JPS61235797A - Organopolysiloxane composition for shielding neutron - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to an organopolysiloxane composition for neutron shielding.

[Prior art] Neutrons from nuclear reactors, nuclear fuel reprocessing plants, cycloton devices, radioactive isotopes, etc. have high energy;
Furthermore, when they collide with other substances, they generate gamma rays, which can seriously harm the human body, so there is a need for materials that can safely and reliably shield these neutrons.

Among neutrons, fast neutrons are diffused by elastic collisions with hydrogen atoms of approximately the same mass, so it is known that materials with high hydrogen atom density are effective in shielding fast neutrons.

Conventionally, as an organopolysiloxane composition for neutron shielding, a composition made by blending fine boron carbide powder with an organopolysiloxane composition has been known (Japanese Patent Laid-Open No. 53-7
3000 and JP-A-54-1798).

On the other hand, flame-retardant compositions are also known, which are made by blending aluminum hydroxide fine powder with condensation reaction-curing or peroxide catalyst-curing organopolysiloxane compositions (Japanese Patent Publication No. 53
-35982 publication, JP-A-54-90349 publication,
JP-A-58-65751 and JP-A-59-19
(See Publication No. 864).

[Problem to be Solved by the Invention 1] However, the boron carbide-containing organopolysiloxane composition has a drawback in that its neutron shielding performance, particularly its fast neutron shielding performance, is insufficient.

In addition, condensation reaction-curing organopolysiloxane compositions containing fine aluminum hydroxide powder cure from the surface, making it difficult to cure uniformly to the inside, and producing harmful by-products. Furthermore, a peroxide catalyst-curable organopolysiloxane composition mixed with aluminum hydroxide fine powder required high-temperature heat treatment to cure, and had the disadvantage of poor on-site workability. . Moreover, none of these organopolysiloxane compositions was intended for neutron shielding.

The present invention aims to eliminate the drawbacks of the prior art described above, and provides an organopolysiloxane composition for neutron shielding that has excellent neutron shielding performance and excellent field workability.

[Means for Solving the Problem 1 The above object is as follows: (a) General formula RaR'bSiO4-a-b)/2 (wherein R is a monovalent organic group having no aliphatic unsaturated bond, R1
is an alkenyl group, a is an integer of 0 to 2, b is 1 or 2,
organopolysiloxane 1 having at least two units represented by (a+b is an integer from 1 to 3) in one molecule
00 parts by weight (b) General formula RcHdSiO4-c--d)/2 (wherein, R is the same as above, C is an integer of 0 to 3, d is an integer of 1 to 3, c+d is an integer of 1 to 3 Organohydrodiene polysiloxane fluid having at least two units represented by in one molecule so that the amount of silicon-bonded hydrogen atoms is 0.5 to 5.0 equivalents per equivalent of alkenyl group in component (a). (c) 30 to 300 parts by weight of aluminum hydroxide fine powder with an average particle diameter of 50μ or less, (d) Thickener
0 to 30 parts by weight and (e)'PI1. This can be achieved by a neutron-shielding organopolysiloxane composition characterized by comprising a medium amount of a platinum-based compound.

To explain this, 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, and includes alkyl groups such as methyl group, ethyl group, and propyl group, L2-phenylethyl group, 2-phenylpropyl group, and chloromethyl group. , cyanoethyl group, 3
・3.3-) IJ Examples include a substituted alkyl group such as a fluoropropyl group, an aryl group such as a phenyl group, and a tolyl group, or a substituted aryl group. R1 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 or7-polysiloxane has the general formula % (wherein R is a monovalent organic group having no aliphatic unsaturated bond,
R1 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). It may also contain organosiloxane units. Examples of the organosiloxane unit include units represented by the general formula % (wherein R is the same as above and e is an integer from 1 to 3). In the orga-nopolysiloxane of this component, it is preferable that 70% or more of the total R is a methyl group from the viewpoint of ease of synthesis, balance of mechanical properties required after curing and appropriate viscosity of the composition, and a small amount of hydroxyl group,
Alternatively, it may contain an alkoxy group such as a methoxy group, ethoxy group, propoxy group, or methoxyethoxy group. The molecular structure may be linear, branched, cyclic, or network-like, but linear, branched, and cyclic are preferred. Furthermore, the position of the unit represented by the general formula % (in the formula, R%R', a, and b are the same as above) may be at the end of the molecule, in the middle of the molecule, or both. You can. The viscosity is not particularly limited, and ranges from 50 centiboise at 25°C to what is called silicone raw rubber can be used, but it is preferably 100 to 1oooooo centiboise, and when on-site workability is important, 150 to 1ooooo.

