JPH0644072B2 - Organopolysiloxane composition for gamma ray shielding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an organopolysiloxane composition for ray shielding. More specifically, the present invention relates to a line-shielding organopolysiloxane composition that cures in a state where heavy metal fine powder having a line-shielding effect is uniformly dispersed.

[Prior Art] Radiation such as α-rays, β-rays, rays, and neutrons is emitted from nuclear reactors, nuclear fuel reprocessing plants, cycloton devices, radioisotopes, etc. There is a demand for a material that adversely affects the human body, equipment, devices, etc. and shields this line safely and reliably.

Conventionally, a curable organopolysiloxane containing crystalline silica as a filler and lead powder added thereto has been used as a line-shielding organopolysiloxane composition.

[Problems to be Solved by the Invention] However, since a line shielding material composition obtained by adding lead powder to a curable organopolysiloxane having crystalline silica as a filler cannot add a large amount of lead powder, line shielding is not possible. It had the drawback of low performance.

Further, the composition causes separation and settling of lead powder during curing,
It has a drawback that a homogeneous cured product cannot be obtained.

The present invention aims to solve the above-mentioned drawbacks of the prior art, and provides a curable organopolysiloxane composition having a large line-shielding property and exhibiting a uniform line-shielding property in a cured product.

[Means for Solving Problems] The above-mentioned objects are (a) general formula (In the formula, R is a monovalent organic group having no aliphatic unsaturated bond,
R ¹ is an alkenyl group, a is an integer of 0 to 2, b is 1 or 2, and a + b is an integer of 1 to 3) 100 parts by weight of an organopolysiloxane having at least two units in one molecule. B) General formula (In the formula, R is the same as above, c is an integer of 0 to 3, and d is 1 to
An organohydrogenpolysiloxane fluid having at least two units represented by an integer of 3 and c + d is an integer of 1 to 3) in one molecule. A silicon atom-bonded hydrogen atom is an alkenyl group 1 in the component (a).
0.5 to 5.0 equivalents per equivalent (c) Heavy metal fine powder 50 to 2000 parts by weight, (d) Silica fine powder having a specific surface area of 30 m ² / g or more by the BET method and / or organo This can be achieved by a line-shielding organopolysiloxane composition comprising 0.5 to 30 parts by weight of a polysiloxane raw rubber and (e) a catalytic amount of a platinum compound.

To explain this, the component (a) used in the present invention is an organopolysiloxane having an alkenyl group in the molecule. In the above formula, R is a monovalent organic group having no aliphatic unsaturated bond, which includes an alkyl group such as a methyl group, an ethyl group and a propyl group, a 2-phenylethyl group, a 2-phenylpropyl group and a chloro group. Methyl group, cyanoethyl group, 3
-Substituted alkyl group such as 3.3-trifluoropropyl group, aryl group or substituted aryl group such as phenyl group and tolyl group, methoxy group, ethoxy group, propoxy group,
An alkoxy group such as a methoxyethoxy group is exemplified. R ¹ is an alkenyl group, examples of which include a vinyl group, an allyl group, and a propenyl group, with a vinyl group being preferred.
The organopolysiloxane has the general formula (In the formula, R is a monovalent organic group having no aliphatic unsaturated bond,
R ¹ is an alkenyl group, a is an integer of 0 to 2, b is 1 or 2, and a + b is an integer of 1 to 3), and it is necessary to have at least two units in one molecule. The organosiloxane unit may be included. Other organopolysiloxane units may be represented by the general formula (In the formula, R is the same as above, and e is an integer of 1 to 3). The organopolysiloxane of this component preferably has a methyl group content of 70% or more of the total R from the standpoint of balance between easy synthesis, mechanical properties required after curing, and appropriate viscosity of the composition, and a small amount of hydroxyl group. May be included. The molecular structure may be linear, branched, cyclic or network, but linear, branched or cyclic is preferable. Also the general formula The position of the unit represented by the formula (wherein R, R ¹ , a and b are the same as above) may be at the terminal of the molecule, in the middle of the molecule, or at both of them. The viscosity is not particularly limited, and from 50 centipoise at 25 ° C. to what is called silicone raw rubber can be used, but it is preferably 100 to 1,000,000 centipoise, and when the workability on site is emphasized, 150 to 100,000 centipoise is more preferable. preferable.

