JPH0378425B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to a rubber composition containing powdered lead having properties such as soundproofing, vibration damping, X-ray shielding, prevention of adhesion of marine organisms, and corrosion protection. [Prior art] Conventionally, powdered or thread-like lead and lead compounds are blended into rubber, for example, JIS Z-4801 "Lead-containing rubber sheet and lead-containing vinyl chloride sheet for X-ray shielding", Japanese Patent Publication No. 60-40458. No. ``Decorative film containing metal foil and powder''
X-ray protective sheets as described in
It is well known that it is used in soundproof sheets, vibration damping materials, etc. The lead powder blended for this purpose is usually produced by an atomization method, a stamp mill method, or a ball mill method. The surface of the lead powder produced by such conventional methods is oxidized during the manufacturing process or during storage, resulting in a dark gray or blackish gray color. Therefore, there is a limit to the amount of lead powder mixed with rubber that has an oxide film on the surface.For example, if a volume ratio of lead powder of 15% or more is added to the compounded rubber, the dough will become hard and uniform. No dispersion could be obtained. Therefore, the conventional rubber compositions containing lead naturally have limited effectiveness in achieving the above-mentioned purposes. [Problems to be Solved by the Invention] The present invention advantageously solves the above-mentioned problems, improves the effect of its original intended use several times, and enables new fields of effective use. In other words, by blending lead powder, which has an active metal surface with almost no oxide film on the surface, into compounded rubber and arranging it in multiple layers, it has characteristics that are significantly different compared to conventional lead compounded rubber. The rubber composition has the following properties. [Means for Solving the Problems] That is, the gist of the present invention is to provide powdered lead, which has almost no oxide film on its surface, in a volume fraction of 15 to 85% of the compounded rubber. A rubber composition characterized in that powdered lead is arranged in almost a laminated manner. The powder foil lead referred to in the present invention has a thickness of approximately 0.06 to 1.0 mm.
More than 80% of them are between 4 and 325 mesh in size, and the average apparent density is about 2.5gr/
Refers to scaly lead of cm ³ or less. The compounded rubber referred to in the present invention refers to the rubber that is the main material, to which conventional rubber compounding agents such as reinforcing agents, fillers, softeners, crosslinking agents, crosslinking aids, lubricants, antioxidants, etc. are added as appropriate depending on the purpose. It is added to rubber.
For these compounded rubbers, the volume fraction of powdered lead is
It is added in an amount of 15% to 75% to form the desired rubber composition. Therefore, the powdered lead to be laminated inside the rubber in the present invention is a powdered foil that has a silvery white active metal surface with almost no oxide film on its surface (approximately 0.1% or less). As the foil lead, for example, scaly powder lead obtained by Japanese Patent Application No. 153749/1984 (JP Patent Application No. 13504/1982) entitled "Method for Producing Powdered Scale Lead" is used. When lead of uniform weight is crushed along the sliding surface of a face-centered cubic crystal structure to produce foil, fatty acids, which are rubber compounding agents, are used as a crushing aid and antioxidant (hereinafter referred to as an auxiliary crushing agent). Particularly useful is a lead foil whose surface is coated with this auxiliary crushing agent at the same time as the active silvery-white crushed surface of the lead foil is generated. In the present invention, the auxiliary pulverizing agent used in producing powdered lead foil is mainly an organic compound auxiliary pulverizing agent, and hydrocarbon-based auxiliary agents include liquid paraffin, natural paraffin, microwax, synthetic paraffin, and low molecular weight polyethylene ( polyethylene wax) chlorinated hydrocarbon fluorocarbon, etc.
Further, fatty acid-based fatty acids include higher fatty acids, oxyfatty acids, and derivatives thereof. Further, fatty acid amide, alkylene bis fatty acid amide, etc. are examples of fatty acid amide. Further, examples of esters include fatty acid lower alcohol esters, fatty acid polyhydric alcohol esters, fatty acid polyglycol esters, and the like. Also, alcohol-based substances include polyhydric alcohols, polyglycols, polyglycerols, and the like. In addition, metal soaps include lead stearate, zinc stearate, aluminum stearate, calcium stearate, cadmium stearate, etc. In addition, mixtures of the above may be used as appropriate. Furthermore, mineral oil-based mineral spirits, petroleum-based kerosene, etc. can also be used. These auxiliary crushing agents are in the form of fine powders or liquids, and in particular, in the case of fine powders, those that do not easily aggregate between particles are preferred. It is also effective to appropriately select the above-mentioned auxiliary crushing agents alone or in combination of two or more. When producing powdered lead foil, the above-mentioned auxiliary crushing agents are used. For example, powdered lead foil using stearic acid, lead stearate, and aluminum stearate as auxiliary crushing agents is added to rubber. Rubber compositions were prepared and their physical properties and dispersibility were measured. Almost the same results were obtained, and no influence of the type of auxiliary crushing agent on the rubber composition was observed. In addition, the powdered lead foil used in the present invention is obtained by subjecting conventionally produced dark gray or blackish gray foil pieces having an oxide film on the surface to a reduction treatment to remove the oxide film.
Furthermore, it is also possible to use a lead foil which has been subjected to a surface activation treatment if necessary and has a silvery-white active surface and is immediately coated with an antioxidant that satisfies the following conditions. That is, the antioxidant is selected from those suitable as rubber compounding agents when blended with rubber, such as process oil,
