JPH08305375A - Composition for acoustic lens - Google Patents

Abstract

PURPOSE: To provide compsn. for an acoustic lens capable of forming the acoustic lens with which an acoustic impedance is made approximate to the acoustic impedance of a living body by maintaining a sound velocity at 950 to 1,100m/sec and in which the ultrasonic attenuation rate in a high-frequency region is low and resolution is high. CONSTITUTION: The compsn. for the acoustic lens consists of (A) 100 pts.wt. silicone rubber comps. mainly composed of diorganopolysiloxane and (B) 5 to 40 pts.wt. organo-siloxane expressed by general formula R<1> (R<1> 2 SiO)x (R<1> R<2> SiO)y SiR<1> 3 (R<1> is a univalent hydrocarbon group or hydrogen atom, R<2> is an alkyl group, polyether group, X is an integer of >=0, Y is an integer of >=1).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a composition for an acoustic lens, in particular, the acoustic velocity can be maintained at 950 to 1,100 m / sec to bring the acoustic impedance close to that of a living body, and the amount of ultrasonic attenuation in a high frequency region is small, The present invention relates to an acoustic lens composition that can form an acoustic lens with high resolution and that is useful as an acoustic lens material for a probe for an ultrasonic diagnostic apparatus.

[0002]

2. Description of the Related Art An acoustic lens of a probe for an ultrasonic diagnostic apparatus focuses ultrasonic waves and closely adheres to the living body to match the acoustic impedance (density × sound velocity) of the living body and reduce reflection of the ultrasonic waves. Since it is required that the amount of ultrasonic attenuation of the lens itself is small, silicone rubber compounds containing diorganopolysiloxane as the main component have been widely used for this acoustic lens composition. ing. Then, in this lens composition, in order to match the acoustic impedance of a living body, an inorganic polyfiller such as silica, alumina, or titanium oxide is added to the base organopolysiloxane to increase its density, and It has been proposed to add an organic resin such as nylon to increase the speed of sound (see JP-A-58-216294 and JP-A-62-11897).

[0003]

However, the silicone rubber used for this kind of application has a super-conductivity of an acoustic lens made from this composition when a filler and an organic resin are added in order to increase its density and sound velocity. There is a problem that the sound wave attenuation amount becomes large, and this solution is demanded.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a composition for an acoustic lens which solves the above disadvantages and problems, which is 100% by weight of a silicone rubber compound containing A) diorganopolysiloxane as a main component. Part, B) General formula (1) R ¹ (R ¹ ₂ SiO) _X (R ¹ R ² SiO) _Y SiR ¹ ₃ ··· (1) [wherein R ¹ is the same or different, Substitution or 1 of substitution
Valent hydrocarbon group or hydrogen atom, R ² is the same or different, 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 organopolysiloxane.

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

[0006]

The composition for acoustic lens of the present invention has the above-mentioned (A).
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 composed mainly of diorganopolysiloxane, which is composed of (a) diorganopolysiloxane and (b) a filler. a),
Examples of component (b) include the following.

Examples of the diorganopolysiloxane as the component (a) include those represented by the following general formula (2) XO-[(SiR ₂ ) O] _n -X (2) . This R is an alkyl group such as a methyl group, an ethyl group, 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, or a carbon atom thereof. An unsubstituted or substituted monovalent hydrocarbon group selected from a chloromethyl group, a trifluoroalkyl group, a cyanomethyl group, etc., in which some or all of the bonded hydrogen atoms are substituted with a halogen atom, a cyano group, etc. A group, a vinyl group, a phenyl group and a trifluoropropyl group are preferable, and at least 50 mol% thereof is preferably a methyl group and 0.001 to 5 mol% thereof is preferably a vinyl group. Alternatively, X is preferably a trimethylsilyl group, a dimethylvinylsilyl group, or a hydrogen atom, and it is usually preferable that the viscosity at 25 ° C. is in the range of 100 to 10,000,000 cSt, which may be a single type or a combination of two or more types. May be used.

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 increasing the amount of talc, sericite, bentonite, etc. are exemplified, but the average particle size of these fillers is 5 μm or less, preferably 2 μm or less in order to reduce ultrasonic attenuation. It is good to say If the content of these fillers is less than 30 parts by weight with respect to 100 parts by weight of the component (a), it is not possible to expect an increase in the density of this composition, and if it exceeds 200 parts by weight, the ultrasonic attenuation will be large. Since it may occur, the amount 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 by a device such as a kneader, Banbury mixer, roll or the like which is usually used for producing a silicone rubber composition, and may be heat-treated as necessary.

