WO2024019035A1

WO2024019035A1 - Degradable rubber composition, rubber member, sealing member, and method for producing degradable rubber composition

Info

Publication number: WO2024019035A1
Application number: PCT/JP2023/026218
Authority: WO
Inventors: 樹来小林; 和洋高原; 卓磨小林; 康志海老原; 壮慶東瀬; 京介久保田
Original assignee: 興国インテック株式会社; 株式会社クレハ
Priority date: 2022-07-21
Filing date: 2023-07-18
Publication date: 2024-01-25

Abstract

Provided are: a degradable rubber composition which has sealing performance required of rubber members of sealing members and which after having been exposed to a fluid, e.g., water, over a given time period, can break into pieces even without receiving external stress and is thereby made easily removable; a rubber member; a sealing member; and a method for producing the degradable rubber composition. The degradable rubber composition comprises a degradable rubber component including a millable rubber material composed of hydrolyzable rubber molecules and an acidic hydrolysis accelerator which is a powder that becomes acidic upon contact with water and which accelerates the hydrolysis of the rubber molecules upon contact with water. The acidic hydrolysis accelerator is contained in an amount of 40 parts by mass or more per 100 parts by mass of the degradable rubber component.

Description

Degradable rubber composition, rubber member, sealing member, and method for producing a degradable rubber composition

The present invention relates to a degradable rubber composition, a rubber member, a sealing member, and a method for producing a degradable rubber composition, and particularly to a degradable rubber composition, a rubber member, and a sealant that naturally disintegrate after a predetermined period of time. The present invention relates to a member and a method for producing a degradable rubber composition.

Conventionally, a hydraulic fracturing method as shown in FIG. 6 has been employed to extract hydrocarbon resources such as oil and natural gas existing in underground layers. FIG. 6 is an explanatory diagram showing an overview of the hydraulic fracturing method. In the hydraulic fracturing method, first, the underground layer 50 is excavated from the well 10 on the ground surface 11 using a drill or the like, and reaches the mining layer 51 where hydrocarbon resources confined underground, for example, several thousand meters deep, are distributed. An excavated hole 13 is formed. Next, by injecting fluid such as water at high pressure into the formed excavation hole 13, the rock of the mining layer 51 is crushed and cracks 15 are generated in the rock of the mining layer 51. Hydrocarbon resources trapped in the mining layer 51 are released from the cracks 15 generated in this way (see, for example, Patent Document 1).

In the hydraulic fracturing method, in order to generate cracks 15 in the mining layer 51 by the pressure of fluid, the drill hole 13 is sealed at one or more locations with a sealing member 100 such as a frac plug, and a part of the drill hole 13 is sealed. It is necessary to form a space sealed by the sealing member 100. At this time, the sealing member 100 needs to have a function of suppressing fluid from flowing out from the space.

On the other hand, in order to take out the hydrocarbon resources released by the hydraulic fracturing method through the borehole 13, it is necessary to remove the sealing member 100 from the borehole 13. As a method for facilitating the removal of the sealing member 100 from the borehole 13, a sealing member 100 that is decomposed by being exposed to an environment in which a fluid such as water is present in the borehole 13 for a predetermined period of time is used. There is a way. As such a sealing member 100, one is known that is composed of a resin member made of a degradable resin such as polylactic acid and a rubber member made of a degradable rubber component.

Japanese Patent Application Publication No. 2015-59376

However, even if the degradable rubber component used as the rubber member of the sealing member 100 is exposed to an environment where a fluid such as water is present for a predetermined period of time and hydrolysis progresses, the degradable rubber component remains in a gel-like or clay-like state. A state of high viscosity is maintained. Specifically, even if the hardness of conventional degradable rubber components reaches zero, they will not break into small pieces unless external force is applied to them. That is, in the conventional sealing member 100, the rubber member maintains its shape and remains in the excavated hole 13 without collapsing. In order to remove the remaining sealing member 100 from the excavated hole 13, stress is removed from the outside of the sealing member 100 by inserting a drill or the like into the excavation hole 13 and crushing the sealing member 100 with the drill or the like. It is necessary to add and break it into small pieces. Therefore, due to its high viscosity, it may stick to the tip of the drill and obstruct the work, and may interfere with the separation work of the liquid after recovery. From the above, the sealing member 100 has the sealing performance as a rubber member, and after being continuously exposed to a fluid such as water for a predetermined period of time, it can be easily broken into small pieces without applying stress from the outside. There is a need for a rubber member that can be removed.

