JP3105151B2 - Composition for acoustic lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a composition for an acoustic lens, in particular, it is possible to keep the acoustic impedance close to a living body while maintaining the sound velocity at 950 to 1,100 m / sec, and to reduce the amount of ultrasonic attenuation in a high frequency region. The present invention relates to a composition for an acoustic lens which is useful as an acoustic lens material of a probe for an ultrasonic diagnostic apparatus, which can form an acoustic lens having a high resolution.

[0002]

2. Description of the Related Art An acoustic lens of a probe for an ultrasonic diagnostic apparatus converges an ultrasonic wave, closely adheres to a living body, matches the acoustic impedance (density × sonic velocity) of the living body, and reduces the reflection of the ultrasonic wave. For this acoustic lens composition, a silicone rubber compound containing diorganopolysiloxane as a main material has been widely used because it is a necessary condition that the ultrasonic attenuation of the lens itself is small. ing. Then, with respect to this lens composition, in order to match the acoustic impedance of a living body, an inorganic filler such as silica, alumina, or titanium oxide is added to the base organopolysiloxane in order to increase its density. In order to increase the speed of sound, there have been proposed ones in which an organic resin such as nylon is blended (see JP-A-58-216294 and JP-A-62-11897).

[0003]

However, the silicone rubber used for this kind of application, when blended with a filler or an organic resin in order to increase its density and sound speed, can be used as an ultrafine acoustic lens made from this composition. There is a problem that the amount of sound attenuation becomes large, and this solution is required.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a composition for an acoustic lens which solves such disadvantages and problems, which comprises: A) 100% by weight of a silicone rubber compound containing diorganopolysiloxane as a main material. part, B) the general formula ^{(1) R 1 (R 1} 2 SiO) X (R 1 R 2 SiO) Y SiR 1 3 ······ (1) [ wherein the R ¹ is the same or different, non Substitution or substitution 1
A hydrocarbon group or a hydrogen atom, R ² is the same or different, and C _a H _{2a + 1} (a is an integer of 5 or more) or CH ₂ CH ₂ CH ₂ O (C
₂ H ₄ O) _b (C ₃ H ₆ O) _c R ¹ (b and c are integers of 0 or more, and b +
c is an integer of 1 or more), X is an integer of 0 or more,
Y is an integer of 1 or more], and 5 to 40 parts by weight of an organopolysiloxane.

That is, the present inventors relate to an acoustic lens of a probe for an ultrasonic diagnostic apparatus, and the acoustic impedance (sound speed × density) of the acoustic lens is the acoustic impedance of a living body (1.4).
~ 1.6) × 10 ⁶ kg / m ²・ sec.
As a result of various investigations to obtain a material having a small amount of ultrasonic attenuation even at 950 to 1,100 m / sec, as a means to bring the acoustic impedance of silicone rubber closer to the target, some organic groups of diorganopolysiloxane It has been found that it is effective to increase the overall sound speed by adding an alkyl group, polyether group, phenyl group, or fluoroalkyl group-introduced one. In this case, especially, the organic group of the diorganopolysiloxane is a higher alkyl group. The present invention has been completed by confirming that when the polyether group is used, it is possible to obtain a high effect, a high acoustic impedance close to a target, and a small amount of ultrasonic attenuation.

[0006]

The composition for an acoustic lens of the present invention is as described in (A) above.
It is composed of a silicone rubber compound as a component and an organopolysiloxane as a component (B). The silicone rubber compound as the component (A) is mainly composed of diorganopolysiloxane, which is composed of (a) diorganopolysiloxane and (b) a filler. a),
The following are exemplified as the component (b).

The diorganopolysiloxane as the component (a) is exemplified by the following general formula (2): XO-[(SiR ₂ ) O] _n -X (2) . R represents an alkyl group such as a methyl group, an ethyl group, or a butyl group; an alkenyl group such as a vinyl group or an allyl group; an aryl group such as a phenyl group or a tolyl group; a cycloalkyl group such as a cyclohexyl group; An unsubstituted or substituted monovalent hydrocarbon group selected from a chloromethyl group, a trifluoroalkyl group, a cyanomethyl group, or the like, in which a part or all of the bonded hydrogen atoms are substituted with a halogen atom, a cyano group, or the like; Groups, vinyl groups, phenyl groups and trifluoropropyl groups are preferred, at least 50 mol% of which are methyl groups, and 0.001 to 5 mol% are preferably vinyl groups. Alternatively, X is preferably a trimethylsilyl group, a dimethylvinylsilyl group, or a hydrogen atom, and it is generally preferable that the viscosity at 25 ° C. is in the range of 100 to 10,000,000 cSt, but this is a single type or a combination of two or more types. May be used.