Specific examples of this component include dimethylvinylsilyl group end-blocked dimethylpolysiloxane, dimethylallylsilyl group endblocked dimethylpolysiloxane, dimethylpropenylsilyl group endblocked dimethylpolysiloxane, phenylmethylvinylsilyl group endblocked diphenylsiloxane / dimethylsiloxane. Copolymer, dimethylvinylsilyl group end-blocked methylvinylsiloxane / dimethylsiloxane copolymer, dimethylsilanol group endblocked methylvinylsiloxane / dimethylsiloxane copolymer, vinylpolysilsesquioxane, dimethylvinylsiloxane unit and Si
Examples of the copolymer include O ₂ units, and one or more of these may be used.

The component (b) used in the present invention has the general formula (In the formula, R is the same as above, c is an integer of 0 to 3, and d is 1 to
An organohydrogenpolysiloxane fluid having at least two units represented by an integer of 3 and c + d is an integer of 1 to 3) in the molecule. The organohydrogenpolysiloxane fluid of this component may contain other organosiloxane units, and other organosiloxane units may be of the general formula (In the formula, R and e are the same as the above). The molecular structure may be linear, branched, cyclic or network. Also the general formula The unit represented by the formula (wherein R, c, and d are the same as above) may be at the terminal of the molecule, in the middle of the molecule, or both. The viscosity is not particularly limited as long as it becomes liquid at room temperature, but it is preferably 3 to 10,000 centipoise at 25 ° C.

Specific examples of this component include dimethylhydrogensilyl end-capped dimethylsiloxane / methylhydrogensiloxane copolymer fluid, trimethylsilyl end-capped dimethylsiloxane / methylhydrogensiloxane copolymer fluid, dimethylphenylsilyl end-capped Examples include dimethylsiloxane / methylhydrogensiloxane copolymer fluid, trimethylsilyl group end-blocked methylhydrogenpolysiloxane fluid, cyclic methylhydrogenpolysiloxane fluid, and copolymer fluid consisting of dimethylhydrogensiloxane units and SiO ₂ units. You may use 1 type (s) or 2 or more types.

The addition amount of the component (b) is such that the silicon atom-bonded hydrogen atom in the component (b) is 0.5 per equivalent of the alkenyl group in the component (b).
It is necessary to use an amount of about 5.0 equivalents. This is because if it is less than this range, it cannot be sufficiently cured, and if it is more than this range, foaming occurs.

(C) component used in the present invention is a heavy metal fine powder,
The heavy metal has an atomic number of 70 or more and a specific gravity of 8 or more. Examples of this include tantalum, tungsten, osmium, iridium, gold, thallium, lead, bismuth, thorium, and uranium, and tungsten, lead, bismuth, thorium, in terms of availability and cost.
Uranium is preferred, and lead is more preferred.

The heavy metal fine powder of this component preferably has an average particle size of 150 μ or less. If the average particle size is larger than this, the dispersibility in the composition before curing will be poor, and it will easily settle during curing and after curing. This is because the composition of is not homogeneous.

The addition amount of this component is 50 to 2000 parts by weight with respect to 100 parts by weight of the component (a), and more preferably 100 to
It is 1500 parts by weight. This is because if the amount of the component (C) added is less than 50 parts by weight, the γ-ray shielding performance is insufficient,
On the other hand, if the amount is more than 2000 parts by weight, the viscosity of the composition before curing becomes too high and the handling becomes inconvenient.

The component (d) used in the present invention is 30 m ² / g by the BET method.
It is a silica fine powder and / or an organopolysiloxane raw rubber having the above specific surface area.

Examples of the fine silica powder include dry silica, wet silica, and those obtained by surface-treating these with halogenosilanes, alkoxysilanes, silazanes, and low polymerization degree organopolysiloxanes.

As the organopolysiloxane raw rubber having no alkenyl group, a substantially general formula is used. An example is an organopolysiloxane which is composed of a unit represented by the formula (wherein R and e are the same as those described above) and is in a raw rubber state at room temperature. The molecular weight thereof is preferably 300,000 or more, and more preferably 500,000 or more. The organopolysiloxane raw rubber may contain a small amount of hydroxyl groups. The molecular structure is linear, branched, or the like.

The addition amount of this component is 0.5 to 30 parts by weight with respect to 100 parts by weight of the component (a). This is because if it is less than 0.5 part by weight, the effect of preventing separation is insufficient, and if it is more than 30 parts by weight, the viscosity of the composition before curing becomes too high, which causes inconvenience in handling.

The component (e) used in the present invention is a platinum-based catalyst, which includes fine particle platinum, fine particle platinum adsorbed on a carbon powder carrier, chloroplatinic acid, alcohol-modified chloroplatinic acid, chloroplatinic acid. Examples thereof include an olefin complex, a coordination compound of chloroplatinic acid and vinyl siloxane, platinum black, palladium, a rhodium catalyst and the like.