Rubber plasticizers, liquid rubber softeners such as vegetable oil, and rubber lubricants with a melting point below the processing temperature of rubber, such as higher fatty acids, metal soaps, paraffins, polyethylene glycols, and low molecular weight polyethylene. Also included are rubber solutions such as rubber pastes, rubber latexes, and rubber adhesives. When these compounding agents and rubber solutions are added to rubber,
It is uniformly dispersed in the rubber and behaves effectively as a conventionally used rubber compound. In addition, all the rubbers normally used in the rubber industry can be used as the compounded rubber of the present invention, such as natural rubber rubber, butadiene rubber, polyisoprene rubber, chloroprene rubber, isobutylene rubber, Olefin rubber,
Silicone rubber, acrylic rubber, urethane rubber, fluorine rubber, polynorbornene rubber, etc. are appropriately selected and used. The rubber composition of the present invention can be crosslinked as necessary depending on its use, functionality, processability, price, etc. When crosslinking is carried out, a conventional crosslinking method for rubber compounds can be used if necessary. Furthermore, the term "laminated" as used in the present invention refers to the fact that as a result of the operation of uniformly dispersing the powdered lead in the compounded rubber, a large number of the powdered lead foils are arranged in a certain direction inside the rubber compound in a substantially layered manner. In this case, this lamination is achieved by repeatedly passing between kneading rolls during mixing of the compounded rubber and the powdered lead foil, so that the powdered lead foil is arranged in a large number of substantially parallel layers. In addition, the lamination rate can be improved by a mixing operation using a Banbury mixer, a Henschel mixer, etc., and especially a rolling operation using a calender, etc. In addition to these methods, layering can also be effectively carried out by extrusion work using an extruder, molding work using an injection molding machine, rocking work using a vibration molding machine, and arrangement using polarity in an electromagnetic field. These methods are to be selected. To explain this lamination arrangement, in the examples of the present invention, it is shown as a lamination ratio, which means that in the cross section of the rubber composition containing powdered lead, the powdered lead is in a certain direction or within about 30 degrees from that direction. This refers to the ratio of multiple laminated layers arranged in layers at different angles, measured using a stereomicroscope, and expressed as a percentage. In the present invention, "substantially laminated" refers to an arrangement of powdered lead of approximately 70% or more as a result of visual observation at 25x magnification using a stereomicroscope, as shown in FIG. 2, for example. Therefore, in the present invention, when powdered lead coated with a coating that is an antioxidant coating and a rubber compounding agent as described above is blended into rubber, those coatings diffuse into the rubber and are At the same time, the active lead powder surface comes into contact with the rubber component, preventing the generation of voids at the interface, exhibiting a unique binding force, and exhibiting various unique effects. It is. To explain the relationship between the compounded rubber and powdered lead when the powdered lead of the present invention is added to compounded rubber, this powdered lead is extremely easy to disperse into compounded rubber, and The hardness does not increase (that is, the Mooney viscosity is lower than that obtained by the atomization method, and it does not increase much even when the amount of lead increases), and the volume fraction of powdered lead is approximately 75% compared to the compounded rubber. %, it exhibits flexibility as a rubber, and in terms of the physical properties of the compound, it has a high elongation at break.
In addition to being characterized by low hardness and low tensile stress, an even more significant feature is that it has a scale-like shape, which allows it to be arranged in multiple layers very well. Next, we will discuss how the powdered lead having the above-mentioned characteristics behaves in rubber. Generally, reinforcing agents for rubber are characterized by fine particles, large specific surface area, and high adsorption ability, and furnace black, silica, hard clay, etc. are used for rubber. On the other hand, materials with low reinforcing properties, ie, large particle size, small specific surface area, and low adsorption capacity, such as heavy calcium carbonate and soft clay, are called fillers and can be filled in large amounts. If there is lead powder with an oxide film on the surface of compounded rubber or lead oxide such as lead circle (Pb ₃ O ₄ ) or litharge (PbO), which has an oxide film on the surface of the conventional method, the polarity of the lead powder is different from that of the present invention. It is larger than powdered lead, and the binding force of the rubber molecules is greater. Therefore, it is difficult to fill a large amount of lead powder or lead oxide using conventional methods. However, since the powder foil lead of the present invention has almost no oxide film on its surface, its polarity is small and there is no binding force on the rubber due to polarity, and as mentioned above, the particle size is quite large, with approximately 4 to 325 mesh accounting for 80% or more. Therefore, it is extremely easy to add powdered lead to rubber while maintaining a fresh metal surface with almost no oxide film, and it is possible to achieve a large amount of compounded rubber by adding powdered lead to approximately 75% by volume. Become. Therefore, the powdered lead added to the rubber exhibits good adhesion to the rubber, and there is almost no oxide film on the surface. Even when the changes in stress were measured, the changes remained very small. As mentioned above, the present invention effectively fills rubber with powdered lead, which has almost no oxide film on its surface, in multiple layers, and based on this, as will be explained below, there is a good resistance to minute deformation between the compounded rubber and powdered lead. It exhibits excellent binding properties and exhibits effective properties for achieving the purpose of the present invention. Next, the amount of powdered lead used in the present invention is limited to approximately 15 to 75% in volume fraction, and the reason for this is as shown in Tables 3 and 4 of Examples, the purpose of this invention The results of sound insulation tests and X-ray shielding tests within the range of 15% and below show that the effect is not significant when the volume fraction is 15% or less. In addition, it is possible to add it to rubber at a volume fraction of 75% or more, but the dough after kneading is too hard and the elongation is extremely reduced, making it difficult to perform molding processes such as calendering, and it is difficult to put it into practical use as a product. The upper limit is set at 75% because of the low When the volume fraction is 15% or more, the multi-layered powdered lead is uniformly dispersed in the compounded rubber, and the shape is large and scaly, and it spreads out as a surface.