[0008] As the filler as the component (b), various fillers used in general silicone rubber compositions can be used. Therefore, this includes reinforcing fillers such as fumed silica, precipitated silica, quartz powder, carbon powder, titanium dioxide, aluminum oxide,
Non-reinforcing fillers for the purpose of increasing the amount of talc, sericite, bentonite, etc. are exemplified, and the average particle diameter of these fillers is 5 μm or less, preferably 2 μm or less in order to reduce the amount of ultrasonic attenuation. It is better to If the amount of these fillers is less than 30 parts by weight per 100 parts by weight of the component (a), an increase in the density of the composition cannot be expected, and if it exceeds 200 parts by weight, there is a disadvantage that the ultrasonic attenuation becomes large. Therefore, the content is preferably in the range of 30 to 200 parts by weight, particularly 50 to 150 parts by weight. The components (a) and (b) may be kneaded in an apparatus usually used for producing a silicone rubber composition such as a kneader, a Banbury mixer, a roll, or the like, and may be subjected to a heat treatment if necessary.

The silicone rubber compound as the component (A) of the present invention comprising the component (a) and the component (b) has a small ultrasonic attenuation when the acoustic impedance is brought close to a living body. Various compounding agents can be added as long as the purpose is not impaired. Accordingly, this includes, for example, a reinforcing agent such as a vinyl group-containing silicone resin, diphenylsilanediol, a dispersant such as hexamethyldisilazane, a dimethylpolysiloxane having a low degree of polymerization of less than 100 cSt in viscosity at 25 ° C. A heat resistance improver such as ferrous oxide, ferric oxide, and cerium oxide, and a coloring agent such as a pigment can be added as necessary.

[0010] Next organopolysiloxane as the component (B) in the composition, the above-described manner formula ^{(1) R 1 (R 1} 2 SiO) X (R 1 R 2 SiO) Y SiR 1 3 · ... (1) R ^{1 in} this formula is the same or different, same or different, unsubstituted or substituted monovalent hydrocarbon group or hydrogen atom as R described above, and a methyl group is particularly preferred. This R ² is C _a H _{2a + 1} (a is 5
Or an integer greater than or equal to) or CH ₂ CH ₂ CH ₂ O (C ₂ H ₄ O) _b (C ₃ H ₆ O) _c R ¹ (b
And c are integers of 0 or more, and b + c is an integer of 1 or more), X is an integer of 0 or more, Y is an integer of 1 or more, and the organopolysiloxane has the following composition: This is required to increase the speed of sound of an object, bring acoustic impedance closer to the human body, and reduce the amount of ultrasonic attenuation.

C _a H in R ² in the general formula (1)
_The a of the alkyl group represented by _{2a + 1} increases the sound speed of the composition by a predetermined amount, but it is necessary to be 5 or more in order to make the acoustic impedance close to the living body, and particularly, 8
It is preferably set to 20. If it exceeds 20, the composition may become solid and may not be blended. Specific examples include an octyl group, a decyl group, a dodecyl group, a tridecyl group, a tetradecyl group, and a pentadecyl group. Further, b and c of the polyether group represented by CH ₂ CH ₂ CH ₂ O (C ₂ H ₄ O) _b (C ₃ H ₆ O) _c R ¹ are integers of 0 or more, and Although the sound velocity of the composition is increased by the blending, b + c is required to be an integer of 1 or more because the acoustic impedance is brought close to the human body. Therefore, it is particularly preferable to set it to 5 or more. If it exceeds 100, it may be in a solid state, and it may be difficult to mix it. Note that X is an integer of 0 or more, and Y needs to be an integer of 1 or more in order to increase the speed of sound of the composition. However, the viscosity of the organopolysiloxane is such that it can be easily blended. From 25 ℃
Is preferably 100 to 100,000 cP.

