JPS6212896A - Gamma-ray shielding material - 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 Application Field] The present invention relates to a gamma ray shielding material that is fluid in an uncured state and can be obtained by curing at room temperature.

[Prior Art] Conventionally, a gamma ray shielding material in which silicone rubber is filled with lead powder is known. However, lead powder is toxic, and handling it requires great care due to health issues and other concerns.

In addition, since lead powder is easily oxidized in the air, it causes agglomeration due to oxidation during storage, which adversely affects workability, physical properties of cured products, and fire resistance. There is a limit to the amount of lead powder, and the content of lead powder per unit volume of weight is relatively small. Therefore, it has not been possible to increase the density of the shielding material obtained by using lead powder to 6 or more. Therefore, there has been a demand for the development of a thinner shielding material in order to obtain the necessary gamma ray shielding ability.

[Problems to be Solved by the Invention] The present invention aims at a gamma ray shielding material having a higher density without handling lead powder that requires health precautions.

[Means for Solving the Problems] In order to solve the above problems, the present invention uses a three-component silicone rubber composition to obtain the necessary strength and also adds tungsten powder to the silicone rubber composition. The aim is to obtain a high-density gamma-ray shielding material by blending the

That is, the present invention is based on the general formula (A) (where R is a monovalent hydrocarbon group containing no aliphatic unsaturated bond, R' is a monovalent hydrocarbon group, and n is a compound having a viscosity of (A) of 25°C).
(indicates the number of 100 to 50,000 cSt)
100 parts by weight of a polyorganosiloxane blocked at both ends with a vinyl group represented by (B): (R">2 containing or not containing siO units, (
R'')zsio., 5 units and 5i02 units (in the formula, R'' represents a group selected from monovalent hydrocarbon groups and vinyl groups that do not contain an aliphatic unsaturated bond), and consists of 2
．． 5 to 10 mol% of the polyorganosiloxane copolymer has a vinyl group directly bonded to the silicon atom, and the ratio of units: 5i02 units is 0.4:1 to 1:1. 100 parts by weight, (C) 2 general formula (wherein R has the same meaning as R in (A), m is 2
or more, a has a value of 1.0 to 2.0, b has a value of 0.1 to 1.0, and (a+b) has a value of 1.9 to 3.
0 and has an average of more than two hydrogens directly bonded to silicon atoms per molecule), and one vinyl group of the polyorganosiloxanes (A) and (B) is directly bonded to a silicon atom. A sufficient amount of polyorganohydrogensiloxane to have 0.5 to 5.0 hydrogen atoms, (D): 800 to 3,500 parts by weight per 100 parts by weight of tungsten powder [(A) + (B) + (C)] part, and (E
); relates to a gamma ray shielding material obtained by curing a polyorganosiloxane composition characterized by comprising an effective amount of a platinum catalyst.

[Function] The composition of the present invention contains (A) and/or (B), (C) and (
Since curing will not occur unless D) and (E) coexist, either of them may be stored in separate packaging and mixed immediately before use. For example, the first package contains the total amount of (D) and (
Most of A) and (B), the second packaging is only (C) or (
The entire amount of C) and a portion of (A) and (B), the third packaging is (
It consists of the entire amount of E) and the balance of (Δ) and (B), and the packaging of the above three can be mixed and cured at the time of use.

In the present invention, the monovalent hydrocarbon groups represented by R and R' of the vinyl chain end polyorganosiloxane component (A) include alkyl groups (for example, methyl, ethyl, propyl, butyl, hexyl, octyl, and decyl groups). , aryl groups (such as phenyl, tolyl and xylyl groups), cycloalkyl groups (such as cyclohexyl and cycloheptyl groups), aralkyl groups (such as benzyl, β-phenylethyl and β-phenylpropyl groups), and R
As '', alkenyl groups (vinyl and allyl groups) are further added to the examples. R and R' may be used alone or in combination of two or more, and may be the same or different from each other.