The shielding effect against X-rays and generated sound is significantly increased. The lamination ratio of the powdered lead in the rubber composition of the present invention is approximately 70% after kneading with a kneading roll, and becomes 90% or more after kneading and further processing operations such as calendering. The amount of lead powder added should be set at a volume fraction of 15% to 75%, taking into consideration the purpose of use and characteristics.
Select as appropriate within the range of %. The powdered lead foil of the present invention can be easily kneaded by the kneading method and addition order commonly used in this technical field, and the dispersion is uniform and the multilayer arrangement is dense and ideal ( (See Figure 2). This ideal and precise multi-layer arrangement provides remarkable sound insulation, vibration damping, and X-ray shielding effects compared to conventional lead powder, which exists almost as dots in the rubber. Compared to the conventionally used rubber composition containing powdered lead with an oxide film on the surface at a volume fraction of 38%, for example, the rubber composition containing the powdered lead of the present invention at a volume fraction of 38% has half the It exhibits sufficient effects despite its thickness, and can easily achieve objectives that could not be accomplished conventionally, while also making it possible to significantly reduce weight. Also noteworthy are the ease of handling due to the flexibility of this compound and its sound insulation effect at low frequencies. That is, conventionally used lead plates and lead foils, or laminates using them, have poor restorability and are difficult to maintain smoothness. In comparison, the rubber composition of the present invention has great flexibility even at a high blending ratio, is easy to process when pasting a sheet, and is highly workable, so it has great practical effects. Furthermore, in sound insulation tests, it is natural that the greater the amount of lead powder added, the better the sound insulation effect, considering the increase in the number of laminated layers and the increase in the density of lead in the rubber. Moreover, when comparing the sound insulation test (Table 3) of the lead plate (see Comparative Example 8) of 2mm and the invention examples 1 to 5 of the present invention, the dB value of the 1mm rubber composition sheet when opened is In particular, sheets containing lead powder with a volume fraction of 30% or more show performance close to that of a 2 mm lead plate.For example, a rubber composition containing lead powder with a volume fraction of 47.9% has a performance of 1 mm. /2 thickness and exhibits an effect comparable to that of a lead plate. It was found that the effect is particularly remarkable at low frequencies below 110Hz. Also, a 1 mm thick sheet made of a rubber compound containing powdered lead at a volume fraction of 38% by the conventional method and a 1 mm thick sheet made from a rubber composition containing powdered lead at a volume fraction of 38% according to the present invention. When compared, the difference with the sheet of the present invention is slight, but the sound insulation effect at low frequencies is excellent. Furthermore, since the former cannot be filled in large amounts as mentioned above, the large amount compounded rubber composition of the present invention opens up a new field of effects that could not be achieved in the past. In other words, it has almost the same effect as a lead plate of the same thickness in terms of sound insulation, X-ray protection, and vibration damping, and is also superior in terms of ease of handling and workability due to its flexibility and smoothness. It has excellent beneficial effects. [Examples of the Invention] The present invention will be specifically described below with reference to Examples. The evaluation method of the sound insulation test and the evaluation method of the X-ray test in Examples are as follows. Evaluation method of sound insulation test Test equipment: (1) A sound insulation sheet is pasted on the circumference and bottom of the wooden box.
Sound insulation test equipment with the top open. A sound source that generates various frequencies was housed inside. (2) Sound level meter NA-09 model manufactured by Rion Co., Ltd. Test conditions: (1) Temperature: 25℃ (2) Location: Closed room (3) For hard materials such as lead plates, an iron frame was used as the presser. Test method: Place the sample on top of a sound insulation test device with a sound source inside, make the device completely sealed, place a sound level meter at a distance of 70 cm from the top of the device, and measure the decibel value (dβ) with A weighting.
was measured. Evaluation method of X-ray test Test equipment: X-ray diffraction device JDX-7E model JEOL Ltd.
Manufacturing test method: The X-rays were adjusted to travel straight, and the sample was inserted between the radiation source and the Geiger counter. X-rays were emitted and the number of counts (C/sec) with a Geiger counter was measured. Test conditions: (1) Temperature: 25°C (2) Angle: 0 Example 1 Tables 1-1 and 2-1 show the amount of lead powder mixed into compounded rubber based on chlorinated butyl rubber. Examples and comparative examples shown are shown below. 6 for kneading
Each was molded to a thickness of 1 mm using a calender using an inch mixing roll. The resulting mixture was heated under pressure at 167°C for 20 minutes using a hot press, and its physical properties, lamination ratio, and dispersibility were measured.