Centipoise is more preferred. Further, when component (2) to be described later is not added, it is preferable that the diameter is 1000 centivoise or more from the viewpoint of preventing separation of aluminum hydroxide, which is component (c).

Specific examples of this component include dimethylpolysiloxane endblocked with dimethylvinylsilyl groups, dimethylpolysiloxane endblocked with dimethylallylsilyl groups, dimethylpolysiloxane endblocked with dimethylpropenylsilyl groups, and diphenylsiloxane endblocked with phenylmethylvinylsilyl groups. Siloxane copolymer, dimethylvinylsilyl group end-blocked methylvinylsiloxane/dimethylsiloxane copolymer, dimethylsilanol group endblocked methylvinylsiloxane/dimethylsiloxane copolymer, vinylpolysilsesquioxane, dimethylvinylsiloxane unit and A copolymer consisting of 5i02 units is exemplified, and one of these
A species or two or more species may be used.

(1&min) used in the present invention is expressed by the general formula % (wherein, R is the same as above, C is an integer of 0 to 3, and d is 1 to
The present invention is an ornohydrogenpolysiloxane fluid having at least two units in the molecule represented by an integer of 3 and c+d being an integer of 1 to 3. The Organatsuno A hydrodiene polysiloxane fluid of this component may contain a Pond Olga/siloxane unit, and the Pond Olga/Siloxane unit has the general formula % (where R and e are the same as above). The unit represented by is exemplified. The present component ol-7-hydrodiethylene polysiloxane fluid may contain small amounts of hydroxyl groups or alkoxy groups such as methoxy, ethoxy, propoxy, methoxyethoxy groups. The molecular structure may be linear, branched, cyclic, or network-like. Further, the unit represented by the general formula % (in which R, c, and d are the same as above) may be at the end of the molecule, in the middle of the molecule, or both. Further, the viscosity is not particularly limited as long as it becomes liquid at room temperature, but it is preferably 3 to 1 oooo centiboise at 25°C.

Specific examples of this component include dimethylhydrogensilyl group-endblocked dimethylsiloxane/methylhydrogensiloxane copolymer fluid, trimethylsilyl group endblocked dimethylsiloxane/methylhydrogensiloxane copolymer fluid, dimethylphenylsilyl group endblocker dimethyl Examples include a siloxane/methylhydrodiene siloxane copolymer fluid, a trinotylsilyl end-blocked methylhydrodiene polysiloxane fluid, a cyclic methylhydrodiene polysiloxane fluid, and a copolymer fluid consisting of dimethylhydrodiene siloxane units and 5i02 units, One or more of these may be used.

The amount of component (B) added must be such that the amount of silicon-bonded hydrogen atoms in component (B) is 0.5 to 5.0 equivalents per equivalent of fluorenyl group in component (A). be. This is because if the amount is less than this range, sufficient curing will not be possible, and if it is more than this range, foaming will occur.

Component (iii) used in the present invention is aluminum hydroxide fine powder, and the average particle size is limited to 50 μm or less.

This is because when the average particle size is larger than 50μ, the dispersibility in the composition becomes poor and separation becomes easy.

The amount of this component added is 30 to 300 parts by weight, more preferably 50 to 300 parts by weight per 100 parts by weight of component (A).
The amount is 200 parts by weight.

Component (2) used in the present invention is a thickener, which is added as necessary. Examples of the thickener of this component include fine silica powder, fine carbon powder, and organopolysiloxane raw rubber having no alkenyl group.

Examples of fine silica powder include dry silica, wet silica, or those surface-treated with haloptsilanes, alkoxysilanes, silazane, and low-polymerization degree organopolysiloxanes, and the specific surface area is 5% by BET method.
Those with a weight of 0 m27 g or more are preferably used.

Fine carbon powders include channel black, furnace black, thermal black, acetylene black,
Examples include carbon black fine powder such as lamp black, graphite fine powder, and carbon fiber fine powder, and those having a specific surface area of 30 m27 g or more according to the BET method are preferably used.

