mm, thickness: 6.3 mm) with a groove 60 was prepared. A notch 70 having a length of 2.03 mm was made in the center of the groove 60 of the obtained test piece 50 in parallel with the width direction using a blade to obtain a test piece 50 with a notch (FIG. 2). ). The notch 70 penetrated the test piece 50 in the thickness direction.

FIG. 1 (a) shows a top view of the mold 10, and FIG. 1 (b) shows a side sectional view of the mold 10 as viewed by arrows AA. The mold 10 is provided with a curved convex portion 20 on the bottom surface of the molding space 30.
Further, FIG. 2A shows a top view of the test piece 50 having a groove 60 in which the notch 70 is formed, and FIG. 2B shows a side sectional view of the test piece 50 as viewed from the arrow BB.

(procedure)
As shown in FIG. 3, the test piece 50 obtained in the above (preparation of the test piece) is held between the fixed gripping tool 102 and the movable gripping tool 104 of the testing machine 100 (demacha bending crack tester). It was.
Specifically, the test piece 50 was attached to the grip so that the distance between the two grips was maximized and 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 give an extra strain.
Subsequently, based on the following test conditions, the movable gripping tool 104 was reciprocated in the vertical direction with reference to the fixed gripping tool 102. The movable gripper 104 approaches the fixed gripper 102 from the maximum distance to the reciprocating motion distance (the test piece 50 is bent), and then the movable gripper 104 is separated to the maximum distance (the test piece 50 is flat). One reciprocating motion (one cycle) was defined, and the number of cycles (times) was defined as the number of bends.
The length (mm) of the notch 70 in the test piece 50 when the number of bendings was 10,000, 30,000, and 50,000 was measured using a digital caliper (manufactured by Mitutoyo).
The length of the notch 70 was taken as the average value of the three measured values measured by performing the hoax-type bending resistance test three times. The results are shown in Table 2.
The rate of change in cut length was calculated based on the formula: L ₅ / L ₀ .
L ₀ is the initial cut length before the hoax-type bending resistance test, and L ₁ , L ₃ , and L ₅ are the bending times of 10,000 times, 30,000 times, and 50,000 times after the hoax-type bending resistance test, respectively. The average value of the cut length at the time of.

(Test conditions)
・ Test standard: JIS K 6260 (2017) compliant ・ Testing machine: Demacha bending crack testing machine with low temperature tank (manufactured by Yasuda Seisakusho)
-Test temperature: 23 ± 2 ° C
-Maximum distance between grippers: 75 mm (D _{max in} Fig. 3)
-Reciprocating distance: 57 mm (D _{mv in} Fig. 3)
-Condition adjustment: Before the start of the first test, the mixture was allowed to stand at 23 ° C for 10 minutes. Before the start of the second and third tests, the test was allowed to stand in the same environment for 5 minutes.
・ Test speed: 300 ± 10 times / minute ・ Number of tests: n = 3

In the above <hoax-type bending resistance test>, when the test piece was broken when the number of times of bending was 10,000 times, 30,000 times, and 50,000 times, it was set to 25.0 mm.

Based on the results of the obtained 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 5.

The obtained silicone rubber-based curable compositions of Examples and Comparative Examples were evaluated based on the following evaluation items.

<Making silicone rubber>
The obtained silicone rubber-based curable composition was pressed at 170 ° C. and 10 MPa for 15 minutes to form a sheet having a thickness of 1 mm, and was first cured. Subsequently, it was heated at 200 ° C. for 4 hours and secondarily cured.
From the above, a sheet-shaped silicone rubber (a cured product of a silicone rubber-based curable composition) was obtained.

The hardness was measured at n = 5 in each sample using two samples, and the average value of a total of 10 measurements was taken as the measured value. Tensile stress and elongation at break were measured with three samples, and the average value of the three was used as the measured value. The tear strength was measured with 5 samples, and the average value of 5 was used as the measured value.
The average value of each is shown in Table 2.

(hardness)
Six sheets of the obtained sheet-shaped silicone rubber having a thickness of 1 mm were laminated to prepare a test piece having a thickness of 6 mm. The hardness of the obtained test piece was measured at 25 ° C. according to JIS K6253 (1997) with a Type A durometer.

(Tear strength)
Using the obtained sheet-shaped silicone rubber having a thickness of 1 mm, a crescent-shaped test piece was prepared in accordance with JIS K6252 (2001), and the tear strength of the obtained crescent-shaped test piece was measured at 25 ° C. .. The unit is N / mm.

(Tensile strength)
Using the obtained sheet-shaped silicone rubber having a thickness of 1 mm, a dumbbell-shaped No. 3 test piece was prepared in accordance with JIS K6251 (2004), and the obtained dumbbell-shaped No. 3 test piece was prepared at 25 ° C. The tensile strength of the material was measured. The unit is MPa.

(Breaking elongation)
Using the obtained sheet-shaped silicone rubber having a thickness of 1 mm, a dumbbell-shaped No. 3 test piece was prepared in accordance with JIS K6251 (2004), and the obtained dumbbell-shaped No. 3 test piece was prepared at 25 ° C. The breaking elongation of was measured. The breaking elongation was calculated by [moving distance between chucks (mm)] ÷ [initial distance between chucks (60 mm)] × 100. The unit is%.