【table】

【table】

【table】

【table】

[Table] Invention examples 1 to 1 shown in Tables 1-1 and 1-2
Using the sheets of No. 6 and Comparative Examples 1 to 9, the measured values shown in Table 3 were obtained.

【table】

[Table] From the above data, the rubber composition of the present invention has a considerable effect on a 1 mm sheet compared to a 2 mm lead plate, and has almost the same sound insulation effect on the same 2 mm sheet. When handling lead as a sheet, it is difficult to handle unless an iron workpiece is used, as there is a gap between it and the equipment, making it ineffective. In contrast, the sheet made of the rubber composition of the present invention was extremely soft and flexible and easy to handle.
In addition, the effect at low frequencies is particularly excellent,
It can be seen that it has the same effect as a lead plate, and has a remarkable effect compared to general commercially available urethane sound insulation materials. Figure 1 shows the equipment used in this test. In the figure, 1 is a sound source, 2 is a foil for sound insulation measurement, 3 is a lined lead plate, 4 is a sample sheet, and 5 is a sound level meter. A stereoscopic microscope photograph of a cross section of the rubber composition sheet (Example 2) used in the sound insulation test is shown in FIG. 2, and the same photograph of Comparative Example 4 is shown in FIG. Invention examples 1 to 1 shown in Tables 1-1 and 1-2
Using the sheets of No. 5 and Comparative Examples 1 to 8, the thickness was adjusted respectively.
The measured values in Table 4 were obtained by adjusting to 0.25 mm and 0.1 mm.