Examples of organopolysiloxane raw rubbers that do not have alkenyl groups include organopolysiloxanes that are in the form of raw rubber at room temperature and are substantially composed of units represented by the general formula % (where R and e are the same as above). The molecular weight thereof is preferably 300,000 or more, more preferably 500,000 or more. The present organopolysiloxane raw rubber may contain a small amount of hydroxyl group or alkoxy group such as methoxy group, ethoxy group, propoxy group, or methoxyethoxy group. In addition, the molecular structure is
It may be linear, branched, cyclic or network-like.

The amount of this component added is 0 to 30 parts by weight per 100 parts by weight of component (A), but the thixotropic properties of the mixture consisting of components (A), (B), and (C) are not maintained. When sufficient, the amount of this component added is (a) component 100
The amount is preferably 0.1 to 30 parts by weight.

Component (e) used in the present invention is a platinum-based catalyst, which includes particulate platinum, particulate platinum adsorbed on a carbon powder carrier, chloroplatinic acid, alcohol-modified chloroplatinic acid,
Examples include olefin complexes of chloroplatinic acid, coordination compounds of chloroplatinic acid and vinylsiloxane, platinum black, palladium, and ronium catalysts.

The amount of this component added varies depending on the type of catalyst and is not particularly limited, but it is usually 1 to 2000 ppI11 of the platinum metal itself based on the total amount of organopolysiloxane.
It is said that

In addition, the composition of the present invention may include diatomaceous earth,
Inorganic fillers such as quartz powder, alumina, iron oxide, zinc oxide, gamma ray shielding agents such as lead and lead compounds, boron carbide,
A thermal neutron shielding agent such as lithium heptafluoride, a heat resistant agent, a flame retardant, a pigment, a glass fiber, an adhesion promoter, a curing retarder, and the like may be added.

As the curing retarder, 3-methyl-1-butyn-3-ol, 3,5-dimethyl-1-hexyn-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-hexen-1-yne, and tetravinylsiloxane cyclic body.

The organopolysiloxane composition of the present invention is as described above (
A), (b), (c), (e), and if necessary, (d) components are mixed uniformly in predetermined amounts using conventionally known mixing means such as a roll, Nigoo mixer, Banbury mixer, etc. It can be obtained by When storing this composition, it is preferable to package it in two packages. For example, the component (B) is packaged in the first package, and the component in the pond is packaged in the second package, or the total amount of the component (B) and (
It is also possible to use a method in which a mixture consisting of component (a), component (c), and part of component (d) is placed in the first package, the remaining components are stored in the second package, and these two packages are mixed at the time of use. good.

The organopolysiloxane composition of the present invention can be cured by simply leaving the composition mixed as described above at room temperature.
It may be cured by heating to 0°C.

[Function 1 The organopolysiloxane of component (a) is the main ingredient of the present composition. The organohydrodiene polysiloxane fluid of component (B) exhibits the effect of crosslinking and curing in the presence of the platinum-based catalyst of component (E).
b) component and (t7) component.

The organopolysiloxane component has the effect of shielding neutrons due to the hydrogen atoms in its molecules. (c) Component aluminum hydroxide fine powder has neutron shielding performance, rubber strength, heat resistance,
Shows the effect of imparting flame retardancy. (d) The thickener for
This component is added as necessary, and increases the viscosity of the uncured composition, imparts thixotropy, and prevents separation and sedimentation of the fine aluminum hydroxide powder of component (c). It shows the effect of making the cured composition homogeneous.

By forming an organopolysiloxane rubber-like cured product in which the aluminum hydroxide fine powder of the component (c) is uniformly dispersed, the neutron shielding performance of the organopolysiloxane and the neutron shielding performance of the aluminum hydroxide fine powder are combined. , has the effect of exhibiting superior neutron shielding performance.

[Example 1] Next, the present invention will be explained with reference to an example. In the examples, parts mean parts by weight, and viscosity is a value measured at 25°C.

Example 1 Dimethylpolysiloxane with a viscosity of 2000 centipoise and both ends blocked with dimethylvinylsilyl groups (vinyl group content 0)
．． 24% by weight) 100 parts, 100 parts of fine aluminum hydroxide powder with an average particle size of 15μ, surface treated with hexamethyldisilazane and has a specific surface area of 200m27g by BET method.
5 parts of dry silica and 0.5 parts of a 2-ethylhexanol solution of chloroplatinic acid (platinum content: 0.05% by weight) were added and mixed uniformly to prepare liquid IA.