The present invention has been made in view of the above circumstances, and has the sealing performance of a rubber member as a sealing member, and does not apply stress from the outside after being continuously exposed to a fluid such as water for a predetermined period of time. An exemplary object of the present invention is to provide a degradable rubber composition, a rubber member, a sealing member, and a method for producing a degradable rubber composition that can be easily removed by breaking it into small pieces.

In order to solve the above problems, the present invention has the following configuration.

(1) A degradable rubber component containing a millable rubber material composed of hydrolyzable rubber molecules, and a powder that becomes acidic when it comes into contact with water, and which is capable of hydrolyzing the rubber molecules when it comes into contact with water. and an acidic hydrolysis accelerator, the acidic hydrolysis accelerator being contained in an amount of 40 parts by mass or more based on 100 parts by mass of the decomposable rubber component.

(2) A rubber member formed from the degradable rubber composition described in (1) above.

(3) A sealing member comprising at least a portion of the rubber member described in (2) above.

(4) A degradable rubber component containing a millable rubber material composed of hydrolyzable rubber molecules, and a powder that becomes acidic when it comes into contact with water, and which is capable of hydrolyzing the rubber molecules when it comes into contact with water. A decomposable rubber component comprising a kneading step of kneading raw materials containing an acidic hydrolysis accelerator to promote the degradable rubber component, wherein the acidic hydrolysis accelerator is contained in an amount of 40 parts by mass or more based on 100 parts by mass of the degradable rubber component. A method for producing a rubber composition.

Further objects and other features of the present invention will be made clear by the preferred embodiments described below with reference to the accompanying drawings.

According to the present invention, the sealing member has the sealing performance as a rubber member, and after being continuously exposed to a fluid such as water for a predetermined period of time, it can be easily broken into small pieces without applying stress from the outside. A removable degradable rubber composition, a rubber member, a sealing member, and a method for producing a degradable rubber composition can be provided.

Schematic diagram showing a sealing member formed using the degradable rubber composition of Embodiment 1 Graph showing the results of measuring the surface hardness of the rubber samples of Example 1 and Comparative Examples 1 and 2 Schematic diagram showing the state before and after the rubber sample of Example 1 spontaneously disintegrates Schematic diagram showing the state after the rubber samples of Comparative Examples 1 and 2 are decomposed Graph showing the results of measuring the surface hardness of the rubber samples of Examples 2 to 4 An explanatory diagram showing an overview of the conventional hydraulic fracturing method

[Embodiment 1]
The degradable rubber composition (hereinafter sometimes simply referred to as "degradable rubber composition") according to Embodiment 1 will be described below.

[Degradable rubber composition]
The degradable rubber composition contains a degradable rubber component and a hydrolysis accelerator, and is suitably used as a material for a rubber member constituting a sealing member used, for example, in a hydraulic fracturing method. A rubber member formed using a degradable rubber composition has sealing performance as a rubber member of a sealing member.

Further, a rubber member formed using a degradable rubber composition has the characteristic that after being continuously exposed to a fluid such as water for a predetermined period of time, it breaks into pieces without applying stress from the outside. Specifically, when the hardness of the degradable rubber component of this embodiment reaches 0, it breaks down into small pieces (natural disintegration described below) without applying any external force. In addition, "predetermined time" means the time it takes for the rubber member to naturally disintegrate due to the progress of hydrolysis when the rubber member starts being exposed to a fluid such as water and continues to be exposed thereafter. . In this embodiment, the time required for the rubber member to naturally disintegrate means that when the rubber member begins to be exposed to a fluid such as water and continues to be exposed to it, hydrolysis progresses and the rubber member naturally disintegrates. It means the time until it collapses.

Here, when a rubber member "naturally disintegrates", it means that the rubber member is unable to maintain its shape and collapses into small pieces after being exposed to a fluid such as water for a predetermined period of time. means. If the temperature conditions differ, the "predetermined time" may also change, so the performance as a rubber member needs to be evaluated under constant conditions. In this embodiment, the time (predetermined time) until the rubber member spontaneously disintegrates is evaluated under a certain condition that the rubber member is continuously exposed to water at 93°C. Conventionally, the time it takes for the surface hardness (HsA) of a rubber member composed of hydrolyzable rubber molecules to reach 0 (zero) is a predetermined number of days (for example, 7 days) when exposed to water at 93°C. ) is known to require. Note that the fact that the surface hardness (HsA) of the rubber member becomes 0 (zero) is different from the fact that the rubber member naturally disintegrates. That is, even if the surface hardness (HsA) of the rubber member becomes 0 (zero), the shape of the rubber member may be maintained, and it will not break into pieces unless stress is applied from the outside of the rubber member. Each constituent component of the degradable rubber composition will be explained in order below. Note that details of the hydraulic fracturing method and the sealing member will be described later.