Further, the addition amount of the organopolysiloxane as the component (B) represented by the general formula (1) is too small if less than 5 parts by weight based on 100 parts by weight of the component (A). Cannot increase the speed of sound of objects,
When the amount is more than 40 parts by weight, the mechanical strength of the composition is remarkably reduced. Therefore, it is necessary to set the range of 5 to 40 parts by weight, and the preferable range is 10 to 30 parts by weight. The component (B) can be used alone or in combination of two or more.

The composition for an acoustic lens of the present invention is prepared by uniformly kneading a predetermined amount of the silicone rubber compound as the component (A) and the organopolysiloxane as the component (B) with a roll or a kneader. Obtainable. An acoustic lens can be obtained by crosslinking and molding the obtained composition for an acoustic lens. Benzoyl peroxide, 2,4-
Known organic peroxides such as dichlorobenzoyl peroxide, dicumyl peroxide, and 2,5-di (t-butylperoxy) hexane are added in an amount of about 0.1 to 5 parts by weight based on 100 parts by weight of the composition for acoustic lenses. Then, heating may be performed at a predetermined temperature. When the diorganopolysiloxane in the component (A) contains an unsaturated group such as a vinyl group, two or more hydrogen atoms bonded to a silicon atom that undergoes an addition reaction with the vinyl group are used. The organohydrogenpolysiloxane and platinum catalyst contained therein may be added and cured by the addition reaction. In this case, it is preferable that the amount of hydrogen atoms bonded to silicon atoms is 0.5 to 5 times the amount of unsaturated groups.

In order to form an acoustic lens as a probe for an ultrasonic diagnostic apparatus from the above-described composition for an acoustic lens of the present invention, the composition is molded and cross-linked by a general molding means such as press molding. It can be easily manufactured.

[0015]

EXAMPLES Examples of the present invention and comparative examples will now be described.
The present invention is not limited by these examples. Example 1 75% by weight of dimethylpolysiloxane having both ends of a molecular chain blocked with a dimethylvinylsilyl group and having a viscosity of 100,000 cSt
Base oil with vinyl group content of 0.022 mol / 100 g, consisting of 25% by weight of vinyl resin containing vinyl group and reinforcing resin
40 parts by weight of quartz powder having an average particle size of 1.4 μm to the general formula (3)

Embedded image The composition 1 was obtained by kneading 20 parts by weight of an organopolysiloxane represented by the following formula.

Then, 3.9 parts by weight of methyl hydrogen polysiloxane having a hydrogen group content of 0.0053 mol / g as a curing agent and 10 ppm of a platinum chloroplatinic acid catalyst were added to the composition 1 and mixed. The base compound is placed in a vacuum vessel and defoamed under reduced pressure to prepare a molding compound. The molding compound is press-molded at 150 ° C. for 10 minutes to produce a sheet having a thickness of 1 mm and 2 mm (hereinafter abbreviated as sheet 1). did.

Next, the density of the sheet 1 at 25 ° C. is determined in accordance with JIS C-2123, and the sound speed at 25 ° C. of the sheet 1 is measured by a sound speed measuring device / sing-around type sound speed measuring device U.
The acoustic impedance of the sheet 1 was measured by VM-2 type (trade name, manufactured by Ultrasonic Industry Co., Ltd.) and the product was 1.40 × 10 ⁶ (kg / m ² · sec). The water tank was filled with water at 25 ° C., and an ultrasonic oscillator / function generator FG-350 [trade name of Iwatsu Electronics Co., Ltd.] generated 5 MHz ultrasonic waves in water, and the ultrasonic waves were generated. When the magnitude of the amplitude before and after passing through the sheet 1 was measured by an ultrasonic receiver / oscilloscope VP-5204A (trade name, manufactured by Matsushita Electric Industrial Co., Ltd.), the amount of ultrasonic attenuation in water at 25 ° C. was − It was 0.60db / mm / MHz.