Also, Me3SiO 1 part 2 unit 20 mol%, Me2SiO unit 50 mol%, MeH3i with a viscosity of 20 cm
An IB solution was prepared by uniformly mixing 6 parts of an ornohydrogenpolysiloxane copolymer containing 30 mol % of O units and 1 part of tetramethyl-tetravinyl-cyclotetrasiloxane as a curing retarder.

Next, a liquid part of the IB liquid was added to 100 parts of the IA liquid and mixed uniformly to create a block-shaped cured product measuring 50 cm x 50 cm x 5 cm (cured by being left at room temperature for 3 days). The neutron shielding performance of this cured product was measured using 2520f as a neutron source. As a result, the 1/10 valence layer (attenuation rate is 1/1
The thickness of the test piece at which the value was 0) was 12.6c+n.

Also, mix IA liquid and IB liquid in the same way and make a 3mm thick
A sheet-like cured product was prepared by leaving it at room temperature for 3 days, and the rubber physical properties were measured according to JIS K2SO3.
Hardness 43, tensile strength 9 kg7am2, elongation 100%
Met. Further, when the hydrogen atom content was measured by elemental analysis, it was 6.0% by weight. Note that when the IA solution was stored at room temperature for one month, no separation and sedimentation of fine aluminum hydroxide powder was observed.

Example 2 Dimethylpolysiloxane with a viscosity of 400 centivoids and both ends blocked with dimethylvinylsilyl groups (vinyl group content 0.
51% by weight)), 50 parts of aluminum hydroxide fine powder with an average particle size of 1 μ, 5 parts of dry silica with a specific surface area of 200 m 2 / g by BET method without surface treatment, and a 2-ethylhexanol solution of chloroplatinic acid ( Platinum content 0
．． Add 0.5 part of 05% by weight and mix uniformly to make
A liquid was prepared.

Next, the IB liquid part of Example 1 was added to this 2AAl2O2, mixed uniformly, and a sheet-like cured product with a thickness of 3+ am was left at room temperature for 3 days, and the rubber physical properties were determined according to JIS.
When measured according to K2SO3, the hardness was 43, the tensile strength was 11 kg/cI112, and the elongation was 180%.

Further, when the hydrogen atom content was measured by elemental analysis, it was found to be 6.7% by weight. Note that the 2A solution is 1[1] at room temperature.
After storage for several months, no separation and sedimentation of fine aluminum hydroxide powder was observed.

Example 3 100 parts of dimethylpolysiloxane (vinyl group content: 0.24% by weight) with a viscosity of 2000 centivoise and end-blocked with dimethylvinylsilyl groups, 100 parts of fine aluminum hydroxide powder with an average particle size of 17 μm, and a surface-free Acetylene black 2 with a specific surface area of 60 m27H according to the BET method of treatment
1 part and 0.5 part of a 2-ethylhexanol solution of chloroplatinic acid (platinum content: 0.05% by weight) were added and mixed uniformly to prepare Solution 3A.

Also, Me3Si○ with a viscosity of 20 centipoise, 1 part 2 units 20 mol%, Me2SiO units 50 mol%, MeH8
A solution 3B was prepared by uniformly mixing 6 parts of an organohydrodiene polysiloxane copolymer containing 30 mol % of iO units and 0.015 parts of phenylbutynol as a curing retarder.

Next, 2 parts of 3B liquid were added to 3AAl2O2 and mixed uniformly, and a sheet-like cured product with a thickness of 3cm was left at room temperature for 3 days to create the rubber physical properties were measured according to JIS K6301. Hardness 43, tensile strength 8 kg/a
m2 and elongation was 150%. In addition, elemental analysis revealed that
When the hydrogen atom content was measured, it was 6.0% by weight.

Note that when the 3A solution was stored at room temperature for one month, no separation and sedimentation of fine aluminum hydroxide powder was observed.

Example 4 Dimethylpolysiloxane with a viscosity of 400 centivoids and both ends blocked with dimethylvinylsilyl groups (vinyl group content 0.
51% by weight) 100 parts, 4 parts of dimethylpolysiloxane raw rubber with a molecular weight of 700,000 and end-blocked with dimethylsilanol groups at both ends,
200 parts of aluminum hydroxide fine powder with an average particle size of 3.6μ surface-treated with titanate and 2-chloroplatinic acid.
Ethylhexanol solution (platinum content 0°05% by weight)
0.5 part was added and mixed uniformly to prepare liquid 4A.