At least 50% of the groups represented by R and R' are selected from the group consisting of methyl and vinyl, and in particular preferred compositions all of the groups represented by R and R' are methyl and vinyl groups.

The value of n is determined when the viscosity of component (A) at 25°C is 100 to
50.000cSt, preferably 500-8,0OOc
This is the range where St. The viscosity of component (A) is 100cS
If it is less than 50,0OOc, sufficient physical properties cannot be obtained.
If it exceeds St, it becomes difficult to handle it in an uncured state.

The polyorganosiloquine copolymer as component (B) in the present invention is a component that provides sufficient strength to the composition without containing a reinforcing filler, and is a monovalent copolymer that does not contain aliphatic unsaturated bonds. R″ can be a hydrocarbon or vinyl group
and in which at least the aforementioned proportion of the R'' groups are vinyl groups. R'' groups that are not vinyl groups are of the same range as the R groups of component (A) and their A similar group, in a preferred embodiment thereof, all monovalent hydrocarbon groups that do not contain aliphatic unsaturation are methyl groups. The vinyl group is (R”)zsi
oo, as part of the s group, or (R''>2si.

It can be present as part of the group or both.

Various siloxane units in the copolymer component (B) are ('
R'') asioo, s unit: Ratio of SiO* unit is 0
．． Choose between 4:1 and 1:1. (R”
), when the ratio of SiO0,5 units is less than 0.4, the component (
The stability of B) is poor and it is difficult to synthesize it in a controlled manner, and if it exceeds 1, good mechanical strength cannot be imparted to the cured product.

(Present in an amount equal to 0 to 10 mole %, based on the total number of siloxane units in the R″hsiohsio units. Regardless of where the silicon-bonded vinyl group is located in the copolymer, the silicon-bonded vinyl The group is a copolymer component (B
) should be present in an amount equal to 2.5 to 10.0 mole %.

Copolymer component (B) is a solid resinous material, often prepared as a solution in a solvent such as xylene or toluene, and generally as a 30-75% by weight solution. To facilitate handling of the composition, this solution of copolymer component (B) is usually dissolved in some or all of the vinyl chain-terminated polysiloxane component (A), and the solvent is distilled off from the resulting solution. A mixture of component (A) and copolymer component (B) may be prepared by doing this, or component (B) from which the solvent has been removed may be used.

The amount of component (B) is 0 to 00 parts by weight of component (A).
-100 parts by weight, preferably 10-80 parts by weight.

If mechanical strength is required for the γ-ray shielding material, the component (Il
If 10 parts by weight or more of l) is not included, sufficient strength will not be obtained without a reinforcing filler, and if a reinforcing filler is used in combination, it will be impossible to fill with tungsten, which is necessary for the gamma ray shielding intended in the present invention. Because it will be.

Furthermore, if the amount of component (B) exceeds 100 parts by weight, the viscosity of the uncured composition increases and is difficult to handle.

The polyorganohydrogensiloxane of component (C) in the present invention reacts with components (A> and (B)) to form a network polysiloxane, and therefore has an average number of more than two silicon-bonded hydrogen atoms in the molecule. Such polyorganohydrogensiloxanes may have chain, branched, or cyclic siloxane skeletons, and may be polymers consisting only of siloxane units with silicon-hydrogen bonds. It may also be a copolymer with one or more of triorganosiloxy units, diorganosiloxy units, monoorganosiloxy units, and SiO□ units.

Examples of R include those similar to R in component (A), and one type or a combination of two or more types may be used.
A methyl group and a phenyl group are preferred, and a methyl group is particularly preferred, since they are easy to synthesize, have relatively low viscosity, and provide good physical properties after curing.The average number of silicon bonds in one molecule exceeds two. In order to have a hydrogen atom, m needs to be 2 or more, preferably in the range of 4 to 1,000, for ease of synthesis. When m is less than 4, volatility is high, and when m exceeds 1.000, synthesis and handling become difficult. It is difficult to synthesize those with a less than 1.0 and those with b more than 1.0. When a exceeds 2.0, the component (C
) cannot have the desired 10 while having the necessary silicon-bonded hydrogen atoms, and if b is less than 0.1, the number of m to provide the desired silicon-bonded hydrogen atoms becomes large, and the component (C ) becomes difficult to handle. If the sum of a+b is less than 1.9, it is difficult to synthesize with good control;
If it exceeds this, the required degree of polymerization cannot be obtained.