Example 2 75% by weight of dimethylpolysiloxane having both ends of a molecular chain blocked with a dimethylvinylsilyl group and having a viscosity of 100,000 cSt.
Base oil with a vinyl group content of 0.022 mol / 100 g, consisting of 25% by weight of vinyl resin containing vinyl group and reinforcing silicone resin
60 parts by weight, 40 parts by weight of quartz powder having an average particle diameter of 1.4 μm (the same composition as in Example 1 except for the organopolysiloxane represented by the general formula (3)) and the general formula (4)

Embedded image The composition 2 was prepared by kneading 20 parts by weight of an organopolysiloxane represented by the following formula.

Next, 3.9 parts by weight of methyl hydrogen polysiloxane having a hydrogen group content of 0.0053 mol / g as a curing agent and 10 ppm of platinum chloroplatinic acid catalyst were added to this composition 2 and mixed. The base compound is placed in a vacuum container and defoamed under reduced pressure to prepare a molding compound. The molding compound is press-molded at 150 ° C. for 10 minutes to produce a sheet having a thickness of 1 mm and 2 mm (hereinafter abbreviated as sheet 2). did. Next, the density, sound velocity, acoustic impedance, and ultrasonic attenuation of the sheet 2 were measured in the same manner as in Example 1, and the results shown in Table 1 described later were obtained.

EXAMPLE 3 Reinforcing fumed silica 16 was added to 51 parts by weight of dimethylpolysiloxane having a viscosity of 530 cSt and a vinyl group content of 0.2 mol% in which both ends of the molecular chain were blocked with dimethylvinylsilyl groups. Composition 3 was prepared by kneading 33 parts by weight of a quartz powder having an average particle diameter of 1.4 μm and 20 parts by weight of the organopolysiloxane represented by the above general formula (4).

Then, 0.5 part by weight of 2,5-dimethyl-2,5-di (t-butylperoxy) hexane as a vulcanizing agent was roll-mixed with 100 parts by weight of the composition 3 to prepare a molding compound. Prepare and mold this molding compound 1
A sheet having a thickness of 1 mm and 2 mm (hereinafter abbreviated as sheet 3) was prepared by press molding at 65 ° C. for 10 minutes. Next, the density, sound velocity, acoustic impedance, and ultrasonic attenuation of the sheet 3 were measured in the same manner as in Example 1. As a result, the results shown in Table 1 described later were obtained.

Comparative Example 1 75% by weight of dimethylpolysiloxane having both ends of a molecular chain blocked with a dimethylvinylsilyl group and having a viscosity of 100,000 cSt.
Then, 40 parts by weight of quartz powder having an average particle size of 1.4 μm is added to 60 parts by weight of a base oil having a vinyl group content of 0.022 mol / 100 g composed of 25% by weight of a reinforcing silicone resin containing a vinyl group, and kneaded. Composition 4 [the same compound as in Example 1 except for the organopolysiloxane represented by the general formula (3)] was prepared, and as a curing agent, methyl having a hydrogen group content of 0.0053 mol / g was used as a curing agent. 3.9 parts by weight of hydrogenpolysiloxane and chloroplatinic acid catalyst in platinum amount
After adding and mixing 10 ppm, the base compound was placed in a vacuum vessel and defoamed under reduced pressure to prepare a molding compound.

Next, the molding compound is heated to 150 ° C.
Press for 10 minutes to produce a 1 mm and 2 mm thick sheet (hereinafter abbreviated as sheet 4).
The density, sound velocity, acoustic impedance, and ultrasonic attenuation were measured in the same manner as in Example 1, and the results shown in Table 1 below were obtained.

COMPARATIVE EXAMPLE 2 Reinforcing fumed silica 16 was added to 51 parts by weight of dimethylpolysiloxane having a viscosity of 530 cSt in which both ends of the molecular chain were blocked with dimethylvinylsilyl groups and having a vinyl group content of 0.2 mol%. By weight, 33 parts by weight of quartz powder having an average particle diameter of 1.4 μm are kneaded to prepare composition 5 [the same compound as in Example 3 except for the organopolysiloxane represented by the general formula (4)]. , 100 parts by weight of this composition as a vulcanizing agent
0.5 part by weight of dimethyl-2,5-di (t-butylperoxy) hexane was mixed to prepare a molding compound.