Next, 2 parts of 3B solution from Example 3 was added to 4AAl2O2 and mixed uniformly to form a 50 cm x 50 cm x 5 cm
A block-shaped cured product was prepared (cured by being left at room temperature for 3 days). The neutron shielding performance of this cured product was measured using 252Cf as a neutron source.

As a result, the 10-valent layer was 10.9 cm.

4A again? Mix Ii and 3B solutions in the same way to form a thickness of 3
The sheet-like cured product of (3) was left at room temperature for 3 days, and its rubber properties were measured according to JIS K6301.The hardness was 47, the tensile strength was 10 kg/cm2, and the elongation was io.
%Met. Further, when the hydrogen atom content was measured by elemental analysis, it was 6.0% by weight. Note that when the 4A solution was stored at room temperature for one month, no separation and sedimentation of fine aluminum hydroxide powder was observed.

Comparative Example 1 Dimethylpolysiloxane with a viscosity of 400 centivoise and both ends blocked with dimethylvinylsilyl groups (vinyl group content 0.
51% by weight), 100 parts of crystalline silica fine powder with an average particle size of 5μ, and 0.5 part of a 2-ethylhexanol solution of chloroplatinic acid (platinum content: 0.05% by weight) were added and mixed uniformly. 5A solution was prepared.

Also, 1 part 2 of MeS S i O with a viscosity of 30 cm
20 mol% units, 50 mol% Me2SiO units, MeH
Liquid 5B was prepared by uniformly mixing 5 parts of an ornohydrogenpolysiloxane copolymer containing 30 mol % of 3iO units.

Next, 3 parts of liquid 5B was added to 5AAl2O2 and mixed uniformly to create a block-shaped cured product measuring 50 cm x 50 cm x 5 cm (cured by being left at room temperature for 3 days). The neutron shielding performance of this cured product was measured using 252(:, f as a neutron source. As a result, 1 part decavalent layer was 15,3cI1
It was 1.

Comparative Example 2 Liquid IA and liquid IB were prepared in exactly the same manner as in Example 1, except that 100 parts of fine boron carbide powder with an average particle size of 70 μm was added instead of fine aluminum hydroxide powder, and a block-shaped cured product was created. did.

When the neutron shielding performance of this cured product was measured using 252C as a neutron source, the 1 part decavalent layer was 14.3 ca+.

[Effect of the invention 1] According to the present invention, since the composition is an addition reaction curing type organopolysiloxane composition using a platinum-based catalyst and containing aluminum hydroxide fine powder, it is different from the conventional neutron shielding composition made by adding boron carbide. It has better neutron shielding performance, particularly fast neutron shielding performance, than organopolysiloxane compositions, and has the advantage of being superior in rubber strength, heat resistance, and flame retardancy, and is inexpensive. In addition, it cures uniformly to the inside at room temperature or by slight heating, and does not generate harmful by-products during curing, so it has the advantage of being excellent in workability on site. In addition, when component (2) is added, fine aluminum hydroxide powder does not separate and settle during storage and curing.
Since a more homogeneous cured composition can be obtained, there is an effect that there is almost no difference in neutron shielding performance depending on the location of the cured product.

Therefore, it can be suitably used as a neutron shield in a nuclear power plant (particularly as a penetration seal for a penetration part) or as a neutron shield in a spent nuclear fuel transport container.

Claims (1)

[Claims] (a) General formula RaR^1bSiO(4-a-b)/2
(In the formula, R is a monovalent organic group having no aliphatic unsaturated bond,
100 parts by weight of an organopolysiloxane having at least two units in one molecule, where 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. (b) General formula RcHdSiO(4-c-d)/2 (wherein, R is the same as above, c is an integer of 0 to 3, d is an integer of 1 to 3, and c+d is an integer of 1 to 3. Organohydrogenpolysiloxane fluid having at least two units represented by in one molecule in an amount such that silicon-bonded hydrogen atoms are 0.5 to 5.0 equivalents per equivalent of alkenyl group in component (a) (c) 30 to 300 parts by weight of aluminum hydroxide fine powder with an average particle diameter of 50 μm or less, (d) 0 to 30 parts by weight of a thickener, and (e) a catalytic amount of a platinum compound. Organopolysiloxane composition for use.