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

Next, the organopolysiloxane as the component (B) in this composition has the general formula (1) R ¹ (R ¹ ₂ SiO) _X (R ¹ R ² SiO) _Y SiR ¹ ₃・ ・ ・ (1) is assumed. R ^{1 in} this formula is the same as or different from R described above and is an unsubstituted or substituted monovalent hydrocarbon group or hydrogen atom, and particularly preferably a methyl group. Also, this R ² is C _a H _{2a + 1} (a is 5
Or more integer) 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, 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 this organopolysiloxane has this composition. It is required to increase the sound velocity of an object, bring the acoustic impedance closer to the human body, and reduce the amount of ultrasonic wave attenuation.

C _a H at R ² in the above general formula (1)
_The a of the alkyl group represented by _{2a + 1} increases the speed of sound of the composition at a predetermined amount, but it must be 5 or more in order to bring the acoustic impedance close to that of a living body, and particularly 8
It is preferably set to -20. If it exceeds 20, it may become solid and it may be difficult to mix. Specific examples thereof 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, Although the speed of sound of the composition is increased by blending it, b + c is required to be an integer of 1 or more in order to bring the acoustic impedance close to that of the human body, so this is particularly preferably 5 or more. If it exceeds 100, it may become solid and may be difficult to mix. It is necessary that X is an integer of 0 or more and Y is an integer of 1 or more in order to increase the sound velocity of the composition. However, the viscosity of the organopolysiloxane makes it easy to mix. From 25 ℃
In the above, it 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 when it is less than 5 parts by weight with respect to 100 parts by weight of the above-mentioned component (A). I cannot expect an increase in the speed of sound of objects,
When the amount is more than 40 parts by weight, the mechanical strength of the composition is remarkably lowered, so that 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 acoustic lens composition of the present invention is prepared by uniformly kneading a predetermined amount of the above-mentioned 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 per 100 parts by weight of the composition for an acoustic lens. Then, it may be heated at a predetermined temperature. Further, when the diorganopolysiloxane in the component (A) contains an unsaturated group such as a vinyl group, it has two or more hydrogen atoms bonded to a silicon atom which undergoes an addition reaction with the vinyl group. You may make it harden | cure by adding the organohydrogen polysiloxane which contains and a platinum catalyst, and adding it and carrying out the addition reaction. In this case, it is preferable that the amount of hydrogen atoms bonded to silicon atoms be 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-mentioned composition for acoustic lens of the present invention, this composition is molded and crosslinked 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 invention is not limited by these examples. Example 1 75% by weight of dimethylpolysiloxane having both ends of its molecular chain blocked with dimethylvinylsilyl groups and a viscosity of 100,000 cSt
A base oil consisting of 25% by weight of a vinyl group-containing silicone resin for reinforcement and a vinyl group content of 0.022 mol / 100 g 60
40 parts by weight of quartz powder having an average particle diameter of 1.4 μm and general formula (3)

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

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

Next, the density of this sheet 1 at 25 ° C. was obtained in accordance with JIS C-2123, and the sonic velocity of this sheet at 25 ° C. was measured by a sonic velocity measuring device / singaround type sonic velocity measuring device U.
The acoustic impedance of the sheet 1 was measured by a VM-2 type (trade name, manufactured by Ultrasonic Industries Co., Ltd.), and was 1.40 × 10 ⁶ (kg / m ² · sec). In addition, this product is filled with water at 25 ° C in a water tank, and ultrasonic waves of 5 MHz are generated in water by an ultrasonic oscillator / function generator FG-350 [trade name of Iwatsu Electronics Co., Ltd.] to generate ultrasonic waves. The amplitude before and after passing through the sheet 1 was measured by an ultrasonic receiver / oscilloscope VP-5204A [trade name of Matsushita Electric Industrial Co., Ltd.], and 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 its molecular chain blocked with dimethylvinylsilyl groups 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 a vinyl resin containing a vinyl group and a reinforcing vinyl resin.
To 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 A composition 2 was prepared by kneading 20 parts by weight of the organopolysiloxane represented by

Then, 3.9 parts by weight of methylhydrogenpolysiloxane 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 and mixed with the composition 2 as a curing agent. A base compound is placed in a vacuum container and defoamed under reduced pressure to prepare a molding compound, and this 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 this sheet 2 were measured by the same method as in Example 1, and the results shown in Table 1 below were obtained.

Example 3 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 a vinyl group content of 0.2 mol%, and reinforcing fumed silica 16 A composition 3 was prepared by kneading parts by weight, 33 parts by weight of quartz powder having an average particle diameter of 1.4 μm and 20 parts by weight of the organopolysiloxane represented by the general formula (4).

