JPH0529657B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a room temperature curable polyorganosiloxane composition having gamma ray shielding ability. [Prior Art] Conventionally, a gamma ray shielding material in which silicone rubber is filled with lead powder is known. Conventional gamma-ray shielding materials were used by adding lead powder to the mixture on-site when compounding a two-component silicone rubber solution and pouring it into the area where gamma-ray shielding was required. However, lead dust is toxic;
In particular, handling it directly in an open state is undesirable due to health concerns. Furthermore, since lead powder is easily oxidized in the air, it causes agglomeration due to oxidation during storage, which adversely affects workability and physical properties of the cured product. Furthermore, conventionally used silicone rubber cannot obtain the necessary strength unless it is blended with fillers such as silica, so conventional shielding materials using such silicone rubber compositions have a lower amount of lead powder. However, the content of lead powder per unit volume is relatively small, and therefore a thick shielding material is required to obtain the necessary gamma ray shielding ability. [Problems to be Solved by the Invention] As mentioned above, conventional gamma ray shielding materials have the problem of lead contamination at construction sites due to direct handling of lead powder at construction sites and health problems associated with it.
Because a large amount of lead powder was required per unit volume, a thick gamma-ray shielding material was required. [Means for Solving the Problems] In order to solve the above problems, the present inventors have achieved the following by using a silicone rubber composition having a special combination of vinyl group-containing polyorganosiloxanes as a base polymer. The necessary strength can be obtained without adding fillers such as silica, and by adding lead powder as a component of silicone rubber in a sealed container in advance, it can be used directly in open systems such as construction sites. Eliminates the opportunity to come into contact with lead powder. That is, the present invention provides (A): general formula (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 a number that makes the viscosity of (A) 100 to 50,000 cSt at 25°C.) 100 parts by weight of polyorganosiloxane with both ends capped with vinyl groups, (B): (R″) ₂ containing or not containing SiO units,
(R″) ₃ Consists of _0.5 SiO units and ₂ SiO 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 3 SiO units 20 to 100 parts by weight of a polyorganosiloxane copolymer in which 10 mol% has a vinyl group directly bonded to a silicon atom, and the ratio of (R″) ₃ SiO _0.5 units:SiO ₂ units is 0.4:1 to 1:1. , (C): general formula (In the formula, R is in the same range as R in (A), m
is a number greater than or equal to 2, a has a value of 1.0 to 2.0, b has a value of 0.1 to 1.0, and (a+b) is 1.9
3.0 and has an average of at least two hydrogen atoms directly bonded to silicon atoms per molecule), and each vinyl group of the polyorganosiloxanes (A) and (B) is directly bonded to a silicon atom. 600 to 600 parts of lead powder produced by melt spraying to 100 parts by weight of polyorganohydrogensiloxane (D): [(A) + (B) + (C)] in an amount sufficient to have 0.5 to 5.0 hydrogen atoms. 2000 parts by weight, and (E): an effective amount of a platinum catalyst. The composition of the present invention comprises (A) and/or (B) and (C) and (D) and (E).
Since they will not cure unless they coexist, either of them may be stored in separate packaging and mixed immediately before use. For example, the first package is the total amount of (D)
Most of (A) and (B), the second package is only (C) or the whole amount of (C) and a part of (A) and (B), the third package is the whole amount of (E) and (A)
and the remainder of (B), and the above three packages 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 (e.g. phenyl, tolyl and xylyl groups), cycloalkyl groups (e.g. cyclohexyl and cycloheptyl groups), aralkyl groups (e.g. benzyl, β-phenylethyl and β-phenylpropyl groups), and as R' further includes alkenyl groups (vinyl and allyl groups). 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 of the groups represented by R and R'
50% is selected from the group consisting of methyl and phenyl, in a preferred particular composition R and
All of the groups represented by R' are methyl and phenyl groups. The value of n is determined when the viscosity of component (A) at 25℃ is 100~
50,000 cSt, preferably in the range of 500 to 20,000 cSt. If the viscosity of component (A) is less than 100 cSt, sufficient physical properties cannot be obtained, and if it exceeds 50,000 cSt, it becomes difficult to handle in an uncured state. The polyorganosiloxane 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 carbonized copolymer that does not contain aliphatic unsaturated bonds. It may be defined as a polyorganosiloxane copolymer containing R'' groups which can be hydrogen or vinyl groups, 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 scope as the R group of component (A) and similar groups, and in a preferred embodiment thereof, all of the monovalent carbon hydrogen groups that do not contain aliphatic unsaturation are methyl groups. The vinyl group can be present as part of the (R″) ₃ SiO _0.5 group, or as part of the (R″) ₂ SiO group, or both. Copolymer The various siloxane units in component (B) are
(R″) ₃ Select so that the ratio of SiO _0.5 units to SiO ₂ units is 0.4:1 or 1:1. (R″) If the ratio of ₃ SiO _0.5 units is less than 0.4, component (B) may be unstable. If it exceeds 1, good mechanical strength cannot be imparted to the cured product. (R″) ₂ SiO units are present in an amount equal to 0 to 10 mol%, based on the total number of siloxane units in the copolymer. Where silicon-bonded vinyl groups are located in the copolymer, Regardless, the silicon-bonded vinyl group has 2.5 to 2.5 to
It should be bound at 10.0 mol%. 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. Generate (A)
and copolymer component (B). The amount of component (B) is 20 to 100 parts by weight of component (A).