[Degradable rubber component]
The degradable rubber component includes a millable rubber material. Here, "millable rubber material" means a kneaded type rubber material, that is, a rubber material that can be kneaded. A kneaded type rubber material is a rubber material that is solid at room temperature before vulcanization, and is distinguished from a liquid injection type rubber material. Since millable rubber materials are solid at room temperature, they are suitable for kneading using kneaders, rollers, etc. Even if a large amount of powdered additives are added, the additives will not be absorbed within the millable rubber material by kneading. Can be uniformly dispersed. In the case of liquid-pouring rubber materials, they are liquid at room temperature, so if a large amount of powdered additives are added, the solubility limit may be reached, phase separation may occur, or the additives may become lumps. It may be difficult to disperse the material evenly.

Examples of millable rubber materials include materials containing at least one member selected from the group consisting of urethane rubber, natural rubber, isoprene rubber, ethylene propylene rubber, butyl rubber, styrene rubber, acrylic rubber, aliphatic polyester rubber, and chloroprene rubber. Can be done. In this embodiment, thermoplastic elastomers such as polyester thermoplastic elastomers and polyamide thermoplastic elastomers, which are materials having properties similar to those of millable rubber materials, can also be included in the concept of millable rubber materials.

Millable rubber materials are composed of hydrolyzable rubber molecules. The hydrolyzable rubber molecule is preferably a rubber molecule having a hydrolyzable functional group in the main chain of the rubber molecule. The rubber molecule may have a hydrolyzable functional group not only in the main chain but also in the crosslinked portion. Examples of hydrolyzable functional groups include urethane groups, ester groups, amide groups, carboxyl groups, hydroxyl groups, and silyl groups. The hydrolyzable functional group may be present in some or all of the repeating units constituting the rubber molecule.

It is preferable that the mass average molecular weight of the rubber molecules constituting the millable rubber material is, for example, 10,000 or more. When the mass average molecular weight is 10,000 or more, handling and workability as a millable rubber tends to be good. The mass average molecular weight of the rubber molecules constituting the millable rubber material can be adjusted according to the content ratio of the hydrolysis accelerator and hydrolysis inhibitor, which will be described later, so that the rubber member will naturally maintain its properties after being exposed to fluids such as water. You can control the time it takes to collapse.

As the millable rubber material, urethane rubber is preferable from the viewpoint of controlling sealing performance such as hardness and elasticity as a rubber member, and controlling decomposition performance and disintegration performance. Urethane rubbers include ester-type urethane rubbers, ether-type urethane rubbers, etc., and ester-type urethane rubbers having a hydrolyzable functional group are particularly preferred. In addition to the millable type (kneaded type), urethane rubber includes thermoplastic type, liquid injection type, etc. However, since the hydrolysis accelerator described later is a powder, it is necessary to use a predetermined amount or more of the hydrolysis accelerator. Millable type urethane rubber is preferable in order to incorporate it into the degradable rubber composition.

The degradable rubber component preferably contains a millable rubber material as a main component. The degradable rubber component may contain rubber materials other than the millable rubber material as long as the properties of the millable rubber material used in this embodiment are not affected.

[Hydrolysis accelerator]
The hydrolysis accelerator is a powder that becomes acidic or basic when it comes into contact with water, and is a component that promotes hydrolysis of the rubber molecules of the degradable rubber component. Here, "powder" means a substance that is powder or particulate at room temperature and in a state not in contact with water (dry state), and the particle size is 200 μm or less. When this powder comes into contact with water, its aqueous solution becomes acidic or basic. This acidic or basic aqueous solution promotes hydrolysis of rubber molecules. In the present embodiment, a powder that exhibits acidity when in contact with water and that promotes hydrolysis of rubber molecules of a degradable rubber component when in contact with water is referred to as an acidic hydrolysis promoter. In the present embodiment, a powder that exhibits basicity upon contact with water and that promotes hydrolysis of rubber molecules of a degradable rubber component upon contact with water is referred to as a basic hydrolysis promoter.

Examples of the acidic hydrolysis accelerator include mineral powders such as silica, clay, talc, aluminum sulfate, barium sulfate, calcium sulfate, and alumina colloid. Note that the acidic hydrolysis accelerator is not limited to mineral powder. As the acidic hydrolysis accelerator, these substances may be used alone, or a plurality of substances may be used in combination.