The amount of this component added depends on the type of catalyst,
Although not particularly limited, the amount of the platinum metal itself is usually 1 to 2000 ppm with respect to the total amount of the organopolysiloxane.

In the composition of the present invention, if necessary, graphite fine powder, carbon fiber fine powder, diatomaceous earth, quartz powder, alumina, iron oxide, zinc oxide, zinc carbonate, etc. may be used as long as the object of the present invention is not impaired. Inorganic fillers, boron carbide, lithium fluoride, neutron shielding agents such as metal hydride compounds, heat-resistant agents, flame retardants, pigments, glass fibers, adhesion promoters, curing retarders and the like may be added.

As the curing retarder, 3-methyl-1-butyn-3-ol, 3.5-dimethyl-1-hexyne-3-ol,
3-methyl-1-penten-3-ol, alkynyl alcohols such as phenylbutynol, 3-methyl-3
Examples include -penten-1-yne, 3,5-dimethyl-3-hexene-1-yne, and a methylvinylsiloxane cyclic compound.

The organopolysiloxane composition of the present invention has been described above.
A predetermined amount of each of the components (a), (b), (c), (d) and (e) is applied to a roll, a kneader mixer, a Banbury mixer,
It can be obtained by uniformly mixing by a conventionally known mixing means such as a planetary mixer. When storing this composition, it is preferable to pack it in two or three packages. For example, the component (b) can be used as the first package and the other components can be used as the second package, or the total amount of the component (b) can be used. The mixture consisting of (a) component, (c) component and a part of (d) component may be used as the first package and the other remaining components may be used as the second package, or (a) component, (d) component and (e) ) Component as the first package, (b) component as the second package, and (c) component as the third package.
The method of storing as a package and mixing these two packages or three packages at the time of use may be adopted.

The organopolysiloxane composition of the present invention can be cured by simply leaving the composition mixed as described above at room temperature.
You may heat and harden at 0 degreeC.

[Function] The organopolysiloxane as the component (a) is the main ingredient of the present composition. (B) The organohydrogenpolysiloxane fluid of component (e) is added in the presence of the platinum-based catalyst of component (e).
It exhibits the effect of crosslinking and curing with the component (a). The heavy metal fine powder as the component (c) has the function of imparting γ-ray shielding performance. The fine silica powder and / or the alkenyl group-free organopolysiloxane raw rubber of the component (d) increases the viscosity of the composition before curing and imparts thixotropy, and separates the heavy metal fine powder of the component (c). It has the effect of preventing settling to give a homogeneous cured composition.

EXAMPLES Next, the present invention will be described with reference to examples. In the examples, "parts" means "parts by weight", and the viscosity is a value measured at 25 ° C. Me represents a methyl group.

Example 1 100 parts of dimethylpolysiloxane (vinyl group content: 0.25% by weight) blocked at both ends with a viscosity of 2000 centipoise (vinyl group content: 0.25% by weight); Done B
Dry silica 10 having a specific surface area of 300 m ² / g by ET method
Parts and 0.5 parts of a 2-ethylhexanol solution of chloroplatinic acid (platinum content: 0.05% by weight) were added and uniformly mixed to prepare a 1A solution.

An organohydrogenpolysiloxane copolymer 1 having a viscosity of 20 centipoise and comprising 20 mol% of Me ₃ SiO1 / 2 units, 50 mol% of Me ₂ SiO units and 30 mol% of MeHSiO units.
A uniform mixture of 00 parts, dimethylpolysiloxane (vinyl group content 1.0% by weight) blocked with dimethylvinylsilyl groups at both ends and a viscosity of 100 centipoise, and 20 parts of tetramethyl-tetravinyl-cyclotetrasiloxane as a curing retarder. 1B solution was prepared.

Next, 1 part of 1B liquid was added to 1 part of 1A liquid, mixed uniformly, and poured into a cylindrical container having a diameter of 18 mm to a height of 100 mm. After being left to cure at room temperature for 1 day, the cylinder was sampled in three parts with heights of 90 to 100 mm (upper part), 40 to 50 mm (middle part) and 0 to 10 mm (lower part), and the specific gravity was measured. It was 0.02, 5.02 and 5.04, and it was confirmed that the lead powder was uniformly dispersed.

Separately, a sheet-like cured product having a thickness of 3 mm was left standing at room temperature for 3 days, and the rubber physical properties were measured according to JIS K6301. The hardness was 54, the tensile strength was 7.6 kg / cm ² , and the elongation was 170%. there were. When 1A solution was stored at room temperature for 1 month, no separation and settling of lead powder was observed.
It could be easily mixed with the liquid B, and the same cured physical properties as in the initial stage were obtained.