100 parts by weight, preferably 20 to 80 parts by weight. If the amount of component (B) is less than 20 parts by weight, sufficient mechanical properties cannot be obtained unless a reinforcing filler is blended, and it is intended in the present invention to blend a reinforcing filler in an amount that satisfies the mechanical properties. Filling with lead necessary for gamma ray shielding becomes impossible. Furthermore, if the amount of component (B) exceeds 100 parts by weight, the viscosity of the uncured composition increases, making it 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 of at least two silicon-bonded hydrogen atoms in the molecule. It is something that we have. Such a polyorganohydrogensiloxane may have a chain, branched, or cyclic siloxane skeleton, and may be a polymer consisting only of siloxane units having silicon-hydrogen bonds, or may be a polymer consisting only of siloxane units having silicon-hydrogen bonds, as well as triorganosiloxy units and diorganosiloxane units. It may also be a copolymer with one or more of siloxy units, monoorganosiloxy units, and SiO ₂ 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. Methyl groups and phenyl groups are preferred, with methyl groups being particularly preferred, in view of the properties obtained. In order to have an average of at least two silicon-bonded hydrogen atoms in one molecule, m needs to be 2 or more, preferably in the range of 4 to 1000, for ease of synthesis. If m is less than 2, it will be highly volatile, and if it exceeds 1000, it will be difficult to synthesize and handle. It is difficult to synthesize those with a less than 1.0 and those with b more than 1.0. If a exceeds 2.0, the component
It is not possible to obtain the desired m while (C) has the necessary silicon-bonded hydrogen atoms, and if b is less than 0.1, the number of m required to provide the desired silicon-bonded hydrogen atoms becomes large, and the component (C ) becomes difficult to handle. a+
If the sum of b is less than 1.9, it is difficult to synthesize with good control, and if it exceeds 3.0, 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 5.0 per vinyl group contained in components (A) and (B). The amount is sufficient. This is because 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 mechanical properties may deteriorate. Component (D) used in the present invention is lead powder produced by melt spraying. Average particle size is preferably 1μ
~0.5mm, more preferably 100 meshes (147μ). Lead powder of less than 1 μm is difficult to manufacture, and its surface is easily oxidized and its state changes easily. If it exceeds 0.5 mm, the sedimentation rate during mixing will increase and the strength of the composition after curing will be low. The amount of component (D) is 600 to 2000 parts by weight, preferably 800 to 2000 parts by weight, based on 100 parts by weight of the total amount of components (A), (B), and (C).
In the range of 1500 parts by weight. If it is less than 600 parts by weight, a sufficient gamma ray shielding effect cannot be obtained, and if it exceeds 2000 parts by weight, it becomes difficult to mix components (A) + (B) + (C), making it difficult to perform injection work on site. , the strength of the cured composition decreases. The platinum catalyst component (E) used in the present invention is silicon-
Includes all known platinum catalysts effective for effecting reactions between hydrogen bonds and silicon-bonded vinyl groups.
Examples of component (E) include platinum black, chloroplatinic acid, platinum-olefin complexes, platinum-vinylsiloxane complexes, platinum-phosphine complexes, platinum-phosphite complexes, and platinum alcoholates. Regardless of the type of platinum catalyst used, the catalyst typically contains between 10 -3 and 10 ^-3 platinum per mole of silicon-bonded vinyl groups in the composition.