In the degradable rubber composition, the content of the acidic hydrolysis accelerator is 10 parts by mass or more, preferably 20 parts by mass or more, and 40 parts by mass or more, based on 100 parts by mass of the degradable rubber component. More preferably, the amount is 40 parts by mass, particularly preferably 40 parts by mass. When the content of the acidic hydrolysis accelerator is 10 parts by mass or more, the decomposition of the degradable rubber component is promoted, and the decomposed substance (hereinafter referred to as decomposed product) becomes clay-like, and the clay-like shape is maintained. . When the content of the acidic hydrolysis accelerator is 20 parts by mass or more, the decomposed product collapses due to external force. When the content of the acidic hydrolysis accelerator is 40 parts by mass or more, the decomposed product naturally disintegrates without applying external force. By setting the content of the acidic hydrolysis accelerator in the degradable rubber composition to 40 parts by mass or more based on 100 parts by mass of the degradable rubber component, the rubber can be continuously exposed to a fluid such as water for a predetermined period of time. It is possible to obtain a degradable rubber composition constituting a sealing member whose molecules suitably disintegrate naturally and which can be easily removed by breaking into small pieces without applying external stress.

The hydrolysis promoter contains an acidic hydrolysis promoter, and may further contain a basic hydrolysis promoter to the extent that the effect of the acidic hydrolysis promoter is not impaired.

Examples of the basic hydrolysis promoter include basic oxides such as metal oxide particles, salts of weak acids and strong bases, and metal hydroxides. Examples of the basic oxide include magnesium oxide, potassium oxide, and calcium oxide. Examples of the salts of weak acids and strong bases include sodium carbonate, sodium hydrogencarbonate, and calcium carbonate. Examples of the metal hydroxide include sodium hydroxide and potassium hydroxide. Note that the basic hydrolysis promoter is not limited to the above-mentioned basic oxides, salts of weak acids and strong bases, or metal hydroxides. As the basic hydrolysis accelerator, these substances may be used alone, or a plurality of substances may be used in combination.

In the degradable rubber composition, the content of the basic hydrolysis accelerator is 1 part by mass or more based on 100 parts by mass of the degradable rubber component. By setting the content of the basic hydrolysis accelerator in the degradable rubber composition to 1 part by mass or more per 100 parts by mass of the degradable rubber component, rubber molecules are Hydrolysis is further promoted, and the time required for rubber molecules to spontaneously disintegrate can be shortened.

[Hydrolysis inhibitor]
The degradable rubber composition may further contain a hydrolysis inhibitor in addition to the degradable rubber component and the hydrolysis promoter. The hydrolysis inhibitor is a component that inhibits the hydrolysis of rubber molecules promoted by the hydrolysis promoter. As the hydrolysis inhibitor, for example, a component that reacts with the carboxylic acid at the end of the carboxyl group produced by hydrolysis of rubber molecules and inhibits the chain reaction of the hydrolysis reaction can be used.

Examples of the hydrolysis inhibitor include polymeric carbodiimide compounds. As the hydrolysis inhibitor, these substances may be used alone, or a plurality of substances may be used in combination.

The properties of the hydrolysis inhibitor are not particularly limited, but for example, powder can be used. By using the millable rubber material, the powder hydrolysis inhibitor can be kneaded well.

In the degradable rubber composition, the content of the hydrolysis inhibitor is preferably 1 part by mass or more based on 100 parts by mass of the degradable rubber component. By appropriately adjusting the content of the hydrolysis inhibitor in the degradable rubber composition according to the mass average molecular weight of the millable rubber material and the content of the hydrolysis accelerator, hydrolysis of rubber molecules can be delayed and sealing can be achieved. The sealing function as a member can be maintained. That is, by increasing the content of the hydrolysis inhibitor in the degradable rubber composition, the decomposition of the degradable rubber composition can be further delayed.

[Other ingredients]
The degradable rubber composition may contain, for example, a reinforcing agent, etc., as appropriate, in addition to the above-mentioned constituent components.

A reinforcing agent is added for the purpose of improving the strength of a rubber member when the degradable rubber composition is used as a sealing member. Examples of reinforcing agents include silica and carbon black. In addition, when a mineral powder such as silica is used as an acidic hydrolysis accelerator, the mineral powder may function both as an acidic hydrolysis accelerator and as a reinforcing agent. can. Examples of the acidic hydrolysis promoter include mineral powders such as silica, clay, talc, aluminum sulfate, barium sulfate, calcium sulfate, and alumina colloid.

[Method for producing degradable rubber composition]
The method for producing the degradable rubber composition is not particularly limited, and general production methods can be employed. That is, the degradable rubber composition can be produced by a manufacturing method including, for example, a kneading step of kneading raw materials containing at least a degradable rubber component and an acidic hydrolysis accelerator, and a vulcanization step of crosslinking the kneaded raw materials. can be manufactured.

The kneading method for kneading the raw materials in the kneading step is not particularly limited, and can be performed by methods such as open rolls, pressure kneaders, and Banbury mixers.