Example 2 Phenylmethylsiloxane / dimethylsiloxane copolymer having a viscosity of 10,000 centipoise and blocked at both ends with dimethylvinylsilyl groups (phenylmethylsiloxane unit 30 mol%, dimethylsiloxane unit 70 mol%, vinyl group content 0.14 wt%) 100 parts, 500 parts of lead powder having an average particle diameter of 20 μ, 2 parts of dry silica having a specific surface area of 200 m ² / g by the BET method, and 2-ethylhexanol solution of chloroplatinic acid (platinum content 0.05% by weight). 5 parts were added and uniformly mixed to prepare a 2A solution.

Also, an organohydrogenpolysiloxane copolymer 1 having a viscosity of 30 centipoise and consisting of 15 mol% of MeHSiO 1/2 unit, 60 mol% of Me ₂ SiO unit and 25 mol% of MeHSiO unit.
00 parts and 20 parts of tetramethyl tetravinylcyclotetrasiloxane as a curing retarder are mixed uniformly and 2
Solution B was prepared.

Next, 0.5 part of the 2B solution was added to 100 parts of the 2A solution, mixed uniformly, and poured into a cylindrical container having a diameter of 18 mm to a height of 100 mm. After curing at room temperature for 1 day, the cylinder was sampled in three parts with heights of 90 to 100 mm (upper part), 40 to 50 mm (middle part) and 0 to 10 mm (lower part), and the specific gravity was measured. It was 0.055, 4.05 and 4.06, and it was confirmed that the lead powder was uniformly dispersed.

Separately, a sheet-like cured product having a thickness of 3 mm was left standing at room temperature for 3 days, and the rubber physical properties were measured according to JIS K6301. The hardness was 42, the tensile strength was 6.6 kg / cm ² , and the elongation was 160%. there were. When solution 2A was stored at room temperature for 1 month, separation and settling of lead powder was not observed, and it could be easily mixed with solution 2B to obtain the same cured physical properties as in the initial stage.

Example 3 A dimethylpolysiloxane having a viscosity of 500 centipoise and blocked with dimethylvinylsilyl groups at both ends (vinyl group content: 0.
51 parts by weight) 100 parts, lead powder 120 having an average particle size of 40μ
0 part, 15 parts of dimethylpolysiloxane raw rubber having a molecular weight of 700,000 and blocked at both ends with dimethylsilanol groups and a solution of chloroplatinic acid in 2-ethylhexanol.
0.5% by weight) was added and mixed uniformly to prepare 3A liquid.

Next, for 100 parts of this 3A solution, 1 used in Example 1 was used.
0.5 part of solution B was added and mixed uniformly, and the mixture was poured into a cylindrical container having a diameter of 18 mm to a height of 100 mm. After curing at room temperature for 1 day, the cylinder is 90-100 mm high (upper part),
The specific gravity was measured by sampling three parts of 40 to 50 mm (middle part) and 0 to 10 mm (bottom part), and the specific gravity was 5.80, 5.81 and 5.83, respectively, and the lead powder was uniformly dispersed. It was confirmed.

Separately, a sheet-like cured product having a thickness of 3 mm was left standing at room temperature for 3 days, and the rubber physical properties were measured according to JIS K6301. The hardness was 48, the tensile strength was 6.1 kg / cm ² , and the elongation was 150%. there were. When solution 3A was stored at room temperature for 1 month, separation and settling of lead powder was not observed, and it could be easily mixed with solution 1B to obtain the same cured physical properties as in the initial stage.

Comparative Example 1 Exactly the same as Example 1 except that dry silica was not added.
Liquids A and 1B were prepared. To 100 parts of this liquid 1A, 1 part of liquid 1B was added and mixed uniformly, and the mixture was poured into a cylindrical container having a diameter of 18 mm to a height of 100 mm. After being left to cure at room temperature for 1 day, the cylinders have a height of 90-100 mm (upper part), 40-50 mm (middle part) and 0-10 mm (lower part).
As a result of measuring the specific gravity by sampling the three parts of
It was 4.53, 4.94 and 5.05, respectively, and the lead powder was not uniformly dispersed, and separation and sedimentation occurred during curing.

Separately, a sheet-like cured product having a thickness of 3 mm was left standing at room temperature for 3 days, and the rubber properties were measured according to JIS K6301. The hardness was 51, the tensile strength was 6.7 kg / cm ² , and the elongation was 160%. there were. When solution 1A was stored at room temperature for 1 month, lead powder separated and settled at the bottom, and it was difficult to mix with solution 1B.