Use in sufficient quantities to make 10 ^-6 gram atoms. [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 capped at both ends with vinyl groups and having a viscosity of 3000 cSt at 25°C, 60 mol% SiO ₂ units, 37.2 mol%
Mix 70 parts of a 50% toluene solution of a copolymer consisting of _0.5 units of Me ₃ SiO and 2.8 mol% MeViSiO units, gradually reduce the pressure and heat to 80°C at 100 mmHg to distill off the toluene and remove the vinyl groups. A polyorganosiloxane containing mixture was obtained. This mixture was placed in a closed kneader, and 1000 parts of lead powder with an average particle size of 200 mesh (74μ) obtained by melt spraying (average particle size 17μ) was charged, and the mixture was kept sealed until uniform. mixed with. To this, Me ₃ SiO [Me ₂ SiO] ₆ [MeHSiO] ₆・
5 parts of SiMe ₃ 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 30°C for 24 hours. The specific gravity of this cured product was 5.4. This rubber-like cured product (sample) was placed in the measuring device shown in FIG. 1, and gamma rays from ⁶⁰ Co were applied in the thickness direction to measure the amount of transmission. Similar measurements were carried out on concrete samples of the same size, and the gamma ray transmission amount was compared, and the gamma ray transmission amount of the rubber-like cured product according to the present invention was 44% of that of the concrete sample. Example 2 55 parts of a polyorganosiloxane having a viscosity of 4500 cSt at 25°C, both ends capped with vinyl groups, and consisting of 6 mol% diphenylsiloxane units and the remaining dimethylsiloxy units, and 52.5 mol% SiO ₂ units, 44.5 mol% _Me3SiO units and 3.0 mol%
90 parts of a 50% toluene solution of a copolymer consisting of MeViSiO units was mixed and desoluted in the same manner as in Example 1 to obtain a vinyl group-containing polyorganosiloxane mixture. This mixture was placed in a closed kneader, and 900 parts of lead powder with an average particle diameter of 100 mesh (147 μm) obtained by melt spraying was added thereto and mixed in a closed state until uniform. to this

A composition of the present invention was obtained by mixing 7.5 parts of the formula and 30/1 million parts of the same platinum catalyst used in Example 1 as platinum atoms. This was defoamed and cast into the same mold as in Example 1, and left at 50°C for 6 hours to obtain a rubber-like cured product with a specific gravity of 5.1. When the gamma ray transmission amount of this rubber-like cured product was measured in the same manner as in Example 1, it was 47% of that of the concrete sample. Example 3 60 parts of polydimethylsiloxane, which has a viscosity of 2000 cSt at 25°C and is capped with vinyl groups at both ends, and 80 parts of a 50% toluene solution of the same copolymer used in Example 1 were mixed as in Example 1. In the same manner, a vinyl group-containing polyorganosiloxane mixture was obtained.
This was mixed with 1100 parts of the same lead powder used in Example 1 in a closed kneader, and the mixture was sealed in a metal can to obtain packaged sample A. Next, polydimethylsiloxane, which has a viscosity of 3500 cSt at 25°C and is capped at both ends with vinyl groups, is used.
100 parts of the same polymethylhydrogensiloxane as used in Example 1 were mixed with 100 parts of the mixture and sealed in a glass bottle to obtain 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 storing these packaged samples A, B, and C at room temperature for one month after each preparation, the weight ratio of A:B:C=100:
Mix at a ratio of 10:10, defoamer, cast in the same manner as in Example 1, and leave at 30°C for 24 hours to determine the specific gravity.
A rubbery cured product of 5.2 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 found that
It was 46%. Example 4 70 parts of the same polydimethylsiloxane end-capped with vinyl groups as used in Example 1 and a 50% toluene solution of the same branched polyorganosiloxane copolymer used in Example 1 Packaging sample D was obtained in the same manner as packaging sample A in Example 3 from 60 parts and 1000 parts of the same lead powder used in Example 2. Next, polydimethylsiloxane, which has a viscosity of 10,000 cSt at 25°C and is blocked at both ends with vinyl groups, is used.
100 parts of the same polymethylhydrogensiloxane as used in Example 2 were mixed with 100 parts of the mixture and sealed in a glass bottle to obtain packaged sample E. In addition, 300/1 million parts of platinum-torphenyl phosphite complex with platinum atoms were mixed with polydimethylsiloxane, which was used in Example 1 and whose ends were blocked with vinyl groups, and the mixture was sealed in another glass bottle. , packaging sample F was obtained. After storing these packaged samples D, E, and F at room temperature for one month after their respective preparation, the weight ratio of D:E:
The mixture was mixed at a ratio of F=100:10:10, defoamed, cast in the same manner as in Example 1, and left at 50°C for 6 hours to obtain a rubber-like cured product with a specific gravity of 5.0. When the gamma ray transmission amount of this rubber-like cured product was measured in the same manner as in Example 1, it was 48% of that of the concrete sample. Example 5 63 parts of a polyorganosiloxane having a viscosity of 6000 cSt at 20°C, capped at both ends with vinyl groups and consisting of 5 mol% methylvinylsiloxy units and the remainder dimethylsiloxy units, and 55 mol% SiO ₂ units, 41.5 mol% _{Me3SiO 0.5} units and 3.5 mol%
74 parts of a 50% toluene solution of a copolymer consisting of _0.5 units of MeViSiO was mixed and desoluted in the same manner as in Example 1 to obtain a vinyl group-containing polyorganosiloxane mixture. This mixture and 1000 parts of the same lead powder used in Example 1 were charged and mixed in a closed state until uniform. 4.5 parts of Me ₃ Si [MeHSiO] ₁₁ SiMe ₃ and 100/1 million parts of the same platinum catalyst used in Example 3 as platinum atoms were added and mixed to obtain the composition of the present invention. This was cast into the same mold as in Example 1 and left at 50°C for 6 hours to obtain a rubber-like cured product with a specific gravity of 5.4. The amount of γ-ray transmission of this rubber-like cured material was measured in the same manner as in Example 1, and was found to be 44% that of the concrete sample.