After obtaining the degradable rubber composition, there are no particular limitations on the method for producing, for example, a rubber member. For example, a degradable rubber member can be produced by putting a degradable rubber composition into a predetermined mold and vulcanizing it under predetermined vulcanization conditions.

The vulcanization conditions for vulcanizing the degradable rubber composition can be, for example, a temperature in the range of 120°C to 200°C and a time of about 5 to 60 minutes. When the temperature is less than 120°C, the decomposition of the crosslinking agent does not proceed and the crosslinking reaction of the rubber does not occur. Moreover, when the temperature exceeds 200° C., the compound (high molecular compound (polymer)) deteriorates. On the other hand, when the temperature is in the range of 120°C to 200°C, crosslinking of the rubber occurs and no deterioration of the polymer occurs. The same applies to the time range. As the vulcanizing agent, sulfur, organic peroxide, etc. can be used. Examples of the organic peroxide include peroxyketal, dialkyl peroxide, diacyl peroxide, and peroxy ester.

[Hydraulic fracturing method]
Next, the hydraulic fracturing method will be explained. The hydraulic fracturing method, which is one example in which the sealing member of this embodiment is used, is the same as the method described with reference to FIG. 6, and the description thereof will be omitted with reference to FIG. However, as described later, the sealing member of this embodiment is formed using the degradable rubber composition according to this embodiment, and the material of the rubber member is different from that of the conventional sealing member 100. different.

[Sealing member 1]
FIG. 1 is a schematic diagram showing a sealing member formed using a degradable rubber composition according to Embodiment 1. For example, as shown in FIG. 1, the sealing member 1 includes a main body 2 having a substantially cylindrical shape extending in the longitudinal direction L, and a sealing member 1 disposed on both ends of the main body 2 in the longitudinal direction L so as to be slidable in the longitudinal direction L. The rubber member 3 includes a pair of sleeves 4 and a rubber member 3 disposed between the pair of sleeves 4. FIG. 1(a) is a schematic diagram showing a state in which the pair of sleeves 4 are in a predetermined position and the rubber member 3 is not compressed. FIG. 1(b) is a schematic diagram showing a state in which the pair of sleeves 4 are moved toward the center in the longitudinal direction L (toward the rubber member 3), and the rubber member 3 is compressed. Here, the "longitudinal direction L" is the direction in which the substantially cylindrical tube of the sealing member 1 extends, the direction in which the central axis extends, and the direction in which the sealing member 1 moves in the excavated hole 13. be. Moreover, "both end sides in the longitudinal direction L" means the front end side and the rear end side when the sealing member 1 moves within the excavated hole 13.

[Rubber member 3]
The rubber member 3 is a member formed from the degradable rubber composition according to the first embodiment. As described above, the rubber member 3 is a tubular member that is disposed between the pair of sleeves 4 and covers the periphery of the main body 2. As shown in FIG. 1(b), the rubber member 3 is deformed by being compressed by the pair of sleeves 4, and expands in a direction substantially perpendicular to the longitudinal direction. As a result, the sealing member 1 has a larger diameter (a diameter substantially perpendicular to the longitudinal direction) at the rubber member 3 portion. As the rubber member 3 expands in this manner, the rubber member 3 and the wall surface of the excavated hole 13 come into close contact with each other, making it possible to seal the excavated hole 13.

After the sealing member 1 finishes its role of sealing the excavated hole 13, the rubber member naturally collapses and is removed. The rubber member 3 is formed from the degradable rubber composition according to the present embodiment, and the degradable rubber composition constituting the rubber member 3 of the sealing member 1 has a sealing function and a predetermined After a period of time, it has the ability to break into small pieces without applying external stress. The parts of the sealing member 1 other than the rubber member 3, that is, the main body 2 and the pair of sleeves 4, may be formed from a degradable rubber composition or from other degradable materials. It may be something that is done. Examples of such degradable materials include polyglycolic acid (PGA) and polylactic acid (PLA). It is preferable that the portions of the sealing member 1 other than the rubber member 3 be decomposed in approximately the same time as the decomposition time of the degradable rubber composition. Note that the degradable rubber composition of this embodiment is not limited to the above-mentioned hydraulic fracturing method, and may be used in other methods that require sealing performance, decomposition performance, and disintegration performance.

Hereinafter, specific examples of the present invention will be described with reference to Examples. Note that the present invention is not limited to the following examples.

[Example 1]
100 parts by mass of polyester-based millable urethane rubber as a degradable rubber component and 40 parts by mass of silica as an acidic hydrolysis accelerator and reinforcing agent were used as raw materials. The degradable rubber component was kneaded using an open roll, a hydrolysis accelerator was added as an additive, and the mixture was further kneaded to obtain the degradable rubber composition of Example 1.