(Evaluation of durability)
Using the silicone rubber-based curable composition obtained in each Example and each Comparative Example, it was cured under the conditions of 170 ° C. for 5 minutes and 200 ° C. for 4 hours, and a tubular member having a thickness of 1 mm × an inner diameter: 2 mm. (Tube) was created. A durability test sample in which a steel wire (TRUSCO steel wire small winding type wire diameter 1.6 mm × 15 m) was inserted into the obtained tubular member was prepared and a durability test was performed. Specifically, the 90 ° bending test of the durability test sample was repeated 100 times to determine the durability. Cylindrical members with no abnormal appearance after the test were marked with ◯, and those with cracks or breakage after the test were marked with x.

It was found that the silicone rubber-based curable compositions of Examples 1 to 3 were superior in durability to repeated bending deformation as compared with Comparative Examples 1 and 2. The molded product of the silicone rubber-based curable composition of Examples 1 to 3 can be suitably used for a flexible member, preferably a wearable device, and more preferably a substrate for a wearable device.

10 Mold 20 Convex part 30 Molding space 50 Test piece 60 Groove 70 Notch 100 Testing machine 102 Fixed gripper 104 Movable gripper

Claims (11)

Vinyl group-containing organopolysiloxane (A) and
A silicone rubber-based curable composition containing silica particles (C).
Using a test piece made of a cured product of the silicone rubber-based curable composition, a hoax-type bending resistance test conforming to JIS K 6260 is performed, and the number of bendings is 50,000 times, which is measured based on the following procedure. The rate of change in cut length (L ₅ / L ₀ ) in the test piece is 1.1 or more and 11.5 or less.
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 a test piece having a predetermined shape in accordance with JIS K 6260.
At the center of the obtained test piece, a notch having a predetermined length penetrating the test piece is made parallel to the width direction. Let L ₀ be the initial cut length.
Subsequently, the test piece with a notch is installed between the gripping tools of the testing machine, a hoax-type bending resistance test is performed based on the following test conditions, and the cutting length in the test piece after a predetermined number of bendings ( mm) is measured.
The cut length shall be the average value when the hoax type bending resistance test is performed three times. Let L _{5 be} the average value of this cut length.
The rate of change in cut length is calculated based on the formula: L ₅ / L ₀ .
(Test conditions)
・ Test standard: JIS K 6260 compliant ・ Testing machine: Demacha bending crack tester ・ Test temperature: 23 ± 2 ℃
・ Maximum distance between grippers: 75 mm
・ Reciprocating distance: 57mm
・ Test speed: 300 ± 10 times / minute ・ Number of tests: n = 3 The silicone rubber-based curable composition according to claim 1.
When a hoax-type bending resistance test based on the above procedure is performed and the cutting length in the test piece when the number of bendings is 10,000 is L ₁ , L ₁ / L ₀ is 1.0 or more. Satisfy 0 or less,
Silicone rubber-based curable composition. The 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 10 parts by weight or more and 35 parts by weight or less with respect to 100 parts by weight of the vinyl group-containing organopolysiloxane (A). The silicone rubber-based curable composition according to any one of claims 1 to 3.
A silicone rubber-based curable composition having a tear strength of 25 N / mm or more, which is measured under the following conditions.
(Measurement conditions for tear strength)
A crescent-shaped test piece is prepared using the cured product of the silicone rubber-based curable composition, and the tear strength of the obtained crescent-shaped test piece is measured at 25 ° C. in accordance with JIS K6252 (2001). The silicone rubber-based curable composition according to any one of claims 1 to 4.
A silicone rubber-based curable composition having a breaking elongation of a cured product of the silicone rubber-based curable composition measured under the following conditions of 500% or more.
(Measurement conditions for elongation at break)
A dumbbell-shaped No. 3 test piece was prepared in accordance with JIS K6251 (2004) using the cured product of the silicone rubber-based curable composition, and the obtained dumbbell-shaped No. 3 test piece was broken at 25 ° C. Measure the elongation. The breaking elongation is calculated by [moving distance between chucks (mm)] ÷ [initial distance between chucks (60 mm)] × 100. The unit is%. The silicone rubber-based curable composition according to any one of claims 1 to 5.
A silicone rubber-based curable composition having a durometer hardness A of 10 or more and 70 or less, which is a cured product of the silicone rubber-based curable composition measured under the following conditions.
(Measurement conditions for durometer hardness A)
A sheet-shaped test piece was prepared using the cured product of the silicone rubber-based curable composition, and the durometer hardness A of the obtained sheet-shaped test piece was measured at 25 ° C. in accordance with JIS K6253 (1997). To do. The silicone rubber-based curable composition according to any one of claims 1 to 6.
A silicone rubber-based curable composition in which the tensile strength of the cured product of the silicone rubber-based curable composition measured under the following conditions is 5.0 MPa or more.
(Measurement conditions for tensile strength)
A dumbbell-shaped No. 3 test piece was prepared using the cured product of the silicone rubber-based curable composition, and the obtained dumbbell-shaped No. 3 test piece was prepared at 25 ° C. in accordance with JIS K6251 (2004). Measure the tensile strength. The silicone rubber-based curable composition according to any one of claims 1 to 7.
A silicone rubber-based curable composition having a specific surface area of silica particles (C) measured by the BET method of 200 m ² / g or more and 500 m ² / g or less. The silicone rubber-based curable composition according to any one of claims 1 to 8.
A silicone rubber-based curable composition used for forming a molded product for a flexible member. The silicone rubber-based curable composition according to any one of claims 1 to 9.
A silicone rubber-based curable composition used to form a molded product for a wearable device. A structure comprising a cured product of the silicone rubber-based curable composition according to any one of claims 1 to 10.

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