It was hot. [Effects of the Invention] According to the present invention, the problem of lead toxicity is solved because there is no direct contact with lead powder at an open construction site. In addition, lead fine powder is easily oxidized, but by supplying it mixed with silicone as in the present invention, lead oxidation and accompanying particle aggregation can be prevented during storage, improving workability and physical properties of cured products. can be kept. Furthermore, since the amount of lead added is significantly increased, a high-density shielding material with a specific gravity of 5 or more, which has not been previously available, can be obtained, and it can be used as a shielding material with excellent gamma ray shielding properties.

[Brief explanation of the drawing]

The figure is a schematic cross-sectional view of an apparatus for measuring the γ-ray shielding effect of a shielding material. In the figure: 1... ⁶⁰ Co radiation source, 2... Lead shielding wall, 3... Sample, 4... Dosimeter, 5... Chamber containing sample, A... Distance between source and dosimeter (800 mm) ),B…
… ⁶⁰ Thickness of the lead shielding wall on the Co radiation source side (150 mm), C… Depth of the chamber (250 mm), D… Thickness of the lead shield wall on the dosimeter side (100 mm), F… γ-ray passageway (diameter) 20
mm), E...Thickness of the sample (130mm).

Claims (1)

[Claims] 1 (A): General formula (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 a number that makes the viscosity of (A) 100 to 50,000 cSt at 25°C.) 100 parts by weight of polyorganosiloxane with both ends capped with vinyl groups, (B): (R″) ₂ containing or not containing SiO units,
(R″) ₃ Consists of _0.5 SiO units and ₂ SiO 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 3 SiO units 20 to 100 parts by weight of a polyorganosiloxane polymer in which 10 mol% has a vinyl group directly bonded to a silicon atom, and the ratio of (R″) ₃ SiO _0.5 units: SiO ₂ units is 0.4:1 to 1:1; (C): General formula (In the formula, R is in the same range as R in (A), m
is a number greater than or equal to 2, a has a value of 1.0 to 2.0, b has a value of 0.1 to 1.0, and (a+b) is 1.9
3.0 and has an average of at least two hydrogen atoms directly bonded to silicon atoms per molecule), and each vinyl group of the polyorganosiloxanes (A) and (B) is directly bonded to a silicon atom. 600 to 600 parts by weight of lead powder per 100 parts by weight of polyorganohydrogensiloxane (D) [(A) + (B) + (C)] sufficient to have 0.5 to 5.0 hydrogen atoms.
A curable polyorganosiloxane composition having gamma ray shielding ability, comprising: 2000 parts by weight, and (E) an effective amount of a platinum catalyst. 2 The entire amount of the first package (D) and most of (A) and (B), the second package
Claim 1 where the package consists of only (C) or the whole amount of (C) and a part of (A) and (B), and the third package consists of the whole amount of (E) and the balance of (A) and (B). A curable polyorganosiloxane composition having gamma ray shielding ability as described in 1. 3. The curable polyorganosiloxane composition having gamma ray shielding ability according to claim 1, wherein at least 50 mol% of R, R', and R'' are methyl groups. 4. R' and R'' are methyl groups. A curable polyorganosiloxane composition having gamma ray-shielding ability according to claim 1, comprising a group and a vinyl group. 5. The curable polyorganosiloxane composition having gamma ray shielding ability according to claim 1, wherein (A) has a viscosity of 500 to 20,000 cSt at 25°C. 6. The curable polyorganosiloxane composition having gamma ray shielding ability according to claim 1, wherein the amount of (B) is 20 to 80 parts by weight. 7. The curable polyorganosiloxane composition having gamma ray shielding ability according to claim 1, wherein m is 4 to 1000. 8 The amount of lead powder is [(A) + (B) + (C)] per 100 parts by weight
The curable polyorganosiloxane composition having gamma ray shielding ability according to claim 1, wherein the amount is 800 to 1500 parts by weight. 9. The curable polyorganosiloxane composition having gamma ray shielding ability according to claim 1, wherein the lead powder has a particle size of 1 μm to 0.5 mm.