The obtained decomposable rubber composition was placed in a mold and vulcanized by heating under pressure at 120 to 200°C for 5 to 60 minutes. An organic peroxide was used as a vulcanizing agent. In this way, a cube-shaped rubber sample with one side of 20 mm was produced. A plurality of rubber samples were produced corresponding to each immersion time described below.

[Degradability evaluation test]
Each rubber sample and ion-exchanged water with a volume 10 times the volume of the rubber sample were placed in a 200 mL glass bottle, and each rubber sample and ion-exchanged water were immersed in an oven set at 93°C. I left it for a while. The immersion time was 1 day, 3 days, 5 days, 7 days, 9 days, and 11 days.

Each rubber sample left in the oven for each immersion period was taken out from the ion exchange water and left at room temperature to dry. Thereafter, the surface hardness (HsA) of each rubber sample was measured using a durometer type A (JIS K 6253 Kobunshi Keiki Co., Ltd.). The surface hardness was measured 3 seconds after applying a load of 1 kg. Note that the value measured before the rubber sample was immersed in ion-exchanged water was used as the surface hardness on day 0.

Figure 2 shows the measurement results of surface hardness. FIG. 2 is a graph showing the results of measuring the surface hardness of the rubber samples of Example 1 and Comparative Examples 1 and 2. In the graph of FIG. 2, the vertical axis shows the surface hardness (HsA), and the horizontal axis shows the immersion time (days). The measurement results of Example 1 are indicated by "●" (black circles) in FIG. It can be seen that the surface hardness (HsA) of the rubber sample of Example 1 became 0 (zero) 7 days after the start of immersion.

FIG. 3 is a schematic diagram showing the state before and after the rubber sample of Example 1 spontaneously disintegrates. FIG. 3(a) is a schematic diagram showing a state immediately after the rubber sample 30 is produced. At this point, the rubber sample 30 maintains a cubic shape of 20 mm on one side, and the decomposition of the degradable rubber component has not progressed. Note that this state before immersion is the same not only in Example 1 but also in other Examples and Comparative Examples. FIG. 3(b) shows the rubber sample 30 shown in FIG. 3(a) placed in a glass bottle 34 containing ion-exchanged water 36, and shows the state after the rubber sample 30 spontaneously disintegrated seven days after immersion was started. FIG. FIG. 3(b) shows that small pieces 32 of the naturally disintegrated rubber sample 30 are precipitated in the ion-exchanged water 36 at the bottom of the glass bottle 34. The small pieces 32 of the naturally disintegrated rubber sample 30 shown in FIG. 3(b) are broken down into small pieces of, for example, 1 mm or less, and are powdered when taken out from the glass bottle 34. From these results, it can be seen that the rubber sample 30 of Example 1 spontaneously disintegrated 7 days after the start of immersion.

[Comparative example 1]
A rubber sample was prepared in the same manner as in Example 1, except that the content ratio of the hydrolysis accelerator was 20 parts by mass based on 100 parts by mass of the degradable rubber component, and the surface hardness (HsA) was measured. The measurement results of Comparative Example 1 are indicated by "□" (open squares) in FIG. It can be seen that the surface hardness (HsA) of the rubber sample of Comparative Example 1 became 0 (zero) 7 days after the start of immersion.

FIG. 4 is a schematic diagram showing the state of the rubber samples of Comparative Examples 1 and 2 after they are decomposed. FIG. 4(a) shows the rubber sample 300 of Comparative Example 1 put into a glass bottle 34 containing ion-exchanged water 36, and after the rubber sample 300 of Comparative Example 1 has decomposed, that is, 7 days after starting immersion. 3 is a schematic diagram showing the appearance of a rubber sample 300 of Comparative Example 1. FIG. FIG. 4A shows that although the rubber sample 300 is decomposed, it does not spontaneously disintegrate, and maintains a cubic shape similar to the state immediately after the rubber sample 300 of Comparative Example 1 was produced. This point differs from FIG. 3(b), which shows the state after the rubber sample 30 spontaneously disintegrates in Example 1. Rubber sample 300 of Comparative Example 1 had a surface hardness (HsA) of 0 (zero) (decomposed) after 7 days from the start of immersion, but had a clay-like high viscosity and a cubic shape. was maintained. That is, rubber sample 300 of Comparative Example 1 did not disintegrate spontaneously.