The amount of component (C) is such that the amount of hydrogen atoms directly bonded to silicon atoms contained in component (C) is 0.5 to 5 per vinyl group contained in component (A) and component (B). This is enough to make 0 pieces. If the number is less than 0.5, a rubber-like elastic body cannot be obtained, and if it exceeds 5.0, foaming may occur or the mechanical properties may deteriorate.

Component (D) used in the present invention is tungsten powder.

The average particle size is preferably 1 μ to 0.5 mm.

If the tungsten powder is less than 1 μm, the high density targeted by the present invention cannot be obtained, and if it exceeds 0.5 mm, the sedimentation rate during mixing will increase, making it impossible to obtain a uniform density composition.

The amount of component (D) is in the range of 600 to 3500 parts by weight, preferably 800 to 2500 parts by weight, based on 100 parts by weight of the total amount of components (A), (B), and (C). If it is less than 600 parts by weight, a sufficient gamma ray shielding effect cannot be obtained;
If the amount exceeds parts by weight, it becomes difficult to knead components (A) + (B) + (c), making on-site injection work difficult and reducing the strength of the cured composition.

The platinum catalyst component (E) used in the present invention includes all known platinum catalysts that are effective in effecting the reaction between silicon-hydrogen bonds and silicon-bonded vinyl groups.

Examples of component (E) include platinum black, platinum-olefin complexes, platinum-vinylsiloxane complexes, platinum-phosphine complexes, and platinum-phosphite complexes.

Regardless of the type of platinum catalyst used, the catalyst is usually used in an amount sufficient to provide 10@-3 to 10@-6 gram atoms of platinum per mole of silicon-bonded vinyl groups in the composition.

[Examples] The present invention will be described below based on Examples. In the examples, all parts are by weight. In the examples, Me represents a methyl group and Vi represents a vinyl group.

Example 1 65 parts of polydimethylsiloxane having a viscosity of 3,000 cSt at 25°C and capped at both ends with vinyl groups;
60 mol% Sigh units, 37.2 mol% Me3S
35 parts of a copolymer consisting of iOo, 5 units and 2.8 mol % of MeViSiO units were mixed to obtain a vinyl group-containing polyorganosiloxane mixture. This mixture was placed in a closed kneader, 1.000 parts of tungsten powder having an average particle size of 17 μm was added thereto, and the mixture was mixed under closed conditions until uniform.

To this, Me+SiO[MezSiO]a[MeH3io
] 35 parts of 6-5ide and 50/1,000,000 parts of zero-valent platinum triphenyl phosphite complex in terms of platinum atoms were added and mixed to obtain a composition of the present invention. This composition was defoamed, cast into a mold with a thickness of 130 I, and left to stand at 30° C. for 24 hours to obtain a rubber-like cured product according to the present invention. The density of this cured product was 7.3.

Place this rubber-like cured product (sample) on the measuring device shown in the figure,
60co gamma rays were applied in the thickness direction and the amount of transmission thereof was measured. Similar measurements were carried out on concrete samples of the same size, and the gamma ray transmission amount was compared.
It was 3%. In the figure, 1 is the Co source, 2 is the lead shielding wall, 3 is the sample, 4 is the dosimeter, 5 is the chamber containing the sample, A is the distance between the source and the dosimeter [(800 mm), and the mouth is 1 is the depth of the chamber (250 mm>, 2 is the thickness of the lead shield wall on the dosimeter side is 100 mm), and 2 is the gamma ray passage (diameter 20 mm).
, E is the thickness of the sample (130 m+s).