【table】

[Table] As a result of the X-ray shielding test, it was found that when 300 parts or more of powdered lead was added, it had a considerable shielding effect, and when 500 parts or more was added, the shielding effect was almost close to that of a lead plate. Example 2 Table 5 shows blending examples and physical property values of powdered lead and chlorinated butyl depending on the type of auxiliary crushing agent.

【table】

[Table] From the above results, it was confirmed that the type of auxiliary crushing agent had no effect on lead powder. Example 3 Table 6 shows a carbon black formulation example and physical property values of chlorinated butyl rubber. Based on the following formulation, knead using a 6-inch mixing roll, and use the same roll to mix the mixture to a thickness of 2.
It was formed into a sheet of 1.0 mm thick, and heated under pressure for 20 minutes at a temperature of 167°C using a heat press. The measured value is the 6th below.
Shown in the table.

【table】

[Table] Example 4 Table 7 shows a blending example and physical property values of a carbon blend of chloroprene rubber and powdered lead. According to the following formulation example, kneading was performed using a 6-inch mixing roll, and the mixture was formed into a 2 mm sheet using the same roll.
The resulting compound sheet was heated to 167°C using a heat press.
The mixture was heated under pressure for 20 minutes at a temperature of .

【table】

[Table] Example 5 Table 8 shows a comparative example of the type of crosslinking agent in a carbon compound of chloroprene rubber and powdered lead and its characteristic values. Based on the formulation example below, kneading was carried out using a 6-inch mixing roll, and the mixture was formed into a 2 mm sheet using the same roll. The obtained compound sheet was heated under pressure at a temperature of 167° C. for 10 minutes using a heat press.

【table】

[Table] Example of using lead phosphate 6 Table 9 shows a blending example and physical property values of silicone rubber and powdered lead. Based on the following formulation example, kneading was performed using a 6-inch mixing roll, and the mixture was formed into a sheet with a thickness of 2 mm using the same roll. The obtained compound sheet was heated under pressure at a temperature of 170° C. for 20 minutes using a heat press.

【table】

【table】

[Table] Example 7 Table 10 shows a compounding example and physical property values of compounded rubber mainly composed of chlorinated butyl rubber and lead oxide. Based on the formulation example below, kneading was carried out using a 6-inch mixing roll, and the mixture was formed into a 2 mm sheet using the same roll. The resulting compound sheet was heated using a heat press.
It was heated under pressure at a temperature of 167°C for 20 minutes.

〔Effect of the invention〕

As mentioned above, the rubber composition of the present invention allows a large amount of powdered lead foil having an active metallic lead surface to be uniformly arranged in multiple layers, and at the same time provides good bonding between the rubber molecules and the powdered lead foil during minute deformation. Due to the effect of creating adhesion, it is superior to conventional products in soundproofing, vibration damping, X-ray shielding, radiation shielding, prevention of marine organisms adhesion, corrosion prevention, etc., without impairing the properties of rubber such as flexibility and flexibility. This shows an extremely remarkable effect that cannot be obtained.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of the sound insulation test equipment used in the examples, and Fig. 2 is the powdered lead obtained by the present invention.
A stereoscopic micrograph (x25) showing the cross-sectional structure of the rubber composition (Example 2) containing 500 parts by weight. Figure 3 is a conventional example containing 500 parts by weight of commercially available lead powder (atomized method, passed through 200 meshes). A stereoscopic micrograph showing the cross-sectional structure of the rubber composition (Comparative Example 4) (×
25). 1: Sound source, 2: Sound insulation measurement box, 3: Lead plate lined, 4: Sample sheet, 5: Sound level meter.

Claims (1)

[Claims] 1 The volume fraction of powdered lead, which has almost no oxide film on its surface, is 15 to 75% of the compounded rubber.
1. A rubber composition containing powdered lead, characterized in that the powdered lead is arranged in a substantially laminated manner.