[Comparative example 2]
A rubber sample was prepared in the same manner as in Example 1, except that the content ratio of the hydrolysis accelerator was 30 parts by mass based on 100 parts by mass of the degradable rubber component, and the surface hardness (HsA) was measured. The measurement results of Comparative Example 2 are indicated by "△" (open triangle) in FIG. It can be seen that the surface hardness (HsA) of the rubber sample of Comparative Example 2 became 0 (zero) 7 days after the start of immersion.

FIG. 4(b) shows the rubber sample 310 of Comparative Example 2 put into a glass bottle 34 containing ion-exchanged water 36, and after the rubber sample 310 of Comparative Example 2 has decomposed, that is, 7 days after starting immersion. 3 is a schematic diagram showing the state of a rubber sample 310 of Comparative Example 2. FIG. In FIG. 4(b), the rubber sample 310 has decomposed but has not spontaneously disintegrated. Seven days after the start of immersion, the rubber sample 310 of Comparative Example 2 is poked with a stick, that is, by applying an external force. It shows a state where the shape has been destroyed. Rubber sample 310 of Comparative Example 2 had a surface hardness (HsA) of 0 (decomposed) 7 days after the start of immersion, but had a clay-like high viscosity. That is, rubber sample 310 of Comparative Example 2 did not disintegrate spontaneously. By applying stress from the outside to the rubber sample 310 of Comparative Example 2, the shape collapsed.

[Example 2]
A rubber sample was prepared in the same manner as in Example 1, and the surface hardness (HsA) was measured. The measurement results are shown in FIG. FIG. 5 is a graph showing the results of measuring the surface hardness of the rubber samples of Examples 2 to 4. The measurement results of Example 2 are indicated by "●" (black circles) in FIG. It can be seen that the surface hardness (HsA) of the rubber sample of Example 2 became 0 (zero) 7 days after the start of immersion, as in Example 1. Similarly to Example 1, the rubber sample of Example 2 had spontaneously disintegrated 7 days after the start of immersion.

[Example 3]
A rubber sample was prepared in the same manner as in Example 1, except that 3 parts by mass of a polymeric carbodiimide compound as a hydrolysis inhibitor was added to 100 parts by mass of the degradable rubber component, and the surface hardness (HsA) was measured. The measurement results of Example 3 are indicated by "▲" (black triangle) in FIG. It can be seen that the surface hardness (HsA) of the rubber sample of Example 3 became 0 (zero) 9 days after the start of immersion. The rubber sample of Example 3 had spontaneously disintegrated as in Example 1 9 days after the start of immersion. This shows that the addition of the hydrolysis inhibitor suppressed the hydrolysis of the degradable rubber component. From the graph in FIG. 5, it can be seen that the surface hardness (HsA) of the rubber sample of Example 3 was maintained at about 80 until about 5 days after the start of immersion, and then the surface hardness decreased to 0 HsA on the 9th day. . From this, in the rubber sample of Example 3, the decrease in surface hardness was suppressed by the action of the hydrolysis inhibitor until about 5 days after the start of immersion, and after that, the surface hardness was suppressed due to the progress of hydrolysis of the degradable rubber component. It is assumed that the hardness has decreased.

[Example 4]
A rubber sample was prepared in the same manner as in Example 1, except that 4.5 parts by mass of a polymer carbodiimide compound was added as a hydrolysis inhibitor per 100 parts by mass of the degradable rubber component, and the surface hardness (HsA) was measured. did. The measurement results of Example 4 are indicated by "■" (black squares) in FIG. It can be seen that the surface hardness (HsA) of the rubber sample of Example 4 became 0 (zero) 11 days after the start of immersion. The rubber sample of Example 4 spontaneously disintegrated 11 days after the start of immersion, as in Example 1. This shows that the addition of the hydrolysis inhibitor suppressed the hydrolysis of the degradable rubber component. From the graph in FIG. 5, it can be seen that the surface hardness (HsA) of the rubber sample of Example 4 was maintained at about 80 until about 5 days after the start of immersion, and then the surface hardness decreased to 0 HsA on the 11th day. . From this, it can be seen that in the rubber sample of Example 4, the decrease in surface hardness was suppressed by the action of the hydrolysis inhibitor until about 5 days after the start of immersion, and after that, the surface hardness was suppressed due to the progress of hydrolysis of the degradable rubber component. It is assumed that the hardness has decreased. In addition, compared to Example 3, the rubber sample of Example 4 has a larger amount of hydrolysis inhibitor added, so even after the 5th day from the start of immersion, hydrolysis is suppressed due to the action of the hydrolysis inhibitor. It is presumed that the decrease in surface hardness (the slope of the graph) became more gradual, and the time from the start of immersion to natural collapse became longer.