Example 2 55 parts of a polyorganosiloxane having a viscosity of 4,500 cSt at 25°C, capped at both ends with vinyl groups, consisting of 6 mol% diphenylsiloxane units and the remainder dimethylsiloxane units, and 52.5 mol% 90 parts of a 50% toluene solution of a copolymer consisting of 5i02 units, 44.5 mol% Me*SiO units, and 3.0 mol% MeViSiO units were mixed, and the pressure was gradually reduced to l Q Q
Toluene was distilled off by heating to 30°C at m m tl g to obtain a vinyl group-containing polyorganosiloxane mixture. This mixture was charged into a closed kneader, 900 parts of tungsten powder having an average particle size of 147 μm was charged, and the mixture was mixed in a closed state until the mixture became uniform.

To this, [MezSiO+-+Na)lsiO]s
A composition of the present invention was obtained by mixing 7.5 parts and 30/1 million parts of the same platinum catalyst used in Example 1 in terms of platinum atoms. This composition was defoamed and cast into the same mold as in Example 1, and left at 50°C for 6 hours, resulting in a density of 6.
A rubbery cured product of No. 7 was obtained. When the gamma ray transmission amount of this rubber-like cured product was measured in the same manner as in Example 1, it was 36% of that of the concrete sample.

Example 3 60 parts of polydimethylsiloxane, which has a viscosity of 2,000 cSt at 25°C and is capped with vinyl groups at both ends, and 40 parts of the same copolymer as used in Example 1 are mixed to produce a vinyl group-containing polyorgan. A siloxane mixture was obtained. This was mixed with 1,100 parts of the same tungsten powder as used in Example 1 in a closed kneader, and the mixture was sealed in a metal can to obtain packaged sample A.

Next, polydimethylsiloxane 100, which has a viscosity of 3,500 cSt at 25°C and is capped at both ends with vinyl groups, was used.
100 parts of the same polydimethylhydrogen siloxane as used in Example 1 were mixed with the glass bottle and sealed in a glass bottle to obtain a packaged sample B.

In addition, 500/1 million parts of platinum-tetramethyltetravinylcyclotetrasiloxane complex with platinum atoms were mixed with 100 parts of polydimethylsiloxane, which has both ends capped with vinyl groups as above, and the mixture was sealed in another glass bottle. ,
Packaging sample C was obtained. After each of these packaged samples A, B, and C was prepared, one copy was stored at room temperature for a month, and the weight ratio of A
:B:C=110:1:1, defoamed, cast in the same manner as in Example 1, and left at 30°C for 24 hours to obtain a rubber-like cured product with a density of 7.1. Ta.

When the gamma ray transmission amount of this rubber-like cured product was measured in the same manner as in Example 1, it was 34% of that of the concrete sample.

Example 4 65 parts of polydimethylsiloxane having a viscosity of 3,000cSt at 25°C and having both ends capped with vinyl groups;
0 mol% SiO2 units, 37.2 mol% MesS+
70 parts of a 50% toluene solution of a copolymer consisting of Oo, s units and 2.8 mol% MeViSiO units was mixed, and the mixture was gradually reduced in pressure and heated to 80°C at 100,100 nm to distill off the toluene and produce vinyl. A group-containing polyorganosiloxane mixture was obtained. This mixture was charged into a closed kneader, and tungsten powder with an average particle size of 17μ was 2.1
30 parts were charged and mixed under closed conditions until uniform.

To this, Me, SiO[MezSiO]s[MeHsio
]a ・SiMe* 5 parts and the heating product of chloroplatinic acid and 2-ethylhexanol are converted to platinum atoms and are 50/
1 million parts were added and mixed to obtain a composition of the present invention.

This composition was defoamed and cast into a mold with a thickness of 130 mm.
A rubber-like cured product according to the present invention was obtained by standing at 0° C. for 24 hours. The density of this cured product was 10.2.

The amount of hydrogen per 1 g of this rubbery cured product is 3.8 vIg (
The amount of hydrogen per 1 cI113 of the rubbery cured product was 28 B>.