Comparative Example 2 Dimethylpolysiloxane having a viscosity of 500 centipoise and blocked at both ends with a dimethylvinylsilyl group (vinyl group content: 0.
51 parts by weight) 100 parts, lead powder 470 having an average particle diameter of 40μ
Parts, 100 parts of crystalline silica having a specific surface area of 2 m ² / g, and 0.5 parts of a 2-ethylhexanol solution of chloroplatinic acid (platinum content 0.05% by weight) are added and uniformly mixed to obtain 4
Solution A was prepared.

An organohydrogenpolysiloxane copolymer 1 having a viscosity of 20 centipoise and consisting of 20 mol% of MeHSiO 1/2 unit, 50 mol% of Me ₂ SiO unit and 30 mol% of MeHSiO unit.
A uniform mixture of 00 parts, dimethylpolysiloxane having a viscosity of 100 centipoise and blocked with dimethylvinylsilyl groups at both ends (vinyl group content 1.0% by weight), and 10 parts of tetramethyl tetravinyl cyclotetrasiloxane as a curing retarder was uniformly mixed. 4B solution was prepared.

Next, to 100 parts of 4A liquid, 1 part of 4B liquid was added and mixed uniformly, and the mixture was poured into a cylindrical container having a diameter of 18 mm to a height of 100 mm. After being left to cure at room temperature for 1 day, the cylinder was sampled in three parts with a height of 90 to 100 mm (upper part), 40 to 50 mm (middle part) and 0 to 10 mm (lower part), and the specific gravity was measured. It was 0.15, 3.39, and 3.49, and the lead powder was not uniformly dispersed, causing separation and sedimentation during curing.

Separately, a sheet-like cured product having a thickness of 3 mm was left standing at room temperature for 3 days, and the rubber physical properties were measured according to JIS K6301 to find that the hardness was 66 and the tensile strength was 14.6 kg / c.
It was m ² and the elongation was 60%. When solution 4A was stored at room temperature for 1 month, lead powder separated and settled at the bottom, making it difficult to mix with solution 4B.

Comparative Example 3 In Comparative Example 2, lead powder was further added in an amount of 57 when preparing the 4A liquid.
Although 0 part was added (the amount that gives a specific gravity of 5.0 after curing), the viscosity was extremely increased, and it was not possible to mix uniformly, and molding / processing could not be performed.

EFFECTS OF THE INVENTION The present invention provides a conventional crystalline silica because it is an addition reaction-curable organopolysiloxane composition using a platinum catalyst containing silica fine powder and / or an organopolysiloxane raw rubber having no alkenyl group. Compared to the γ-ray shielding material in which the heavy metal fine powder is added to the curable organopolysiloxane using as a filler, there is almost no separation and sedimentation of the heavy metal fine powder during storage, and the separation and sedimentation of the heavy metal fine powder during curing Since it does not occur, the heavy metal fine powder in the cured product is uniformly dispersed, so that it has the characteristic that it has a uniform γ-ray shielding performance in any part of the cured product.

Therefore, it is suitable for use as a shielding material for hospitals and laboratories that handle X-rays and γ-rays, a γ-ray shield in a nuclear power plant (especially a penetration seal for a penetration part), or a γ-ray shield for a spent nuclear fuel transportation container. be able to.

Claims (2)

[Claims] 1. A general formula (In the formula, R is a monovalent organic group having no aliphatic unsaturated bond,
R ¹ is an alkenyl group, a is an integer of 0 to 2, b is 1 or 2, and a + b is an integer of 1 to 3) 100 parts by weight of an organopolysiloxane having at least two units in one molecule. B) General formula (In the formula, R is the same as above, c is an integer of 0 to 3, and d is 1 to
An organohydrogenpolysiloxane fluid having at least two units represented by an integer of 3 and c + d is an integer of 1 to 3) in one molecule. A silicon atom-bonded hydrogen atom is an alkenyl group 1 in the component (a).
0.5 to 5.0 equivalents per equivalent (c) Heavy metal fine powder 50 to 2000 parts by weight, (d) Silica fine powder and / or alkenyl having a specific surface area of 30 m ² / g or more by the BET method. A line-shielding organopolysiloxane composition comprising 0.5 to 30 parts by weight of a group-free organopolysiloxane raw rubber and (e) a catalytic amount of a platinum-based compound. 2. The line-shielding organopolysiloxane composition according to claim 1, wherein the heavy metal fine powder is lead.