From the above, the degradable rubber composition according to the present invention contains 40 parts by mass or more of a hydrolysis accelerator per 100 parts by mass of the degradable rubber composition, so that it can be easily immersed in water at 93°C. It has been shown that it is possible to form a rubber member that naturally disintegrates after a predetermined period of time.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these, and various modifications and changes can be made within the scope of the gist. For example, the present invention includes the following gist.

(Purpose 1) A degradable rubber component containing a millable rubber material composed of hydrolyzable rubber molecules, and a powder that becomes acidic when it comes into contact with water, and when it comes into contact with water, the rubber molecules are hydrolyzed. and an acidic hydrolysis accelerator that promotes this, and the acidic hydrolysis accelerator is intended to be contained in an amount of 40 parts by mass or more based on 100 parts by mass of the decomposable rubber component.

According to this, the sealing member has the sealing performance as a rubber member, and after being continuously exposed to a fluid such as water for a predetermined period of time, it can be easily removed by breaking it into small pieces without applying external stress. It is possible to provide a degradable rubber composition capable of

(Purpose 2) It is a powder that shows basicity when it comes into contact with water, and contains a basic hydrolysis accelerator that promotes the hydrolysis of the rubber molecules when it comes into contact with water, and promotes the basic hydrolysis. The agent may be contained in an amount of 1 part by mass or more based on 100 parts by mass of the decomposable rubber component.

According to this, the hydrolysis of the degradable rubber component can be further promoted.

(Purpose 3) The rubber molecules may have a mass average molecular weight of 10,000 or more.

According to this, it is possible to select a millable rubber material that is within a more suitable size range for being naturally disintegrated.

(Purpose 4) The rubber member is intended to be formed from the degradable rubber composition according to any one of Purposes 1 to 3.

(Purpose 5) The sealing member is intended to include the rubber member of Purpose 4 as at least a part thereof.

According to Purpose 4 and Purpose 5, the sealing member has the sealing performance as a rubber member, and after being continuously exposed to a fluid such as water for a predetermined period of time, it can be broken into small pieces without applying stress from the outside. It is possible to provide a rubber member and a sealing member that can be easily removed.

(Purpose 6) A degradable rubber component containing a millable rubber material composed of hydrolyzable rubber molecules, and a powder that becomes acidic when it comes into contact with water, and when it comes into contact with water, the rubber molecules are hydrolyzed. The method includes a kneading step of kneading raw materials containing an acidic hydrolysis accelerator that promotes the degradable rubber component, and the acidic hydrolysis accelerator is contained in an amount of 40 parts by mass or more based on 100 parts by mass of the degradable rubber component. Purpose.

According to this, the sealing member has the sealing performance as a rubber member, and after being continuously exposed to a fluid such as water for a predetermined period of time, it can be easily removed by breaking it into small pieces without applying external stress. A method for producing a degradable rubber composition can be provided.

1,100 Sealing member 2 Main body 3 Rubber member 4 Sleeve 5 Conduit 10 Well 11 Ground surface 13 Excavation hole 15

Cracks

30, 300, 310 Rubber sample 32 Small piece of rubber sample 34 Glass bottle 36 Ion exchange water 50 Underground layer 51 Mining layer L longitudinal direction

Claims

a degradable rubber component including a millable rubber material composed of hydrolyzable rubber molecules;
an acidic hydrolysis promoter, which is a powder that becomes acidic when it comes into contact with water, and which accelerates the hydrolysis of the rubber molecules when it comes into contact with water;
Contains
The decomposable rubber composition, wherein the acidic hydrolysis accelerator is contained in an amount of 40 parts by mass or more based on 100 parts by mass of the decomposable rubber component.
It is a powder that becomes basic when it comes into contact with water, and contains a basic hydrolysis promoter that accelerates the hydrolysis of the rubber molecules when it comes into contact with water,
The degradable rubber composition according to claim 1, wherein the basic hydrolysis accelerator is contained in an amount of 1 part by mass or more based on 100 parts by mass of the degradable rubber component.
The degradable rubber composition according to claim 1 or 2, wherein the rubber molecules have a mass average molecular weight of 10,000 or more.
A rubber member formed from the degradable rubber composition according to claim 1.
A sealing member comprising the rubber member according to claim 4 as at least a part thereof.
A degradable rubber component including a millable rubber material composed of hydrolyzable rubber molecules, and a powder that becomes acidic when it comes into contact with water, which accelerates the hydrolysis of the rubber molecules when it comes into contact with water. Including a kneading step of kneading raw materials containing a hydrolysis accelerator,
The method for producing a degradable rubber composition, wherein the acidic hydrolysis accelerator is contained in an amount of 40 parts by mass or more based on 100 parts by mass of the degradable rubber component.