When the gamma ray transmission amount of this rubber-like cured product was measured in the same manner as in Example 1, it was 24% of that of the concrete sample.

[Effects of the Invention] According to the present invention, the tungsten powder used is less toxic than lead powder, and the problem of lead toxicity is solved. In addition, tungsten powder is difficult to oxidize and maintains uniform fire resistance. Moreover, a high-density shielding material with a density of 6 or more can be obtained. Furthermore, a mixture with the same density has a higher hydrogen equivalent than a lead powder mixture, making it useful as a neutron shielding material.

BRIEF DESCRIPTION OF THE DRAWINGS The figure is a schematic cross-sectional view of an apparatus for measuring the gamma ray shielding effect of a shielding material. In the figure, 1 is the Co source, 2 is the lead shielding wall, 3 is the sample, 4 is the dosimeter, 5 is the chamber that accommodates the sample, A is the distance 1i (800 mm) between the source and the dosimeter, and the mouth is The thickness of the lead shielding wall on the Co source side is 150n+m), and C is the depth of the chamber (250n+m).
(nua), second is the thickness of the lead shielding wall on the dosimeter side (100 mm)
, to is the gamma ray passage (diameter 20 mm), and e is the sample thickness 1
30mm).

Claims (9)

[Claims] (1) (A): General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (In the formula, R is a monovalent hydrocarbon group that does not contain an aliphatic unsaturated bond, R' is a monovalent hydrocarbon group, and n is ( The viscosity of A) is 25℃
(indicates the number of 100 to 50,000 cSt)
100 parts by weight of polyorganosiloxane with both ends capped with vinyl groups represented by (B): (R″)_2 Containing or not containing SiO units, (
R″)_3SiO_0_._5 units and SiO_2 units (
In the formula, R'' represents a group selected from a monovalent hydrocarbon group containing no aliphatic unsaturated bond and a vinyl group), and 2.5 to 10 mol% of the silicon atoms are vinyl groups directly bonded to the silicon atom. and (R″)_3SiO_0_. _5 units:
0 to 100 parts by weight of a polyorganosiloxane copolymer having a ratio of SiO_2 units of 0.4:1 to 1:1, (C): General formula [(R)_a(H)_bSiO_(_4_-_a_-_
b_)_/_2]_m (in the formula, R has the same meaning as R in (A), m is a number of 2 or more, and a is 1.0 to 2
．． has a value of 0, b has a value of 0.1 to 1.0, and (a
+b) is 1.9 to 3.0, with an average of 2 per molecule.
0.5 to 5.0 hydrogen atoms directly bonded to silicon atoms per vinyl group of the polyorganosiloxanes (A) and (B). 600 to 3,500 parts by weight of tungsten powder, and (E
): A γ-ray shielding material obtained by curing a polyorganosiloxane composition characterized by comprising an effective amount of a platinum catalyst. (2) The gamma ray shielding material according to claim 1, wherein the amount of (B) is 10 to 80 parts by weight. (3) The first packaging is the entire amount of (D) and most of (A) and (B), and the second packaging is only (C) or the entire amount of (C) and (A)
and a portion of (B), and the third package comprises the entire amount of (E) and the remainder of (A) and (B). (4) The gamma ray shielding material according to claim 1, wherein at least 50 mol% of R, R', and R'' are methyl groups. (5) The gamma ray shielding material according to claim 1, wherein R, R', and R'' are a methyl group and a vinyl group. (6) The viscosity of (A) is 500 to 8,00 at 25°C
The gamma ray shielding material according to claim 1, which has a particle diameter of 0 cSt. (7) The gamma ray shielding material according to claim 1, wherein m is 4 to 1,000. (8) The amount of tungsten powder is [(A) + (B) + (C)
] The γ-ray shielding material according to claim 1, wherein the content is 800 to 2,500 parts by weight per 100 parts by weight. (9) The gamma ray shielding material according to claim 1, wherein the tungsten powder has a particle size of 1 μm to 0.5 mm.