Next, the molding compound was heated at 165 ° C.
To form a sheet having a thickness of 1 mm and 2 mm (hereinafter abbreviated as sheet 5). The density, sound velocity, acoustic impedance, and ultrasonic attenuation of the sheet 5 are measured in the same manner as in Example 1. As a result, the results shown in the following Table 1 were obtained.

[0026]

[Table 1]

Comparative Example 3 75% by weight of dimethylpolysiloxane having both ends of a molecular chain blocked with a dimethylvinylsilyl group and having a viscosity of 100,000 cSt.
Base oil with a vinyl group content of 0.022 mol / 100 g, consisting of 25% by weight of vinyl resin containing vinyl group and reinforcing silicone resin
60 parts by weight and 40 parts by weight of quartz powder having an average particle size of 1.4 μm [the same compound as in Example 1 except for the organopolysiloxane represented by the general formula (3)] and the general formula (5)

Embedded image The composition 6 was prepared by kneading 20 parts by weight of an organopolysiloxane represented by the following formula. To the obtained composition 6, 3.9 parts by weight of methyl hydrogen polysiloxane having a hydrogen group content of 0.0053 mol / g as a curing agent and 10 ppm of platinum in a chloroplatinic acid catalyst were added and mixed. The mixture was placed in a container and defoamed under reduced pressure to prepare a molding compound. This molding compound is heated at 150 ° C for 10
Then, a sheet having a thickness of 1 mm and 2 mm (hereinafter abbreviated as sheet 6) was prepared by press molding for 1 minute. When the acoustic impedance and ultrasonic attenuation of the sheet 6 were measured in the same manner as in Example 1, the results shown in the following Table 2 were obtained.

Comparative Example 4 Both ends of the molecular chain were blocked with dimethylvinylsilyl groups, the viscosity was 530 cSt, and the vinyl group content was 0.2 mol%. 51 parts by weight of dimethylpolysiloxane was added to 16 parts by weight of reinforcing fumed silica. Parts and 33 parts by weight of quartz powder having an average particle diameter of 1.4 μm (the same as in Example 3 except for the organopolysiloxane represented by the general formula 4) and 20 parts by weight of nylon powder-SP-500 (trade name, manufactured by Toray Industries, Inc.) Was kneaded to prepare Composition 7.
2,5-dimethyl-2,5-di (t-butylperoxy) hexane as a vulcanizing agent was added to 100 parts by weight of the obtained composition 7.
0.5 parts by weight of a roll were mixed to prepare a molding compound. This compound was press-molded at 165 ° C. for 10 minutes to produce a sheet having a thickness of 1 mm and 2 mm (hereinafter abbreviated as sheet 7). When the acoustic impedance and ultrasonic attenuation of the sheet 7 were measured by the same method as in Example 1, the results shown in Table 2 below were obtained.

[0029]

[Table 2]

[0030]

Industrial Applicability The present invention relates to an acoustic lens composition. This composition can maintain an acoustic impedance close to the body by maintaining a sound speed of 950 to 1,100 m / sec, and can provide an ultrasonic wave in a high frequency region. Since an acoustic lens having a small amount of attenuation and a high resolution can be formed, it has an advantage that it is useful as an acoustic lens material of a probe for an ultrasonic diagnostic apparatus.

Continuation of the front page (56) References JP-A-62-11897 (JP, A) JP-A-1-95157 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G10K 11 / 30 G01N 29/00-29/28 C08L 83/04-83/08 A61B 8/00-8/15 H04R 1/00-31/00 340

Claims (1)

(57) Reference number P071057 [Claims] 1. A) Silicone rubber compound based on diorganopolysiloxane
100 parts by weight, B) the general formula ^{(1) R 1 (R 1} 2 SiO) X (R 1 R 2 SiO) Y SiR 1 3 [ here R ¹ is the same or different, unsubstituted or substituted 1
A hydrocarbon group or a hydrogen atom, R ² is the same or different, and C _a H _{2a + 1} (a is an integer of 5 or more) or CH ₂ CH ₂ CH ₂ O (C
₂ H ₄ O) _b (C ₃ H ₆ O) _c R ¹ (b and c are integers of 0 or more, and b +
c is an integer of 1 or more), X is an integer of 0 or more,
Y is an integer of 1 or more], and 5 to 40 parts by weight of an organopolysiloxane.