Then, 100 parts by weight of this composition 3 was roll-mixed with 0.5 part by weight of 2,5-dimethyl-2,5-di (t-butylperoxy) hexane as a vulcanizing agent to obtain a molding compound. Prepare and compound this molding 1
A sheet having a thickness of 1 mm and 2 mm (hereinafter abbreviated as sheet 3) was produced 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 by the same method as in Example 1, and the results shown in Table 1 below were obtained.

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

Then, the molding compound was heated to 150 ° C.
By press-molding for 10 minutes to produce a sheet having a thickness of 1 mm and 2 mm (hereinafter abbreviated as sheet 4).
When the density, sound velocity, acoustic impedance, and ultrasonic attenuation of were measured in the same manner as in Example 1, the results shown in Table 1 below were obtained.

Comparative Example 2 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 a vinyl group content of 0.2 mol%, and reinforcing fumed silica 16 Part 5 and 33 parts by weight of quartz powder having an average particle size of 1.4 μm were kneaded to prepare a composition 5 [the same composition 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
A molding compound was prepared by mixing 0.5 part by weight of dimethyl-2,5-di (t-butylperoxy) hexane.

Then, the molding compound was heated to 165 ° C.
A sheet having a thickness of 1 mm and 2 mm (hereinafter abbreviated as sheet 5) is produced by press molding for 10 minutes, and the density, sound velocity, acoustic impedance and ultrasonic attenuation of this sheet 5 are measured in the same manner as in Example 1. The results shown in Table 1 below were obtained.

[0026]

[Table 1]

Comparative Example 3 75% by weight of dimethylpolysiloxane having both ends of its molecular chain blocked with dimethylvinylsilyl groups and 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 a vinyl resin containing a vinyl group and a reinforcing vinyl resin.
40 parts by weight of quartz powder having an average particle size of 1.4 μm in 60 parts by weight [the same composition as in Example 1 except for the organopolysiloxane represented by the general formula (3)] and the general formula (5)

Embedded image Composition 6 was prepared by kneading 20 parts by weight of the organopolysiloxane represented by To the resulting composition 6, 3.9 parts by weight of methyl hydrogen polysiloxane having a hydrogen group content of 0.0053 mol / g and a chloroplatinic acid catalyst (10 ppm in terms of platinum amount) were added as a curing agent and mixed, and then the base compound was vacuumed. The mixture was placed in a container and defoamed under reduced pressure to prepare a molding compound. Apply this molding compound at 150 ° C for 10
A sheet having a thickness of 1 mm and 2 mm (hereinafter abbreviated as sheet 6) was produced by press molding for one minute. When the acoustic impedance and the amount of ultrasonic attenuation of this sheet 6 were measured by the same method as in Example 1, the results shown in Table 2 below were obtained.

Comparative Example 4 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 a vinyl group content of 0.2 mol%, and 16 parts by weight of reinforcing fumed silica. Parts and 33 parts by weight of quartz powder having an average particle size of 1.4 μm (same as 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.
100 parts by weight of the obtained composition 7 was added to 2,5-dimethyl-2,5-di (t-butylperoxy) hexane as a vulcanizing agent.
0.5 parts by weight were roll-mixed to prepare a molding compound. This compound was press-molded at 165 ° C. for 10 minutes to prepare a sheet having a thickness of 1 mm and 2 mm (hereinafter abbreviated as sheet 7). When the acoustic impedance and the amount of ultrasonic attenuation of this sheet 7 were measured in the same manner as in Example 1, the results shown in Table 2 below were obtained.

[0029]

[Table 2]

[0030]

EFFECTS OF THE INVENTION The present invention relates to an acoustic lens composition, which is capable of maintaining the acoustic velocity at 950 to 1,100 m / sec to bring the acoustic impedance close to that of the body and ultrasonic waves in the high frequency range. Since an acoustic lens having a small amount of attenuation and high resolution can be formed, it has an advantage that it is useful as an acoustic lens material for a probe for an ultrasonic diagnostic apparatus.

Claims (1)

Reference number P071057 [Claims] 1. A silicone rubber compound containing A) a diorganopolysiloxane as a main material.
100 parts by weight, B) General formula (1) R ¹ (R ¹ ₂ SiO) _X (R ¹ R ² SiO) _Y SiR ¹ ₃ [wherein R ¹ is the same or different, unsubstituted or substituted 1
Valent hydrocarbon group or hydrogen atom, R ² is the same or different, 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 organopolysiloxane.